Triplophysa daryoae, Sheraliev & Kayumova & Peng, 2022

Sheraliev, Bakhtiyor, Kayumova, Yorkinoy & Peng, Zuogang, 2022, Triplophysa daryoae, a new nemacheilid loach species (Teleostei, Nemacheilidae) from the Syr Darya River basin, Central Asia, ZooKeys 1125, pp. 47-67 : 47

Triplophysa daryoae sp. nov.

Figs 1 , 2 , 3 English common name: Sokh stone loach Uzbek common name: So‘x yalangbalig‘i Russian common name: Сохский голец

Holotype.

SWU 20211207001, male, 78.5 mm SL; Uzbekistan, Fergana Region, Sokh District, Sokh River, near Limbur village, an exclave of Uzbekistan surrounded by Kyrgyzstan, Syr Darya basin, 40°3.1528'N, 71°5.8195'E, altitude 1054 m, December 07, 2021, collected by B. Sheraliev and Y. Kayumova.

Paratypes.

SWU 20211207002-011, 10, 49.0-94.0 mm SL; BSFC 0023, 4, 62.1-82.4 mm SL; Uzbekistan, Fergana Region, Sokh District, Sokh River, near the Limbur village, exclave of Uzbekistan, Syr Darya basin, 40°2.7387'N, 71°6.288'E, altitude 1054 m, April 12, 2021, collected by Y. Kayumova. BSFC 0024, 3, 74.1-81.3 mm SL, same data as holotype.

Diagnosis.

Triplophysa daryoae is distinguished from congeners by a combination of characters. It is distinguished from T. ferganaensis by possessing a truncate caudal fin with 13-14 branched rays (vs emarginate, 16 rays), 9 pores in the pre-opercular mandibula (vs 7-8), and a slenderer body (body depth at dorsal-fin origin 1.4-1.8 times the HL vs 1.2-1.4). It is distinguished from T. strauchii by absence of the posterior chamber of the air bladder (vs developed, with a long tube), possessing 9-10 inner gill rakers on the first gill arch (vs 12-16), and no obvious skin mottling (vs mottling). Triplophysa daryoae is also distinguished from T. dorsalis , T. dorsonotata , and T. elegans by having a truncate caudal fin (vs emarginate) and lacking a posterior chamber of the air bladder (vs developed in T. dorsalis and T. elegans ). It is distinguished from T. sewerzowi , T. tenuis , and T. ulacholica by the dorsal-fin origin opposite to the pelvic-fin insertion (vs anterior to vertical line of pelvic fin origin).

Description.

Morphometric data of T. daryoae are given in Table 2 . Dorsal-fin rays iii, 6(2) or 7(16); anal-fin rays ii, 5; pectoral-fin rays i, 9(1), 10(16), or 11(1); pelvic-fin rays i, 6; caudal-fin rays, 13-14 (6+7 [5]; 7+7 [13]); vertebrae, 4+35 (N = 2); gill rakers, 9-10 in the inner row of first gill arch (N = 4). Cephalic lateral-line system, 2 supratemporal, 6 supraorbital, 4+10-11 infraorbital, and 9 pre-operculum mandibular pores.

Body elongate; posterior portion gradually compressed from dorsal fin to caudal-fin origin. Dorsal profile slightly convex from the snout to the insertion of the anterior dorsal fin (Fig. 1 ). Deepest point of body slightly anterior to dorsal-fin origin; body depth at dorsal-fin origin 12.4-15.3% of SL. Head compression, maximum width always greater than depth; head maximum width 63.2-73.2% of HL. Snout slightly pointed, length shorter, equal, or slightly longer than postorbital length; snout length 34.9-47.3% of HL. Anterior and posterior nostrils adjacent; anterior nostril as short tube with elongated barbel-like tip; tip of nostril barbel not reaching the anterior margin of eyes. Eyes normal; diameter 12.5-17.1% of HL (Fig. 2 ). Mouth inferior, gape arched; mouth width 16.1-24.3% of HL. Rictus situated below the anterior nostril. Lips thick with furrows and papillae; upper lip pectinate, without medial notch; lower lip wide, interrupted in middle, with mental lobes and two highly developed ridges. Upper jaw covered by the upper lip; processus dentiformis absent. Three pairs of barbels: inner rostral barbel reaching rictus, length 19.8-30.2% of HL; outer rostral barbel reaching anterior margin of eye, length 22.7-42.0% of HL; maxillary barbel reaching posterior margin of eye, length 22.0-37.4% of HL.

