Saturday, March 4, 2023

[Ichthyology • 2023] Eulophias spinosior • A New Deep-Water Eulophiid Fish (Perciformes: Zoarcoidei: Eulophiidae) from Japan

Eulophias spinosior
Nakayama, Yamakawa, Takami & Endo, 2023

The genus Eulophias, which is an enigmatic group of the suborder Zoarcoidei, previously comprised two rare species: Eulophias tanneri Smith, 1902 (type species and a senior synonym of Eulophias owashii Okada and Suzuki, 1954) and Eulophias koreanus Kwun and Kim, 2012. Here we describe a new species, Eulophias spinosior, based on 71 specimens (94.9–182.3 mm in standard length, SL) collected from the upper slope of the northwestern Pacific off southern Japan at depths of 257–555 m. It readily differs from its two congeners in having 133–143 dorsal-fin spines, 109–116 anal-fin soft rays, 5–6 pectoral-fin rays, and 146–156 total vertebrae, and in lacking a dark band posterior to the eye and a series of dark blotches midlaterally on the trunk and tail. Regarding bathymetric distribution, the new species occurs much deeper than E. koreanus and E. tanneri. Eulophias spinosior, new species, is sexually dimorphic, with males having large, stout, modified canines at the tips of the premaxillary and dentary (vs. only slightly enlarged in females). Dentition of males also differs from that of females in that most teeth are uniserially arranged in each jaw (vs. distinct two rows anteriorly).

Fresh specimens of Eulophias spinosior.
(A–E) BSKU 118798, paratype, sex undetermined, 155.0 mm SL, Tosa Bay, 300 m depth, soon after capture;
(F) BSKU 118835, paratype, sex undetermined, 135.3 mm SL, Tosa Bay, 300 m depth, freshly thawed.

(A, F) Lateral views; (B) close-up lateral, (C) dorsal, and (D) ventral views of the head and trunk; (E) close-up lateral view of the posterior part of the tail.

Eulophias spinosior, new species 
 New standard Japanese name: Toge-itoginpo

Diagnosis.—Eulophias spinosior is readily distinguished form its two congeners by having 133–143 dorsal-fin spines (vs. 124–128 and 116–125 in E. koreanus and E. tanneri, respectively), 109–116 anal-fin soft rays (vs. 102–103 and 90–100, respectively), 146–156 total vertebrae (vs. 141–143 and 132–143, respectively), and 5–6 pectoral-fin rays (vs. 7 in both E. koreanus and E. tanneri). In addition, the new species is unique among the genus in lacking prominent dark markings on the sides of the head and body, whereas E. koreanus and E. tanneri have a dark band posterior to the eye and a series of dark blotches midlaterally on the trunk and tail.

Etymology.— The specific epithet spinosior is derived from the comparative of the Latin adjective spinosus, meaning thorny, spiny, or prickly, in alluding to a greater number of dorsal-fin spines of the new species among Eulophias.

Naohide Nakayama, Takeshi Yamakawa, Munehiro Takami and Hiromitsu Endo. 2023. Description of A New Deep-Water Eulophiid Fish (Perciformes: Zoarcoidei) from Japan. Ichthyology & Herpetology. 111(1); 87-97. DOI: 10.1643/i2021047