The invasive freshwater jellyfish Craspedacusta sowerbii: silent invasion of an unknown species?

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Guillaume Marchessaux, Kristína Slovák Švolíková, Barbora Števove, and 15 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7392176/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Biological invasions are a major driver of biodiversity loss, yet inconspicuous or “cryptic” species often escape public and scientific attention. The freshwater jellyfish Craspedacusta sowerbii, likely native to China and now present on six continents, exemplifies such silent invasions. Despite its broad distribution, the species’ ecology and societal perception remain poorly understood. We conducted a 24-month, multilingual online survey across 17 European countries (n = 1,388) to assess public awareness, perceptions, and management views regarding C. sowerbii. Results reveal limited knowledge: over 80% of respondents did not know its scientific name, 49% misidentified its freshwater habitat as marine, and only 33% recognized it as non-native. While its aesthetic qualities were often praised, mass occurrences provoked caution, and direct contact was rare and typically harmless. Bayesian Network analysis indicated that direct observation—rather than demographic factors or ecological knowledge—was the strongest predictor of concern and support for increased public discussion. Although most respondents did not perceive C. sowerbii as a major local threat, many recognized potential ecological implications and supported greater awareness and governance measures. This study underscores how visual subtlety and low media coverage limit detection and prioritization of cryptic invasive species, with implications for early warning systems and policy. Leveraging citizen science to enhance recognition and reporting could improve detection of such species, complementing formal monitoring networks. We advocate integrating cryptic invasions into invasive alien species management frameworks, emphasizing experiential engagement alongside conventional ecological data to address overlooked yet potentially impactful species. Biological sciences/Ecology/Invasive species Social science/Environmental studies Global change Hydrozoa Invasive Freshwater species Perception Survey Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Biological invasions are among the primary drivers of global biodiversity loss (Bellard et al. 2016). According to the IPBES Global Assessment Report (Roy et al. 2023), they are now recognized as the fifth main cause of species extinction, following changes in land and sea use, direct exploitation of organisms, climate change, and pollution. The exponential increase in trade, globalization, and international transport has significantly facilitated the introduction and establishment of species outside their native ranges. By 2023, the IPBES estimated that over 37,000 alien species had been introduced into new ecosystems, with at least 3,500 classified as invasive, causing significant ecological, economic, and health impacts (Pascual et al. 2023; Roy et al. 2023). Nevertheless, not all biological invasions are perceived in the same way, whether by scientists, managers, or the general public. Some invasive species quickly attract attention due to their spectacular effects or direct impact on human activities, such as the Asian hornet ( Vespa velutina Lepeletier, 1836) in Europe (Keeling et al. 2017) and the zebra mussel ( Dreissena polymorpha Pallas, 1771) in North America (Strayer 1991). Conversely, other invasions pass relatively unnoticed: their progress is silent, their effects less obvious, or their life cycle (or certain stages thereof) largely unobservable (Spear et al. 2021). These so-called “cryptic” invasions ( sensu Latombe et al. 2017) nonetheless make up a significant part of the current introduction dynamics, and their underestimation can be detrimental to the overall understanding of the ongoing ecological changes. Public perception often differs from that of conservation managers, which can complicate management efforts and priorities for invasive species (Gozlan et al. 2013). Moreover, it plays a critical role in shaping monitoring strategies, influencing policy decisions, and guiding citizen science participation (Courchamp et al. 2018). Several studies have recently highlighted attention bias toward small aquatic non-native species or those lacking an immediately identifiable economic impact (Seebens et al. 2017; Essl et al. 2020; Seebens et al. 2021). Species such as the bloody-red mysid Hemimysis anomala , a mysid shrimp native to the Caspian Sea, or the spiny waterflea Bythotrephes longimanus , a planktonic predator from the Great Lakes of North America, have long remained understudied despite their role as ecosystem engineers (Yan et al. 2011; Wittmann et al. 2016). Similarly, some ctenophores, such as Mnemiopsis leidyi (A. Agassiz, 1865), were only fully recognized as invasive several years after their introduction, despite contributing to fisheries collapse in the Black Sea (Shiganova 2000). Yet, the growing involvement of the public in biodiversity monitoring highlights the potential of the “power of many”: when well-informed and adequately supported, collective observation efforts can counteract attention biases and enhance early detection of inconspicuous or understudied species. Public participation not only helps fill critical data gaps but also fosters more inclusive and responsive monitoring systems capable of detecting subtle ecological signals that might otherwise go unnoticed by conventional surveillance (Dickinson et al. 2010; Pocock et al. 2017). In recent years, public participation in biodiversity monitoring has become an increasingly valuable tool for detecting or tracking biological invasions. However, its effectiveness largely depends on public awareness and the recognizability of species, which remain major challenges for organisms that are unknown or difficult to observe (Ricciardi et al. 2017). Craspedacusta sowerbii, the world’s most widespread freshwater jellyfish, exemplifies this type of discreet invasion. Likely native to the Yangtze River basin in China (Fritz et al. 2007), this hydrozoan was first described outside its native range in 1880, in an ornamental pond in London (Lankester, 1880). Since then, it has been reported on six continents, through the involuntary transport of propagules (polyp or podocyst stages) associated with aquatic plants or submerged substrates (Dumont 1994; Marchessaux et al. 2022b; Lüskow et al. 2024). In Europe, its presence is now well documented in many countries, including France, Germany, Italy, Spain, and the Czech Republic, though its distribution remains highly uneven across the regions (Marchessaux et al. 2021). Despite its wide distribution, C. sowerbii remains surprisingly understudied (Lüskow et al. 2024). Most publications focus on occurrence records or descriptive studies of its life cycle, which alternates between a tiny benthic polyp and a planktic medusa visible only at certain times of the year (Lüskow et al. 2024). Its actual ecological impact is still poorly understood, although some studies suggest it may disrupt pelagic food webs, notably by competing with fish larvae or macroinvertebrates (Thomas 1950, 19; Dodson and Cooper 1983). In addition, the species often escapes standard detection (Moore et al. 2025): its appearance is sporadic, localized, sometimes limited to a few days per year, making it very difficult to monitor. Given this biological and media invisibility, it is legitimate to question whether the invasion of C. sowerbii is perceived and recognized as such by the general public, particularly in Europe, where awareness of non-native species varies considerably depending on geographical and cultural contexts. Hence, the aim of the study is to assess, using survey data and citizen observations, the level of public knowledge and perception of C. sowerbii in 17 European countries to better understand the societal and cognitive factors influencing the visibility of a biological invasion. This study hypothesized that C. sowerbii is poorly known to the public and that its ecological implications go largely unnoticed. Findings from this study can inform targeted public engagement and monitoring strategies, improve the design of citizen science platforms, and contribute to a broader understanding of how societal factors mediate the detectability of biological invasions—particularly those that are inconspicuous yet ecologically significant (Groom et al. 2019). Enhancing public awareness of cryptic invasive species such as C. sowerbii could support earlier detection and more effective management responses, thereby reinforcing prevention strategies and biodiversity conservation policies. Materials and methods Survey strategies An online questionnaire survey (in Google Form format) was carried out to assess public awareness about the invasion of freshwater jellyfish Craspedacusta sowerbii across 17 European countries (Supplementary Figure 1). The questionnaire was accessible for 24 months starting in March 2023. We used the “snowball” method to collect responses to the questionnaires, beginning with previously identified networks such as Facebook groups oriented towards citizen sciences (e.g., photography, hiking, excursions), major institutions in natural sciences (e.g., IUCN), nature managers, university mailing lists, and personal networks of co-authors. Participants were also encouraged to share the questionnaire within their respective networks to help reach a broader panel of respondents. Additional outreach was achieved by sharing the questionnaire online via press and TV communication (Marchessaux et al. 2023; Marchessaux et al. 2024), as well as through dissemination via project mailing lists and stakeholder databases managed by co-authors. The questionnaire was created based on a review of the available literature on public perception of invasive species (Varble and Secchi 2013; Huth et al. 2016; Vandendriessche et al. 2016; Cerveira et al. 2022; Marchessaux et al. 2024) and was further refined by the co-authors to address country-specific aspects. The questionnaire was translated into multiple languages by the co-authors and distributed in 17 the following European countries: Bosnia and Herzegovina, Denmark, France, Georgia, Germany, Hungary, Italy, Norway, Poland, Portugal, Romania, Russia, Slovakia, Spain, Türkiye, Ukraine, and