Unveiling the molecular identity of the diminutive cyprinid, Horadandia brittani (Teleostei: Cyprinidae), a species endemic to Southern India

Abstract Horadandia brittani is a small cyprinid fish species found in the coastal floodplains of southern India. For almost 50 years, the Horadandia genus was monotypic with only one species (Horadandia atukorali) confined to Sri Lanka until the discovery of H. brittani in south-western India in 1992. Despite being described as a separate species, H. brittaniwas later considered a synonym of H. atukorali until 2013 when researchers recognized it as a distinct species based on some morphological differences. However, no one had yet generated DNA sequences to validate the identity of H. brittani and its evolutionary relationship with its closely related species. To address this gap, this study was conducted to generate DNA sequences and validate the identity of H. brittani using molecular data. The results showed that H. brittani is genetically distinct from H. atukorali with mitochondrial cytochrome C oxidase (COI) gene distance values ranging from 3.21-3.63%. The study also established the phylogenetic relationships between these two species, confirming H. brittani as a valid species based on COI gene sequences. These sequences can be used to identify H. brittani quickly and accurately in the future.