A histology-free description of a new species of the genus Tetrastemma (Nemertea: Hoplonemertea: Monostilifera) from Hawaii and India

Abstract

<jats:p>A new species of the genus Tetrastemma Ehrenberg, 1831, T. freyae sp. nov., is described and illustrated from Hawaii and India. The description is based on light microscopy examination of the external and internal morphology, as well as on two gene markers (cytochrome c oxidase subunit I and histone H3 DNA). </jats:p>

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

“…Overall, our findings concerning the composition of the sampled deep-sea fauna are in accordance with that already reviewed in Chernyshev (2020). In all samples of the deep-sea expeditions to the Kuril-Kamchatka Trench, the Vema Fracture Zone, and the Costa Rica margin, eumonostiliferous hoplonemerteans and palaeonemerteans comprise the highest number of sampled individuals (Chernyshev & Polyakova 2018b.…”

A molecular phylogeny of Tetrastemma and its allies (Nemertea, Monostilifera)

“…The sample of Tetrastemma freyae Chernyshev et al. (2020), which emerges in the North Pacific clade, was collected from Hawaii but the species also occurs in India; the two differ by p‐distances of 1.3% for COI and 0.3% for H3 (Chernyshev et al., 2020). Besides Tetrastemma , the North Pacific subclade contains species of Quasitetrastemma , viz., Q. nigrifrons (Coe, 1904), Q. stimpsoni (Chernyshev, 1992), and the undescribed species labelled Q .…”

“…olgarum , also are indeed separate species, belonging to different subclades and not even sister species (Figure 2). On the other hand, Tetrastemma freyae is found off the coast of India and Hawaii (Chernyshev et al., 2020), which may be evidence that among Tetrastemma , species in the tropics may be more widespread.…”

“…The genus was established for the species Tetrastemma flavidum Ehrenberg, 1828, found among tubiporid corals in the Red Sea, near El‐Tor, Egypt (Ehrenberg, 1828–1831), making it one of the oldest nemertean genera (with its precedence being 1828, not 1831 as often attributed in some literature). At about 106 currently accepted species, it also is one of the three most speciose nemertean genera behind Cerebratulus and Amphiporus and approximately equal with Lineus (Gibson, 1995; Kajihara et al., 2008; Chernyshev, 2016; Chernyshev et al., 2020; Kajihara, 2021; Norenburg et al, 2021). Starting with uncertainty about the identity of the type species T. flavidum , the concept of Tetrastemma has experienced considerable twists and turns over the years among different authors.…”

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

“…Several species in Tetrastemma were described based on internal morphology; however, the internal characters were inferred to be almost homogenous within the genus by taxonomic reappraisal based on molecular phylogeny (Chernyshev et al 2021). Recent examples of a histology-free approach based on characteristics studied in-vivo and molecular data are descriptions of T. freyae Chernyshev et al, 2020, T. cupido Hookabe, Kohtsuka & Kajihara, 2021, and T. parallelos Abato, Yoshida & Kajihara, 2022 Here, we establish three new species based on specimens collected in 2019-2021 from the lower sublittoral to upper bathyal zones of Sagami Bay and the Nishi-Shichito Ridge. The descriptions are histology-free, based on characters of living specimens examined with a light microscope.…”