the United Kingdom. The questionnaire was divided into six sections, and had an average completion time of approximately 10-12 minutes to maximize participation (Supplementary Figure 1). To minimize response bias, respondents were invited to respond anonymously and voluntarily. The first part of the survey collected anonymous demographic information, including gender, age and city of residence. The second part focused on respondents’ interactions with C. sowerbii , including their familiarity with the species name and any personal observations. The third part explored the aesthetic perceptions of the species, including its physical appearance and if respondents had ever been stung by C. sowerbii . The fourth part addressed perceptions of the species’ origins, asking if respondents considered C. sowerbii native or introduced to Europe. Finally, the last two parts aimed to assess public knowledge of the species’ ecology and views on its management and prioritization, respectively. To avoid influencing responses, we chose never to explicitly name the species we were studying (in this case, Craspedacusta sowerbii ), even at the end of the questionnaire, but a panel of pictures of the species was given to the respondents in the questionnaire (Supplementary Figure 1). Similarly, in all communications promoting the survey, we simply specified that this study concerned an emerging ecological phenomenon in Europe, without ever mentioning what it was. Data analysis Given the noteworthy difference in the number of responses collected per country (minimum: 1 for Ukraine, likely due to the ongoing war during the survey period; maximum: 247 for Slovakia), we chose to process all responses collectively to reflect European citizens’ perception of the C. sowerbii invasion. Accordingly, all country-level data were aggregated into a data matrix comprising all responses. The data were processed in alignment with the 6-panel structure of the questionnaire, allowing us to monitor its organization and the evolution of responses according to the various categories. For the first panel, we created a map presenting the countries included in the study. Using QGIS software (version 3.40.1), we highlighted and color-coded each country based on the number of responses received. The frequency distributions of respondent age and gender were calculated and then visualized using a histogram and a pie chart created with SIGMAPLOT 12.5. Responses for the remaining categories were converted to percentages and plotted accordingly. The figure formats were selected to best represent the trends observed in the collected data. To support our hypothesis that the invasion of C. sowerbii is poorly understood, we highlighted the proportion of “I don't know” responses in dark grey across all graphs. To contextualize the species invasion of each country and the number of replies, we have plotted the number of C. sowerbii occurrences and the total number of replies per country, and we performed a Generalized Linear Model (GLM) analysis using R Studio software (version 2024.12.0). To explore the interdependence of individual responses and detect any demographic, geographic, or independent effects related to respondent characteristics, a Bayesian Network (BN) was constructed to model the conditional dependencies among the measured variables. A BN is a graphical probabilistic model in which each node represents a random variable and each directed arc encodes a conditional dependency relationship between two variables (Pearl 1988). The structure of the network was learned using the hill-climbing (hc) algorithm, which optimizes a log-likelihood score by exploring possible structures under the constraint of graph acyclicity (Koller and Friedman 2009). The entire process was carried out using the “bnlearn” package (Scutari, 2025) in R Studio. After learning the structure of the Directed Acyclic Graph (DAG), the conditional parameters of the network were estimated using a frequentist approach (bn.fit), which allowed for defining the conditional distributions of each variable given its parents in the graph (Spirtes et al. 2000). Conditional inference was performed using the likelihood weighting method via the “cpquery” function of the “bnlearn” package (Scutari, 2025). This method relies on weighted simulations from the learned network. The number of simulated samples was set to 10,000 to ensure sufficient convergence. The network visualization was carried out using the “Rgraphviz”, “igraph”, and “visNetwork” packages within an interactive Shiny interface. The resulting DAG illustrates the structure of conditional dependencies among the variables, where each node represents a variable, and each arrow indicates a direct influence in the joint factorization of the model. Results A total of 1,388 questionnaires were completed between 3 March 2023 and 31 December 2024 (Figure 1A). The spatial distribution of respondents shows broad coverage across all countries included in the study (Figure 1A), with the number of responses ranging from 1 (in Ukraine) to 247 (in Slovakia). The sample consisted of 38% male respondents, 61% female and 1% who did not specify their gender. Respondents were between 18 and 84 years old, with a majority (64%) falling within the 18–40 age group (Figure 1B). Regarding the relationship between the number of replies per country and the number of reported occurrences of C. sowerbii (Supplementary Figure 2), notable discrepancies emerged. For instance, countries such as France, and Germany reported numerous occurrences despite fewer responses, whereas others, like Slovakia and Türkiye contributed many responses but reported few or no occurrences (Supplementary Figure 2). We observe that 23% of respondents report going outdoors into nature every day, while 14% never do so (Figure 1C). Regarding the species visibility (Figure 2A), 48% of respondents reported having seen it, while 52% stated they had never observed it. When asked to identify the organism (Figure 2B), 83% recognized it as a jellyfish, whereas 14% did not know what it was. Common misidentifications included comb jellies, tunicates, and fish. When asked about the scientific name of the species (Figure 2C), 81% indicated they did not know it, and only 10% correctly identified C. sowerbii . Confusion with marine species such as Aurelia aurita and Mnemiopsis leidyi was common. The reported locations of observation (Figure 2D) revealed significant misconceptions: 49% of respondents claimed to have seen the species in the sea, which is incorrect as C. sowerbii is strictly freshwater. Furthermore, 26% saw it through media (TV, newspapers), 10% in a lake, and 9% in a public aquarium – environments more consistent with the species’ ecology. Observations in artificial basins, rivers, or quarries were less frequent. The activities during which the species was observed (Figure 2E) varied broadly: the majority (40%) observed it while swimming, 20% while walking, 17% during aquarium visits, 11% while diving, and 9% while boating. Very few respondents reported sightings in private aquariums or at sea. Finally, the seasonal distribution of observations (Figure 2F) showed that most sightings occurred in summer (71%), followed by autumn (14%), spring (11%), and only a small proportion (4%) in winter. In terms of aesthetic perception and emotional responses to mass encounters and stinging experiences, people commonly described the species as “beautiful” (21%), “sublime” (18%), and “delicate” (18%; see Figure 3A). Additional terms like “fragile” (15%) and “aesthetic” (14%) further underscore a generally positive perception. Respondents’ emotional responses to encountering large numbers of individuals showed a tendency toward caution: 65% reported feeling “careful”, while 54% “nervous”and 51% felt “scared”, though these feelings varied in intensity (split between “a little” and “yes”; Figure 3B). More positive emotions, such as feeling “relaxed,” “confident,” or “calm”, were less commonly reported. Specifically, 49% did not feel relaxed, 45% did not feel confident, and 40% did not feel calm in such situations (Figure 3B). Regarding direct contact, the vast majority of respondents ( 92%) had reported never having been stung by C. sowerbii . Among those who had, over half (56%) reported no pain at all (score 0), 14% reported moderate pain (score 3), and 13% mild pain (score 2; Figure 3C). Other pain levels were rare with very mild (6%), severe (8%), and very severe (3%) pain (Figure 3C). Overall, the data suggest that C. sowerbii is perceived positively in terms of appearance, but mass encounters may provoke caution or apprehension. Direct contact is rare, and when it occurs, it typically results in minimal or no pain. The analysis highlights a general lack of public knowledge regarding the geographical origins of C. sowerbii and its status in Europe (Figure 4). When asked to identify the species’ country of origin, the most common response was “I don’t know” (13%). Among those who provided an answer, China was the most frequently cited (11%), correctly corresponding to the species’ most likely native range in the freshwater systems of the Yangtze River basin. However, range of other countries were mentioned from all continents, such as Türkiye, Australia, the USA, Croatia, and Greece, with highly scattered responses spanning countries from all continents, including South Africa, Brazil, Germany, India, and Madagascar, reflecting widespread uncertainty and misinformation (Figure 4A). In a follow-up question about whether the species is native or non-native to Europe, 51% of respondents indicated that they did not know, 33% correctly identified C. sowerbii as non-native and invasive, while 16% incorrectly believed it to be native (Figure 4B). These results reveal a clear gap in public understanding of the species’ biogeography. The evaluation of public knowledge about the main vector of introduction of C. sowerbii showed that the most frequent response was “I don’t know” (26%; Figure 5A), followed closely by boats (25%), a widely recognized pathway for aquatic invasive species. Regarding factors driving the species’ proliferation, global change was the most commonly referenced (28%), followed by overfishing and predator removal (16%) and invasive species vectors (13%). Twelve percent of respondents answered that they did not know, while