Gymnothorax indicus, Mohapatra, Anil, Ray, Dipanjan, Smith, David G. & Mishra, Subhrendu Sekhar, 2016

Mohapatra, Anil, Ray, Dipanjan, Smith, David G. & Mishra, Subhrendu Sekhar, 2016, A new species of elongate unpatterned moray eel of the genus Gymnothorax (Muraenidae: Muraeninae) from the Bay of Bengal, Zootaxa 4150 (5), pp. 591-598 : 592-597

Gymnothorax indicus sp. nov.

Figs. 1−3 , Tables 1−3

Proposed common name: Indian unpatterned moray

Holotype. ZSIF 11370 /2 (355 mm), Shankarpur , West Bengal, India (Trawling Site 21 ̊06.55 'N, 87 ̊58.68 'E), 22 December 2014.

Paratypes. MARC/ZSI/F4412 (305 mm), MARC/ZSI/F4413 (335 mm) and ZSI F 11371/2 (310 mm), collection details same as for holotype.

Diagnosis. This species belongs to the elongate, brown unpatterned group of moray eels which share the following combination of characters: anus at about mid-point of body; snout blunt and short; eyes comparatively large and slightly closer to rictus than to tip of snout; dorsal-fin margin black; 5 mandibular pores; maxillary teeth uniserial, sharply pointed; MVF: 9-79-194.

Description. Proportions of TL: preanal length 2.0, predorsal length 10.1–10.6, head length 8.0–8.9, depth at gill opening 23.5–23.7, depth at anus 30.5–32.2. In head length: snout 8.1–8.7, horizontal eye diameter 6.9–9.1, upper jaw length 4.2–4.8. Vertebrae: predorsal 9, preanal 79, total 194.

Body slender, elongate and tapering, anus at about midpoint. Dorsal and anal fins continuous with caudal fin around tail tip; dorsal-fin origin before gill opening, anal-fin origin immediately behind anus; pectoral and pelvic fins absent. Head long, snout blunt and short, eye relatively large, lower jaw slightly shorter than upper. Anterior nostril tubular and long, nearly reaching the tip of snout. Posterior nostril a simple round pore, situated above and behind anterior margin of eye. Gill opening a small slit on side below mid-line. Branchial pores 3, anterior to gill opening, two of which are before dorsal-fin origin; no lateral-line pores on body. Supraorbital pores 3: first (ethmoidal) near tip of snout just above lip, second above base of anterior nostril, third on snout between anterior and posterior nostrils. Infraorbital pores 4: first just behind base of anterior nostril, second on upper lip about midway between anterior nostril and anterior edge of eye, third below anterior margin of eye, fourth below posterior margin of eye. Mandibular pores 5, all before rictus.

Teeth in jaws smooth, sharply pointed, not greatly enlarged, needle-like and depressible; intermaxillary teeth in a single outer series, about 6 (7) on each side, the anterior tooth on each side enlarged and fang-like; no median teeth; maxillary teeth uniserial, about 14–16 on each side; vomerine teeth 8, uniserial; dentary teeth uniserial, 19– 20.

Colour. When fresh, body uniformly pale brown without spots or patterns; margin of dorsal and anal fins dark; eye rim pale. On preservation, colour faded from brown to light brown.

Distribution. The species is currently known only from the West Bengal coast of India in the northern Bay of Bengal.

Etymology. The species is named with reference to the country ‘India’, from within the Exclusive Economic Zone of which the specimens were captured by a trawler.

Discussion. Böhlke (1997) reviewed the taxonomy of eight species of elongate unpatterned morays known from the Indo-Pacific region: Gymnothorax albimarginatus , ‘G’. dorsalis , G. phasmatodes , G. prolatus , G. sagmacephalus , G. verrilli , Pseudechidna brummeri and Strophidon sathete . Böhlke & Randall (2000) described another elongate unpatterned moray, Gymnothorax polyspondylus , from Hawaii based on a single specimen. Later Loh et al. (2011) described another species Gymnothorax melanosomatus , with a key for nine species of elongate morays excluding G. verrilli . Loh et al. (2015) added another new species, Gymnothorax pseudomelanosomatus , to this group. The new species described herein brings the total to twelve species of elongate unpatterned moray eel from the Indo-Pacific region. A comparison of characters of all twelve species is given in Table 2 and their comparative meristics of those from Indian waters are given in Table 3 .

Characters Gymnothorax G. albimarginatus G. melanosomatus G. phasmatodes G. prolatus G. polyspondylus

indicus sp. nov.

