Gnathophis ajithi, Kodeeswaran & Karmovskaya, 2025

Kodeeswaran, Paramasivam & Karmovskaya, Emma S., 2025, Three new species of the congrid eel genus Gnathophis (Anguilliformes: Congridae) from the Arabian Sea, Zootaxa 5725 (1), pp. 89-105 : 90-96

Gnathophis ajithi sp. nov.

( Figures 1 , 2 , 3A , 4A , Table 1)

Holotype. IO /OV/ ANG/00054 , 343 mm TL, off Kollam , India, Arabian Sea ( 8° 57’ N; 75° 33’ E), 450 m depth, bottom trawl, P. Kodeeswaran, 16 January 2024.

Paratypes. Five specimens, 347–484 mm TL: IO / OV/ ANG/00057 , 410–415 , 2 specimens, collected together with the holotype; ZSI/ EBRC / F 18778, 347 mm TL, 1 specimen, off Kollam , India, Arabian Sea ( 8° 40’ N; 75° 32’ E), 264 m depth, bottom trawl, P. Kodeeswaran, 16 January 2024; ZSI/ EBRC / F 18777, 435 mm TL, 1 specimen, off Mangalore, India, Arabian Sea ( 12°36’ N 74°12’ E), 350 m depth, bottom trawl, P. Kodeeswaran, 16 January 2024; ZSI/ EBRC / F 18779 , 484 mm TL, 1 specimen, collected together with the holotype.

Diagnosis. A moderate size species of the genus Gnathophis differs from its congeners in having the following combination of characters: elevated pores above adpressed pectoral fin; small eye, 15.7–17.7% HL; lateral-line pores before anus 27–33; total vertebrae 124 (122–126); vertebrae formula: 8–10/28–34/33–38/122–126; stomach grey to black.

Description. Measurements in percentage of TL and HL, and counts data are given in Table 1. Body moderately elongate, anterior portion cylindrical in cross section, following posterior portion more compressed; tail tip somewhat attenuate; anus just anterior to mid-body length, length 2.6 (2.3–2.7) times in TL. Dorsal-fin origin at level of slightly in front of mid-length of pectoral fin length, confluent with caudal and anal fins. Anal-fin origin just behind anus. Pectoral fin well-developed with narrow base and pointed distally. Gill opening smaller than eye diameter, upper end of gill opening just below at lower edge of pectoral-fin base. Interbranchial much broader than gill opening and eye.

Head large, in comparison with less slender body, deepest at gill opening; snout moderate and not much pointed, length 1.5 (1.4–1.7) times eye diameter, slightly projecting beyond lower jaw; lower jaw longer than snout; fleshy tip of snout projecting anteriorly beyond intermaxillary tooth patch; rictus just anterior to mid-eye. Tubular anterior nostril at tip of snout, directed ventrally. Elliptical posterior nostril in front of mid-eye level, with a slightly raised rim.

Lateral-line pores complete, visible in front of anus, anterior part of lateral-line canal convex dorsally and curves smoothly downwards over the base of the pectoral fin, 2 nd and 7 th –8 th through 13 th –15 th pores elevated.

Head pores small; SO pores 6, the first (ethmoidal) pore and the second on ventral tip of snout, the third on dorsal side of snout, the fourth pore slightly larger just behind the third, the fifth above and anterior of eye and the sixth above and posterior edge of eye. IO pores 8, the first 4 pores along upper lip, the fifth behind rictus; 3 behind eye. Mandibular pores 7, six before rictus, and one after rictus; PO pores 2. ST pores 3.

Teeth small, pointed to blunt and curved backwards. Intermaxillary teeth in about 5 to 6 transverse rows with backward-curved teeth, connected to maxillary and vomerine teeth, anterior portion slightly exposed when mouth closed. Maxillary teeth in bands, anteriorly with 5 rows of pointed teeth, middle portion with 2 rows, inner teeth blunt and outer teeth pointed, posterior portion narrower with single row. Vomerine teeth blunt, form a long-elongated patch, in about 4 transverse rows, and terminate with two teeth posteriorly. Mandibular teeth in bands, anterior portion with 3–4 rows, and narrow posterior portion.

Swimbladder extends slightly beyond anus and stomach does not reach anus.

Colouration. Live colouration. Body dorsally olive-greenish and belly silvery-white. Bright silvery band runs parallel to and below lateral-line pores after anus, which becomes pale brownish posteriorly. Melanophores, pigment traces of leptocephalus, on ventral side of body from gill opening to tail tip, dense, tapering posteriorly. Dorsal and anal fins milky white with dark margin. Caudal fin dark and tail tip white. Pectoral fin translucent with greenish to dark patches at base and dorsal margin. Head slightly darker than body. Snout tip lime green, then a little darker. Back of head brownish-dark, supratemporal commissure lighter. Stomach grey to black and peritoneum slivery. Dorsal and ventral of lateral-line pores whitish. Gill-opening white. Eyes bright with dark pupil surrounded by golden iris. Colouration after preservation. Body becomes paler than fresh. Pectoral fin translucent.

Size. The largest specimen examined is 484 mm TL.

Distribution. Indian Ocean: off Kerala and off Karnataka, Arabian Sea. Known only from type specimens collected at depths of 264– 450 m.