others mentioned pollution (8%), natural evolution (6%), ocean acidification (5.9%), eutrophication (5.7%), and rarity of predators (5.4%), suggesting an awareness of complex ecological pressures, albeit with varying levels of scientific accuracy (Figure 5B). On the question of feeding habits, 34% of respondents correctly identified zooplankton as the primary food source, followed by phytoplankton (29%). Sixteen percent responded with “I don’t know,” while smaller proportions incorrectly selected fish (7%), jellyfish (6%), mollusks (5%), and insects (3%), reflecting a partial understanding of the species’ trophic role (Figure 5C). Overall, the results pointed to fragmented but occasionally accurate public perceptions of C. sowerbii ’s ecology. The analysis of public perceptions concerning the management and societal relevance of C. sowerbii as a potentially invasive species highlights a diversity of opinions across local, global, and ecological contexts (Figure 6). When asked whether the species is perceived as problematic, 36% of respondents did not consider it a local issue (“0 (no)”), while others rated its importance with increasing concern: 18% (“1 (a little)”), 29% (“2 (middle)”), 11% (“3 (a lot)”), and 6% (“4 (very much)”), indicating a predominantly low perception of a local threat (Figure 6A.a). However, views shifted slightly when considering its global impact: 14% stated it is not a problem at all, but 30% rated it as a moderate concern(“2 (middle)”), and 23% viewed it as a significant global issue (“3 (a lot)”) (Figure 6A.b). Similarly, when framed as a minor problem, 38% still rated it at “0 (no)”, though 30% gave it a relatively high concern (“2 (middle)”), and 22% scored it(“3 (a lot)”, revealing nuanced views on the severity of its presence (Figure 6A.c). Regarding personal or ecological concern, 28% reported no concern at all, while 30% rated their concern at a moderate level (“2 (middle)”), suggesting a degree of ambivalence (Figure 6B.a). Nonetheless, many respondents found the species interesting, with 30% assigning it a mid-level score (“2 (middle)”), and another 30% placing it in higher interest categories (“3 (a lot)” and “4 (very much)” combined) (Figure 6B.b). Ecological concern appeared more pronounced, with 31% ranking it at the highest level (“4 (very much)”), indicating a growing recognition of its environmental relevance (Figure 6B.c). Finally, when asked whether the species warrants greater public discourse and institutional attention, 30% supported increased discussion and 28% rated its importance at “3 (a lot)” (Figure 6C.a). Public education was also favored, with 33% calling for broader awareness (“2 (middle)”) and another 28% (“3 (a lot)”) assigning it high importance (Figure 6C.b). Twenty-seven percent of participants believed regional governments should reinforce management efforts (“2 (middle)”), while an additional 26% (“3 (a lot)”) and 24% (“4 (very much)”) emphasized the need for moderate to strong policy actions (Figure 6C.c). Overall, this section reflects a thoughtful yet varied public perspective: while C. sowerbii is not broadly seen as an immediate or personal threat, there is clear recognition of its ecological significance and strong support for increased public engagement and governance. The Bayesian Network diagram illustrates the interrelationships among respondents’ perceptions, knowledge, and interactions with C. sowerbii , as well as their views on its management (Figure 7). The central node (2), corresponding to whether individuals have seen the species, is closely linked to questions about situational context (e.g., where, when, and during which activity the species was observed), suggesting that direct experience with C. sowerbii significantly shapes broader attitudes. Node 2.1 (knowledge of the species) appears as a critical bridge between observation and perceptions of the phenomenon’s seriousness (e.g., nodes 9.1, 9.7), implying that familiarity influences both concern and perceived threat (Figure 7). The right-hand cluster of brown nodes (9.x) represents a detailed structure of opinions on management, ranging from personal concern (9.1) to recommendations for public awareness and governmental action (9.8, 9.9), reflecting a progression from individual impact to societal-level responses (Figure 7). Peripheral nodes related to species knowledge (7.x, 8.x) are less connected, indicating that while such knowledge is collected, it may play a secondary role compared to direct interactions in shaping opinions. The respondents’ country of origin (node 1.3) plays a secondary role, acting as a modulator of species knowledge and the perceived importance of communication. Overall, the graph reveals that management perceptions are more strongly influenced by personal experience and recognition of the species than by scientific or origin-based knowledge (Figure 7). Discussion The results of our study confirm a worrying issue: Craspedacusta sowerbii , although widespread on six continents (with only Antarctica remaining uncolonized), remains virtually unknown to the general public in Europe. Over 80% of respondents did not know the species’ scientific name, and almost half were unaware of the type of environment in which it thrives – with frequent confusion between this freshwater jellyfish and marine species noted in our survey. These figures illustrate a profound lack of recognition of a well-established invasion (Marchessaux et al. 2021; Lüskow et al. 2024). This lack of awareness is symptomatic of a broader bias towards non-native species. While emblematic species attract considerable scientific, media, and political attention because of their direct or spectacular impact, others go unnoticed – not because of their lack of impact, but because of their ecological subtlety or visual discretion (Latombe et al. 2017; Seebens et al. 2021). These species, known as “cryptic invasions”, represent a significant proportion of currently expanding non-native species, but whose trajectories remain underestimated (Essl et al. 2020). This imbalance is well documented in the literature. Many aquatic species, such as Hemimysis anomala or Bythotrephes longimanus , have long been ignored despite their role in the ecosystem's services (Yan et al. 2011; Wittmann et al. 2016). However, some inconspicuous non-native species, such as the apple snail Pomacea canaliculata , require close monitoring (Yang et al. 2019). This differentiated attention, often linked to the visibility or immediate economic impact of species, distorts our overall understanding of invasion processes. Our study also highlights that C. sowerbii is not just a natural curiosity, but an unknown invasive species, whose global spread could be amplified by climate change (Marchessaux et al. 2021; Marchessaux et al. 2022b; Lüskow et al. 2024). Recent studies show that rising temperatures not only favor the polyp-medusa transition (Winata et al. 2024), but also facilitate the geographic expansion of the species into more temperate zones (Marchessaux et al. 2022b). This phenomenon raises concerns about the future acceleration of its spread, especially since the species often escapes detection by conventional standard monitoring protocols (Moore et al. 2025). The seasonal appearance of the medusa form, its morphological subtlety, and its brief visibility window make it extremely difficult to detect, posing a challenge for biomonitoring networks. In this context, a citizen-based survey represents a valuable tool to assess public perception and awareness of C. sowerbii and to complement existing knowledge on its temporal and spatial presence. However, it is important to clarify that such an approach cannot reliably inform on ecological impact, species spread, or broader ecological patterns. To avoid any ambiguity, we emphasize that this type of data should not be considered a substitute for ecological monitoring or formal impact assessments, but rather as a complementary source of information, particularly useful for generating hypotheses and guiding further scientific investigation. Our work makes an original methodological contribution to the study of biological invasions. Thanks to our transnational participatory survey (over 1,300 respondents in 17 European countries), we were able to identify conditional interdependencies between individual characteristics, direct experience with the species, and perception of its management. The Bayesian Network reveals that visual recognition and direct observation are the primary factors influencing both interest in the species and willingness to engage in further discussion about it. Socio-demographic variables (age, country, gender) have a marginal effect, while biological or taxonomic knowledge plays a secondary role. These results confirm that, in the case of a little-publicized species, personal experience overweights scientific information in shaping public opinion – a finding in line with Varble and Secchi (2013) and Vandendriessche et al. (2016) on marine invasions. The perception of jellyfish varies greatly depending on cultural context and personal experience, oscillating between aesthetic fascination and aversion linked to fear or disgust (Vandendriessche et al. 2016). In our study, however, the majority of people found C. sowerbii beautiful and fascinating. Despite their generally poor reputation, some jellyfish species are increasingly appreciated for their beauty, strangeness, and ecological importance (Vandendriessche et al. 2016; Marchessaux et al. 2022a). On the other hand, with regard to the blue crab invasion in the Mediterranean, a species that received a lot of media coverage, public perception was negative. The species was poorly perceived, likely because people had access to abundant information about its ecological impact (Marchessaux et al. 2023; Marchessaux et al. 2024). This approach opens new perspectives for integrating cryptic or visually discrete species into awareness-raising and management strategies. Rather than seeking to pass on biological data alone, it may be more effective to leverage field experiences, citizen observations, and contextual encounters. This implies a paradigm shift in scientific communication, where visual and sensory pedagogy can complement traditional science outreach methods. Few examples in the current literature illustrate how non-native species can go unnoticed, while still being ecologically significant. This