Analysis of the persistence and particle size distributional shift of sperm-derived environmental DNA to monitor Jack Mackerel spawning activity

Environmental DNA (eDNA) analysis holds great promises as an efficient and noninvasive method to monitor not only the presence and biomass of organisms but also their spawning activity. In eDNA analysis-based monitoring of spawning activity, the detection of sperm-derived eDNA is a key point; however, its characteristics and dynamics are completely unknown. The present study focuses on the persistence and particle size distribution (PSD) of eDNA derived from the sperm of Japanese jack mackerel. First, we investigated the time-dependent degradation and the PSD of sperm-derived eDNA by artificially adding sperm to fish eDNA-free seawater. Next, we kept fish in tanks and examined the changes in DNA concentration and PSD before and after spawning. The data obtained from the two experiments showed that the degradation of sperm-derived eDNA proceeded rapidly, with PSD shifting to a smaller size, regardless of the DNA region (Cyt b or ITS1). Additionally, it was shown that the nuclei and mitochondria released from sperm through degradation had a size distribution that was not simply dependent on each organelle size. The results of this study will contribute to elucidating the characteristics and dynamics of eDNA specifically during the spawning season and to further developing eDNA analysis as a powerful tool for the monitoring of spawning activity. Abstract Figure