Barathrites iris Zugmayer, 1911

Ohashi, Shinpei, Imamura, Hisashi & Yabe, Mamoru, 2012, Record of a Rare Ophidiid Fish, Barathrites iris (Actinopterygii: Teleostei: Ophidiiformes), from off Southern Japan, Species Diversity 17 (2), pp. 169-172 : 169-171

Barathrites iris Zugmayer, 1911

[New Japanese name: Kogashira-ashiro] ( Figs 1–2 ; Tables 1–2)

Barathrites iris Zugmayer, 1911: 193 (type locality: southwest of Azores, 31°44′N, 42°39′W); Belloc 1949: 14, pl. 3 (list of type specimens); Nybelin 1957: 282, pl. 6 (key and description, off Surinam, Atlantic); Cohen and Nielsen 1978: 25 (short description, tropical Atlantic and Pacific?); Nielsen 1986: 1159 (key and short description, northern mid-Atlantic); Arruda 1997: 109 (list, southwest of Azores); Nielsen et al. 1999: 53 (key and list, Atlantic); Nielsen and Robins 2003: 968 (key and list, Atlantic); Garrido-Linares and Acero P. 2006: 293 (list, Atlantic).

Barathrites abyssorum Roule, 1916: 17 (type locality: Monaco Trench, Atlantic); Belloc 1949: 14 (list of type specimens); Nybelin 1957: 284, 333 (key and description,

Monaco Trench, Atlantic); Cohen and Nielsen 1978: 25 (discussion of synonymy with Barathrites iris ).

Material examined. NSMT-P 98868 , 2 specimens ,

230.2–413.0 mm SL, off eastern coast of Kagoshima Prefecture, southern Japan, Pacific Ocean (31°32.15′N, 133°43.2′E – 31°33.13′N, 133°44.14′E), 4,856–4,864 m depth, R / V Hakuho-maru, cruise number KH-02-03, station number TH-1, 15 September 2002 .

Diagnosis. A species of Barathrites with no basibranchial tooth patches, a small eye (horizontal eye diameter 10.7–12.3% HL), and a short pre-dorsal-fin region (predorsal-fin length 17.1–18.9% SL).

Description. Counts and measurements are given in Table 1. Body elongate and compressed. Head short, its length 33.5–33.8% of pre-anal-fin length. Snout rounded. Two pairs of nostrils; anterior one small without fleshy raised rim, situated on anterior margin of snout; posterior one larger, situated at midpoint between anterior nostril and anterior margin of eye. Mouth relatively small, subterminal; maxilla slightly extending beyond posterior margin of eye. Vomerine and palatine with small granular teeth. Vomerine tooth patch triangular. Palatine tooth patch broad anteriorly, narrow posteriorly. Basibranchial tooth patch absent. Eye circular, small; its diameter 10.7–12.3% HL. Preopercle soft; its posterior margin without spines. Opercular spine single, strong. Gill opening wide, upper end beyond upper portion of pectoral-fin base. Anterior gill arch with developed but rather short rakers. Rudimentary gill rakers present in front of and behind each developed gill raker. Pseudobranchial filaments short. Small cycloid scales present on head, body, and basal 2/3 portion of dorsal and anal fins. Pectoral fin short, its length 32.0–41.2% of distance from pelvic-fin base to anal fin origin. Dorsal and anal fins with long base, continuous with caudal fin; dorsal fin originating above pectoral-fin base; anal fin originating below 31st or 32nd dorsal-fin ray. Pelvic fin short; length of inner ray 19.8–23.9% of distance between pelvic-fin base and anal-fin origin; origin of pelvic fin situated below hind margin of preopercle; 2 pelvic-fin rays connected by fin membrane except for their tips; inner ray slightly longer than outer. Caudal fin slender. Anus situated just anterior to anal fin origin.

Color in alcohol. Ground color of body and head pale. Anterior part of head and opercle dark. Abdomen slightly dark.

Distribution. Known from southwest of the Azores and off Surinam, Atlantic Ocean, at depths of 3,465 –5,044 m ( Zugmayer 1911; Nybelin 1957; Nielsen et al. 1999), and off Kagoshima, southern Japan, Pacific Ocean at a depth of 4,856 –4,864 m (this study; Fig. 2 ).

Remarks. The present two specimens collected off Japan agree with the generic characters of the genus Barathrites indicated by Nielsen et al. (1999) in having two pelvicfin rays, five to six long gill rakers on the anterior gill arch, and a small head (33.5–33.8% of pre-anal-fin length) and eye (1.6–1.8% SL).

Nielsen et al. (1999) recognized that the two valid species of Barathrites , B. iris and B. parri , are distinguishable from each other by the basibranchial tooth patches (absent in B. iris vs present in B. parri ) and the number of branchiostegal rays (six vs seven, respectively). Additionally, these species differ from each other in the horizontal eye diameter (11.4– 11.7% vs 14.6% HL), pre-dorsal-fin length (18.1–18.8% vs 21.5% SL), and body depth at the anal-fin origin (15.4– 16.3% vs 18.9% SL, respectively) ( Nybelin 1957). The larger of the two present specimens (413.0 mm SL) does not fit this concept of B. iris because it has asymmetrical branchiostegal rays (six on the right, seven on the left) and a deeper body (body depth 19.3% SL) ( Table 2). However, its other features [absence of basibranchial tooth patches, a small eye (horizontal eye diameter 10.7% HL), and a short pre-dorsal-fin region (pre-dorsal-fin length 17.1% SL)] agree with those of B. iris . Therefore, we consider the differences between the two specimens (number of branchiostegal rays and body depth) as manifestations of intraspecific variation.

Although Cohen and Nielsen (1978) suggested the occurrence of Barathrites in the Pacific Ocean, and Nielsen et al. (1999) also suggested that Barathrites iris might occur in the Pacific and the Indian oceans, they did not refer to any documented records. This study confirms the occurrence of the genus, and specifically of Barathrites iris , in the Pacific Ocean.

Figures

Fig. 1. Barathrites iris, NSMT-P 98868, 230.2mm SL, Pacific Ocean off Kagoshima Prefecture, southern Japan.

Fig. 2. Sampling locality of Barathrites iris (indicated by a circle).