Indoreonectes mahadeoensis, Ghosh & Bhat & Johnson, 2025

Ghosh, Meghma, Bhat, Anuradha & Johnson, Jeyaraj Antony, 2025, Indoreonectes mahadeoensis, a new species of river loach from headwaters of the Narmada River, India (Teleostei: Nemacheilidae), Zootaxa 5693 (4), pp. 537-550 : 539-543

Indoreonectes mahadeoensis sp. nov. ( Figs 1 & 2 , Table 1 )

Holotype: WII/NWR/Type_F 04, 53.0 mm, SL, Mahadeo stream, near Pachmarhi , Satpura Tiger Reserve , Narmadapuram District, Madhya Pradesh, India ( 22.4164° N, 78.4252° E, 1129 m above mean sea level); M. Ghosh, 4 June 2022.

Paratypes: WII/NWR/Type_F 05, 9 ex. 31.0–45.0 mm SL, same data as holotype .

Diagnosis. Indoreonectes mahadeoensis is distinguished from all its congeners by the presence of 8 branched rays in the dorsal fin, 7 branched rays in the anal fin, and by a unique combination of the following characters: nasal barbels reaching anterior border of eye, dorsal-fin origin positioned posterior to vertical line drawn from pelvic-fin origin, and broken bars along lateral surface of body. In addition, Indoreonectes mahadeoensis can be separated from its congeners by a divergence of 11.2 to 18.6% (uncorrected P-distance) in the mitochondrial cyt b gene sequences.

Description. Body almost cylindrical at anterior, sub-cylindrical towards middle and, elongated and laterally compressed towards posterior end. At dorsal-fin origin, body width 7.4 to 11.8 times in standard length and depth 5.2 to 8.0 times in standard length. Head conical ( Fig. 2A ), its length 3.6 to 4.6 times in standard length. Snout round and smooth, its length 2.3 to 2.6 times in head length. Eye dorso-laterally positioned, closer to tip of snout than to posterior margin of operculum. Eye diameter 4.5 to 7.3 times in head length, and inter-orbital width 2.2 to 2.6 times in head length. Pre-dorsal outline convex gradually rising up to dorsal-fin origin. A distinct hump behind nape, and post-dorsal outline rising up to base of caudal fin. Caudal peduncle short, its length as equal to caudal peduncle depth. Scales minute, embedded in skin.

Mouth ventral, semi-circular, with thick, fleshy lips. Upper lip continuous and lower lip interrupted medially by groove ( Fig. 2B ). Barbels 4 pairs. Nasal barbel well-developed ( Fig. 2C ), 2 pairs of rostral barbels (1 outer rostral barbel and 1 inner rostral barbel), maxillary barbel and outer rostral barbel almost equal in length. Nasal barbel long, reaching in front of eye. Inner rostral barbel reaching posteriorly to anterior margin of eye. Maxillary barbel not reaching posterior border of operculum.

Dorsal-fin origin slightly posterior to vertical from pelvic-fin origin, its insertion closer to caudal-fin base than tip of snout. Dorsal fin with 3* (10) simple and 8* (10) branched rays, its origin positioned posterior to vertical line drawn from pelvic-fin origin. Pectoral fin with 1* (10) simple and 8 (7), 9* (3), branched rays, its length equal to head length. Pelvic fin with 1* (10) simple and 6 (1), 7* (9) branched rays, its length almost equal to head length. Anal fin with 3* (10) simple and 7* (10) branched rays, its length 1.2 to 1.5 times head length. Caudal fin rounded, with 9+9* (10) branched rays.

Coloration in life. Body pale yellow, darker on dorsal, than lateral profile. Brownish-black irregular broken bars on lateral and dorsal side of body. Lateral and dorsal side bars separate from each other. Lateral bars narrower than inter-bar spaces. Complete bars present along caudal peduncle. A conspicuous spot on dorsal side of head, in addition to several head spots ( Fig. 2A ). Lower and upper lips grey in colour due to concentrated pigments ( Fig. 2B ), no spots on cheeks ( Fig. 2C ). Dorsal-fin anterior spot well developed. Dorsal-fin membrane hyaline with 3 rows of black spots on rays (1 complete row and 2 incomplete rows). Pelvic, pectoral and anal fins hyaline. Caudal fin also hyaline, with 4 rows of dark brown spots on rays; last row towards tip comparatively darker than remaining rows ( Fig. 1 ).

Habitat. Indoreonectes mahadeoensis was collected from a deep gorge-like area mainly composed of undercut bedrock and large boulders ( Fig. 3 ). The substratum was filled with sand and gravel. The habitat was characterized by the presence of riffles, that were either flowing to meet their downstream tributaries, or ending up in small pools. The water quality parameters recorded during specimen collection ( June 2022) were: temperature 23.5°C, pH 7.76, conductivity 51 µS and dissolved oxygen 5.3 mg /l. The riparian vegetation along the entire stretch of the riverscape comprised primarily Terminalia arjuna (Arjuna) and Syzygium cumini (Jamun) . Indoreonectes mahadeoensis cooccurs with Devario aequipinnatus and Garra mullya .