lack of attention from both the general public and scientists is likely due to a shortage of “stories, images, and striking symbols” ( sensu Nixon 2011), which diminishes the visibility of progressive environmental issues, such as biodiversity loss, climate change, and chemical pollution, in the cultural imagination and on political agendas (Nixon 2011). Lidström et al. (2016) build on Rob Nixon’s idea of “slow violence”, arguing that we also need to examine its converse: how complex and multifaceted environmental phenomena are often reduced to quick, simple, evocative and pervasive narratives that permeate science, legislation, public policy, and civic action, and to study how these narratives can stifle, rather than open up, possibilities for new socio-ecological engagements. The classic “invasive alien species” (IAS) narrative transforms complex ecological, biological, economic, and cultural systems into a simple “good versus evil” confrontation, pitting clearly “natural” and “unnatural” entities against each other (Lidström et al. 2016). The authors call for a representative balance by promoting complex, relational narratives that allow for more diverse solutions, broadened management practices, and strengthened innovative socio-ecological commitments (Lidström et al. 2016). In this vein, our study advocates for a more systematic consideration of cryptic and visually discrete species in policies aimed at combating IAS. The current focus on emblematic species – often marine, terrestrial, or charismatic – leads us to underestimate invasive dynamics that are silent, but potentially structuring for ecosystems (Ricciardi et al. 2017). Criteria such as “small size”,” visual rarity“, or ”not directly dangerous" should not exclude a species from watch lists (Marchessaux et al. 2022a). Craspedacusta sowerbii is a typical example: a widely distributed and potentially impactful species that is overlooked by conventional assessment grids (Moore et al. 2025) and often understudied by scientists (Lüskow et al. 2024). The citizen science approach employed in our study highlighted these aspects. Engaging citizens in participatory science can also aid in detecting species whose invasions are silent, as seen in the case of the ladybird Harmonia axyridis in Central America (Hiller and Haelewaters 2019). In conclusion, our study has shown that one of the world’s most widespread invasive species is poorly known and largely overlooked by the public, who lack access to adequate information and awareness-raising efforts. Therefore, we urge management authorities, environmental Non-Governmental Organizations (NGOs), and researchers to integrate these invisible species into their action plans, mainly because we do not know whether this species (in its polyp or jellyfish form) hurts the native biodiversity of the invaded sites. Behind their apparent discretion lie weak signals of global change which, if ignored today, could escalate into ecological emergencies shortly. Declarations The anonymous questionnaire used in this study did not collect any personal data from participants that could be used to formally identify them. Participants took part in the study voluntarily. The need for consent was waived by the approving ethics committee (D.R. n. 3267). Acknowledgements The authors would like to thank all the partners in this study who shared the questionnaire in each country, and we would also like to thank all the respondents who took the time to contribute to this study. Work of AA and ÁB was funded by the National Research Development and Innovation Office, Hungary (project MEC_N:148923). Authors contributions G.M. and F.L. contributed to the study conception and design. Material preparation and data collection were performed by all authors. The first draft of the manuscript was written by G.M. and F.L., and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Conceptualization: G.M., F.L. (equal); Methodology: G.M., F.L. (equal); Formal analysis and investigation: G.M., F.L. (equal); Writing – original draft preparation: G.M., F.L. (equal); Writing – review and editing: all authors; Supervision: G.M., F.L. (equal). Data Availability The data presented in this study are all available in the figures in this manuscript. References Bellard, C., P. Cassey, and T. M. Blackburn. 2016. Alien species as a driver of recent extinctions. Biology letters 12. The Royal Society: 20150623. 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The spread, establishment and impacts of the spiny water flea, Bythotrephes longimanus, in temperate North America: a synopsis of the special issue. Biological Invasions 13. Springer Science and Business Media LLC: 2423–2432. doi:10.1007/s10530-011-0069-9. Yang, Q., S. Liu, C. He, R. H. Cowie, X. Yu, and K. A. Hayes. 2019. Invisible apple snail invasions: importance of continued vigilance and rigorous taxonomic assessments. Pest Management Science 75. Wiley: 1277–1286. doi:10.1002/ps.5241. Additional Declarations There is NO Competing Interest. Supplementary Files Supplementarymaterials.docx Supplementary materials Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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In panel A, the abbreviations correspond to the countries’ names: BH: Bosnia and Herzegovina, DA: Denmark, FR: France, GO: Georgia, GE: Germany, HU: Hungary, IT: Italy, NO: Norway, PO: Poland, PT: Portugal, RO: Romania, RU: Russia, SL: Slovakia, SP: Spain, TU: Türkiye, UR: Ukraine, and UK: United Kingdom.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-7392176/v1/73579adbb37fd066f99fbacf.png"},{"id":89538225,"identity":"fd0b5790-ec5a-463d-b0fd-5849db2be8c7","added_by":"auto","created_at":"2025-08-21 05:52:26","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":228425,"visible":true,"origin":"","legend":"\u003cp\u003ePublic perception of \u003cem\u003eCraspedacusta sowerbii \u003c/em\u003e(panel 2 of the questionnaire): (A) “Have you seen this species?” (B) “Do you know what the species is?”, (C) “Do you know the scientific name of this species?”, (D) “Where did you observe this species? (E) During which activity?”, and (F) “When did you observe this species?”\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-7392176/v1/d51024a3c56452a8cdf9b009.png"},{"id":89538008,"identity":"5f48e226-ccb8-43dd-96b5-4506a0c0ca83","added_by":"auto","created_at":"2025-08-21 05:44:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":398220,"visible":true,"origin":"","legend":"\u003cp\u003ePublic perception of \u003cem\u003eCraspedacusta sowerbii \u003c/em\u003e(panel 3 of the questionnaire): (A) “For you, this species is”, (B) “When you encounter a large number of this species, you feel”, (C) “Have you been stung by this species?”\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-7392176/v1/06a3d67727b614d5f3aa64b4.png"},{"id":89537323,"identity":"556e8c9c-2e76-42e7-9479-d24988fab909","added_by":"auto","created_at":"2025-08-21 05:36:26","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":322492,"visible":true,"origin":"","legend":"\u003cp\u003ePublic knowledge of \u003cem\u003eCraspedacusta sowerbii\u003c/em\u003eorigins (panel 4 of the questionnaire): (A) “For you, this species is native to?” (B) “For you, this species is?”\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-7392176/v1/56c24d084816e29c528cc43b.png"},{"id":89538010,"identity":"2d2af416-27d9-41c0-8481-46602edc5345","added_by":"auto","created_at":"2025-08-21 05:44:26","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":148709,"visible":true,"origin":"","legend":"\u003cp\u003ePublic knowledge of \u003cem\u003eCraspedacusta sowerbii \u003c/em\u003e(panel 5 of the questionnaire): (A) “If for you this species is invasive, can you tell us what the main introduction vector of this species is?” (B) “For you, the main cause(s) of this species proliferating is/are?”, (C) “For you, this species eats”.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-7392176/v1/e22d75d8465a0791986557e8.png"},{"id":89537321,"identity":"e85f1420-dcd5-47ec-a9a5-3552cfc0a5d0","added_by":"auto","created_at":"2025-08-21 05:36:26","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":359836,"visible":true,"origin":"","legend":"\u003cp\u003eManagement of \u003cem\u003eCraspedacusta sowerbii \u003c/em\u003e(panel 6 of the questionnaire): (A) “Is \u003cem\u003eCraspedacusta sowerbii \u003c/em\u003ea problem?”, (B) “Is \u003cem\u003eCraspedacusta sowerbii \u003c/em\u003ea concern for you?”, (C) “Do we need to talk more about \u003cem\u003eCraspedacusta sowerbii\u003c/em\u003e?”\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-7392176/v1/075673673daecc8bc9ae17c4.png"},{"id":89537320,"identity":"258e116e-5b01-4249-b4e5-48351f14a171","added_by":"auto","created_at":"2025-08-21 05:36:26","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":110961,"visible":true,"origin":"","legend":"\u003cp\u003eDirected Acyclic Graph (DAG) representing the conditional dependencies among respondents’ answers in the survey on the hydrozoan species \u003cem\u003eCraspedacusta sowerbii\u003c/em\u003e. Each node corresponds to a specific survey question, grouped into five thematic categories: respondent characteristics (purple), interactions with \u003cem\u003eC. sowerbii\u003c/em\u003e (blue), knowledge about the species’ origins (dark green), ecological knowledge of the species (light green), and perceptions and management of the phenomenon (orange). Arrows indicate conditional dependencies between variables, inferred from the data using the hill-climbing structure learning algorithm under an acyclicity constraint. This model supports the identification of potential demographic or geographic effects on responses, as well as dependency chains between knowledge, experience, and perception of issues related to \u003cem\u003eC. sowerbii\u003c/em\u003e.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-7392176/v1/8274c3380784043c0f2788e8.png"},{"id":89944001,"identity":"45a50a1f-3f20-44d3-bc02-9ec1dc07c0dc","added_by":"auto","created_at":"2025-08-26 16:44:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2227805,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7392176/v1/175fe8ee-5f7d-40b9-9d68-f9020fead5a4.pdf"},{"id":89537316,"identity":"bd9342ac-1901-4236-8e04-e336ee41fbb0","added_by":"auto","created_at":"2025-08-21 05:36:26","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1142014,"visible":true,"origin":"","legend":"Supplementary materials","description":"","filename":"Supplementarymaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-7392176/v1/fc35c299aaaa2f288309e4bd.