Nemerteans of the Vema-TRANSIT expedition: First data on diversity with description of two new genera and species

Approximately 30 nemertean specimens were obtained from the samples collected with an epibenthic sledge during the Vema-TRANSIT expedition (2014-2015) to the Vema Fracture Zone. A preliminary molecular phylogenetic analysis of eight samples revealed four eumonostiliferan and three tubulanid species. Abyssonemertes kajiharai gen. et sp. nov. and Nemertovema hadalis gen. et sp. nov. are described based on morphological and DNA (16S, 18S, 28S, COI, and H3) data; the latter species is the deepest known nemertean to date. It was collected in the Puerto Rico Trench from a depth of 8336-8339 m. A preliminary molecular phylogenetic analysis based on the five genes indicates that three tubulanid species form a monophyletic group with the only previously known abyssal tubulanid (Tubulanidae gen. sp. IZ 45557) from the abyssal plain adjacent to the Kuril-Kamchatka Trench, but the four eumonostiliferan species belong to three different clades. Additionally, a roadmap on the most pressing questions and issues on abyssal and hadal nemerteans is provided. This is based on the processing of the nemertean material collected during the four deep-sea expeditions SoJaBio, KuramBio I, SokhoBio, and KuramBio II and shall provide a direction for future studies.