Cirolanidae) from Vietnam, with Notes on the Taxonomy of Bathynomus jamesi

Abstract

A new supergiant species of Bathynomus A. Milne-Edwards, 1879 from Vietnam is described. Bathynomus vaderi sp. nov. is characterised by its wide, rectangular clypeal region with parallel lateral margins, concave distal margin, and narrowly acute apex; the distally narrowing and posteriorly curved coxa of pereopod 7; and the presence of 11 upwardly curved pleotelson spines. The new Bathynomus is the fourth species with upwardly curved pleotelson spines and the second supergiant in the South China Sea. The taxonomy of B. jamesi Kou, Chen & Li, 2017 from the South China Sea is also discussed based on a large series of specimens. Previously reported differences in body form and pleotelson spines, which suggest that there may be two forms or species, are regarded as intraspecific variation for the time being. The contemporary culinary trend and fishing of Bathynomus in Vietnam, which have contributed to this discovery, are also discussed.

Key words: Deep sea, fisheries, morphology, new taxon, taxonomy, seafood

Bathynomus vaderi sp. nov., paratype ♂ (258 mm) (ZVNU 110001), Vietnam, colour in life
A dorsal view B body, ventral view C cephalon, anterior view.

A–D Bathynomus vaderi sp. nov., holotype ♂ (266 mm) (ZRC 2022.0621), Vietnam
E–H B. jamesi Kou, Chen & Li, 2017, ♂ (320 mm) (MNHN IS.2290), Philippines
A, E clypeal region B, F pereon lateral view C, G pleotelson, dorsal view D, H pleotelson, lateral view.

Abbreviations: c6 = coxa of pereopod 6; c7 = coxa of pereopod 7.

Bathynomus vaderi sp. nov.

Diagnosis: Clypeal region with lateral margin parallel, distal margin concave, apex narrowly acute, transversely rectangular (Figs 4C, 5C, 6C, 9A). Coxa of pereopod 7 narrows distally, curved posteriorly (Figs 5D, 6D, E, 9B). Distinct row of setae present between pleotelson spines; 11 upwardly curved pleotelson spines; pleotelson 0.6 as long as wide (Figs 5A, 9D); pleotelson vaulted laterally (Figs 6E, 9C). Appendix masculina slightly shorter than or reaching to end of endopod of pleopod 2 (Fig. 10A).

Etymology: The species named after the most famous Sith Lord in the Star Wars movie series, Darth Vader, whose helmet resembles the head of the new Bathynomus species.

Peter K. L. Ng, Conni M. Sidabalok and Thanh Son Nguyen. 2025. A New Species of supergiant Bathynomus A. Milne-Edwards, 1879 (Crustacea, Isopoda, Cirolanidae) from Vietnam, with Notes on the Taxonomy of Bathynomus jamesi Kou, Chen & Li, 2017. ZooKeys. 1223: 289-310. DOI: doi.org/10.3897/zookeys.1223.139335