Sinocyclocheilus longicornus Luo, Xu, Wu, Zhou & Zhou, 2023

Xu, Cheng, Luo, Tao, Zhou, Jia-Jun, Wu, Li, Zhao, Xin-Rui, Yang, Hong-Fu, Xiao, Ning & Zhou, Jiang, 2023, Sinocyclocheilus longicornus (Cypriniformes, Cyprinidae), a new species of microphthalmic hypogean fish from Guizhou, Southwest China, ZooKeys 1141, pp. 1-28 : 1

Sinocyclocheilus longicornus Luo, Xu, Wu, Zhou & Zhou sp. nov.

Figs 4 , 5

Material examined.

Holotype. GZNU 20210503002, 135.9 mm total length (TL), 109.8 mm standard length (SL), adult male collected by Jia-Jun Zhou and Tao Luo on May 6, 2021 in Hongguo Town , Panzhou City, Guizhou Province, China (25.6576°N, 104.4044°E; ca. 1852 m a.s.l.) . Paratypes. Fourteen adult male specimens from the same locality as the holotype: GZNU20210503001, GZNU20210503003-03013, GZNU20210503015-503016, 84.3-116.4 mm SL, collected by Tao Luo, Jia-Jun Zhou, and Xing-Liang Wang on May 6, 2021 .

Diagnosis.

Sinocyclocheilus longicornus sp. nov. can be distinguished from all other congeners by the following combination of characters: (1) having a single, relatively long horn-like structure on the back of the head; (2) body scaleless, albinotic body without pigmentation; (3) reduced eyes; (4) dorsal-fin rays, ii, 7; (5) pectoral-fin rays, i, 13; (6) anal-fin rays, iii, 5; (7) pelvic-fin rays, i, 7; (8) lateral line pores 38-49; (9) gill rakers well developed, 9 on first gill arch; (10) tip of the pelvic-fin rays not reaching the anus when pelvic-fin rays extended backward.

Description.

Body moderately elongate and compressed. Dorsal profile convex from nape to dorsal-fin; greatest body depth at dorsal-fin insertion; ventral profile slightly concave, tapering gradually toward the caudal-fin; greatest body depth slightly anterior to dorsal-fin insertion.

Head short, compressed laterally, length longer than maximum head width, depth longer than maximum head width. large and long anterior horn-like structure present on back of head not forked at tip, at about 45° angle to horizontal and curved downward at tip. Reduced eyes present in upper half of head; eye diameter less than interorbital distance; interorbital distance larger than distance between posterior nostrils. Snout short, U-shaped, and projecting beyond lower jaw in dorsal view, less than half head length.

Mouth subterminal, with slightly projecting upper jaw. Two pairs of nostrils, anterior and posterior nostrils neighboring, nares at 1/3 between snout tip and anterior margin of eye; anterior nares possessing an anterior rim with a posterior fleshy flap forming a half-tube. Two pairs of barbels; rostral barbels long, insertion of rostral barbel in front of anterior nostril, not reaching anterior edge of operculum when rostral bent backward; maxillary barbel slightly shorter compared to rostral barbel, tip surpassing eye but not reaching anterior edge of operculum when bent backward. Gill opening large, opercular membranes connected at isthmus, gill rakers well developed, nine on first gill arch. Pharyngeal teeth in three rows with counts of 2, 3, 5-5, 3, 2; pharyngeal teeth strong and well developed, with curved and pointed tips.

Dorsal fin with two unbranched and seven branched rays; last unbranched dorsal-fin ray hard at base, softening toward tip, with strong serrations along posterior edge; distal margin slightly concave, origin slightly anterior to, or superior to, pelvic-fin insertion and closer to caudal-fin base than to snout tip. Pectoral fin long with one unbranched and 13 branched rays; tip of depressed fin extending about midway between pectoral fin and pelvic-fin insertion; extending from posterior to pelvic-fin insertion and reaching to 35.44% of pelvic-fin length. Pelvic-fin long with one unbranched and seven branched rays, insertion slightly in front of dorsal-fin insertion, tip of the pelvic-fin rays not reaching the anus when pelvic-fin rays extended backward. Anus closer to anal-fin insertion than pelvic-fin insertion; anal fin with three unbranched and five branched rays; tip of anal-fin not reaching to caudal-fin base. Caudal fin with 17 branched rays and 14 unbranched rays, strongly forked; upper and lower lobes broadly pointed, unequal in length and shape.