Etymology

The species is named after its type locality— Mahadeo stream, flowing across the Gupt Mahadeo Temple near Pachmarhi hills, within the Satpura Tiger Reserve in Madhya Pradesh, Central India.

Genetic divergence and phylogeny

Our cyt b gene dataset comprised 1067 base pairs. Both ML and BI analyses resulted in the same tree topology ( Fig. 4 ) and was largely congruent with Jadhav et al. (2024). Indoreonectes mahadeoensis was recovered within Indoreonectes , and showed a sister group relationship with I. amrabad , I evezardi , I. kalsubai , I. neeleshi and I. telanganaensis , but with low bootstrap value ( UFB 58), and strong posterior probability value (PP 1) ( Fig. 4 ). The uncorrected P-distance in the cyt b gene sequences between Indoreonectes mahadeoensis and its congeners ranges between 11.2–18.6% ( Table 2 ).

Figures

FIGURE 1. Indoreonectes mahadeoensis, Holotype, WII/NWR/Type_F 04, 53.0 mm SL; India: Madhya Pradesh: Satpura Tiger Reserve: Pachmarhi: Mahadeo stream, lateral view.

FIGURE 2. Dorsal (A), ventral (B) and lateral (C) head view of Indoreonectes mahadeoensis, Holotype, WII/NWR/Type_F 04, 53.0 mm SL.

FIGURE 3. Mahadeo stream near Pachmarhi, Satpura Tiger Reserve, Madhya Pradesh, the type locality of Indoreonectes mahadeoensis (Photograph data: stream located adjacent to the Mahadeo Temple, located about 10 km from Pachmarhi Cantonment; 4 June 2022; wide camera 26 mm, f 1.8 12 MP; photo credit: Meghma Ghosh).

FIGURE 4. Bayesian tree using cyt b dataset showing relationships among members of the genus Indoreonectes. Nodal support values are Bayesian posterior probabilities (BPP) above and ML ultrafast bootstrap (UFB) values below. Scale bar=substitutions per site.

Tables

TABLE 1. Morphometric data of the holotype (WII/NWR/Type_F 04) and nine paratypes (WII/NWR/Type_F 05) of Indoreonectes mahadeoensis sp. nov. Data of holotype included in the calculation of mean; SD, standard deviation; and range.

Characters	Indoreonectes mahadeoensis sp. nov. (n=10)
	Holotype	Mean	SD	Range
Total length (mm)	64.1	48.6	7.4	38.3–64.1
Standard length ( SL, mm)	53.0	40.4	6.5	30.7–53.0
Head length ( HL, mm)	11.6	9.7	1.4	8.1–11.6
% inSL
Head length	32.1	25.1	2.9	21.4–32.1
Predorsal length	60.2	58.8	4.6	55.4–70.9
Dorsal-fin origin to caudal-fin base	49.4	47.0	3.0	43.4–54.3
Prepectoral length	21.9	23.9	2.0	21.1–27.4
Prepelvic length	50.7	51.3	4.7	40.8–59.2
Preanus length	72.9	72.6	1.9	69.4–75.7
Preanal-fin length	79.9	79.5	4.2	72.5–88.1
Body depth (at dorsal-fin origin)	15.2	15.3	2.0	12.6–17.2
Body depth (at anus)	14.9	14.3	1.3	12.6–17.1
Body width (at dorsal-fin origin)	13.4	10.7	1.8	8.4–13.6
Body width (at anus)	8.1	6.7	0.9	5.6–8.1
Height of dorsal fin	19.2	19.4	1.5	17.7–22.8
Length of dorsal-fin base	12.1	11.3	1.8	9.3–4.5
Length of pectoral fin	22.4	21.1	1.7	18.8–23.1
Length of pelvic fin	19.1	19.8	2.4	16.6–26.0
Length of anal fin	17.1	18.3	2.4	15.9–23.4
Length of anal-fin base	8.9	9.0	1.3	7.3–11.8
Length of caudal fin	21.1	23.7	2.2	21.1–29.3
Depth of caudal peduncle	13.4	13.6	1.5	12.0–17.2
Length of caudal peduncle	13.7	13.2	0.7	11.7–14.0
% inHL
Head depth	59.5	48.4	6.8	41.2–59.5
Head width	73.3	57.2	8.2	45.8–73.3
Snout length	45.7	42.1	5.8	37.3–56.8
Eye diameter	20.3	18.3	1.9	16.5–21.8
Interorbital width	45.7	38.3	4.0	31.4–45.7
Width of mouth	54.3	51.6	6.8	43.2–59.1