A histology-free description of the branched-proboscis ribbonworm Gorgonorhynchus albocinctus sp. nov. (Nemertea: Heteronemertea)

Abstract

A new species of heteronemertean with branched proboscis, Gorgonorhynchus albocinctus sp. nov., is described based on the external feature and DNA sequences from a specimen collected subtidally among coral rubbles at a depth of about 6 m in a reef area around Taketomi Island in the Yaeyama Islands, southwestern Japan. It can be classified in the genus because the mode of proboscis branching is dichotomous, rather than alternating laterally. From the two known congeners G. repens Dakin andFordham, 1931 and G. bermudensis Wheeler, 1940, the new species can be differentiated by having a brown body colour with a white band near the tip of the head. The new species is placed in a molecular phylogenetic context with a maximum-likelihood analysis using the nuclear 18S rRNA and 28S RNA genes, as well as the mitochondrial cytochrome c oxidase subunit I gene, together with 20 species of heteronemerteans, for which those sequences were available in the public databases. The results indicate that G. albocinctus is closely related to Cerebratulus leucopsis (Coe, 1901), a species that is supposed to have a non-branched proboscis.

Histology-free Descriptions for Seven Species of Interstitial Ribbon Worms in the Genus <i>Ototyphlonemertes</i> (Nemertea: Monostilifera) from Vietnam

“…Although some of the previous taxonomic descriptions of Ototyphlonemertes species involved histological sectioning (e.g., Chernyshev 2007;Kajihara 2007) like in many other groups of nemerteans (Gibson 1985), we establish new species without histology in this paper (cf. Strand and Sundberg 2011;Kajihara 2015).…”

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 )].…”

“…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 )]. 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 )].…”

Cutting the ribbon: bathyal Nemertea from seeps along the Costa Rica margin, with descriptions of 2 new genera and 9 new species

“…Therefore, it has been proposed by Sundberg et al (2016a) that the description of new nemertean species is regarded as valid if it includes accurate information on type locality and deposition of type material, a description of external morphology, and at least a DNA COI barcode. Since then, several new nemertean species have been described in this way (e.g., Strand & Sundberg 2011;Kajihara 2015;Kajihara et al 2018;Chernyshev et al 2020). This goes hand in hand with the turbo-taxonomic approach where short diagnoses and descriptions are linked with appropriate DNA sequence data.…”