Lateral line complete, slightly straight, curved upward at the anus position, originating from posterior margin of operculum and extending to end of caudal peduncle. Body scaleless, lateral line pores 38-49.

Coloration of holotype. In life, body overall white, slightly pink posterior to dorsal fin; barbels and gills red (Fig. 5 ); with white granular nuptial organs on dorsal surfaces of horn-like structure on back of head and snout (Fig. 5 ). In 10% formalin, body overall light yellow; posterior part of operculum and all fins partially transparent (Fig. 4 ).

Comparative morphology.

Sinocyclocheilus longicornus sp. nov. is assigned to the Sinocyclocheilus angularis species group based on phylogenetic analysis and the shared presence of the anterior horn-like structure on the back of the head (Fig. 2 ; Zhao and Zhang 2009). Comparative data of Sinocyclocheilus longicornus sp. nov. with the 21 recognized species in the S. angularis and S. microphthalmus species groups are given in Table 3 .

Sinocyclocheilus longicornus sp. nov. differs from 55 species in the S. cyphotergous , S. jii , and S. tingi species groups by the presence of a horn-like structure on the back of the head (vs. absent). From the 21 species in the S. angularis and S. microphthalmus species groups, Sinocyclocheilus longicornus sp. nov. can be distinguished from S. altishoulderus , S. jiuxuensis , S. brevibarbatus , S. microphthalmus , S. zhenfengensis , and S. mashanensis by having a long horn-like structure on the back of the head (vs. absent or indistinct), further distinguished from S. brevibarbatus , S. mashanensis , S. simengensis , S. zhenfengensis by reduced eyes (vs. normal); differs from S. furcodorsalis , S. hyalinus , S. anatirostris , S. aquihornes , S. tianlinensis , S. anshuiensis , S. convexiforeheadus , and S. tianeensis by reduced eyes (vs. absent).

Sinocyclocheilus longicornus sp. nov. differs from S. angularis by having a relatively long horn-like structure (14.7 ± 1.5 mm vs. 10.6 ± 1.9 mm; p -value <0.01, Table 4 ), long rostral and maxillary barbels (p -value <0.05, Table 4 ), two unbranched dorsal-fin rays (vs. three), pectoral-fin rays (ii, 13 vs. i, 15-18), pelvic-fin rays (i, 7 vs. i, 8-10), gill rakers (nine vs. seven), and body scaleless (vs. body covered with thin scales); from S. bicornutus by single horn-like structure on the back of the head (vs. forked), dorsal fin rays (ii, 7 vs. iii, 7), pectoral-fin rays (ii, 13 vs. i, 15-18), body scaleless (vs. body covered with thin scales), and tip of the pelvic-fin rays not reaching the anus when pelvic-fin rays extended backward (vs. beyond the anus); from S. broadihornes and S. simengensis by dorsal fin rays (ii, 7 vs. iii, 6-7), anal-fin rays (iii, 5 vs. ii, 5), and lateral line pores (38-49 vs. 35-37 in S. broadihornes and 56-57 in S. simengensis ); from S. flexuosdorsalis by having a relatively long horn-like structure (vs. short), dorsal-fin rays (ii, 7 vs. iii, 8), pectoral fin rays (ii, 13 vs. i, 12-13), snout length to standard length ratio is small (12.4% vs.14.4%), body scaleless (vs. body covered with scales), and tip of the pelvic-fin rays not reaching the anus when pelvic-fin rays extended backward (vs. beyond the anus); from S. tileihornesy by dorsal-fin rays (ii, 7 vs. iii, 7), anal-fin rays (iii, 5 vs. ii, 5), pelvic-fin rays (i, 7 vs. ii, 6-7), pectoral fin rays (ii, 13 vs. i, 12-15), pelvic fin rays (i, 7 vs. i, 6), lateral line pores (38-49 vs. 35-37), gill rakers (9 vs. 6-8), and tip of the pelvic-fin rays not reaching the anus when pelvic-fin rays extended backward (vs. beyond the anus).

