Exploring the basal topology of the heteronemertean tree of life: establishment of a new family, along with turbotaxonomy of Valenciniidae (Nemertea: Pilidiophora: Heteronemertea)

Abstract

With about 480 known species, Pilidiophora (phylum Nemertea) has been regarded as consisting of Hubrechtiiformes (~20 spp.) and Heteronemertea (~460 spp.). Most (~87%) of the latter belong to Lineidae (> 400 spp.), while the systematics of non-lineid heteronemerteans remains largely untouched. To explore the phylogeny of non-hubrechtiiformid, non-lineid pilidiophorans, we performed multilocus molecular phylogenetic analyses with five genes (18S, 28S, H3, 16S and COI) from 41 newly sequenced specimens. Pilidiophora comprised Hubrechtellidae, Lineidae, Valenciniidae, the new family Eopilidiidae and a not formally named family-level heteronemertean taxon. Eopilidion misakiense gen. et sp. nov. is described from a specimen from Japan, but whether it belongs to Heteronemertea remains unclear. Apart from this new species, the following 11 new species of valenciniids are established, based on molecular sequences and external morphology (localities in parentheses): Baseodiscus giribeti sp. nov. (Panama), B. kakuii sp. nov. (Japan), B. komatsui sp. nov. (Japan), B. narusei sp. nov. (Japan), B. ohtsukai sp. nov. (Japan), B. paracelensis sp. nov. (Vietnam), B. profundus sp. nov. (Russian Far East), B. urgorrii sp. nov. (Spain), B. zebra sp. nov. (Japan), Oxypolella hiebertae sp. nov. (Vietnam) and Valencinura jambio sp. nov. (Japan).

Ribbon worms (phylum Nemertea) from Bodega Bay, California: A largely undescribed diversity

“…The phylum is known to possess large numbers of cryptic species, that is, morphologically indistinguishable, but nevertheless distinct, species (e.g., Chen et al 2010 ; Leasi and Norenburg 2014 ; Hao et al 2015 ; Hiebert and Maslakova 2015a ). Given that morphological approaches often fail to distinguish between look-alikes, DNA-based approaches are increasingly used to identify and delimit species, resolve phylogenies, and infer biogeographical patterns (e.g., Chernyshev et al 2021a ; Mendes et al 2021 ; Kajihara et al 2022a , 2022b ).…”

Three new species in Tetrastemma Ehrenberg, 1828 (Nemertea, Monostilifera) from sublittoral to upper bathyal zones of the northwestern Pacific

“…A histology-free description with DNA barcoding has been progressively introduced to nemertean systematics in the past decade (e.g., Kajihara 2015 ; Gonzalez-Cueto et al 2017 ; Simpson et al 2017 ; Kajihara et al 2018 , 2022 ; Chernyshev et al 2020 ; Hookabe et al 2021a , b ; Leiva et al 2021 ; Abato et al 2022 ). This approach has been applied to two cases, one of which is a description of species with internal characters interspecifically differentiated and observable without histology (e.g., number of proboscis branches in Gorgonorhynchus Dakin & Fordham, 1931 [ Kajihara 2015 ; Hookabe et al 2021a )].…”

“…This approach has been applied to two cases, one of which is a description of species with internal characters interspecifically differentiated and observable without histology (e.g., number of proboscis branches in Gorgonorhynchus Dakin & Fordham, 1931 [ Kajihara 2015 ; Hookabe et al 2021a )]. In the other case, especially when internal morphology is uniform between most species in a genus, a species description has been performed solely based on characters examined in-vivo (shape of head, body coloration and markings, number of eyes, blood color, and stylet apparatus) [e.g., Baseodiscus Diesing, 1850 ( Kajihara et al 2022 ) and Ototyphlonemertes Diesing, 1863 ( Kajihara et al 2018 )]. Recent descriptions of species in the genus Tetrastemma Ehrenberg, 1828, fitting the latter case, have been performed based on characters of living specimens without histological observations ( Chernyshev et al 2020 ; Hookabe et al 2021b ; Abato et al 2022 ).…”