Koima, Anoop & Dahanukar & Raghavan, 2024

Anoop, V. K., Dahanukar, Neelesh & Raghavan, Rajeev, 2024, Koima, a new genus of nemacheilid loach from the Western Ghats, India (Cypriniformes: Nemacheilidae), Zootaxa 5538 (2), pp. 101-126 : 104-107

Koima , new genus urn:lsid:zoobank.org:act:D599B312-2872-4916-9F54-2005095FC1C3

Figs. 2–5

Type species: Mesonoemacheilus remadevii Shaji 2002

Diagnosis: Koima is distinguished from all other genera within the family Nemacheilidae by its unique colour pattern, comprising a yellowish-brown ground colour, single row of black spots on lateral line, all fins hyaline, and absence of uniform banding pattern on dorsal side. Additionally it can be distinguished by the combination of the following characters: modified pectoral-fin rays covered by a membrane, with wide thick segmentation on first unbranched and branched rays, and tubercles on first four pectoral-fin rays; upper lip with narrow deep incision and lower lip with wide interruption; well-developed barbels, outer rostral barbels (with skinny projections between them) reaching beyond posterior end of eye; mouth gape lesser than interorbital width; head sharp and bluntly pointed, its length one-fourth of standard length; nostrils situated near to eye than tip of snout; suborbital flap thick, wide and larger than nostril; dorsal-fin origin opposite to pelvic fin; pelvic fin not reaching anal opening,; caudal peduncle length and depth almost equal; forked caudal fin, its length twice that of caudal peduncle depth; presence of an adipose crest, lower crest reaching end of anal fin; cephalic lateral line with 6–7 supraorbital pores, 4+12 infraorbital, 9 preoperculo-mandibular and 3 supratemporal pores; total vertebrae 35–36, insertion of dorsal fin after 11 th or 12 th vertebrae, and insertion of anal fin after 22 nd vertebrae.

It is further distinguished from all currently known members of family Nemacheilidae occurring in the Western Ghats, and the Indian subcontinent by various combinations of characters. Koima is distinguished from Mesonoemacheilus , Schistura and Turcinoemacheilus by its modified pectoral fin with a membrane, thickly segmented first unbranched and branched fin rays, tubercles on pectoral-fin rays, and upper lip with a narrow deep incision. Koima is further distinguished from Mesonoemacheilus by the presence of a lower adipose crest (vs. absence), absence of a banding pattern on the dorsal side (vs. presence of broad bands), and an absence of bands on the caudal fin (vs. presence of multiple bands); from the currently known members of the genus Schistura by the shape of the caudal fin (forked vs. emarginate or truncate), the presence of spots on the body (vs. bands), and a well-developed axillary pelvic lobe (vs. absent, or not developed); and from Turcinoemacheilus by the position of the pelvic-fin origin (opposite to vs. in front of dorsal-fin origin), broad and elongated body (vs. slender), and anus opening near anal-fin origin (vs. displaced far anteriorly, closer to pelvic fins). Koima is further distinguished from the Western Ghats endemic genus Nemachilichthys by having the upper lip with a narrow deep incision and lower lip with a wide interruption (vs. upper lip with median groove and 2 to 4 large papillae on either side, and lower lip with deep median groove and 2–4 large papillae on either side), and fewer branched dorsal-fin rays (7–8 vs. 10); and from the endemic peninsular Indian genus Indoreonectes by the presence of a nasal flap (vs. short nasal barbel), a complete lateral line extending beyond the anal fin (vs. incomplete lateral line not extending beyond the anal fin), a forked (vs. rounded) caudal fin, and a pointed, broad head (vs. round, short head).

Koima is distinguished from Paracanthocobitis by having a forked (vs. truncate) caudal fin, a suborbital flap (vs. suborbital groove), no papillae or pad on lips (vs. upper lip with several rows of papillae and a strongly papillated lower lip with pad), dorsal fin origin opposite to pelvic fin origin (vs. dorsal-fin origin anterior to pelvic fin origin); and from Nemacheilus by the lower adipose crest reaching the anal-fin base (vs. no adipose crest), the upper lip with a narrow deep incision (vs. furrowed), and all fins hyaline (multiple rows of spots on dorsal and caudal fins).

Etymology: The generic name, Koima is derived from the Malayalam (local language of Kerala State, India) word used as a vernacular name for loaches. Gender feminine.

Included species: Koima remadevii ( Shaji 2002) and Koima monilis ( Hora 1921) .

Figures

FIGURE 2. Pectoral fin of Koima remadevii. UBR, unbranched ray; TB, tubercles; BR1–10, Branched fin ray 1–10; SM, special fin membrane; BR1, modified branched.

FIGURE 3. Modified pectoral-fin of Koima remadevii, arrow mark showing first branched pectoral-fin ray.

FIGURE 4. Differences in mouth structure (arrows indicate lower and upper lip interruptions, and papillated pad) of various nemacheilid loach genera of the Western Ghats: A - Koima; B - Mesonoemacheilus; C - Nemachilichthys (from Keskar et al. 2015); D - Schistura; E - Paracanthocobitis; and F - Indoreonectes.

FIGURE 5. Representative images of nemacheilid loach genera of the Western Ghats. A: Koima remadevii (54.65 mm SL); B: Koima monilis (62.57 mm SL); C: Mesonoemacheilus triangularis (43.18 mm SL); D: Nemachilichthys ruppelli (78.0 mm SL), E: Paracanthocobitis mooreh (50.0 mm SL); F: Indoreonectes keralensis (52.0 mm SL); G: Nemacheilus stigmofasciatus (33.25 mm SL); and H: Schistura denisoni (42.5 mm SL). All photos by VK Anoop except Nemachilichthys ruppelli ©Ralf Britz and Indoreonectes keralensis © Beta Mahatvaraj.