Homatula gelao Xiao, 2025

Homatula gelao Xiao sp. nov.

Holotype.

• ZVTC 20200601 , 127.56 mm SL. Guizhou Province: Zunyi City: Daozheng County: Huaixi-He, a stream tributary to Furong-jiang of Wujiag basin, at Huaiping Village (28°43'39.2124"N, 107°45'2.7072"E, roughly 632.5 m above sea level) of Jiucheng Town; collected by G. B. Xiao, Gui Bang Xiao, 06 January 2020 (Fig. 2 View Figure 2 ). GoogleMaps

Paratypes.

• ZVTC 20200602 – ZVTC 202006029 , 28 specimens, 98.3–135.5 mm SL, other data same as holotype GoogleMaps .

Diagnosis.

A member of the elongate-bodied group of Homatula defined by having a slender body with a uniform depth (9.2 % – 14.4 % of SL), a complete lateral line, and a scarcely scaled or scaleless predorsal body. H. gelao resembles H. variegata in the presence of a broadly rounded (vs. truncate or obliquely truncate) caudal fin and scales sparsely scattered on the predorsal body (vs. predorsal body unscaled or sparsely scaled on the dorsum and flank), which distinguishes both from all other species of this group ( H. berezowskii , H. guanheensis , H. laxiclathra , H. longidorsalis , H. oxygnathra , and H. tigris ). It differs from H. variegata in possessing a body coloration of 17–18 brown vertical bars narrower than interspaces, particularly on the Caudal peduncle flank (vs. dense, undulating vertical bars slightly wider or equal to interspaces); a thick brown-black stripe running along dorsal midline from behind head to dorsal fin origin; and symmetrical black vertical bars on sides of body (vs. light brown spots on the dorsum and irregular markings on the sides of the body); and a longer (vs. equal) distance from the origin of the anal fin to the origin of the pelvic fin than the distance from the origin of the anal fin to the base of the caudal fin.

Description.

Morphometric measurements were taken from type specimens given in Table 2 View Table 2 , and see Fig. 2 View Figure 2 for a general appearance of body. Body elongated, anteriorly cylindrical and posteriorly compressed laterally, nearly with uniform depth from behind head to caudal fin base. Head, thorax, and abdomen scaleless. Dorsum and flanks of predorsal body sparsely covered with tiny scales buried beneath skin. Lateral line complete, with 97–110 perforated scales. Adipose crest extending along dorsal midline of caudal peduncle, anteriorly ends close to above the posterior end of anal-fin base.

Head small and short, about one-sixth of SL, slightly depressed and wider than deep. Snout pointed in lateral view and pointedly rounded in dorsal and ventral view; eyes small and elliptical, positioned dorsally in the anterior half of head; diameter less than interorbital width. Anterior nostril with a flap-like tube. Mouth inferior and arched; lips slightly thick, fleshy, and non-folded. Three pairs of barbels, two pairs of rostral barbels, and one pair of maxillary barbels; outer rostral barbels longer than inner ones; the inner barbels are invisible when viewed dorsally.

Fins flexible. Dorsal fin with three simple and eight branched rays; distal margin convex; origin closer to snout tip than to caudal fin base. Pectoral fin with two simple and eight branched rays; tip of pectoral fin extending, not reaching halfway to pelvic-fin insertion. Pelvic fin with 1 and 6 1 / 2 branched rays; tip of pelvic fin not extending midway between pelvic-fin origin and anal-fin origin. The insertion point of the ventral fin is directly below the dorsal fin, between the unbranched fin and the first branched fin of the dorsal fin. Anal fin has two simple and five branched rays, with a convex distal margin; origin is closer to caudal fin base than to pelvic-fin insertion. Caudal fin rounded with 21 (10 + 11) branched rays, and the upper lobe slightly longer than lower lobe.

Intestines have no loop, slightly bending at bottom of U-shaped stomach but not Z-shaped, and then extending backwards to posterior part of body (Fig. 5 View Figure 5 ). Air bladder bipartite; anterior chamber is enclosed in a bony capsule and posterior one degenerated. Vertebrae 4 + 41-43 counted from 5 specimens (Fig. 6 View Figure 6 ).

Coloration.

