Gymnothorax tamilnaduensis, Kodeeswaran & Kantharajan & Mohapatra & Ajith Kumar & Kumar Sarkar, 2023

Kodeeswaran, Paramasivam, Kantharajan, Ganesan, Mohapatra, Anil, Ajith Kumar, T. T. & Kumar Sarkar, Uttam, 2023, A new short brown unpatterned moray eel (Anguilliformes, Muraenidae) from the southeast coast of India, Bay of Bengal, Zoosystematics and Evolution 99 (1), pp. 253-260 : 253

Gymnothorax tamilnaduensis sp. nov.

Figs 2 , 3 , 4 , 5

Type material.

The holotype and paratype specimens are deposited at the National Fish Repository of the ICAR-National Bureau of Fish Genetic Resources (Ministry of Agriculture and Farmers Welfare, Govt. of India). Holotype. NBFGR/MURGTAM (487 mm TL), collected from trawl landings at Mudasalodai fish landing centre, off Cuddalore coast, Bay of Bengal, 11°29'N, 79°46'E, 26 June 2022, coll. by G. Kantharajan and P. Kodeeswaran.

Paratypes. Three specimens, NBFGR/ MURGTAM.2 (296 mm TL); EBRC/ ZSI/F14687 (2: 272-451 mm TL), were collected along with the holotype.

Diagnosis.

A new species of a short brown unpatterned moray eel with the following combination of characters: series of lines of small dark spots present on head and a single line of black spots on mid-line of body, origin of dorsal fin at middle of rictus and gill opening, anus just before mid-body, pre-anal length 45.7-47.4% TL, snout blunt and very short, 6.5-7.7 mm in HL, eye small, teeth serrated, uniserial, ethomovomerine teeth five on each side with one tooth on mid-point, vomerine with eight teeth in a series, jaw pores with white rim, anal-fin margin whitish, 3 pre-dorsal vertebrae, 56-59 pre-anal vertebrae, 139-150 total vertebrae.

Description

(all measurements in mm). A medium-sized, moderately elongated eel with tapering body, anus just before mid-body, pre-anal length 45.7-47.4% TL, depth at gill opening 19.8-32.8 in TL, depth at anus 31.1-49.0 in TL. Head moderate, 7.8-8.2 in TL, snout blunt, and very short, 6.5-7.7 in HL, both jaws almost equal, upper jaw 2.5-3.0 in HL, lower jaw 2.4-2.8 in HL, eye small, 9.1-12.2 in HL, at middle of upper jaw, far from rictus, interorbital space 7.0-12.6 in HL. Dorsal-fin origin before gill opening, at mid-length of rictus and gill opening, pre-dorsal length 9.3-11.0 in TL, anal fin starts just after anus, gill opening a minute diagonal slit, 8.0-11.3 in HL. Teeth serrated, uniserial; five pointed ethomovomerine teeth on each side, one tooth on mid-point, three median ethomovomerine teeth, middle tooth larger than other two, maxillary teeth uniserial, 12-13 on each side, uniserial vomerine with eight teeth; lower jaw teeth uniserial, 16-17 teeth on each side, three anterior teeth enlarged (Fig. 3 ). Head pores moderate-sized, three supraorbital pores, four infraorbital pores, six mandibular pores before rictus, cephalic pores in white rims. Branchial pores two behind the dorsal-fin origin (Fig. 4 ). Three pre-dorsal vertebrae, 56-59 pre-anal vertebrae, 139-150 total vertebrae.

Counts and measurements of the holotype in mm: TL 487.8, pre-anal length 223.1, tail length 260.7, trunk length 155, pre-dorsal length 44.4, head length 59.6, depth at anus 15.7, width at anus 12.3, snout length 9.2, eye diameter 5.7, upper jaw length 23.9, interorbital width 8.5, gill opening 6.8. Vertebral formula 3-59-150.

Colouration.

In fresh condition, body uniform chocolate brown, head with numerous line marks, ventral-most portion of lower body pale, dorsal fin brown, dorsal-fin margin black, anal-fin margin whitish, head pores with white rim, series of small dark spots forming several lines on head and a single line of black spot-on mid-line of body (Fig. 2 ). After preservation, body tanned, series of small dark spot lines remain the same in the head and body (Fig. 5 ).

Distribution.

