Eptatretus wadgensis, Augustina & Sreeram & Sukumaran & Jose, 2022

Augustina, Treasa, Sreeram, Miriam Paul, Sukumaran, Sandhya & Jose, Anjaly, 2022, A new species of six-gilled hagfish (Myxinidae: Eptatretus) from the Lakshadweep Sea, Zootaxa 5162 (2), pp. 120-134 : 122-125

publication ID	https://doi.org/ 10.11646/zootaxa.5162.2.2
publication LSID	lsid:zoobank.org:pub:58C2CCFF-56DA-4A1D-8A61-2E72930020BB
DOI	https://doi.org/10.5281/zenodo.6809920
persistent identifier	https://treatment.plazi.org/id/B29E4700-5C6A-47F8-B0FF-D6BF3D4FAD58
taxon LSID	lsid:zoobank.org:act:B29E4700-5C6A-47F8-B0FF-D6BF3D4FAD58
treatment provided by	Plazi
scientific name	Eptatretus wadgensis
status	sp. nov.

Treatment

Eptatretus wadgensis sp. nov.

(Common name: Wadge Bank hagfish)

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 , Table 1 View TABLE 1 )

Materials examined. Holotype. CMFRI DNR GC.1.1.1.1, 400 mm TL, female, Wadge Bank , Lakshadweep Sea, India, 7 ° 35 ΄ 14 ΄΄ N, 76 ° 45 ΄ 45 ΄΄ E, continental shelf, ~ 300 m, deep-sea bottom trawl, Jose Antony, 19 March 2021.

Paratypes. CMFRI DNR GC.1.1.1.2, 325 mm TL, female, Wadge Bank , Lakshadweep Sea, India, 7 ° 27 ΄ 35 ΄΄ N, 77 ° 56 ΄ 01 ΄΄ E, continental shelf, ~ 300 m, deep-sea bottom trawl, Jose Antony, 17 April 2021 ; CMFRI DNR GC.1.1.1.3, 340 mm TL, male and CMFRI DNR GC.1.1.1.4, 308 mm TL, female, Wadge Bank , Lakshadweep Sea, India, 7 ° 15 ΄ 00 ΄΄ N, 77 ° 47 ΄ 33 ΄΄ E, continental shelf, ~ 250 m, deep-sea bottom trawl, Jose Antony, 15 January 2021 .

Diagnosis. A six-gilled species of Eptatretus with 3/3 multicusp pattern, 9–10 anterior unicusps, and 7–8 posterior unicusps; posterior tip of dental muscle reaching up to the mid-region of 2 nd gill pouch; total cusps 44–48; total pores 67–69 (prebranchial 12–13, branchial 6, trunk 39–40, and tail 8–11). Uniformly brown colouration on the dorsal and ventral region when fresh ( Fig. 2A View FIGURE 2 ) and dark brown when preserved in formalin.

Description. Collected specimens ranged from 308–400 mm TL. Morphometrics as percentage TL presented in Table 1 View TABLE 1 . Body nearly cylindrical and eel-like with velvety smooth skin which lacks scales. Body slightly deeper than wide near prebranchial, branchial, and trunk regions. Cloaca and tail region strongly compressed with tail margin blunt and irregular. Rostrum short and rounded. Presence of two conspicuous eyespots on either side of head. Nasal papilla absent. Preocular length (3.6–4.6% TL) shorter than branchial length (7.7–10.6% TL). Three pairs of barbels on head with first and second short, slender, approximately equal in size (0.7–0.8% TL) and laterally arranged near nostril. Third pair of barbels slightly longer (0.8–0.9% of TL) and placed near mouth. Six gill pouches corresponding to six gill apertures arranged in straight-line approximately at equal distance. Pharyngocutaneous-duct aperture large in size, confluent with 6 th gill aperture on left side ( Fig. 2B View FIGURE 2 ).

Two rows of comb-like teeth with sharp tips slightly curved rearward. Anterior and posterior row of dentition on either side with last teeth slender and smaller in size; outer row consisting of a 3-cusp multicusp and 9–10 unicusps; inner row comprises of a 3-cusp multicusp and 7–8 unicusps; total number of cusps 44–48. Palatine tooth present with triangular shaped broad base ( Fig. 4 View FIGURE 4 ). Dental muscles broad, long with posterior tip reaching up to mid-region of 2 nd gill pouch ( Fig. 3 View FIGURE 3 ).

Slime pores segmentally arranged along a straight line on either side ranging from prebranchial to tail regions. Six branchial slime pores placed posterior to six gill apertures on each side with a minor deviation in straight-line alignment of slime pores occurring downward along branchial region. Ventral aorta bifurcating at 4 th or between 4 th and 5 th gill pouch. All six EBDs are arranged in equidistance with 6 th EBD convergent with PCD on left side ( Fig. 3 View FIGURE 3 ). Ventral fin-fold low, beginning from midpoint of trunk region and extending up to cloaca. Caudal fin starts posterior to cloaca and extends around tail.

Colouration: Body uniformly brown on dorsal and ventral regions in fresh specimens. First pair of large barbels dark brown, remaining two pairs of short barbels light brown. Eyespot pale or whitish. Slime pores conspicuous white spots. A dark brown colour around pale gill apertures. Ventral finfold dark brown and caudal fin reddish brown ( Fig. 2A View FIGURE 2 ). Specimens dark brown when preserved in formalin.

Distribution: Only known from Wadge Bank, Lakshadweep Sea, India

Etymology: The species is named wadgensis alluding to the geographical region where it was collected.