Physiculus lakshadeepa, Idrees Babu & Ho & Mariyambi & Sureshkumar, 2022

Idrees Babu, K. K., Ho, Hsaun-Ching, Mariyambi, P. C. & Sureshkumar, S., 2022, Two new species of the codling fish genus Physiculus from Lakshadweep, India (Gadiformes: Moridae), Zootaxa 5104 (1), pp. 111-124 : 115-118

Physiculus lakshadeepa sp. nov.

Common name: Lakshadweep codling

Figs. 3‒5 , Table 1

Holotype. MTRLDST 00112, 164 mm SL, 192 mm TL, India, Lakshadweep, East Coast of Kavaratti Island , 10°33’49.9”N, 72°39’4.0”E, from 350 m depth, 9 April 2018.

Paratypes. MTRLDST 00113, 125 mm SL, 143 mm TL; MTRLDST 00114, 183 mm SL, 224 mm TL; both collected with holotype.

Etymology. The specific name is derived from the type locality, Lakshadweep.

Diagnosis. A species of Physiculus with light organ situated at about the middle of pelvic-fin base and anus; light organ small, anus rather forward in position, closer to the light organ; gular region smooth without scales; Physiculus lakshadeepa differs from the Indian congeners in having relatively high first dorsal fin, with first ray filamentous, except for that of P. capensis , P. beckeri and P. roseus ; P. lakshadeepa differs from P. capensis in having scales on snout (vs snout smooth) and teeth in equally sized (vs in graded series); from P. beckeri in having 84‒95 scales in longitudinal series (vs 115‒130) and less tall first dorsal fin; and from P. roseus in having fewer second dorsal-fin rays and more gill rakers. Compared with the other species in the Pacific Ocean, P. lakshadeepa resembles only P. chigodarana , which has the first dorsal fin distinctly higher than the second. However, P. lakshadeepa differs from the latter in lacking gular scales (vs present in P. chigodarana ), fewer second dorsal-fin rays; fewer anal fin rays; light organ situated rather backward; anus situated rather backward (InV-An 41.7‒58.2% InV-af vs 38.7‒43.7%); more gill rackers, and fewer vertebrae.

Description. The morphometric data given in Table 1 is for the holotype, followed by the range of measurements from the paratypes in parentheses, except when otherwise indicated. Body slender and long, compressed posteriorly; head moderately small, depressed anteriorly; eye large 24.7% (19.1‒28.5%) in HL; interorbital space broad, 30.1% (25.4‒30.7%) in HL; snout broad and rounded, length 24.7% (24.7‒25.9%) in HL, protruding slightly beyond the upper jaw. Mouth large, gape extending to a vertical through posterior margin of eye, teeth small, equally sized; vomerine and palatine toothless. Barbel on chin much shorter than orbit diameter, length 7.5% (3.2‒11.6­%) in HL.

Gill rakers on the first gill arch small, varying from spinous tubercles to small clubs, spinous initially at tips and progressively more spinous towards the angle on lower branch and spinous at tips on the upper branch. Abdominal cavity reaching the 13th pterygiophore of the anal fin.

Scales small and deciduous, 90 (84‒95) in longitudinal series; 7 (6­‒7) scale rows between the first dorsal-fin base and lateral line. Cycloid scales cover the head and body, except for the branchiostegal membrane and the gular region are completely scaleless. Continuous tube of lateral line reaching 10th ray of the second dorsal fin, followed by discontinuous short tubes on the lateral line reaching caudal peduncle. Caudal fin rounded and fan-shaped, well separated from dorsal and anal fins. Caudal peduncle short than orbit diameter, its length 17.1% (17.1‒19.7%) HL.

First dorsal fin higher than second, first dorsal-fin ray elongated and filamentous, its length 6­2.8% HL (51.7% in 1 paratype and broken in another one). A very small gap separates the first from the second dorsal fins. Origin of first dorsal fin slightly behind a vertical through the pectoral-fin base; the origin of the second dorsal fin at a vertical through 4th anal-fin ray. Pelvic fin slender, two outermost rays slightly filamentous, extending to 7th ray of the anal fin. The pectoral fin extends up to the 7th ray of the second dorsal fin.

Ventral light organ small in size, externally prominent as a circular scale less fossa in advance of the anus, its diameter 6­.0% (6­.0‒9.6­%) InV-af; distance from inter ventral line to anterior margin of light organ 29.0% (24.4‒ 29.0%) InV-af; distance from posterior margin of the light organ to anterior margin of anus 22.6­% (17.4‒22.6­%) InV-af, and distance from inter ventral line to anterior margin of anus 58.2% (41.7‒58.2%) InV-af.

Vertebrae: 12 (11‒12) precaudal, 37 (37‒38) caudal, and 49 (49) in total.

Colouration. When fresh, head and body dark brown, slightly reddish on tail, caudal fin base dark brown and abdomen silvery blue. Branchiostegal membranes black; first dorsal fin pink, with broad black margin; second dorsal fin pink, gradually becoming red posteriorly, with narrow black margin; pectoral fin red with black base; pelvic fin dark brown; anal fin red with black margin; caudal fin deep red with posterior third black. Colour when preserved, head and body light brown and abdomen silvery.

Figures

FIGURE 3. Physiculus lakshadeepa sp. nov., holotype, MTRLDST 00112, preserved. A. Lateral view. B. Ventral of the abdomen. C. Radiograph.

FIGURE 4. Physiculus lakshadeepa sp. nov., paratype, MTRLDST 00113, preserved. A. Lateral view. B. ventral view of abdomen. C. Radiograph.

FIGURE 5. Physiculus lakshadeepa sp. nov., fresh condition, from the holotype???. A. Lateral view of anterior body, fresh condition. B. Close-up of high first dorsal fin with first ray filamentous. C. Ventral view of abdomen showing the pelvic-fin base, light organ and anus.