Uropterygius cyamommatus, Huang & Liao & Tan, 2023

Huang, Wen-Chien, Liao, Te-Yu & Tan, Heok Hui, 2023, Uropterygius cyamommatus, a new moray eel (Anguilliformes: Muraenidae) from anchialine caves in Christmas Island, Australia, and Panglao Island, the Philippines, Raffles Bulletin of Zoology 71, pp. 268-278 : 270-273

Uropterygius cyamommatus , new species

Common name: Bean-eyed snake moray ( Figs. 3–7 , Table 1)

Holotype. WAM P.35403.001 (361 mm TL, male); Christmas Island, Australia: Whip Cave (10°25.377ʹS 105°42.081ʹE), a cave system with a narrow cave mouth and lower chambers filled with anchialine water affected by tidal changes; baited fish trap, 01 February 2010, coll. H.H. Tan et al.

Paratypes. Four specimens (333 – 401 mm TL). NMMB-P37200 (380 mm, male), WAM P.35404.001 (390 mm, female), ZRC 56488-1 (401 mm, female), ZRC 56488- 2 (333+ mm*, male; * for tail tip damaged but hypural plate intact); Christmas Island, Australia: Freshwater Cave (10°30.796ʹS 105°37.448ʹE), a cave with a large but steep Description. Data is presented for holotype first, paratypes and non-type specimens in parentheses. Proportions in percentage of TL: tail length 59.0 (56.3–61.1), trunk length 31.0 (29.7–33.8), head length 10.0 (8.9–9.9), depth at gill opening 3.5 (3.2–5.2), depth at anus 3.2 (2.6–4.6). Proportions in percentage of HL: length of upper jaw 28.7 (26.8–33.1), length of lower jaw 28.3 (25.5–32.6), interorbital width 11.1 (12.1–14.4), snout length 13.1 (14.0–17.0), eye diameter 3.9 (3.0–4.6). Vertebral counts: Pre-anus vertebrae 58 (56–62), pre-dorsal fin vertebrae 137 (130–138), pre-anal fin vertebrae 138 (131–139), total vertebrae 146 (141–149) .

A small-sized slender moray eel, anus well anterior to midpoint of body, tail long, body laterally compressed with depth nearly consistent throughout whole fish, tail tip blunt, caudal fin short ( Fig. 3 ). Dorsal and anal fins inconspicuous, restricted to the posterior end of tail. Gill opening small, oval, below lateral midline of body, about same size with eye. Eyes very small, above mid-jaw ( Fig. 4 ), two paratypes ( NMMB-P37200 and WAM P.35404.001) with a reduced left eye embedded in skin ( Fig. 5A ). Snout blunt, nasal cavity somewhat enlarged. Jaws short, subequal in length, teeth not visible when mouth closed. Anterior nostril a stubby tube, shorter than eye diameter, its base in a depression close to tip of snout. Posterior nostril an oval hole located above anterior margin of eye, without a conspicuous raised rim .

Three supraorbital pores, first on tip of snout immediately above lip; second just next to upper base of anterior nostril, at the level of horizontal middle line of eye; third on upper margin of snout at the same level of posterior nostril, above and posterior to the first infraorbital pore. Four infraorbital pores arranging equidistantly, first just below base of anterior nostril; second on the midpoint between anterior nostril base and anterior margin of eye; third below middle point of eye; fourth below and posterior to eye. Second supraorbital and first infraorbital pores in depression of anterior nostril base. Typically six preoperculo-mandibular pores but with a variation from four to seven pores, all along lower jaw, aData not including ZRC 56488-2 due to damaged tail.

bData not including ZRC 63039 due to damaged tail.

last (generally sixth) pore posterior to corner of mouth. One branchial pore on posterior-dorsal area of head, closer to corner of mouth rather than gill opening ( Fig. 4 ).