Etymology. The species name ajithi is given in honor of the Indian marine biologist and Ph.D. guide of the first author, T. T. Ajith Kumar for his enormous contribution to marine biodiversity and conservation of marine livings.

Remarks. This species is similar to Australian species Gnathophis grahami Karmovskaya & Paxton, 2000 by having elevated lateral-line pores above adpressed pectoral fin, overlapping vertebral counts, but readily differs in having fewer precaudal vertebrae (33–38 vs. 38–43 in G. grahami ), fewer POM pores (7+2 vs. 8+3), smaller eye (15.7–17.7% HL and 58.6–70.4% SnL vs. 20.2–26.9% HL and 70.4–87.8% SnL). This species also has a similar total number of vertebrae and lateral-line preanal pores to Pacific species Gnathophis heterognathos ( Bleeker, 1858) but is easily distinguished by its smaller eye size (15.7–17.7% HL vs. 18.5–26.7% HL), larger head (18.0–19.1% TL vs. 17.3–17.6% TL), longer predorsal length (19.4–20.7% TL vs. 17.7–18.9% TL), colour of peritoneum (silvery vs. pale with pigmented).

It is distinguished from such species as Gnathophis asanoi Karmovskaya, 2004 , Gnathophis bracheatopos Smith & Kanazawa, 1977 , Gnathophis capensis ( Kaup, 1856) , Gnathophis ginanago ( Asano, 1958) , Gnathophis habenatus (Richardson, 1848) , Gnathophis leptosomatus Karrer, 1983 , Gnathophis longicauda ( Ramsay & Ogilby, 1888) , Gnathophis neocaledoniensis Karmovskaya, 2004 , Gnathophis parini Karmovskaya, 1990 , and Gnathophis umbrellabius ( Whitley, 1948) in having elevated lateral-line pores above pectoral fin (vs. not elevated in the species mentioned above).

Gnathophis ajithi differs from the species such as Gnathophis andriashevi Karmovskaya, 1990 , Gnathophis bathytopos Smith & Kanazawa, 1977 , Gnathophis castlei Karmovskaya & Paxton, 2000 , Gnathophis codoniphorus Maul, 1972 , Gnathophis johnsoni Prokofiev et al. 2025 , Gnathophis mystax ( Delaroche, 1809) , Gnathophis tritos Smith & Kanazawa, 1977 , and Gnathophis xenica ( Matsubara & Ochiai, 1951) in having fewer total vertebrae (122–126 vs. 131–142 in G. andriashevi , 128–133 in G. bathytopos , 126–133 in G. castlei , 144 in G. codoniphorus , 130–134 in G. johnsoni , 134–141 in G. mystax , 136–138 in G. tritos , 151–157 in G. xenica ). And the new species has more total number of vertebrae than Gnathophis heterolinea ( Kotthaus, 1968) (122–126 vs. 120 in latter). Gnathophis ajithi differs from Gnathophis smithi Karmovskaya, 1990 , in having fewer total vertebrae (122–126 vs. 127–135 in G. smithi ), fewer precaudal vertebrae (33–38 vs. 44–47), fewer POM pores (7+2 vs. 8+3), smaller eye (15.7–17.7% HL vs. 19.9–25.1% HL), colour of peritoneum (silver vs. black).

Further, Gnathophis ajithi differs from Australian species ( Karmovskaya & Paxton 2000) such as Gnathophis macroporis in having fewer precaudal vertebrae (33–38 vs. 43–48), fewer POM pores (7+2 vs. 8+3), smaller eye (15.7–17.7% HL vs. 22.2–28.1% HL) and from Gnathophis melanocoelus in having fewer POM pores (7+2 vs. 8+3), smaller eye (15.7–17.7% HL vs. 22.5–25.6% HL), and from Gnathophis microps in having fewer precaudal vertebrae (33–38 vs. 39–41), fewer POM pores (7+2 vs. 8+2), shorter snout length (24.5–26.8% HL vs. 27.1–29.2% HL), swimbladder extends slightly beyond anus (vs. close to anus) and from Gnathophis nasutus in having smaller eye (15.7–17.7% HL vs. 18.6–27.1% HL), longer trunk (19.7–24.4% TL vs. 15.1–18.8% TL), head shorter than trunk, HL 74.7–96.1% PAL (vs. head longer than trunk, HL 102.6–129.6 % PAL), fewer POM pores (7+2 vs. 8+2), swimbladder extends slightly beyond anus (vs. end at anus or slightly beyond).

Figures

FIGURE 1. Holotype of Gnathophis ajithi sp. nov., IO/OV/ANG/00054, 343 mm TL, off Kerala, Arabian Sea, India. Bar indicates dorsal-fin origin.

FIGURE 2. Head of Gnathophis ajithi sp. nov., IO/OV/ANG/00054, holotype. A. Lateral view; B. Dorsal view; C. ventral view.

FIGURE 3. Lateral view of head, showing sensory pores. A. Gnathophis ajithi; B. Gnathophis anilmohapatrai; Gnathophis arabicus. SO, supraorbital pores; IO, infraorbital pores; M, mandibular pores; PO, preoperculomandibular pores; ST, supratemporal pores.

FIGURE 4. Tooth pattern on upper jaw. A. Gnathophis ajithi; B. Gnathophis anilmohapatrai; C. Gnathophis arabicus.