Traccatichthys punctulatus, Qin & Zhou & Du & Lin, 2025

Qin, Zhi-Xian, Zhou, Jia-Jun, Du, Li-Na & Lin, Feng, 2025, Traccatichthys punctulatus sp. nov., a new species of stone loach (Pisces, Nemacheilidae) from Guangxi, southern China, Zoosystematics and Evolution 101 (3), pp. 1013-1021 : 1013-1021

Traccatichthys punctulatus sp. nov.

Fig. 1

Type material.

Holotype. • KIZ 2005013850 , male, 47.4 mm standard length (SL); Dazhang River at Dazhang Township (23.8686 ° N, 109.8946 ° E), Jinxiu Yao Autonomous County, Laibin City, Guangxi, P. R. China; collected by J. Yang, Y. F. Huang, and D. P. Kong on October 23, 2005 .

Paratypes. China, Guangxi: Jinxiu Yao Autonomous County • KIZ 2005013849 , 2005013860–63 , five specimens, 40.1–63.7 mm SL, same as holotype • KIZ 2005009271–75 , five specimens, 49.7–62.5 mm SL, from Gufan River at Toupai Town (24.3435 ° N, 110.1235 ° E), collected by D. P. Kong and J. Yang on October 18, 2005 • KIZ 2005013245–46 , two specimens, 52.1–58.2 mm SL, Gumai River in Liuxiang Township (23.9595 ° N, 110.0332 ° E), collected by J. Yang, Y. F. Huang, and D. P. Kong on October 23, 2005 .

Other materials.

• DLN 20240034 –36, preserved in 99 % ethanol for molecular study, collected by J. H. Luo in Tongmu Town (24.1708 ° N, 109.9829 ° E), Jinxiu Yao Autonomous County, Laibin City, Guangxi, China, in April 2024 .

Diagnosis.

Traccatichthys punctulatus sp. nov. can be distinguished from all congeners by having many small spots organized in a single row along the mid-lateral line from the upper extremity of the gill opening to the caudal-fin base on the flank; a nearly-triangular black blotch on the caudal-fin base; lateral oblique brownish stripes confined only to the anterior half of body and more or less fused to constitute an oblong blotch not exceeding the adpressed tip of the pelvic-fin rays; no submarginal black streaks on the caudal-fin lobes; caudal fin with 3–4 rows of irregular spots.

Description.

Morphometric and meristic data given in Table 1 . Body elongated, broad anteriorly and tapering posteriorly. Body deeper than wide, with maximum body depth at dorsal-fin origin being 17.7 % – 21.1 % of SL, gradually declining from dorsal-fin origin to caudal-fin base. Snout blunt, slightly longer than lateral head length. Mouth arched and subterminal. Both lips papillated; upper lip bearing two rows of papillae, with two median papillae larger than lateral ones, and outer papillae slightly larger than inner papillae. Lower lip interrupted medially, forming wide V-shaped notch. Jaws covered by lips, with well-developed processus dentiformis on upper jaw. Nostrils closely set; anterior nostril elongated into tubular projection with pointed tip and posterior nostril oval. Eyes relatively large, with their diameter slightly smaller than interorbital width. Three pairs of barbels: inner rostral barbels reaching posterior nostril and outer rostral barbel extending to middle point of eye; maxillary barbel extending to vertical through posterior margin of eye.

Dorsal fin with three unbranched and 11–13 branched rays, with truncate distal margin; origin nearer to snout tip than to caudal-fin base, and inserted slightly before pelvic-fin insertion. Pectoral fin with one unbranched and 10–11 branched rays; inserted immediately anterior to vertical through posteriormost point of operculum; tip of adpressed fins reaching dorsal-fin origin. Pelvic fin with one unbranched and seven branched rays; inserted closer to anal-fin origin than to pectoral-fin insertion; tip of adpressed fins not reaching anus. Anal fin with three unbranched and five branched rays, originating equidistant to pelvic-fin insertion and caudal-fin base, or below or slightly anterior to vertical line of dorsal-fin tip; tip of adpressed fin not reaching caudal-fin base. Caudal fin slightly concave, with 16–17 branched rays, slightly longer than deep (caudal-peduncle length / its depth 1.0–1.3). Irregular spots on dorsal, anal, and caudal fins; dorsal and anal fins with marginal stripes. Among the 12 examined specimens, individual variation in the dorsal surface (before the dorsal-fin) coloration was observed, with 10 specimens showing a plain, light gray back without markings and two displaying distinct patterning (Fig. 1 E – G ).

