Morphology of Lineopselloides albilineus (Nemertea: Heteronemertea: Lineidae) from Japanese waters, with complementary redescription of the holotype

Abstract

Re-examination of the holotype of the heteronemertean, Lineopselloides albilineus Gibson, 1990, hitherto only known by its original description on a single specimen from Hong Kong, indicated that the peculiar morphology of the foregut-intestine junction in the holotype, which formed the basis of the establishment of this currently monotypic genus, might have resulted from an artifact during fixation; the rhynchocoel wall ruptured inward in a region where the foregut caecum extending backward below the foregut. Six individuals referable to L. albilineus based on their external appearances were collected from four localities in Japan. All of them possessed an intestinal caecum extending anteriorly below the foregut, a feature characteristic to Aetheolineus pulcherrimus Senz, 1993, Chilineus glandulosus (Bürger, 1895), Lineopsella islandica (Friedrich, 1958), Lineopsella pacifica Friedrich, 1970, Lineopsella trilineata (Schmarda, 1859) and Micrura ambigua Friedrich, 1958. The taxonomic status of the genus Lineopselloides should be re-appraised by additional material from Hong Kong in future studies.