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"The invasive freshwater jellyfish Craspedacusta sowerbii: silent invasion of an unknown species?","fulltext":[{"header":"Introduction","content":"\u003cp\u003eBiological invasions are among the primary drivers of global biodiversity loss (Bellard et al. 2016). According to the IPBES Global Assessment Report (Roy et al. 2023), they are now recognized as the fifth main cause of species extinction, following changes in land and sea use, direct exploitation of organisms, climate change, and pollution. The exponential increase in trade, globalization, and international transport has significantly facilitated the introduction and establishment of species outside their native ranges. By 2023, the IPBES estimated that over 37,000 alien species had been introduced into new ecosystems, with at least 3,500 classified as invasive, causing significant ecological, economic, and health impacts (Pascual et al. 2023; Roy et al. 2023).\u003c/p\u003e\n\u003cp\u003eNevertheless, not all biological invasions are perceived in the same way, whether by scientists, managers, or the general public. Some invasive species quickly attract attention due to their spectacular effects or direct impact on human activities, such as the Asian hornet (\u003cem\u003eVespa velutina\u0026nbsp;\u003c/em\u003eLepeletier, 1836) in Europe (Keeling et al. 2017) and the zebra mussel (\u003cem\u003eDreissena polymorpha\u0026nbsp;\u003c/em\u003ePallas, 1771) in North America (Strayer 1991). Conversely, other invasions pass relatively unnoticed: their progress is silent, their effects less obvious, or their life cycle (or certain stages thereof) largely unobservable (Spear et al. 2021). These so-called \u0026ldquo;cryptic\u0026rdquo; invasions (\u003cem\u003esensu\u003c/em\u003e Latombe et al. 2017) nonetheless make up a significant part of the current introduction dynamics, and their underestimation can be detrimental to the overall understanding of the ongoing ecological changes. \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePublic perception often differs from that of conservation managers, which can complicate management efforts and priorities for invasive species (Gozlan et al. 2013). Moreover, it plays a critical role in shaping monitoring strategies, influencing policy decisions, and guiding citizen science participation (Courchamp et al. 2018). Several studies have recently highlighted attention bias toward small aquatic non-native species or those lacking an immediately identifiable economic impact (Seebens et al. 2017; Essl et al. 2020; Seebens et al. 2021). Species such as the bloody-red mysid \u003cem\u003eHemimysis anomala\u003c/em\u003e, a mysid shrimp native to the Caspian Sea, or the spiny waterflea \u003cem\u003eBythotrephes\u003c/em\u003e \u003cem\u003elongimanus\u003c/em\u003e, a planktonic predator from the Great Lakes of North America, have long remained understudied despite their role as ecosystem engineers (Yan et al. 2011; Wittmann et al. 2016). Similarly, some ctenophores, such as \u003cem\u003eMnemiopsis leidyi\u0026nbsp;\u003c/em\u003e(A. Agassiz, 1865), were only fully recognized as invasive several years after their introduction, despite contributing to fisheries collapse in the Black Sea (Shiganova 2000). Yet, the growing involvement of the public in biodiversity monitoring highlights the potential of the \u0026ldquo;power of many\u0026rdquo;: when well-informed and adequately supported, collective observation efforts can counteract attention biases and enhance early detection of inconspicuous or understudied species. Public participation not only helps fill critical data gaps but also fosters more inclusive and responsive monitoring systems capable of detecting subtle ecological signals that might otherwise go unnoticed by conventional surveillance (Dickinson et al. 2010; Pocock et al. 2017).\u003c/p\u003e\n\u003cp\u003eIn recent years, public participation in biodiversity monitoring has become an increasingly valuable tool for detecting or tracking biological invasions. However, its effectiveness largely depends on public awareness and the recognizability of species, which remain major challenges for organisms that are unknown or difficult to observe (Ricciardi et al. 2017).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCraspedacusta sowerbii,\u0026nbsp;\u003c/em\u003ethe world\u0026rsquo;s most widespread freshwater jellyfish, exemplifies this type of discreet invasion. Likely native to the Yangtze River basin in China (Fritz et al. 2007), this hydrozoan was first described outside its native range in 1880, in an ornamental pond in London (Lankester, 1880). Since then, it has been reported on six continents, through the involuntary transport of propagules (polyp or podocyst stages) associated with aquatic plants or submerged substrates (Dumont 1994; Marchessaux et al. 2022b; L\u0026uuml;skow et al. 2024). In Europe, its presence is now well documented in many countries, including France, Germany, Italy, Spain, and the Czech Republic, though its distribution remains highly uneven across the regions (Marchessaux et al. 2021).\u003c/p\u003e\n\u003cp\u003eDespite its wide distribution, \u003cem\u003eC. sowerbii\u003c/em\u003e remains surprisingly understudied (L\u0026uuml;skow et al. 2024). Most publications focus on occurrence records or descriptive studies of its life cycle, which alternates between a tiny benthic polyp and a planktic medusa visible only at certain times of the year (L\u0026uuml;skow et al. 2024). Its actual ecological impact is still poorly understood, although some studies suggest it may disrupt pelagic food webs, notably by competing with fish larvae or macroinvertebrates (Thomas 1950, 19; Dodson and Cooper 1983). In addition, the species often escapes standard detection (Moore et al. 2025): its appearance is sporadic, localized, sometimes limited to a few days per year, making it very difficult to monitor. Given this biological and media invisibility, it is legitimate to question whether the invasion of \u003cem\u003eC. sowerbii\u003c/em\u003e is perceived and recognized as such by the general public, particularly in Europe, where awareness of non-native species varies considerably depending on geographical and cultural contexts.\u003c/p\u003e\n\u003cp\u003eHence, the aim of the study is to assess, using survey data and citizen observations, the level of public knowledge and perception of \u003cem\u003eC. sowerbii\u003c/em\u003e in 17 European countries to better understand the societal and cognitive factors influencing the visibility of a biological invasion. This study hypothesized that \u003cem\u003eC. sowerbii\u003c/em\u003e is poorly known to the public and that its ecological implications go largely unnoticed. Findings from this study can inform targeted public engagement and monitoring strategies, improve the design of citizen science platforms, and contribute to a broader understanding of how societal factors mediate the detectability of biological invasions\u0026mdash;particularly those that are inconspicuous yet ecologically significant (Groom et al. 2019). Enhancing public awareness of cryptic invasive species such as \u003cem\u003eC. sowerbii\u003c/em\u003e could support earlier detection and more effective management responses, thereby reinforcing prevention strategies and biodiversity conservation policies.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003e\u003cstrong\u003eSurvey strategies\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAn online questionnaire survey (in Google Form format) was carried out to assess public awareness about the invasion of freshwater jellyfish \u003cem\u003eCraspedacusta sowerbii\u0026nbsp;\u003c/em\u003eacross 17 European countries (Supplementary Figure 1). The questionnaire was accessible for 24 months starting in March 2023. We used the \u0026ldquo;snowball\u0026rdquo; method to collect responses to the questionnaires, beginning with previously identified networks such as Facebook groups oriented towards citizen sciences (e.g., photography, hiking, excursions), major institutions in natural sciences (e.g., IUCN), nature managers, university mailing lists, and personal networks of co-authors. Participants were also encouraged to share the questionnaire within their respective networks to help reach a broader panel of respondents. Additional outreach was achieved by sharing the questionnaire online via press and TV communication (Marchessaux et al. 2023; Marchessaux et al. 2024), as well as through dissemination via project mailing lists and stakeholder databases managed by co-authors.\u003c/p\u003e\n\u003cp\u003eThe questionnaire was created based on a review of the available literature on public perception of invasive species (Varble and Secchi 2013; Huth et al. 2016; Vandendriessche et al. 2016; Cerveira et al. 2022; Marchessaux et al. 2024) and was further refined by the co-authors to address country-specific aspects. The questionnaire was translated into multiple languages by the co-authors and distributed in 17 the following European countries: Bosnia and Herzegovina, Denmark, France, Georgia, Germany, Hungary, Italy, Norway, Poland, Portugal, Romania, Russia, Slovakia, Spain, T\u0026uuml;rkiye, Ukraine, and the United Kingdom.\u003c/p\u003e\n\u003cp\u003eThe questionnaire was divided into six sections, and had an average completion time of approximately 10-12 minutes to maximize participation (Supplementary Figure 1). To minimize response bias, respondents were invited to respond anonymously and voluntarily. The first part of the survey collected anonymous demographic information, including gender, age and city of residence. The second part focused on respondents\u0026rsquo; interactions with \u003cem\u003eC. sowerbii\u003c/em\u003e,\u003cem\u003e\u0026nbsp;\u003c/em\u003eincluding their familiarity with the species name and any personal observations. The third part explored the aesthetic perceptions of the species, including its physical appearance and if respondents had ever been stung by \u003cem\u003eC. sowerbii\u003c/em\u003e. The fourth part addressed perceptions of the species\u0026rsquo; origins, asking if respondents considered \u003cem\u003eC. sowerbii\u003c/em\u003e native or introduced to Europe. Finally, the last two parts aimed to assess public knowledge of the species\u0026rsquo; ecology and views on its management and prioritization, respectively.