Morphometric and molecular characterization of Euchromadora atypica (Nematoda: Chromadoridae): first record from the Indian Ocean

Abstract

The free-living marine nematode genus Euchromadora de Man, 1886 (Chromadoridae) currently comprises 11 valid species, many of which exhibit restricted geographic distributions. In the present study, Euchromadora atypica Blome, 1985 is reported for the first time from the Indian Ocean, based on specimens collected from rocky substrates along the eastern coast of India (Odisha). Species identification was confirmed through detailed morphological and morphometric analyses and further supported by molecular characterization using two ribosomal gene loci [Small Subunit (SSU) and Large Subunit (LSU)]. Bayesian inference phylogenetic analyses incorporating available sequences representing all genera of Chromadoridae recovered well-supported major clades corresponding to generic lineages within the family. The SSU-based phylogeny placed E. atypica within a strongly supported monophyletic Euchromadora clade, whereas the LSU-based analysis grouped the Indian specimen, E. atypica , with E. ezoensis in a well-supported subclade. This study provides the first molecular characterization of E. atypica , extends its known distribution to the Indian Ocean, and enhances current understanding of phylogenetic relationships within the family Chromadoridae. In addition, a comprehensive map illustrating the global distribution of all valid Euchromadora species is presented.