Heteronemertea Burger 1892

Order Heteronemertea Bürger, 1892

One single heteronemertean specimen (SIO-BIC N254), representing a member of Lineidae McIntosh, 1873, was collected in associated with experimentally deployed wood at 1887 m depth at the Jaco Scar methane seep. This specimen is 45 mm long and has a diameter of 5 mm. The body is translucent and of pale whitish coloration. It possesses a long caudal cirrus (Fig. 3C). It forms a clade with three undescribed lineids collected in the abyssal vicinity of the Kuril-Kamchatka Trench (Fig. 5). Based on the concatenated analysis, this clade cannot be attributed to any of the known heteronemertean genera. Pairwise distances of the COI gene between Lineidae sp. SIO-BIC N254 and those three heteronemerteans are around 14%. Since no material for histological sectioning is left, we do not describe this species herein, also due to the convoluted taxonomy of Lineidae, that needs extensive revision and goes beyond the scope of our study. However, the sequence data is published in order to facilitate future studies on deep-sea Lineidae.