Coloconger maculatus Ho & Tang, 2021

Ho, Hsuan-Ching, Tang, Chi-Ngai & Chu, Tah-Wei, 2021, Coloconger maculatus sp. nov., a species of short-tail eel from eastern Taiwan (Anguilliformes: Colocongridae), Zootaxa 5016 (2), pp. 271-282 : 272-274

Coloconger maculatus Ho & Tang , sp. nov.

English name: Caudal-spot short-tail eel lsid:zoobank.org:act: 352EA242-25BF-428C-BDA2-54BAB9087587

Figs. 1‒4 ; Tables 1‒2

Holotype. NMMB-P 35247, 520 mm TL, off Fu-gang , Taitung, eastern Taiwan, northwestern Pacific Ocean, ca. 300 m, 26 Feb. 2021, collected by hook and line, purchased from a local auction.

Diagnosis. A species of Coloconger that differs from its congeners by having a large black blotch on rear portion of tail with a white posterior end, and the following combination of characters: head small, HL 15.7% TL; ST 4, middle two in pair; SO 7, two pores over posterior nostril; IO 12 or 14; POM 14; dorsal-fin rays 226 and anal-fin rays 122; PAV 77 and TV 145; rictus through a vertical of posterior margin of pupil; snout shorter than eye diameter; PO-DO 69.4% pectoral-fin length; and body brownish-gray dorsally, light gray ventrally, and dorsal fin dark gray.

Description. Morphometric and meristic data are also provided in Table 1. Head length 6.4 times in TL (15.7% TL); deepest body depth 7.8 (12.8%); predorsal 4.8 (21.0%); preanal 1.7 (60.4%); trunk length 2.2 (44.7%); tail length 2.5 (39.6%); body depth at pectoral-fin base 9.7 (10.3%); body width at pectoral-fin base 11.8 (8.5%); body depth at anus 10.6 (9.4%); body width at anus 19.3 (5.2%). Snout length 4.0 times in HL (25.0% HL); eye diameter 3.5 (28.7%); interorbital width 3.2 (31.5%); snout-rictus length 2.2 (45.1%); lower-jaw length 2.3 (44.0%); postorbital width 1.9 (53.9%); gill-opening height 4.7 (21.2%); interbranchial width 3.2 (31.5%); pectoral-fin length 2.1 (48.4%); pectoral-fin base 4.8 (20.7%); PO-DO 3.0 (33.6%).

Dorsal-fin rays 226; anal-fin rays 122; number of dorsal-fin rays before anal-fin origin 103. Vertebrae: PDV 14, PCV ca. 75, PAV 77, CV 68; total 145. Lateral-line pores (tubes): head 4; predorsal 10; preanal 75 (counted as 2 when paired); total ca. 125.

Body short and stubby; skin tight, not loose; deepest area at middle of trunk; depth of head slightly larger than that of tail; head and trunk cylindrical, gradually compressed to tail-tip; trunk long, length 2.8 times HL; tail short, shorter than trunk, posterior end broadly rounded, tail length 1.1 in trunk length.

Dorsal and anal fins well developed confluent with caudal fin. Origin of dorsal fin above posterior half of pectoral fin, predorsal length 1.3 HL; PO-DO 69.4% pectoral-fin length; original of anal fin slightly well posterior to midlength, preanal length 3.8 HL. Pectoral fin broad and slightly pointed, its upper margin flat and lower and posterior margins broadly rounded. Gill opening a large vertical slit, in front of pectoral fin with its upper end extending dorsally to middle of pectoral-fin base.

Head broad and deep; snout short and bluntly rounded, length 0.87 times eye diameter, slightly projects beyond lower jaw; fleshy tip of snout extends anteriorly beyond intermaxillary teeth.Anterior nostril a short tube, at front of snout; posterior nostril large, posterodorsal to anterior nostril, its lower margin at a horizontal through middle eye, bearing a low rim. Eye large, above posterior half of upper jaw, its posterior margin extending beyond a vertical through rictus; interorbital space broad and flat, width 1.1 times eye diameter.

Mouth large, its opening slightly oblique, rictus extending to a vertical through posterior margin of pupil; upper jaw slightly protrudes anterior to lower jaw; upper labial flange weakly developed; lower jaw with a thin fold from tip to rictus.

Head pores ( Figs. 3A, B ) open through fleshy tubes; SO 7 on both sides, first three pores at front of snout, 4 th ‒5 th pores arranged in pair over posterior nostril, 6 th and 7 th on interorbital space; IO 12 on right side, first two behind anterior nostril, followed by five pores along upper jaw, 4 th ‒5 th, 6 th ‒7 th pores arranged in pairs, three closely spaced pores behind rictus, 11 th ‒12 th pores widely-spaced and behind the eye; 14 on left side, first two pores behind anterior nostril, followed by six along upper jaw, 4 th ‒5 th and 6 th ‒7 th pores arranged in pairs, three closely spaced pores behind rictus and 12 th ‒ 14 th pores widely-spaced and behind eye; POM 14 on both side with slightly different arrangements, 8/9 (right/left) along the lower jaw, 6/5 behind rictus, 12 th ‒13 th on right side and 8 th ‒9 th, 11 th ‒12 th, 13 th ‒14 th on left side arranged in pairs; ST 4, middle two pores forming a pair. Additional series of small dermal papillae (or tendrils) behind eye, across supratemporal region, parallel to preopercular canal, neck and at scattered locations elsewhere on head.

Teeth small, each with a flattened tip. Intermaxillary in two transverse rows, not exposed when mouth closed, posterior row complete, continuous with maxillary teeth, anterior row complete and well separated from posterior row; no vomerine teeth; single row of small teeth on upper jaw; two complete rows of teeth on lower jaw, those on inner row clearly smaller than outer row.

Coloration. Freshly caught specimen ( Figs. 1‒2 ) brownish-gray on dorsal half and slivery white on lower half; dorsal fin darker with light margin. After transporting to the lab (frozen), body turned brownish-gray on most parts, ventral portions of head and abdomen light gray; dorsal fin dark. A large dark blotch on rear portion of tail with posterior end bright white when fresh. When preserved, body brownish-gray in general, dorsal fin dark gray and abdominal region light gray; anal fin light gray. Large black blotch on posterior part of tail, posterior end somewhat translucent.

Distribution. Known only from the holotype collected off Fu-gang, Taitung, eastern Taiwan ( Fig. 4 ) on hook and line at an estimated depth around 300 m.

Etymology. The specific name is derived from the distinct black blotch on posterior portion of tail.

Figures

FIGURE 1. Coloconger maculatus sp. nov. NMMB-P35247, holotype. A. Fresh coloration after frozen. B. Freshly dead in the local auction.

FIGURE 2. Coloconger maculatus sp. nov., from the holotype. A. Lateral view. B. Dorsal view of head. C. Lateral view of posterior portion of tail.

FIGURE 3. Coloconger maculatus sp. nov., from the holotype.A. Head pores on lateral view, SO1–3 and IO1–3 at tip of snout are not shown. B. Head pores on dorsal view.

FIGURE 4. Distribution map of Coloconger maculatus sp. nov. (solid triangle), C. japonicus (open dots), and C. scholesi (solid dot, holotype only).