Except for head, body completely covered with small scales and embedded under skin. Lateral line complete, cephalic lateral system with 11–13 + 3 infraorbital canal pores, 7–8 supraorbital canal pores, 3 supratemporal canal pores, and 7–8 preoperculomandibular canal pores. Swim bladder bipartite; anterior chamber fully enclosed by capsule, and posterior chamber well-developed and ovoid, and connected to U-shaped stomach. Intestine short, looping once at midsection (Fig. 2 ). Gill opening large, extending downward beyond pectoral-fin insertion to ventral surface of head; first gill arch with 12–14 inner gill rakers and 0–2 outer gill rakers.

Coloration.

In life, especially during breeding season, all fin rays pale pink, with lighter spots on dorsal and caudal fins (Fig. 1 D ). Many oblique bright green stripes along anterior lateral body and brightly silver spots on caudal-fin base. Distinct small round brown spots neatly arranged along mid-lateral line, gradually shallower from dorsal-fin base forwards. Back and sides light gray, abdomen pale yellow. Prominent blackish stripe from tip of snout through eyes to the occiput. In formalin specimens, dorsum brownish; flank and ventral side yellowish gray. Black stripe from snout tip through eye tending to blend with dark gray of head and dorsum. Fin rays faded, with black pigment deposits on dorsal surface of pectoral-fin rays, and spots on dorsal and caudal fins becoming more distinct.

Etymology.

The specific epithet punctulatus is derived from the Latin word “ punctum ”, meaning “ spot ” or “ point ”, referring to numerous spots observed on the dorsal and caudal fins and along the mid-lateral line of body. This body coloration represents a key unique diagnostic character used to differentiate it from all congeneric species. The common Chinese name suggested here for the new species is “ 斑点沙猫鳅 ” and the English name is “ Spotted Traccatichthys. ” The gender is masculine.

Distribution.

The new species is so far found in streams on the western slope of Dayao mountains in Jinxiu Yao Autonomous County, Laibin City, Guangxi, China, all of them discharging into the Liu-Jiang of the Zhu-Jiang basin (Fig. 3 ).

Phylogenetic analysis and genetic divergence.

Traccatichthys punctulatus sp. nov. formed a separate lineage clustered within a well-supported clade (posterior probability = 1; bootstrap support = 100) alongside T. pulcher , T. taeniatus , T. tuberculum , and T. zispi , in phylogenetic analyses using BI and ML based on the combined dataset of COI and Cyt b gene sequences (Fig. 4 ). Notably, T. punctulatus sp. nov. occupies a basal position within this clade of Traccatichthys , representing an early-diverging lineage in Traccatichthys and underscoring its distinct evolutionary history, which reinforces its status as a separate species. In addition, pairwise uncorrected p - distances between these species ranged from 1.58 % to 10.79 % for the COI gene (Table 2 ), with the maximum observed between T. zispi and T. punctulatus sp. nov. (10.79 %).

Figures

Figure 1. Morphological characteristics of Traccatichthys punctulatus sp. nov. A – C. Lateral, dorsal, and ventral views of holotype KIZ 2005013850; D. Living photograph; E – G. Lateral, dorsal, and ventral views of morphologic variation KIZ 2005013862. Scale bars: 1 cm.

Figure 2. Stomach and intestine of Traccatichthys punctulatus sp. nov. based on morphological examination. Scale bars: 5 mm.

Figure 3. Distribution map of Traccatichthys punctulatus sp. nov.

Figure 4. Bayesian phylogram of Traccatichthys based on a combined dataset of mitochondrial COI and Cyt b sequences. Numbers on branches represent Bayesian posterior probabilities (BPPs) from BI analysis and bootstrap supports (BS) from ML analysis.