Sinocyclocheilus longihornes can be morphologically distinguished from its close relatives S. rhinocerous and S. hyalinus . Sinocyclocheilus longicornus sp. nov. differs from S. hyalinus by eyes small and degenerate (vs. absent), dorsal-fin rays (ii, 7 vs. iii, 7), pelvic-fin rays (i, 7 vs. ii, 6-7), lateral line pores (39-45 vs. 35-37), and tip of the pelvic-fin rays not reaching the anus when pelvic-fin rays extended backward (vs. beyond the anus). Sinocyclocheilus longicornus sp. nov. differs from S. rhinocerous by having a large body size (123.3 ± 11.3 mm vs. 76.5 ± 12.3 mm; p -e = 0.00, Table 3 ), long horn-like structure (14.7 ± 1.5 mm vs. 9.4 ± 2.1 mm; p = 0.00, Table 3 ), dorsal-fin rays (ii, 7 vs. iii, 7), pectoral-fin rays (ii, 13 vs. i, 12), pelvic-fin rays (i, 7 vs. i, 6), gill rakers (9 vs. 8), and a relatively long, single horn-like structure on the back of the head (14.7 ± 1.5 mm vs. 9.4 ± 2.1 mm; p <0.01, Table 4 ). In addition, except for morphological characteristics (eye diameter, mouth width) and some ratios, such as the SL to TL ratio, SL to CPL ratio, SL to PPVL ratio, and HW to IOD ratio, the remaining morphometric values and ratios of Sinocyclocheilus longicornus sp. nov. are significantly greater than those of S. rhinocerous .

Geographical distribution and habitat.

Sinocyclocheilus longicornus sp. nov. is only known from the type locality, a vertical cave some distance from Hongguo Town, Panzhou city, Guizhou, China at an elevation of 2276 m. There was no light inside the cave. Individuals of S. longicornus sp. nov. were located in a small pool ~ 25 m from the cave entrance. The pool was ~ 1.8 m wide and 80 cm deep, with a water temperature of ~ 16 °C at collection time and a water pH of 7.4. The 15 specimens collected on 3 May 2021 were all adult males. Therefore, we believe that the breeding period started from mid-April. Within this cave, Sinocyclocheilus longicornus sp. nov. co-occurred with Triplophysa sp., and Sinocyclocheilus sp. Outside the cave, the arable land was farmed to produce maize, wheat, and potatoes.

Etymology.

The specific epithet longicornus is an invariable noun in apposition, derived from the Latin words longus, meaning long, and cornu or cornus, meaning horn of the forehead, in reference to the presence of a long horn-like structure on the forehead of the species. We propose the English common name Long-Horned Golden-lined Fish and the Chinese common name Cháng Jiǎo Jīn Xiàn Bā (长角金线鲃).

Figures

Figure 2. Phylogenetic tree based on mitochondrial Cyt b + ND 4 genes. In this phylogenetic tree, ultrafast bootstrap supports (UBP) from ML analyses / Bayesian posterior probabilities (BPP) from BI analyses were noted beside nodes. The scale bar represents 0.07 nucleotide substitutions per site. The numbers at the tip of branches corresponds to the ID numbers in Table 2. Different colored rectangular and triangular boxes in addition to the nodes denote the different states of the presence of horn-like structures of species within the genus Sinocyclocheilus.

Figure 4. Lateral view of adult male holotype GZNU 20210503002 of Sinocyclocheilus longicornus sp. nov. in preservative. A left side view B right side view.

Figure 5. Live adult male paratype of Sinocyclocheilus longicornus sp. nov.