In freshly captured individuals, ground color of head and body is fishy-red, with a dark back and light abdomen. A thick brown-black stripe runs along dorsal midline from behind head to dorsal fin origin, with roughly 7–8 black vertical bars, narrower than interspaces, on either side of this thick brownish-black stripe. 17–18 brown or black vertical bars on flank, including 7–8 on both sides of the predorsal, 3–4 below dorsal-fin base, and 4–5 on caudal peduncle. There are regularly arranged brownish-black spots on the base and tip of the dorsal fin and a dark brown vertical bar on caudal-fin base. Caudal fin dark fishy red, sparsely covered with small black spots. All other fins yellowish transparent (Figs 2 View Figure 2 , 3 A View Figure 3 , 4 A View Figure 4 ).

In formalin-preserved specimens, back and flank are earthy yellow, and abdomen is slightly yellowish. All fins milky white, except for black spots on dorsal and caudal fins. Vertical bars on flank paler than those of freshly collected specimens (Fig. 7 A, B View Figure 7 ).

Distribution and habitat.

Homatula gelao is currently known only from the Huaixi-He, a stream tributary to the Furong-Jiang. The type specimens were captured in a 6 km main channel length of the Huaixi-He, with an altitude of 600 to 700 m above sea level. H. gelao was commonly found at the bottom of underwater gravels with swirling currents and the larvae of benthic invertebrates such as Ephemeroptera, Trichoptera, and Plecoptera (Figs 8 View Figure 8 , 9 View Figure 9 ). Coexisting species are A. furongjiangensis ( Xiao, 2024) , S. szechuanensis (Fang, 1930) , M. anguillicaudatus (Cantor, 1842), P. prochilus (Sauvage et Dabry, 1874), and S. kozlovi (Nikolsky, 1903) .

Sexual dimorphism.

No sexual dimorphism was observed.

Etymology.

The specific epithet is named after Gelao (in Chinese spelling) nationality. The type specimens of the new species were collected from the Huaixi-He in Daozhen Gelao Autonomous County, northern Guizhou Province. The Chinese common name for H. gelao is suggested as “ 仡佬荷马条鳅 ”.

Molecular phylogeny and genetic distance

The mitochondrial COI gene sequences, with a length of 649 bp, were identified for 11 samples of H. gelao . After aligning with species of the same Homatula genus, there are 560 conserved sites, 15 variable sites, 3 parsimonious informative sites, and 12 singleton sites. The nucleotide composition of this gene is A = 21.7 %, T = 29.2 %, C = 27.9 %, and G = 21.1 %. The average G + C content varied from 48.9 % to 49.5 %, with an average value of 49.2 %. The resulting phylogenetic tree, yielded based on the mtDNA COI genes using the neighbor-joining method, is depicted in Fig. 10 View Figure 10 . The topology of this tree reveals that samples of H. gelao clustered together into a highly supported distinct lineage. The phylogenetic analysis indicates that H. gelao constitutes a sister group to the clade comprising (( H. guanhensis + H. laxiclathra ) + (( H. longidorsalis + H. robusta ) + ( H. nanpanjiangensis + H. variegata ))). The genetic distances between the sampled species of Homatula ranged from 8.21 % to 12.19 %. The average genetic distance is 9.92 % ± 1.08 %, and the interspecific genetic distance is much greater than 2 % (Table 3 View Table 3 ).

Comparative morphometry

The results demonstrated that KMO = 0.738> 0.70, and Bartlett’s P <0.01, indicating that the morphological traits used in this study are appropriate for PCA analysis ( Kaiser 1974; Schreiber 2021). PCA was performed for 17 morphometric measurements from 28 specimens of H. gelao and 8 specimens of H. variegata . The results showed that in the scatterplot of PC 1 against PC 2 and PC 2 against PC 3, two distinct clusters representing H. gelao and H. variegata were identified (Fig. 11 View Figure 11 ). Specimens of H. gelao were separated from specimens of H. variegata along the PC 1 and PC 3 axes, respectively. There are two morphometric measurements (head length and prepectoral length) with main loadings on the first axis (PC 1), three (dorsal-fin length, anal-fin length, and caudal peduncle depth) on PC 2, and two (head depth and body depth) on PC 3. Characters with main loading included head length, prepectoral length, head depth, and body depth. Major differences were found in head length (15.0–18.9, mean 17.1 in H. gelao vs. 18.7–20.4, mean 19.60 in H. variegata , % of SL), caudal peduncle length (16.9–20.8, mean 19.3 in H. gelao vs. 20.2–22.4, mean 21.4 in H. variegata , % of SL), and dorsal fin length (11.7–16.7, mean 13.8 in H. gelao vs. 6.6–10.3, mean 8.9 in H. variegata , % of SL) (Table 4 View Table 4 ).