Allips concolor McCosker, 1972

Ho, Hsuan-Ching, Hibino, Yusuke & Huang, Jian-Fu, 2018, Note on rare snake eels (Anguilliformes: Ophichthidae) and additional data on three Neenchelys recently described from Taiwan, Zootaxa 4454 (1), pp. 200-214 : 201-204

Allips concolor McCosker, 1972

Figures 1 ¯2; Table 1

Allips concolor McCosker, 1972: 117 (type locality: mouth of Pakehan River, north of Ban Parknam Ranong, 10°57’42”N, 98°35’18”E, Goh Phi, Ranong Province, Thailand). McCosker et al., 2006:265 (listed).

Specimen examined. NMMB-P 27884, 392 mm TL, off Dong-gang fishing port, Pingtung, southwestern Taiwan, South China Sea, 9 Sep. 2016, coll. H.-C. Ho.

Diagnosis. Body extremely elongate, body depth 75¯81 times in TL; trunk very long, longer than tail; tail length 2.4¯ 2.5 in TL. Head markedly rugose, with numerous grooves on surface; snout blunt; eyes small, 2.9¯4.2% of HL; dorsal-fin origin well behind level of gill opening; pectoral fins minute; and dorsal and anal fins received in deep groove. Vertebral formula 21-104-180 (20-96- 174 in holotype) ( McCosker, 1972; this study).

Description of NMMB-P27884. Counts and measurements are generally shown in Table 1.

Body extremely elongate, cylindrical; trunk remarkably long, longer than tail. Head short; head and nape heavily covered by waxy mucosa; snout rounded; a distinct groove ventrally on snout, made by thick lips; anterior nostrils tubular, located anteroventrally on snout, angling 30° anteriorly; posterior nostrils a simple pore, located within mouth, covered by a narrow flap with a broad base; a single barbel between anterior and posterior nostrils; eyes small, rudimentary, covered by transparent skin; lips smooth except barbel, without small papillae; mouth short, rictus behind posterior; eye diameter less than length of snout; lower jaw short, its anterior tip posterior to base of anterior nostril.

Brachial basket convex, supported by 27 branchiostegal rays ( Fig. 2A ), its surface with numerous distinct longitudinal grooves ( Figs. 2B, 2C ); gill opening moderate in size, weakly contracted, located ventrolaterally.

Head pores small but well developed ( Fig. 2C ), indistinct because of the heavy waxy mucosa; ethmoid pore absent; three supraorbital pores; two infraorbital pores along upper lip, and two pores on postorbital; four mandibular pores and two preopercular pores; a single interorbital (frontal) and temporal pore present; lateral-line canal complete; its pores developed but small and indistinct with waxy mucosa; eight pores anterior to level of gill opening and 105 anterior to anus.

Teeth small, pointed, weakly recurved posteriorly ( Fig. 2D ); teeth on maxilla uniserial; teeth on vomer biserial anteriorly and uniserial posteriorly; three intermaxillary teeth arranged in a triangular shape; teeth on dentary mostly uniserial with one pair of inner small teeth anteriorly.

Dorsal and anal fins extremely low, almost buried in agroove; dorsal-fin origin well behind level of gill opening by more than ahead length; caudal fin absent; pectoral fin small, oblong shaped, along upper corner of gill opening.

Coloration. When fresh, dorsal half of body yellowish brown with numerous but scattered chromatophores; ventral half creamy white, without other pigment; all fin white. When preserved, body whitish brown, darker dorsally with numerous chromatophores; dorsally on head and tip of lower jaw grayish brown with numerous small melanophores, gill basket without melanophores; dorsal, anal, and pectoral fins mostly white, end of anal fin weakly obscured.

Distribution. Known from Andaman Sea, northern South China Sea off Taiwan and northern Australia off Northern Territory. Our specimen was collected from relatively shallow area, about 100 meter depth based on the bycatch.

Remarks. The present specimen can be easily identified A. concolor by its characteristic elongate body and long trunk, small eyes, position of dorsal-fin well behind a level of gill opening, extremely short pectoral fins, and states of dorsal and anal fins which are received in deep groove. The differences of all morphological characters including proportional and countable characters are unremarkable except the number of branchiostegal rays. The present specimen has numerous rays than those of the holotype (27 vs. 21). The original description might not include all rays because some rays may have been decalcified when preserved in formaldehyde.

Allips concolor was originally described as a new monotypic genus by McCosker (1972), based on a single specimen collected from the mouth of the Pakehan River, north of Ban Parknam Ranong, Thailand of Andaman Sea. McCosker et al. (2006) reported the species based on three specimens collected from off Northern Territory (CAS 235270). However, few data were provided. The present specimen from Taiwan is the first record from the South China Sea, as well as the northwestern Pacific Ocean. It is possible that A. concolor is more widespread in the Indo-west Pacific Ocean.

McCosker (per. comm., 2018) provided data of holotype and two additional specimens from Australia, the later have vertebral formula 24-93-170 and 21-92-168, respectively. Compared to these specimens, ours has somewhat more preanal and total vertebrae. We provisionally recognize our specimen as Allips concolor and call attention that this may be a different species.

McCosker (1972) described the lateral-line pores of the holotype as impossible to discern because of their reduced state and an overlying waxy precipitate. Based on our removal of the waxy musoca the lateral-line pores appear to be developed similarly to other related ophichthids ( Fig. 2B ). In addition, the lateral-line canal of this species is well developed except for a short distance (8.7 mm) at the tail end of the fish.

Allips concolor has considerable waxy musoca for an ophichthid. The strong musoca and elongate body is similar to that of the Moringuidae , and may be an adaptation for muddy estuary environments.

Figures

FIGURE 1. Allips concolor McCosker, 1972, NMMB-P27884, 392 mm TL. A̅B. fresh condition. C. preserved condition.

FIGURE 2. Allips concolor McCosker, 1972, NMMB-P27884, 392 mm TL. A. radiography of head, arrows point the branchiostegal rays (27 in total). B. closed view of head, after mucosa removed and stained by cyanin-blue. Arrows pointed lateral-line pores. B. head pores. D. upper jaw teeth, anterior to right. Go= gill opening. AN=anterior nostril.