Cabdio crassus, Lalronunga & Singh, 2019

Cabdio crassus , sp. nov.

( Fig. 2 View FIGURE 2 )

Holotype: ZSI FF 8218, 88.1 mm SL; India; Mizoram, Kaladan River, in the vicinity of Kawlchaw village; 23°28’29”N; 92°23’27”E; Lalramliana et al., 24 Nov. 2015. GoogleMaps

Paratypes: ZSI FF 8219, (2), 91.2–94.4 mm SL; PUCMF 17017 (5), 85.8–111.4 mm SL ; PUCMF 17018 (3), 90.0– 95.5 mm SL; (dissected and preserved in glycerin with thymol) data as holotype .

Diagnosis. Cabdio crassus markedly differs from all other valid species of Cabdio ( Fig. 3 View FIGURE 3 ) by having the venter keeled from mid-point of chest, between the posterior base of the pectoral fin and along the abdomen up to the anus, and possessing 11½–12½ (vs. 7–9) branched anal-fin rays. It is further distinguished from C. morar and C. ukhrulensis by possessing more lateral-line scales (45–51 vs. 38–42 in C. morar and 35–37 in C. ukhrulensis ), more predorsal scales (20–23 vs. 17–18 in C. morar and 14 in C. ukhrulensis ) and more lateral transverse scales (½7/1/3½ vs. 5/1/ 2 in both C. morar and C. ukhrulensis ). It also differs from C. jaya in having fewer lateral-line scales (45–51 vs. 52–60), more lateral transverse scales (½7/1/3½ vs. 5/1/3) and more pharyngeal tooth-rows (3 vs. 2).

Description. See Table 1 View TABLE 1 for morphometric data and Figure 2 View FIGURE 2 for general appearance. Body elongate, laterally compressed, body depth greatest at dorsal-fin origin. Dorsal profile rising from tip of snout to dorsal-fin origin, then gradually sloping towards caudal peduncle. Ventral profile convex up to caudal peduncle; dorsal and ventral profile of caudal peduncle slightly concave. Chest and abdomen keeled from mid-point of chest between posterior base of pectoral fin through abdomen till anus. Head compressed along entire length; depth greater than width.

Eye ovoid, located in anterior half of head, visible in both dorsal and ventral view. Snout rounded with cluster of tubercles; its length equal to eye diameter. Mouth subterminal, rictus not reaching vertical through anterior margin of orbit. Barbel absent.

Dorsal fin with 2 (15) unbranched and 6½ (1) or 7½ (14) branched rays, its origin at vertical through posterior base of pelvic fin, posterior margin slightly concave. Pectoral fin with 1 unbranched and 12 (3), 13 (9) or 14 (3) branched rays, adpressed fin tip reaching two-thirds distance between its origin and pelvic-fin origin, axillary scale present at its base. Pelvic fin with 1 unbranched and 7 (15) branched rays, adpressed fin tip reaching midway between its origin and anal-fin origin, axillary scale present at its base. Anus closer to anal-fin origin than to base of last pelvic-fin ray. Anal fin with 3 unbranched and 11½ (2) or 12½ (13) branched rays. Caudal fin forked, with 10 + 9 (15) principal caudal-fin rays, its lobes more or less equal.

Lateral line complete, prominent, curved, with 45 (2), 46 (6), 47 (3), 49 (1), 50 (2), 51 (1) on body plus 1 or 2 scales on caudal-fin base; ½7/1/3 (4) or ½7/1/3½ (11) scales in transverse line from dorsal-fin origin to pelvic-fin origin. Circumpeduncular scales 16 (15), predorsal scales 20 (3), 21 (3), 22 (7) or 23 (2), pre-pelvic and pre-anal region scaled. Five infraorbital bones ( IO 1–5); IO 3 largest, deep, partly overlapping preoperculum; post cleithrum absent; 3 rows of pharyngeal teeth. Vertebrae (abdominal + caudal): 24 + 16 = 40 (1) or 25 + 15 = 40 (1).

Colouration. ( Fig. 2 View FIGURE 2 ) Dorsum brownish, lighter towards flank. Lower half of body and belly silvery or pale white. Caudal fin hyaline with black pigment distally. Other fins hyaline without markings.

Geographical distribution. Known from the main channel of the Kaladan River drainage of Mizoram, India ( Fig. 5 View FIGURE 5 ).

Etymology. The specific name crassus is a Latin adjective meaning stout or thick, referring to the stout or thick body in comparison with other species.

Molecular analysis. In the coi tree, Cabdio crassus is nested within Cabdio (interspecies distance ranges from 7.8 to 12.3%) ( Fig. 1 View FIGURE 1 ). The genetic distance between Cabdio crassus and C. morar is 11.7–12.3%, and between it and C. ukhrulensis is 7.8–8.0%. The inability to collect fresh specimens results in non-availability of tissue sample in the case of C. jaya .

Identity of Cabdio reported in GenBank. Analysis of the generated Cabdio sequences with close species available in the GenBank revealed several potentially misidentified specimens ( Table 3 View TABLE 3 ). Our 7 developed sequences of Cabdio morar (morphologically identified through a thorough comparison of specimens from ZSI, Kolkata and ZSI, Shillong: see Comparative Material, below) clustered in the ML tree with GenBank sequences labelled Salmostoma bacaila (downloaded from the NCBI KT 364775 View Materials , KX266823 View Materials , EU417785 View Materials , EU417786 View Materials , EU417789 View Materials , KJ936881 View Materials , KJ896723 View Materials , KJ896724 View Materials and JN815302 View Materials ) with 0.0–1.2 % K2P distance, indicating that these GenBank sequences in fact represent Cabdio morar . Further, the calculated genetic distance between Cabdio morar and the species labelled as Salmostoma sp. ( JX 260968 View Materials , JX 260969 View Materials ), which is 2.0–3.0%, and between C. morar and Salmostoma sp. ( KY 290071 View Materials ), which is 4.4%, suggested that the latter two may represent species of Cabdio , rather than to Salmostoma . Our sequences of Cabdio ukhrulensis show a very low genetic distance (0.0–0.2%) and cluster together in the ML tree with GenBank sequences labelled C. morar ( AP 011335 View Materials , KJ 909343 View Materials and KJ909344 View Materials ) indicating that they too, are conspecific. Furthermore, the GenBank sequences labelled as Aspidoparia morar ( FJ 459447 View Materials ) and A. jaya ( FJ 459446 View Materials ) clustered together with Salmostoma bacaila ( HM 224244 View Materials , MG 954366 View Materials , NC015549 View Materials , KY290072 View Materials , KY290087 View Materials ) with a low genetic distance of 0.3–0.7 % indicating that they represent the latter species.