\u003c/p\u003e\n\u003cp\u003eTo avoid influencing responses, we chose never to explicitly name the species we were studying (in this case, \u003cem\u003eCraspedacusta sowerbii\u003c/em\u003e), even at the end of the questionnaire, but a panel of pictures of the species was given to the respondents in the questionnaire (Supplementary Figure 1). Similarly, in all communications promoting the survey, we simply specified that this study concerned an emerging ecological phenomenon in Europe, without ever mentioning what it was.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData analysis\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGiven the noteworthy difference in the number of responses collected per country (minimum: 1 for Ukraine, likely due to the ongoing war during the survey period; maximum: 247 for Slovakia), we chose to process all responses collectively to reflect European citizens\u0026rsquo; perception of the \u003cem\u003eC. sowerbii\u003c/em\u003e invasion. Accordingly, all country-level data were aggregated into a data matrix comprising all responses. The data were processed in alignment with the 6-panel structure of the questionnaire, allowing us to monitor its organization and the evolution of responses according to the various categories. For the first panel, we created a map presenting the countries included in the study. Using QGIS software (version 3.40.1), we highlighted and color-coded each country based on the number of responses received. The frequency distributions of respondent age and gender were calculated and then visualized using a histogram and a pie chart created with SIGMAPLOT 12.5. Responses for the remaining categories were converted to percentages and plotted accordingly. The figure formats were selected to best represent the trends observed in the collected data. To support our hypothesis that the invasion of \u003cem\u003eC. sowerbii\u003c/em\u003e is poorly understood, we highlighted the proportion of \u0026ldquo;I don\u0026apos;t know\u0026rdquo; responses in dark grey across all graphs.\u003c/p\u003e\n\u003cp\u003eTo contextualize the species invasion of each country and the number of replies, we have plotted the number of \u003cem\u003eC. sowerbii\u003c/em\u003e occurrences and the total number of replies per country, and we performed a Generalized Linear Model (GLM) analysis using R Studio software (version 2024.12.0).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTo explore the interdependence of individual responses and detect any demographic, geographic, or independent effects related to respondent characteristics, a Bayesian Network (BN) was constructed to model the conditional dependencies among the measured variables. A BN is a graphical probabilistic model in which each node represents a random variable and each directed arc encodes a conditional dependency relationship between two variables (Pearl 1988). The structure of the network was learned using the hill-climbing (hc) algorithm, which optimizes a log-likelihood score by exploring possible structures under the constraint of graph acyclicity (Koller and Friedman 2009). The entire process was carried out using the \u0026ldquo;bnlearn\u0026rdquo; package (Scutari, 2025) in R Studio. After learning the structure of the Directed Acyclic Graph (DAG), the conditional parameters of the network were estimated using a frequentist approach (bn.fit), which allowed for defining the conditional distributions of each variable given its parents in the graph (Spirtes et al. 2000). Conditional inference was performed using the likelihood weighting method via the \u0026ldquo;cpquery\u0026rdquo; function of the \u0026ldquo;bnlearn\u0026rdquo; package (Scutari, 2025). This method relies on weighted simulations from the learned network. The number of simulated samples was set to 10,000 to ensure sufficient convergence. The network visualization was carried out using the \u0026ldquo;Rgraphviz\u0026rdquo;, \u0026ldquo;igraph\u0026rdquo;, and \u0026ldquo;visNetwork\u0026rdquo; packages within an interactive Shiny interface. The resulting DAG illustrates the structure of conditional dependencies among the variables, where each node represents a variable, and each arrow indicates a direct influence in the joint factorization of the model.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 1,388 questionnaires were completed between 3 March 2023 and 31 December 2024 (Figure 1A). The spatial distribution of respondents shows broad coverage across all countries included in the study (Figure 1A), with the number of responses ranging from 1 (in Ukraine) to 247 (in Slovakia). The sample consisted of 38% male respondents, 61% female and 1% who did not specify their gender. Respondents were between 18 and 84 years old, with a majority (64%) falling within the 18\u0026ndash;40 age group (Figure 1B). Regarding the relationship between the number of replies per country and the number of reported occurrences of \u003cem\u003eC. sowerbii\u0026nbsp;\u003c/em\u003e(Supplementary Figure 2), notable discrepancies emerged. For instance,\u0026nbsp;countries such as France, and Germany reported numerous occurrences despite fewer responses, whereas others, like Slovakia and T\u0026uuml;rkiye contributed many responses but reported few or no occurrences (Supplementary Figure 2). We observe that 23% of respondents report going outdoors into nature every day, while 14% never do so (Figure 1C).\u003c/p\u003e\n\u003cp\u003eRegarding the species visibility (Figure 2A), 48% of respondents reported having seen it, while 52% stated they had never observed it. When asked to identify the organism (Figure 2B), 83% recognized it as a jellyfish, whereas 14% did not know what it was. Common misidentifications included comb jellies, tunicates, and fish. When asked about the scientific name of the species (Figure 2C), 81% indicated they did not know it, and only 10% correctly identified \u003cem\u003eC. sowerbii\u003c/em\u003e. Confusion with marine species such as \u003cem\u003eAurelia aurita\u003c/em\u003e and \u003cem\u003eMnemiopsis leidyi\u003c/em\u003e was common. The reported locations of observation (Figure 2D) revealed significant misconceptions: 49% of respondents claimed to have seen the species in the sea, which is incorrect as \u003cem\u003eC. sowerbii\u003c/em\u003e is strictly freshwater. Furthermore, 26% saw it through media (TV, newspapers), 10% in a lake, and 9% in a public aquarium \u0026ndash; environments more consistent with the species\u0026rsquo; ecology. Observations in artificial basins, rivers, or quarries were less frequent. The activities during which the species was observed (Figure 2E) varied broadly: the majority (40%) observed it while swimming, 20% while walking, 17% during aquarium visits, 11% while diving, and 9% while boating. Very few respondents reported sightings in private aquariums or at sea. Finally, the seasonal distribution of observations (Figure 2F) showed that most sightings occurred in summer (71%), followed by autumn (14%), spring (11%), and only a small proportion (4%) in winter.\u003c/p\u003e\n\u003cp\u003eIn terms of aesthetic perception and emotional responses to mass encounters and stinging experiences, people commonly described the species as \u0026ldquo;beautiful\u0026rdquo; (21%), \u0026ldquo;sublime\u0026rdquo; (18%), and \u0026ldquo;delicate\u0026rdquo; (18%; see Figure 3A). Additional terms like \u0026ldquo;fragile\u0026rdquo; (15%) and \u0026ldquo;aesthetic\u0026rdquo; (14%) further underscore a generally positive perception. Respondents\u0026rsquo; emotional responses to encountering large numbers of individuals showed a tendency toward caution: 65% reported feeling \u0026ldquo;careful\u0026rdquo;, while 54% \u0026ldquo;nervous\u0026rdquo;and 51% felt \u0026ldquo;scared\u0026rdquo;, though these feelings varied in intensity (split between \u0026ldquo;a little\u0026rdquo; and \u0026ldquo;yes\u0026rdquo;; Figure 3B). More positive emotions, such as feeling \u0026ldquo;relaxed,\u0026rdquo; \u0026ldquo;confident,\u0026rdquo; or \u0026ldquo;calm\u0026rdquo;, were less commonly reported. Specifically, 49% did not feel relaxed, 45% did not feel confident, and 40% did not feel calm in such situations (Figure 3B). Regarding direct contact, the vast majority of respondents ( 92%) had reported never having been stung by \u003cem\u003eC. sowerbii\u003c/em\u003e. Among those who had, over half (56%) reported no pain at all (score 0), 14% reported moderate pain (score 3), and 13% mild pain (score 2; Figure 3C). Other pain levels were rare with very mild (6%), severe (8%), and very severe (3%) pain (Figure 3C). Overall, the data suggest that \u003cem\u003eC. sowerbii\u003c/em\u003e is perceived positively in terms of appearance, but mass encounters may provoke caution or apprehension. Direct contact is rare, and when it occurs, it typically results in minimal or no pain.\u003c/p\u003e\n\u003cp\u003eThe analysis highlights a general lack of public knowledge regarding the geographical origins of \u003cem\u003eC. sowerbii\u003c/em\u003e and its status in Europe (Figure 4). When asked to identify the species\u0026rsquo; country of origin, the most common response was \u0026ldquo;I don\u0026rsquo;t know\u0026rdquo; (13%). Among those who provided an answer, China was the most frequently cited (11%), correctly corresponding to the species\u0026rsquo; most likely native range in the freshwater systems of the Yangtze River basin. However, range of other countries were mentioned from all continents, such as T\u0026uuml;rkiye, Australia, the USA, Croatia, and Greece, with highly scattered responses spanning countries from all continents, including South Africa, Brazil, Germany, India, and Madagascar, reflecting widespread uncertainty and misinformation (Figure 4A). In a follow-up question about whether the species is native or non-native to Europe, 51% of respondents indicated that they did not know, 33% correctly identified \u003cem\u003eC. sowerbii\u003c/em\u003e as non-native and invasive, while 16% incorrectly believed it to be native (Figure 4B). These results reveal a clear gap in public understanding of the species\u0026rsquo; biogeography.