Ariosoma indicum sp. nov., a new species of congrid eel (Anguilliformes: Congridae: Bathymyrinae) from the Indian waters.

Ariosoma indicum sp. nov. is described herein based on 12 specimens [(335-433 mm total length (TL)] collected off the Arabian Sea of southwest coast of India and 7 specimens from Digha Mohana, off the Bay of Bengal of northeast coast of India. The new species is distinguished from congeners in having the following combination of the characters: anus positioned anterior to middle of total length, pre-anal length 40.0%-43.1% of TL; short wedge-shaped pointed vomerine teeth patch, three or four rows in anterior portion, tapering posteriorly with four uniserial teeth; supraorbital canal with four or five pores; pre-dorsal vertebrae 9-10; pre-anal vertebrae 49-53; total vertebrae 141-146; body greenish-brown in colour; extremities of the lower jaw with minute dark pigmentation patches before the rictus, bicoloured pectoral fin. A. indicum shares few characters with the Indian water species, Ariosoma gnanadossi, but readily differs from the latter in having more pre-anal vertebrae (49-53 vs. 47 in A. gnanadossi); fewer lateral-line pores (130-137 vs. 145); shorter tail (54.9%-57.9% TL vs. 60.1% TL); smaller eye (15.1%-17.7% HL vs. 19.2% HL); smaller interorbital width (11.8%-15.7% HL vs. 18.2% HL); longer upper jaw (26.9%-30.2% HL vs. 19.2% HL). In addition, molecular analysis using partial mitochondrial COI gene suggests that A. indicum is genetically closer to Ariosoma maurostigma and Ariosoma melanospilos with a divergence of 15.0% and 15.8%, respectively, and forms a well-supported monophyletic clade.