DNA Taxonomy Of Paranemertes (Nemertea: Hoplonemertea) With Spirally Fluted Stylets

Paranemertes peregrina Coe,1901 has been reported to be distributed along both eastern and western Pacific coasts. Its proboscis possesses stylets with braided/ spirally fluted appearance, which is not common in nemerteans. Coe (1901,1905) recognized two color patterns from the northwestern America coasts, namely the "brown variety" and the "purple variety".In a later paper, he proposed the names Paranemertes peregrina var. alaskensis Coe,1940 for the "common and of large size northward" form and Paranemertes peregrina var. californiensis Coe,1940 for the "less abundant and smaller southward" form. Moreover, three other nominated species, Paranemertes katoi, Yamaoka 947 from Shimoda, Paranemertes cylindracea Korotkevich,1977 from North Kuril Islands (Paramushir) (recently synonymized with P. peregrina), and Paranemertes sanjuanensis Strieker,1982 from San Juan Island also possess the same type of stylets and have similar external appearance. Therefore, it is interesting and worthy to check the genetic variations among different geographic populations and/or color patterns of these nemerteans.Here the mitochondrial COI,16S rRNA and nuclear 28S rRNA genes were sequenced for 108 specimens collected from 14 localities of Canada, USA, Russia, China and Japan. In conjugation with the available data in GenBank, the genetic variation among different populations was analyzed and phylogenetic trees were reconstructed. The analysis based on COI dataset shows high variation among populations and even between worms from different habitats of the same geographic site. The analyzed 111 individuals were assigned into 7 networks by statistical parsimony, with the Network 1 containing specimens from Bodega Bay (algae habitat) (USA), Network 2 containing specimens from 3 sites of Vancouver Island (Canada), San Juan Island (USA), Paramushir (Russia), Oshoro (Japan), Dalian and Changdao (China), Network 3 containing specimens from Bodega Bay (mudflats), Network 4 containing specimens from Sijiao Island (China), Network 5 containing specimens from Sijiao and Pingtan (China), Network 6 containing specimens from Qingdao (China), and the Network 7 containing a specimen from San Juan Island (i.e. P. sanjuanensis). The inter-network uncorrected p-distances ranged from 0.044 to 0.172 and the mean intra-network uncorrected p-distances varied from 0.001 to 0.005. These networks are well supported by the results of Bayesian and Neighbor-joining analyses on COI data. Phylogeny trees based on 16S rRNA and 28S rRNA datasets are basically similar to the COI trees, but the Networks 1 and 2 are merged into a big clade.Therefore, present molecular analyses support the validity of P. sanjuanensis and the synonymization of P. cylindracea with P. peregrina. Nemerteans previously recorded as P. peregrina may contain several species and sympatric speciation might have been occurred in this nemertean group.