Vertebrae

……continued on the next page Continued.

Characters G.pseudo- G. sagmacephalus G. verrilli Strophidon dorsalis Strophidon sathete Pseudechidna melanosomatus brummeri

Vertebrae

Predorsal 5–7 6 ― 7 5 8 ― 9 8 ― 11 4 ― 7 anal 89 74 ― 78 71 ― 77 62 ― 65 73 ― 82 89 ― 98

Total 202–206 170 ― 176 170 ― 171 154 ― 163 186 ― 208 201 ― 214

Proportion in TL

Preanal length 2.01 ― 2.02 1.9 ― 2.0 2.0 ― 2.0 2.3 ― 2.4 2.3 ― 2.9 2.0 ― 2.3

Head length 11.2 ― 11.4 8.7 ― 10.3 9.4 ― 11 8.4 ― 9.3 8.5 ― 14 11 ― 16 Pseudechidna brummeri has an extremely elongate and slender body with body depth at gill opening about 40 or more in total length, comparable only to Strophidon sathete and Gymnothorax melanosomatus . Following Loh et al. (2015), here we consider ‘G’. dorsalis as Strophidon dorsalis , since the species has the anus located well before mid-body and the eye closer to the tip of the snout than to the rictus. In all other Indo-Pacific elongate, unpatterned eels of the genus Gymnothorax the preanal length lies within the range of 1.6–2.1 in total length. Further, eye diameter in Strophidon dorsalis , S. sathete and Pseudechidna brummeri is smaller in comparison to other Gymnothorax species of this group, at 12–24 in head length. The new species, Gymnothorax indicus , with preanal length 2.0 in TL, body depth at gill opening 23.4–23.7 in TL and eye diameter 6.9–9.1 in head length, is well differentiated from the other three species in the group.

Gymnothorax indicus differs from all other of elongate unpatterned species in having 5 mandibular pores (cf. 6 or 7 pores). Further, the presence of 14–16 maxillary teeth and 19–20 dentary teeth in the new species differentiates it from all other Gymnothorax species in the elongate unpatterned moray group except for G. prolatus , which can be distinguished in having biserial teeth (vs uniserial in G. i n d i c u s), shorter head, longer snout and longer upper jaw ( Table 2 ).

There are more predorsal vertebrae (9) in the new species compared to other species of elongate unpatterned Gymnothorax (4–8) and Pseudechidna (4–7). Although the number of predorsal vertebrae is within the range of Strophidon species, the total vertebrae and the preanal vertebra are higher in comparison to S. dorsalis and, apart from the other differences stated earlier, S. sathete has biserial teeth in the jaws and more teeth in the maxillary and outer dentary. Further, four infraorbital pores in the new species differentiates it from G. dorsalis . Uniserial maxillary teeth differentiate the new species from Gymnothorax melanostomatus , G. prolatus , Strophidon dorsalis , S. sathete and Pseudechidna brummeri .

Total vertebrae in Gymnothorax melanosomatus , G. polyspondylus , G. pseudomelanosomatus and Pseudechidna brummeri are always more than 200, while in G. phasmatodes , G. sagmacephalus , G. verrilli and Strophidon dorsalis they are considerably fewer. Gymnothorax prolatus has slightly fewer total vertebrae than the new species, G. i n d i c u s, and this character is overlapped only in G. albimarginatus and Strophidon sathete . But G. albimarginatus differs from the new species in having fewer predorsal vertebrae, more preanal vertebrae and greater preanal length ( Table 2 ).

The new species resembles G. phasmatodes in having a similar number of preanal vertebrae and proportionately similar preanal length, but the latter species has nostril and head pores with prominent white spots (white spots absent in G. indicus ), margin of dorsal fin whitish (dark in G. i n d i cu s) and fewer vertebrae. Further, it has a shorter head, longer upper jaw and longer snout ( Table 2 ).

Among the long unpatterned moray eels, distribution of G. verrilli is confined to Eastern Central Pacific , between Baja California and Panama . Two recently described species, G. melanosomatus and G. pseudomelanosomatus , are known from Taiwan and G. polyspondylus from Hawaii, whereas, G. sagmacephalus occurred between Taiwan and Japan . One species, G. albimarginatus , is known to have a wider distribution in Western and central Pacific only. Only three species, i.e., P. brummeri , S. sathete and G. phasmatodes , are known to have much wider distribution in the Indo-west Pacific region . Occurrence of G. prolatus , apart from its type locality Taiwan, was recorded very recently from northern Indian Ocean (Mohapatra et al., 2015) and S. dorsalis recorded from northern Bay of Bengal (Ray & Mohapatra, 2015) extending its known range westward from western Pacific. The new species, Gymnothorax indicus sp. nov., forms the sixth long unpatterned moray from Indian Ocean.

