Rhynchoconger randalli, Acharya & Mohanty & Ray & Mishra & Mohapatra, 2022

Acharya, Smrutirekha, Mohanty, Swarup Ranjan, Ray, Dipanjan, Mishra, Subhrendu Sekhar & Mohapatra, Anil, 2022, A new congrid eel, Rhynchoconger randalli sp. nov. (Congridae: Anguilliformes) with a pentagonal pattern of vomer dentition from the Bay of Bengal, Indian waters, Zootaxa 5174 (2), pp. 188-194 : 189-192

Rhynchoconger randalli sp. nov.

Proposed common name: Randall’s conger eel

( Figures 1–4 , Table 1 )

Holotype. EBRC /ZSI/F13832 (596+ mm TL), Paradeep fish landing centre, Odisha, India, depth of capture: 36–40 m, date of collection: 3 Nov. 2021

Paratype. EBRC /ZSI/F13833, 1 (599+ mm TL), Paradeep fish landing centre, Odisha, India, depth of capture: 36–40 m, date of collection: 3 Nov. 2021

Diagnosis. A species of the genus Rhynchoconger clearly distinguished from other congeners in having the following combination of characters: distinct pentagonal vomerine tooth patch ( Figs. 3–4 ); posterior tip of vomer clearly ends with single tooth before anterior level of eye; vomerine tooth patch with 48–52 teeth in 8–9 rows; ethmovomerine tooth patch with 60–64 teeth in 7–8 rows; posterior margin of eye just before rictus; dorsal-fin origin slightly anterior to level of gill opening; predorsal vertebrae 7–8; preanal vertebrae 29–31; dorsal-fin rays before vent 44–47; peritoneum and stomach colour pale.

Description. A long conger eel of the genus Rhynchoconger with reduced tail tip. Body compressed gradually towards tail ( Fig. 1 ). Dorsal-fin origin slightly anterior to level of gill opening. Posterior margin of eye just before rictus. Width and depth of body at gill opening comparatively larger than those at anus. Head comparatively shorter than trunk (92.63–93.68 % of trunk length). Preanal length (PAL) 3.25 times in TL. Eye diameter 7.73–8 in head length (HL). Snout length 4.63‒4.68 in HL. Elongated pectoral fin (13.66‒13.59% PAL; Table 1 ). Anterior nostril tubular on ventrolateral side of snout tip, posterior nostril oval in front of mid-eye. Upper jaw clearly extends beyond tip of lower jaw. Upper jaw with unique pentagon-shaped vomerine tooth patch with pointed posterior end. Ethmovomerine teeth remain uncovered when mouth closed. Ethmovomerine tooth patch broader than long, with 60–64 blunt and granular to conical teeth arranged in 7–8 irregular rows, vomerine tooth patch is longer than broad, with 38–52 teeth arranged in 8–9 rows. Vomer, ethmovomerine, and maxilla clearly separated by narrow space from each other. Jaw and vomerine teeth comparatively smaller than ethmovomerine teeth. Maxillary and mandibular teeth mostly conical and blunt, some granular, starting with 5–6 rows anteriorly and narrowing down to 1–2 rows posteriorly ( Figs. 3–4 ).

Arrangements of head pores: 3 supraorbital pores, 2 pores present on anterior end of snout and comparatively larger 3 rd pore on dorsal side of anterior snout end; 5 infraorbital pores, 1 st pore present on posterior dorsal side end of anterior nostril, along upper half of upper lip, 2 nd –4 th pores visible on head, and 5 th pore behind rictus; no frontal pore; 7+3 preoperculo-mandibular pores, first two very small pores close to each other among 7 pores along lower jaw, located at end of underside of lower jaw, 6 th pore behind rictus, and 7 th pore situated next to rictal pore, 3 preopercular pores, all preopercular pores comparatively larger than mandibular pores ( Fig. 2 ). Lateral-line pores: 7 predorsal pores, 8 prepectoral pores; 29 (29–31) preanal pores; 125+ (not visible to count after 125) total lateral-line pores. Vertebrae: 8 predorsal vertebrae, 29–31 preanal vertebrae, 125+–136+ total vertebrae.

Colour. When fresh, body slightly reddish brown dorsally and pale white ventrally with a silvery streak along the body near the lateral line. From posterior margin of eye to gill opening, a bright silvery patch is observed. The dorsal fin has a black margin from anterior part to posterior end, but the anterior one third portion of anal fin is pale in colour and the rest has a black margin. Pectoral fin pale. Peritoneum and stomach colour pale.

After preservation, the basic pattern of colour remains same. The reddish brown colour turns to faint brown colour in preserved specimen.

Distribution. Collected from the northern part of the Bay of Bengal, Paradeep, Odisha, India.

Etymology. The new species is named in the honour of the renowned ichthyologist John Ernest Randall ( USA), posthumously.

Figures

FIGURE 1. Rhynchoconger randalli sp. nov., holotype, EBRC/ZSI/F13832.

FIGURE 2. Arrangement of sensory pores and anterior lateral-line pores of Rhynchoconger randalli sp. nov., from holotype.

FIGURE 3. Microscopic picture of teeth on upper jaw of Rhynchoconger randalli sp. nov., from holotype.

FIGURE 4. Schematic diagram of teeth on upper jaw of Rhynchoconger randalli sp. nov., from holotype.