Dorsal fin convex, origin opposite to pelvic-fin insertion, situated slightly posterior to midpoint between snout tip and caudal-fin base; upper margin slightly convex; second branched ray longest; depth of dorsal fin always shorter than lateral head length; depth 14.9-18.5% of SL. Anal fin short-based, posterior margin convex; length 13.1-16.7% of SL. Pectoral fins developed; 46.6-61.6% of pectoral-pelvic distance. Tips of depressed pelvic fins reaching the anus and anus separated from the anal-fin origin by a short distance. Caudal peduncle compressed laterally; length 2.2-2.9 times the peduncle depth. Caudal fin truncate, tips rounded; length 86.2-119.9% of caudal-peduncle length.

Body smooth and scaleless; cephalic lateral-line system well developed. Infraorbital and supraorbital canals stretching from the outer rostral barbel base and ethmoid, respectively, uniting in the posterior orbital region and extending posteriorly before converging with the supratemporal canal on the back of the head, and uniting with the lateral canal. Complete lateral line ending at caudal-fin base. Intestine moderately long, with two coils. Stomach U-shaped. Posterior chamber of the air bladder degenerated.

Coloration.

Dorsal profile grayish-brown to pale green without regular blotches in live individuals, and dark gray-brown in preserved specimens. Ventral side of the body ivory with gray tint. Dorsal side of head with small irregular dark melanophores; dorsal side of caudal peduncle with four or five irregular dark brown blotches. All fin membranes hyaline and light gray, without obvious mottling (Figs 1 , 3 ).

Sexual dimorphism.

Mature males presenting granular tubercles on each side of the preorbital region and broadened and thickened external branched pectoral-fin rays dorsally covered by small and condensed epidermal breeding tubercles. Females without tubercles on the head and pectoral-fin rays.

Distribution and habitat.

Triplophysa daryoae sp. nov. is known only from its type locality, the Sokh River, which originates in the Alay mountains and Turkestan range (Fig. 4 ). Presently, Sokh River water is primarily used for irrigation and does not reach Syr Darya. The river is located at an altitude of 700-1500 m and is constantly flowing rapidly; the water is clear and cold (the water temperature was 7.3 °C when the holotype was caught), and the bottom consists of gravel and stone (Fig. 5 ). Triplophysa daryoae cohabited with Cottus spinulosus Kessler, 1872 and Schizothorax eurystomus Kessler, 1872, which are high-altitude fish species.

Etymology.

Triplophysa daryoae is dedicated to Daryo Sheralieva, the lovely daughter of the first author. The specific name is a noun in the genitive case.

Molecular analysis

COI sequence data (Fig. 6 ) showed that Triplopysa daryoae belongs to a group of species with a wide distribution in the Syr Darya, Tarim, and Ili-Balkhash river drainages, an endorheic basin in Central Asia. This group is defined here as the T. dorsalis species group, and our molecular data suggest that it includes T. chondrostoma (Herzenstein, 1888), T. dorsalis , T. dorsonotata , T. elegans , T. ferganaensis , T. sewerzowi , T. strauchii , T. tenuis (Day, 1877), and T. ulacholica . The minimum K2P distances between T. daryoae and its closest relatives T. ferganaensis and T. tenuis were 2.8% and 4.5%, respectively (Table 3 ). Triplophysa daryoae was distinguished from its most closely related congener, T. ferganaensis , by 18 unique and diagnostic nucleotide substitution sites in the COI barcode region (652 bp) (Table 4 ).

Figures

Figure 1. Lateral a dorsal b and ventral c views of Triplophysa daryoae, holotype, SWU 20211207001, male, 78.5 mm SL; Uzbekistan: Sokh River.

Figure 2. Dorsal a and ventral b views of the head of Triplophysa daryoae, SWU 20211207001, holotype, male, 78.5 mm SL.

Figure 3. From top: Triplophysa daryoae, holotype SWU 20211207001, male, 78.5 mm SL, photographed alive immediately upon capture, Uzbekistan: Sokh River; T. daryoae, paratype, BSFC 0024, 72.8 mm SL, Uzbekistan: Sokh River; T. ferganaensis, BSFC 0025, 66.2 mm SL, Uzbekistan: Shahimar-dan stream; T. strauchii, not preserved, about 110 mm SL, Uzbekistan: Oltiariqsoy stream.

Figure 4. Map of the distribution of Triplophysa species in Uzbekistan: T. daryoae (grey diamond); T. ferganaensis (orange star); T. strauchii (black circle); T. dorsalis (blue pentagon); T. elegans (yellow rectangle); and T. uranoscopus (purple triangle).

Figure 5. Sampling locality of the holotype (SWU 20211207001) of Triplophysa daryoae in the Sokh River left tributary of the Syr Darya, in Sokh District, the exclave of Uzbekistan, surrounded by Kyrgyzstan, photograph taken on December 7, 2021.

Figure 6. Bayesian inference tree based on mitochondrial COI gene sequences of 24 Triplophysa species. Maximum likelihood and Bayesian inference analyses resulted in congruent trees. Bootstrap and posterior probability values are shown above nodes on tree if 50 % or higher.