18S analysis of the taxonomic position of an endoparasitic pycnogonid, Nymphonella tapetis(Arthropoda: Pycnogonida: Ascorhynchidae)

We obtained the nucleotide sequence of 18S rDNA of Nymphonella tapetis, a pycnogonid endoparasitic on some bivalves, together with that of other species belonging to Ascorhynchidae Hoek, 1881. The phylogenetic tree based on these sequences as well as those of selected species from a database strongly supports the monophyly of Ascorhynchidae and the inclusion of Nymphonellain the family. Nymphonellaseems to be an aberrant form in the Ascorhynchidae, but multi-gene analysis with more species is required for the exact determination of the taxonomic position of the genus.