Chlopsis sagmacollaris Pogonoski & Tighe

Tighe, Kenneth A., Pogonoski, John J., Hibino, Yusuke, Ho, Hsuan-Ching & Nguyen, Quan Van, 2015, Three new species of the genus Chlopsis (Anguilliformes: Chlopsidae) from the Indo-Pacific, Zootaxa 4060 (1), pp. 19-29 : 20-22

Chlopsis sagmacollaris Pogonoski & Tighe , sp. nov.

Figs. 1 , 2 , 3

Holotype: NMV A 29730 -023 (228 mm total length); Australia: Western Australia: Northwestern Australia, Station 189, Ashmore L30 Transect (12º 28’ 53” S, 123º 25’ 04” E to 12º 29’ 58” S, 123º 25’ 00” E), depth 397– 405 m; captured with beam trawl; RV Southern Surveyor; 0 6 July 2007.

Diagnosis. The high vertebral count combined with the distinctive saddle-shaped pigmentation on the nape of the neck differentiates this species from all others in the genus Chlopsis .

Description. Total vertebrae 142, predorsal vertebrae 12, preanal vertebrae 42, precaudal vertebrae 58, dorsal rays 385, anal rays 357, dorsal rays anterior to anal fin origin 93. Proportions as percent of total length: predorsal length 12.3, preanal length 35.1, head length 10.1, depth at gill opening 2.9, depth at anus 1.5. Proportions as percent of head length: eye diameter 12.2, interorbital width 13.0, snout length 25.2, tip of snout to rictus 41.7, tip of lower jaw to rictus 39.6.

Body moderately elongate, nearly cylindrical ( Fig. 1 ). Dorsal-fin origin approximately two eye diameters posterior to gill opening ( Fig. 2 ). Head moderate in length, relatively deep. Snout relatively broad. Gape moderate, rictus behind posterior margin of eye. Anterior nostril tubular, slightly behind tip of snout, directed anterolaterally. Posterior nostril a postero-ventrally directed low tubular opening (not covered by a flap) on lip in front of eye.

Lateral line on body absent except for one pore in branchial region, dorsal and anterior to gill opening, within dark, dorsal pigment patch ( Fig. 2 ). Supraorbital pores three: first (ethmoidal) at anteroventral tip of snout, second anteromedial to base of anterior nostril, and last above and behind anterior nostril. Infraorbital pores four: first just posterior to anterior nostril, second midway between anterior and posterior nostrils, third just behind posterior nostril, and last below posterior edge of eye. Preoperculomandibular pores five, first near tip of lower jaw and last just behind posterior edge of eye, anterior to rictus.

Maxillary teeth ( Fig. 3 ) conical, slightly recurved, in 2–3 irregular rows with third outer row very irregular; inner row larger than outer, a total of 37–38 teeth in inner row. Mandibular teeth like those of maxilla, except in 2– 3 irregular rows anteriorly, reducing to 2 rows posteriorly, with 30–31 teeth in inner row. Intermaxillary teeth conical, slightly recurved, with approximately 25 teeth in a round patch; median and posterior teeth somewhat enlarged. Vomerine teeth similar in shape and size to enlarged inner rows of maxillary and mandibular teeth; in two longitudinal series, relatively close-set anteriorly, diverging near middle of vomerine tooth rows and then converging near end of tooth rows; total of 27 or 28 teeth in each longitudinal row.

Color of body tan above and distinctly lighter ventrally; ventral light area strongly demarcated from darker dorsum of the snout, starting in front of unpigmented anterior nostril, continuing back above posterior nostril to margin of eye ( Fig. 2 ); posterior to eye, dorsal edge of ventral light area becomes more irregular, but extends back to a distinctly darker, saddle-shaped pigment patch dorsal to gill opening ( Fig. 1 A); ventral light area then tapers to base of anal fin slightly behind anus, but continues along base of anal fin for approximately 2/3 of body length; anal fin remains unpigmented to near tip of tail.

Etymology. The name is derived from the Latin sagma, saddle and collaris, necked, in reference to the distinctive dark pigment patch of the nape of the neck.

Distribution. Known only from the holotype taken off northern Western Australia, between Ashmore Reef and Cartier Island; presumably more widespread in the eastern Indian Ocean and Timor Sea.

Remarks. Chlopsis sagmacollaris has the bicolor pigmentation that is typical of many of the species of Chlopsis . However, it varies from the rest of these species in the following three critical ways. First, C. sagmacollaris has a distinctive, darker pigment patch on the nape of the neck. Second, the overall coloration of C. sagmacollaris is much lighter than the other species with the dorsal pigmentation being light brown to tan rather than the dark brown to grayish brown that is typical of other bicolor species of Chlopsis . Third, the ventral tip of the tail of C. sagmacollaris is relatively unpigmented rather than dark brown to black found in the other bicolor species of Chlopsis .

Figures

FIGURE 1. Holotype of Chlopsis sagmacollaris, NMV A 29730 - 023, 228 mm TL; Ashmore L 30 Transect, Station 189, Northwestern Australia. A. Detail of head showing dorsal patch of pigment.

FIGURE 2. Head of holotype of Chlopsis sagmacollaris, NMV A 29730 - 023.

FIGURE 3. Upper (A) and lower (B) jaws of holotype of Chlopsis sagmacollaris, NMV A 29730 - 023.