Teeth ( Fig. 6 ) conical, slightly elongated, end pointed and slightly retrorse, edge smooth. Intermaxillary, maxillary, and vomerine teeth continuously; peripheral series small, numerous, and equal-sized; inner series longer, fewer, and spaced. Intermaxillary and vomerine plates with 30–45 teeth, approximately arranged in 7–8 rows on intermaxilla and becoming single row on vomerine, except for one paratype ( NMMB-P37200 ) without teeth on vomerine. Maxilla with 20–26 teeth on outer row; 8–13 teeth on inner row, extending to posterior end of outer row. Dentary teeth arranging in 2–3 rows anteriorly and 2 rows posteriorly; teeth on outer row small and equal-sized, 22–32 in number; inner teeth 9–19, larger and more spaced than those of outer, decreasing in size posteriorly, extending to or slightly before the posterior end of outer row; most examined specimens with a middle row of 2–7 teeth on anterior part of dentary, except for two specimens ( NMMB-P37200 and ZRC 46849-2 ) with only two rows of dentary teeth; one paratype ( ZRC 56488-1 ) with an additional one row of two very small teeth on the anteriormost middle part of lower jaw .

Body uniform brown, slightly lighter ventrally, most pale on venter below lower jaw. Anterior nostril (including its base depression), posterior nostril opening, gill opening, oral cavity, and head pores whitish. Numerous small, inconspicuous whitish neuromasts arranged in irregular lines on anterior head region and in one row along lateral line ( Fig. 4 ). Preserved colouration similar to fresh fish except faded ( Fig. 3B ).

Distribution. Currently, this species is only known from anchialine caves in Christmas Island and Panglao Island.

Etymology. From Greek words kúamos (a bean) and ómma (the eye), in reference to its tiny bean-shaped eyes.

Comparisons. The new species belongs to the genus Uropterygius according to a combination of the following characters: (1) three supraorbital pores (vs. four in Anarchias Jordan & Starks, 1906); (2) the anus anterior to the midpoint of body (vs. anus far behind mid-body in Scuticaria Jordan & Snyder, 1901); (3) jaws short and subequal in length (vs. gape very long, lower jaw longer than upper jaw in Channomuraena Richardson, 1848 and Cirrimaxilla Chen & Shao, 1995 ).

Uropterygius cyamommatus can be easily distinguished from the other five uniform brown-coloured species of the genus, viz. U. concolor , U. genie , U. golanii , U. inornatus , and U. xenodontus , by the combination of eye diameter, tail length, vertebrae count, and dentition (Table 2). In comparison, it has distinctively small eyes; its tail length is exclusively long except for U. concolor (56.3–61.1, vs. 52.4–60.0% of TL); and its total vertebral number is only overlapped with U. golanii (141–149, vs. 145–148).

Figures

Fig. 3. Uropterygius cyamommatus, new species, holotype, WAM P.35403.001, 361 mm TL. A, fresh colouration (photographed by HHT); B, preserved colouration (photographed by WCH). Arrows indicate the position of anus.

Fig. 4. Uropterygius cyamommatus, new species, lateral view of head marked with cephalic sensory pores: red for supraorbital pores; green for infraorbital pores; blue for preoperculo-mandibular pores; yellow for the branchial pore. Arrow indicates the gill opening. Photo of WAM P.35403.001, holotype, 361 mm TL (photographed by HHT).

Fig.5. Uropterygius cyamommatus, new species, lateral view of the head region of a specimen without the left eye. A, external view; B, radiograph showing the skeletal structure of orbital region. Photo of NMMB-P37200, paratype, 380 mm TL (photographed by HHT).

Fig. 6. Dentition of Uropterygius cyamommatus, new species, holotype, WAM P.35403.001. Upper jaw (left) and lower jaw (right). Dotted circles represent the sockets of missing teeth. Schematic drawings by WCH.

Fig. 7. Radiograph showing the skeletal structure of Uropterygius cyamommatus, new species, ZRC 46849-1, 352 mm TL (photographed by HHT). Arrow indicates the position of anus.