Figures

FIGURE 1. Gymnothorax indicus sp. nov. (Holotype: 355 mm TL). Pin denotes the origin of the dorsal and anal fins.

FIGURE 2. Lateral view of head and head pores of Gymnothorax indicus sp. nov. (AN: Anterior Nostril; SOP: Supra-orbital pores; PN: Posterior nostril; IOP: Inter-orbital Pores; MP: Mandibular Pores; BP: Branchial pores)

FIGURE 3. Dentition on upper jaw and lower jaw of Gymnothorax indicus sp. nov.

Tables

TABLE 2. Comparative characters of elongate un-patterned moray eels of Indo-Pacific region [based on Bohlke (1997), Bohlke & Randall (2000), Loh et al. (2011), Loh et al. 2015) and present study]

Predorsal 9	4 ― 7	4 ― 7	5 ― 7	6 ― 8	4
Pre anal 79	91 ― 94	105 ― 109	74 ― 80	79 ― 83	89
Total 194	184 ― 195	201 ― 211	160 ― 174	182 ― 187	233
Proportion in TL
Preanal length 2.0	1.7 ― 1.8	1.6 ― 1.8	1.7 ― 2.0	1.9 ― 2.0	2.3
Head length 8.0 ― 8.9	6.9 ― 9.1	9.5 ― 10.6	9.2 ― 11	10 ― 11	10.75
Depth at gill opening 23.5 ― 23.7	11 ― 25	27.1 ― 44.8	27 ― 31	29 ― 29	25
Depth at anus 30.5 ― 32.2	18 ― 32	35.9 ― 50.1	35 ― 48	28 ― 32	27.7
Proportion in HL
Upper jaw length 4.2 ― 4.8	2.7 ― 3.2	2.4 ― 3.1	3.0 ― 3.5	2.4 ― 2.9	2.6
Snout length 8.1 ― 8.7	5.6 ― 6.8	4.9 ― 6.7	5.2 ― 6.9	4.2 ― 5.0	4.4
Eye diameter 6.9 ― 9.1	9.2 ― 13	8.6 ― 12.1	7.5 ― 12.0	7.1 ― 11	9.9
Teeth
Intermaxillary 6 ― 7	6	6 ― 8	6 ― 7	6	6
Median 0	3	0 ― 3	3	1 ― 3	2
Maxillary inner 0	0	6 ― 8	0	4 ― 8	0
Maxillary outer 14 ― 16	7 ― 11	4 ― 7	7 ― 12	16-24	11
Vomerine 8	3 ― 5	0 ― 7	5 ― 10	3 ― 5	3
Dentary inner 0	0	0	4	4	0
Dentary outer 19 ― 20	10 ― 17	10 ― 12	9 ― 18	15 ― 19	11 ― 12
Cephalic pore
Branchial 3	2	2	2-3	2 ― 3	2
Supraorbital 1+2	1+2	1+2	1+2	1+2	1+2
Infraorbital 4	4	4	4	4	4
Mandibular 5	6	6	6-7	6-7	6

TABLE 3. Comparative account with other species from the same region.

Character TL in mm	G. indicus sp. G. prolatus (n = 4) nov. MARC/ZSI/F3707 305–355 303–366	S. dorsalis (n = 4) MARC/ZSI/ F3663 460–490	S. sathete (n = 1) (MARC/ZSI/F1947) 962 mm
Preanal length in TL Head length in TL Body depth at GO in TL	1.95–2.0 1.9–2.0 8.0–8.9 10.0–10.4 23.4–23.7 29.1–30.1	2.3–2.4 8.9–9.0 27.1–27.2	2.7 12.3 37.2
Body depth at anus in TL Upper jaw length in HL Snout length in HL	30.5–32.2 28.0–28.7 4.2–4.8 2.55–2.64 8.1–8.7 5.0–5.3	30.2–30.7 3.09–2.23 7.8–7.9	44.5 3.4 9.8
Eye diameter in HL Predorsal vertebrae Preanal vertebrae	6.9–9.1 7.5–7.9 9 8 79 82	12.2–12.8 9 62	19.2 10 81
Total vertebrae Predorsal % of TL	194 184 7.2–7.7 8.3–8.8	159 7.4–8.4	206 6.5