Species delimitation and phylogenetic analyses reveal cryptic diversity within<i>Cerebratulus marginatus</i>(Nemertea: Pilidiophora)

The heteronemertean Cerebratulus marginatus Renier, 1804 is a well-known representative of the family Lineidae (Nemertea) inhabiting sandy or muddy sediments throughout world. Due to its wide geographic distribution and lack distinctive external morphological features among different populations, species has been considered cosmopolitan. Increasing evidence indicates that nemertean species, including marginatus, described based on morphology are often not supported by genetic data represent complexes cryptic rather than cosmopolitan species. Here, we use delimitation phylogenetic analyses evaluate speciation patterns within putative C. complex. We examined 25 specimens morphologically ascribed closely related using multilocus dataset two mitochondrial markers (16S rRNA, COI) three nuclear (18S 28S H3). Our identified at least four independent lineages populations analysed, indicating samples as might indeed complex Therefore, our results do support cosmopolitanism provide additional suggesting identifications in nemerteans should be exclusively anatomical which accurately reflect evolutionary patterns. study highlights importance molecular addition information delimit boundaries, thereby improving taxonomy providing more accurate picture true diversity this typically neglected phylum.