Ambusher in sponge: a new species of Eunice (Annelida, Eunicidae) commensal within deep-sea Farreidae (Porifera, Hexactinellida) on northwest Pacific seamounts

By

Zhou, Yadong
Zhang, Ruiyan
Shen, Chengcheng
Mao, Qin
Zhang, Mouyingke
Zhang, Dongsheng

Type

Article

Date of Publication

2025

Original Publication

ZooKeys

Volume

1230

Pages

25--36

Subjects

gut content , Morphology , Polychaeta , sponge associated species , taxonomy

Contributed by

Pensoft Publishers

Language

English

Published by

Sofia, Bulgaria Pensoft Publishers

Identifiers

DOI: https://doi.org/10.3897/zookeys.1230.140329

 

Abstract

Deep-sea sponges create complex biogenic structures and attract a wide array of deep-sea organisms, including symbionts. In this study, we describe Eunice siphoninsidiatorsp. nov., a new eunicid species living in the central cavity of deep-sea farreid glass sponges found on northwest Pacific seamounts. The new species closely resembles the Atlantic Eunice norvegica both morphologically and molecularly, but it differs in the relative length of palp compared to peristomium, starting points of subacicular hooks, and shape of pectinate chaetae. A 13% COI genetic distance between the two species further supports the establishment of E. siphoninsidiator as a distinct species. Gut content analyses reveals fragments of barnacles and brittle stars, suggesting a carnivorous diet and a sit-and-wait predatory strategy. The eunicid gains protection from living inside the sponge, which consistently harbored the polychaete in all specimens examined, while the sponge benefits from the cleaning of epibionts, pointing to a potentially mutualistic relationship.