Indian Ocean: off Cuddalore Coast, Bay of Bengal, southeast coast of India. The species were collected at a depth of about 25-30 metres.

Etymology.

The species is named " tamilnaduensis " with reference to the state Tamil Nadu from where it was collected.

Remarks.

The brown unpatterned groups of morays were divided into two groups by Böhlke (1997, 2000): the long brown unpatterned morays (> 150 vertebrae) and the short brown unpatterned morays (<150 vertebrae). The species described herein comes under the short brown unpatterned moray. From Indian waters, only three species of short brown unpatterned morays have been described to date ( Mohapatra et al. 2019). All three short brown unpatterned morays reported from India have smooth teeth, and the new species clearly differs from all three species in having serrated teeth. The new species differs from all the Indian water short brown morays by having jaw pores with white rim (vs. black in G. andamanensis , brown in G. mishrai and dark in G. odishi ); having more total vertebrae (139-150 vs. 135-136 in G. andamanensis , 134 in G. mishrai and 133-138 in G. odishi ); smaller snout (6.5-7.4 in HL vs. 4.4 in G. andamanensis , 6.5 in G. mishrai , 4.3-5.4 in G. odishi ); having a distinct series of lines of small dark spots present on head and a single line of black spot on the mid-line of the body (vs. absent in all the other species).

The new species shares serrate teeth with Gymnothorax atolli (Pietschmann, 1935), G. australicola Lavenberg 1992, G. panamensis (Steindachner, 1876) and G. pindae Smith 1962, but the new species differs from the species mentioned above by having more total vertebrae (139-150 vs. 127-133 in G. atolli , 122-137 in G. panamensis and 110-124 in G. pindae ), fewer predorsal vertebrae (3 vs. 4-6 in G. atolli , 5-6 in G. australicola , 8-12 in G. panamensis and 5-7 in G. pindae ) and uniserial maxillary teeth (vs. biserial in G. atolli , G. australicola and G. panamensis ).

Further, the new species differs from the other unpatterned morays, such as Gymnothorax herrei Beebe & Tee-Van, 1933, G. kontodontos Böhlke, 2000, G. microstictus Böhlke, 2000 and G. pseudoherrei Böhlke, 2000 by having serrate teeth (vs. smooth in all the remaining species); more total vertebrae (139-150 vs. 108-122 in G. herrei , 126-135 in G. kontodontos , 113-121 in G. microstictus , 110-118 in G. pseudoherrei ); more pre-anal vertebrae (56-59 vs. 45-50 in G. herrei , 40-43 in G. kontodontos , 40-44 in G. microstictus , 44-50 in G. pseudoherrei ) (Table 2 ).

Molecular analysis.

Based on the 16s rRNA gene sequences, the new species exhibits 8.0% genetic divergence with G. reticularis sequences in the Kimura 2 parameter. Further, the new species exhibits 10.1% genetic divergence with G. sagmacephalus , followed by G. albimarginatus by 11.2%-12.1%, G. castaneus (11.9%) and G. pictus (12.6%). The Maximum Likelihood tree (Fig. 6 ) shows the new species forms a strongly distinct clade from the congeners with a high bootstrap value supporting the status as a new species.

Figures

Figure 2. Gymnothorax tamilnaduensis sp. nov. holotype, NBFGR / MURGTAM, 487.8 mm TL, fresh colouration, collected from Mudasalodai fish landing centre, off Cuddalore, Bay of Bengal.

Figure 3. Dentition pattern on upper jaw and lower jaw of Gymnothorax tamilnaduensis sp. nov (holotype).

Figure 4. Lateral view of head and cephalic pores of Gymnothorax tamilnaduensis sp. nov. (holotype, NBFGR / MURGTAM). Supraorbital pores (SO) - Blue closed dots, Infraorbital pores (IO) - Green, Mandibular pores (M) - Red, Branchial pores (B) - Black; DFO - dorsal-fin origin, PN - Posterior nostril, AN - Anterior nostril, GO - Gill opening.

Figure 5. Gymnothorax tamilnaduensis sp. nov. holotype, NBFGR / MURGTAM, 487.8 mm TL preserved colouration.

Figure 6. The Maximum Likelihood tree of the genus Gymnothorax plotted with a model of HKY + G + I with 1000 bootstrap replicates, based on 16 s rRNA sequences (500 bp). Each node represents branch support values.