\u003c/p\u003e\n\u003cp\u003eThe evaluation of public knowledge about the main vector of introduction of \u003cem\u003eC. sowerbii\u003c/em\u003e showed that the most frequent response was \u0026ldquo;I don\u0026rsquo;t know\u0026rdquo; (26%; Figure 5A), followed closely by boats (25%), a widely recognized pathway for aquatic invasive species. Regarding factors driving the species\u0026rsquo; proliferation, global change was the most commonly referenced (28%), followed by overfishing and predator removal (16%) and invasive species vectors (13%). Twelve percent of respondents answered that they did not know, while others mentioned pollution (8%), natural evolution (6%), ocean acidification (5.9%), eutrophication (5.7%), and rarity of predators (5.4%), suggesting an awareness of complex ecological pressures, albeit with varying levels of scientific accuracy (Figure 5B). On the question of feeding habits, 34% of respondents correctly identified zooplankton as the primary food source, followed by phytoplankton (29%). Sixteen percent responded with \u0026ldquo;I don\u0026rsquo;t know,\u0026rdquo; while smaller proportions incorrectly selected fish (7%), jellyfish (6%), mollusks (5%), and insects (3%), reflecting a partial understanding of the species\u0026rsquo; trophic role (Figure 5C). Overall, the results pointed to fragmented but occasionally accurate public perceptions of \u003cem\u003eC. sowerbii\u003c/em\u003e\u0026rsquo;s ecology.\u003c/p\u003e\n\u003cp\u003eThe analysis of public perceptions concerning the management and societal relevance of \u003cem\u003eC. sowerbii\u003c/em\u003e as a potentially invasive species highlights a diversity of opinions across local, global, and ecological contexts (Figure 6). When asked whether the species is perceived as problematic, 36% of respondents did not consider it a local issue (\u0026ldquo;0 (no)\u0026rdquo;), while others rated its importance with increasing concern: 18% (\u0026ldquo;1 (a little)\u0026rdquo;), 29% (\u0026ldquo;2 (middle)\u0026rdquo;), 11% (\u0026ldquo;3 (a lot)\u0026rdquo;), and 6% (\u0026ldquo;4 (very much)\u0026rdquo;), indicating a predominantly low perception of a local threat (Figure 6A.a). However, views shifted slightly when considering its global impact: 14% stated it is not a problem at all, but 30% rated it as a moderate concern(\u0026ldquo;2 (middle)\u0026rdquo;), and 23% viewed it as a significant global issue (\u0026ldquo;3 (a lot)\u0026rdquo;) (Figure 6A.b). Similarly, when framed as a minor problem, 38% still rated it at \u0026ldquo;0 (no)\u0026rdquo;, though 30% gave it a relatively high concern (\u0026ldquo;2 (middle)\u0026rdquo;), and 22% scored it(\u0026ldquo;3 (a lot)\u0026rdquo;, revealing nuanced views on the severity of its presence (Figure 6A.c). Regarding personal or ecological concern, 28% reported no concern at all, while 30% rated their concern at a moderate level (\u0026ldquo;2 (middle)\u0026rdquo;), suggesting a degree of ambivalence (Figure 6B.a). Nonetheless, many respondents found the species interesting, with 30% assigning it a mid-level score (\u0026ldquo;2 (middle)\u0026rdquo;), and another 30% placing it in higher interest categories (\u0026ldquo;3 (a lot)\u0026rdquo; and \u0026ldquo;4 (very much)\u0026rdquo; combined) (Figure 6B.b). Ecological concern appeared more pronounced, with 31% ranking it at the highest level (\u0026ldquo;4 (very much)\u0026rdquo;), indicating a growing recognition of its environmental relevance (Figure 6B.c). Finally, when asked whether the species warrants greater public discourse and institutional attention, 30% supported increased discussion and 28% rated its importance at \u0026ldquo;3 (a lot)\u0026rdquo; (Figure 6C.a). Public education was also favored, with 33% calling for broader awareness (\u0026ldquo;2 (middle)\u0026rdquo;) and another 28% (\u0026ldquo;3 (a lot)\u0026rdquo;) assigning it high importance (Figure 6C.b). Twenty-seven percent of participants believed regional governments should reinforce management efforts (\u0026ldquo;2 (middle)\u0026rdquo;), while an additional 26% (\u0026ldquo;3 (a lot)\u0026rdquo;) and 24% (\u0026ldquo;4 (very much)\u0026rdquo;) emphasized the need for moderate to strong policy actions (Figure 6C.c). Overall, this section reflects a thoughtful yet varied public perspective: while \u003cem\u003eC. sowerbii\u003c/em\u003e is not broadly seen as an immediate or personal threat, there is clear recognition of its ecological significance and strong support for increased public engagement and governance.\u003c/p\u003e\n\u003cp\u003eThe Bayesian Network diagram illustrates the interrelationships among respondents\u0026rsquo; perceptions, knowledge, and interactions with \u003cem\u003eC. sowerbii\u003c/em\u003e, as well as their views on its management (Figure 7). The central node (2), corresponding to whether individuals have seen the species, is closely linked to questions about situational context (e.g., where, when, and during which activity the species was observed), suggesting that direct experience with \u003cem\u003eC. sowerbii\u003c/em\u003e significantly shapes broader attitudes. Node 2.1 (knowledge of the species) appears as a critical bridge between observation and perceptions of the phenomenon\u0026rsquo;s seriousness (e.g., nodes 9.1, 9.7), implying that familiarity influences both concern and perceived threat (Figure 7). The right-hand cluster of brown nodes (9.x) represents a detailed structure of opinions on management, ranging from personal concern (9.1) to recommendations for public awareness and governmental action (9.8, 9.9), reflecting a progression from individual impact to societal-level responses (Figure 7). Peripheral nodes related to species knowledge (7.x, 8.x) are less connected, indicating that while such knowledge is collected, it may play a secondary role compared to direct interactions in shaping opinions. The respondents\u0026rsquo; country of origin (node 1.3) plays a secondary role, acting as a modulator of species knowledge and the perceived importance of communication. Overall, the graph reveals that management perceptions are more strongly influenced by personal experience and recognition of the species than by scientific or origin-based knowledge (Figure 7).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe results of our study confirm a worrying issue: \u003cem\u003eCraspedacusta sowerbii\u003c/em\u003e, although widespread on six continents (with only Antarctica remaining uncolonized), remains virtually unknown to the general public in Europe. Over 80% of respondents did not know the species\u0026rsquo; scientific name, and almost half were unaware of the type of environment in which it thrives \u0026ndash; with frequent confusion between this freshwater jellyfish and marine species noted in our survey. These figures illustrate a profound lack of recognition of a well-established invasion (Marchessaux et al. 2021; L\u0026uuml;skow et al. 2024). This lack of awareness is symptomatic of a broader bias towards non-native species. While emblematic species attract considerable scientific, media, and political attention because of their direct or spectacular impact, others go unnoticed \u0026ndash; not because of their lack of impact, but because of their ecological subtlety or visual discretion (Latombe et al. 2017; Seebens et al. 2021). These species, known as \u0026ldquo;cryptic invasions\u0026rdquo;, represent a significant proportion of currently expanding non-native species, but whose trajectories remain underestimated (Essl et al. 2020). This imbalance is well documented in the literature. Many aquatic species, such as \u003cem\u003eHemimysis anomala\u003c/em\u003e or \u003cem\u003eBythotrephes longimanus\u003c/em\u003e, have long been ignored despite their role in the ecosystem\u0026apos;s services (Yan et al. 2011; Wittmann et al. 2016). However, some inconspicuous non-native species, such as the apple snail\u003cem\u003e\u0026nbsp;Pomacea canaliculata\u003c/em\u003e, require close monitoring (Yang et al. 2019). This differentiated attention, often linked to the visibility or immediate economic impact of species, distorts our overall understanding of invasion processes.\u003c/p\u003e\n\u003cp\u003eOur study also highlights that \u003cem\u003eC. sowerbii\u003c/em\u003e is not just a natural curiosity, but an unknown invasive species, whose global spread could be amplified by climate change (Marchessaux et al. 2021; Marchessaux et al. 2022b; L\u0026uuml;skow et al. 2024). Recent studies show that rising temperatures not only favor the polyp-medusa transition (Winata et al. 2024), but also facilitate the geographic expansion of the species into more temperate zones (Marchessaux et al. 2022b). This phenomenon raises concerns about the future acceleration of its spread, especially since the species often escapes detection by conventional standard monitoring protocols (Moore et al. 2025). The seasonal appearance of the medusa form, its morphological subtlety, and its brief visibility window make it extremely difficult to detect, posing a challenge for biomonitoring networks. In this context, a citizen-based survey represents a valuable tool to assess public perception and awareness of \u003cem\u003eC. sowerbii\u003c/em\u003e and to complement existing knowledge on its temporal and spatial presence. However, it is important to clarify that such an approach cannot reliably inform on ecological impact, species spread, or broader ecological patterns. To avoid any ambiguity, we emphasize that this type of data should not be considered a substitute for ecological monitoring or formal impact assessments, but rather as a complementary source of information, particularly useful for generating hypotheses and guiding further scientific investigation.