Kakui, K.; Ono, R.; Ogawa, A. (2026). A new entoproct commensal on holothuroids in the northwestern Pacific abyssal–hadal zone. Deep Sea Research Part I: Oceanographic Research Papers. 230: 104716.

566509

10.1016/j.dsr.2026.104716 [view]

urn:lsid:zoobank.org:pub:6E83079F-0200-4CAA-BF3F-F782B72FFEE5 [view]

Kakui, K.; Ono, R.; Ogawa, A.

2026

230: 104716

Publication

Knowledge on the diversity of Loxosomatidae, a group of solitary entoprocts, remains quite limited for the abyssal and hadal zones. Only three species have been reported from depths below 3500 m, all from the northwestern Pacific. Here, we describe the loxosomatid Loxosomella namacola sp. nov. from Molpadiodemas holothuroids collected from two localities at depths of 6093–6102 m and 7285–7288 m in the Kuril–Kamchatka Trench, northwestern Pacific. Holothuroidea is a novel host group for Loxosomatidae, and our specimens from 7285–7288 m represent the deepest record to date for Entoprocta. Loxosomella namacola sp. nov. has a widened root-like stalk end that is embedded in the host body. This structure suggests a close relationship between L. namacola sp. nov. and Loxosomella marcusorum, which has a star-shaped plate embedded in the body of its echiuran host. We determined partial sequences for the 18S rRNA (18S), 28S rRNA, and cytochrome c oxidase subunit I (COI) genes from L. namacola sp. nov. to aid in future DNA barcoding and for inference of its phylogenetic position in Loxosomatidae (18S only). We observed no nucleotide differences among COI sequences from the same locality, but a 1.53% p-distance between sequences from the two localities. In an 18S-based phylogenetic tree (1508 positions), L. namacola sp. nov. was the sister taxon to its abyssal congener Loxosomella profundorum found on an unidentified anthozoan species in Corallimorpharia.

Abyssal, Deep-Sea

Entoprocta

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