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Systematics, phylogeny and biogeography
RESEARCH ARTICLE

Integrative morphological, mitogenomic and phylogenetic analyses reveal new vent-dwelling scallop species

Yi-Tao Lin A , Ying-Bei Peng A , Chong Chen https://orcid.org/0000-0002-5035-4021 B , Ting Xu C D and Jian-Wen Qiu https://orcid.org/0000-0002-1541-9627 A *
+ Author Affiliations
- Author Affiliations

A Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR, PR China.

B X-STAR, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2‑15 Natsushima‑cho, Yokosuka, Kanagawa 237‑0061, Japan.

C Department of Ocean Science, The Hong Kong University of Science and Technology, Sai Kung, Hong Kong SAR, PR China.

D Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, PR China.

* Correspondence to: qiujw@hkbu.edu.hk

Handling Editor: Gonzalo Giribet

Invertebrate Systematics 39, IS24091 https://doi.org/10.1071/IS24091
Submitted: 30 October 2024  Accepted: 4 January 2025  Published: 10 February 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing.

Abstract

Delectopecten is a small genus of the family Pectinidae (Bivalvia: Pectinida) that remains poorly studied in terms of both morphology and phylogeny. Here, we describe the first member of this genus from deep-sea hydrothermal vent ecosystems, D. thermus sp. nov., based on morphological investigations and molecular analyses of a specimen collected from the Higashi–Ensei vent field (962-m depth) in the northern Okinawa Trough. Morphologically, this new species resembles D. vancouverensis and D. gelatinosus in shell size, shape, auricle size and sculpture. However, D. thermus sp. nov. can be distinguished from its congeneric species (including 9 extant and 12 fossil species) by its unequal auricles (the anterior one being larger than the posterior), inwardly recurved anterior auricle of the left valve and a large byssal notch angle of ~90°. Comparisons of genetic sequences from three mitochondrial and three nuclear gene fragments supported the placement of the new species in the genus Delectopecten. Further phylogenetic analyses using these gene markers support that Delectopecten is monophyletic and positioned as an early diverging clade of the family Pectinidae. Additionally, the mitogenome of D. thermus sp. nov. was assembled and annotated, a first for its genus – revealing significant divergences in gene order compared to other pectinids. The 16S rRNA amplicon analysis of the gill tissue indicated that this vent-dwelling scallop does not exhibit symbiosis with chemosynthetic bacteria. A key to all known species of Delectopecten is provided to aid the identification of species in this understudied genus.

ZooBank: urn:lsid:zoobank.org:pub:D3D5D4AD-EE39-49F0-9782-12A5D6752A67

Keywords: bivalvia, deep sea, Delectopecten, heterotrophy, Higashi–Ensei, hydrothermal vent, identification key, new species, Okinawa Trough, Pectinidae, systematics, taxonomy, trophic mode.

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