\u003c/p\u003e\n\u003cp\u003eOur work makes an original methodological contribution to the study of biological invasions. Thanks to our transnational participatory survey (over 1,300 respondents in 17 European countries), we were able to identify conditional interdependencies between individual characteristics, direct experience with the species, and perception of its management. The Bayesian Network reveals that visual recognition and direct observation are the primary factors influencing both interest in the species and willingness to engage in further discussion about it. Socio-demographic variables (age, country, gender) have a marginal effect, while biological or taxonomic knowledge plays a secondary role. These results confirm that, in the case of a little-publicized species, personal experience overweights scientific information in shaping public opinion \u0026ndash; a finding in line with Varble and Secchi (2013) and Vandendriessche et al. (2016) on marine invasions. The perception of jellyfish varies greatly depending on cultural context and personal experience, oscillating between aesthetic fascination and aversion linked to fear or disgust (Vandendriessche et al. 2016). In our study, however, the majority of people found \u003cem\u003eC. sowerbii\u003c/em\u003e beautiful and fascinating. Despite their generally poor reputation, some jellyfish species are increasingly appreciated for their beauty, strangeness, and ecological importance (Vandendriessche et al. 2016; Marchessaux et al. 2022a). On the other hand, with regard to the blue crab invasion in the Mediterranean, a species that received a lot of media coverage, public perception was negative. The species was poorly perceived, likely because people had access to abundant information about its ecological impact (Marchessaux et al. 2023; Marchessaux et al. 2024). This approach opens new perspectives for integrating cryptic or visually discrete species into awareness-raising and management strategies. Rather than seeking to pass on biological data alone, it may be more effective to leverage field experiences, citizen observations, and contextual encounters. This implies a paradigm shift in scientific communication, where visual and sensory pedagogy can complement traditional science outreach methods.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFew examples in the current literature illustrate how non-native species can go unnoticed, while still being ecologically significant. This lack of attention from both the general public and scientists is likely due to a shortage of \u0026ldquo;stories, images, and striking symbols\u0026rdquo; (\u003cem\u003esensu\u003c/em\u003e Nixon 2011), which diminishes the visibility of progressive environmental issues, such as biodiversity loss, climate change, and chemical pollution, in the cultural imagination and on political agendas (Nixon 2011). Lidstr\u0026ouml;m et al. (2016) build on Rob Nixon\u0026rsquo;s idea of \u0026ldquo;slow violence\u0026rdquo;, arguing that we also need to examine its converse: how complex and multifaceted environmental phenomena are often reduced to quick, simple, evocative and pervasive narratives that permeate science, legislation, public policy, and civic action, and to study how these narratives can stifle, rather than open up, possibilities for new socio-ecological engagements. The classic \u0026ldquo;invasive alien species\u0026rdquo; (IAS) narrative transforms complex ecological, biological, economic, and cultural systems into a simple \u0026ldquo;good \u003cem\u003eversus\u003c/em\u003e evil\u0026rdquo; confrontation, pitting clearly \u0026ldquo;natural\u0026rdquo; and \u0026ldquo;unnatural\u0026rdquo; entities against each other (Lidstr\u0026ouml;m et al. 2016). The authors call for a representative balance by promoting complex, relational narratives that allow for more diverse solutions, broadened management practices, and strengthened innovative socio-ecological commitments (Lidstr\u0026ouml;m et al. 2016).\u003c/p\u003e\n\u003cp\u003eIn this vein, our study advocates for a more systematic consideration of cryptic and visually discrete species in policies aimed at combating IAS. The current focus on emblematic species \u0026ndash; often marine, terrestrial, or charismatic \u0026ndash; leads us to underestimate invasive dynamics that are silent, but potentially structuring for ecosystems (Ricciardi et al. 2017). Criteria such as \u0026ldquo;small size\u0026rdquo;,\u0026rdquo; visual rarity\u0026ldquo;, or \u0026rdquo;not directly dangerous\u0026quot; should not exclude a species from watch lists (Marchessaux et al. 2022a). \u003cem\u003eCraspedacusta sowerbii\u003c/em\u003e is a typical example: a widely distributed and potentially impactful species that is overlooked by conventional assessment grids (Moore et al. 2025) and often understudied by scientists (L\u0026uuml;skow et al. 2024). The citizen science approach employed in our study highlighted these aspects. Engaging citizens in participatory science can also aid in detecting species whose invasions are silent, as seen in the case of the ladybird \u003cem\u003eHarmonia axyridis\u003c/em\u003e in Central America (Hiller and Haelewaters 2019).\u003c/p\u003e\n\u003cp\u003eIn conclusion, our study has shown that one of the world\u0026rsquo;s most widespread invasive species is poorly known and largely overlooked by the public, who lack access to adequate information and awareness-raising efforts. Therefore, we urge management authorities, environmental Non-Governmental Organizations (NGOs), and researchers to integrate these invisible species into their action plans, mainly because we do not know whether this species (in its polyp or jellyfish form) hurts the native biodiversity of the invaded sites. Behind their apparent discretion lie weak signals of global change which, if ignored today, could escalate into ecological emergencies shortly.\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cspan\u003eThe anonymous questionnaire used in this study did not collect any personal data from participants that could be used to formally identify them. Participants took part in the study voluntarily. The need for consent was waived by the approving ethics committee (D.R. n. 3267).\u003c/span\u003e\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e\n\u003cp\u003eThe authors would like to thank all the partners in this study who shared the questionnaire in each country, and we would also like to thank all the respondents who took the time to contribute to this study. Work of AA and \u0026Aacute;B was funded by the National Research Development and Innovation Office, Hungary (project MEC_N:148923).\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eAuthors contributions\u003c/h2\u003e\n\u003cp\u003eG.M. and F.L. contributed to the study conception and design. Material preparation and data collection were performed by all authors. The first draft of the manuscript was written by G.M. and F.L., and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Conceptualization: G.M., F.L. (equal); Methodology: G.M., F.L. (equal); Formal analysis and investigation: G.M., F.L. (equal); Writing \u0026ndash; original draft preparation: G.M., F.L. (equal); Writing \u0026ndash; review and editing: all authors; Supervision: G.M., F.L. (equal).\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eThe data presented in this study are all available in the figures in this manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eBellard, C., P. Cassey, and T. M. Blackburn. 2016. Alien species as a driver of recent extinctions. \u003cem\u003eBiology letters\u003c/em\u003e 12. The Royal Society: 20150623.\u003c/li\u003e\n \u003cli\u003eCerveira, I., V. Baptista, M. A. Teod\u0026oacute;sio, and P. Morais. 2022. What\u0026rsquo;s for dinner? Assessing the value of an edible invasive species and outreach actions to promote its consumption. \u003cem\u003eBiological Invasions\u003c/em\u003e. Springer: 1\u0026ndash;15.\u003c/li\u003e\n \u003cli\u003eCourchamp, F., I. Jaric, C. Albert, Y. Meinard, W. J. Ripple, and G. Chapron. 2018. The paradoxical extinction of the most charismatic animals. \u003cem\u003ePLoS biology\u003c/em\u003e 16. 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Wiley: 1277\u0026ndash;1286. doi:10.1002/ps.5241.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Global change, Hydrozoa, Invasive Freshwater species, Perception, Survey","lastPublishedDoi":"10.21203/rs.3.rs-7392176/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7392176/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Biological invasions are a major driver of biodiversity loss, yet inconspicuous or “cryptic” species often escape public and scientific attention. The freshwater jellyfish Craspedacusta sowerbii, likely native to China and now present on six continents, exemplifies such silent invasions. Despite its broad distribution, the species’ ecology and societal perception remain poorly understood. We conducted a 24-month, multilingual online survey across 17 European countries (n = 1,388) to assess public awareness, perceptions, and management views regarding C. sowerbii. Results reveal limited knowledge: over 80% of respondents did not know its scientific name, 49% misidentified its freshwater habitat as marine, and only 33% recognized it as non-native. While its aesthetic qualities were often praised, mass occurrences provoked caution, and direct contact was rare and typically harmless. Bayesian Network analysis indicated that direct observation—rather than demographic factors or ecological knowledge—was the strongest predictor of concern and support for increased public discussion. Although most respondents did not perceive C. sowerbii as a major local threat, many recognized potential ecological implications and supported greater awareness and governance measures. This study underscores how visual subtlety and low media coverage limit detection and prioritization of cryptic invasive species, with implications for early warning systems and policy. Leveraging citizen science to enhance recognition and reporting could improve detection of such species, complementing formal monitoring networks. We advocate integrating cryptic invasions into invasive alien species management frameworks, emphasizing experiential engagement alongside conventional ecological data to address overlooked yet potentially impactful species.","manuscriptTitle":"The invasive freshwater jellyfish Craspedacusta sowerbii: silent invasion of an unknown species?","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-21 05:36:22","doi":"10.21203/rs.3.rs-7392176/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"03b9d053-8970-4090-b36d-b4de89830e3f","owner":[],"postedDate":"August 21st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":53304912,"name":"Biological sciences/Ecology/Invasive species"},{"id":53304913,"name":"Social science/Environmental studies"}],"tags":[],"updatedAt":"2025-08-26T16:35:56+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-21 05:36:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7392176","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7392176","identity":"rs-7392176","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}