Leptobotia brachycephala, Guo & Zhang, 2021

Guo, Dong-Ming & Zhang, E, 2021, Re-description of the loach species Leptobotia citrauratea (Teleostei, Botiidae), with the description of L. brachycephala from southern Zhejiang Province, China, ZooKeys 1017, pp. 89-109 : 89

Leptobotia brachycephala sp. nov. (Fig. 4a, b)

Holotype.

IHB 201909037510, 63.9 mm SL; China: Zhejiang Province: Qingtian County: a stream discharging into the Ou-Jiang; 28°10'20"N, 120°12'51"E; collected by E Zhang and D.M. Guo, 8 October 2018.

Paratypes.

IHB 2017056858, 2017056869-80, 13 specimens, 54.2-66.8 mm SL; China: Zhejiang Province: Quzhou City: a stream flowing into the Qu-Jiang; 28°57'6"N, 118°51'15"E; collected by D.M. Guo, 15 December 2019.

Non-types examined.

IHB 64VI410-15, 930138-39, 8 specimens, 43.7-60.5 mm SL; China: Zhejiang Province: Longquan City: a stream flowing into the Ou-Jiang; 28°4'12"N, 119°6'54"E; collected in 1964 and 1983.

Diagnosis.

Leptobotia brachycephala , together with L. citrauratea and L. micra , is distinguished from all other congeneric species by the presence (vs. absence) of a row of orange dots or an orange stripe extending along the dorsal mid-line of the body from the nape to the caudal-fin base (Fig. 4a, b : lower). It differs from L. citrauratea and L. micra in having an emarginate (vs. forked) caudal fin with two rounded (vs. broadly pointed) lobes (Figs 1a-c , 4a, b : upper), a shorter head (18.4-22.8% SL vs. 22.5-26.8% SL in L. citrauratea and 23.6-25.9% SL in L. micra ), a slender caudal peduncle (14.6-20.0% SL vs. 12.1-15.8% SL in L. citrauratea and 11.8-13.5% SL in L. micra ), a shorter dorsal fin (9.0-11.6% SL vs. 13.7-18% SL in L. citrauratea and 11.0-4.6% SL in L. micra ) and a shorter anal fin (8.1-11.4% SL vs. 13.0-17.7% SL in L. citrauratea and 15.3-16.8% SL in L. micra ) (Table 2 , Fig. 2 ).

Description.

Morphometric data given in Tables 1 , 2 . See Fig. 4 for lateral and dorsal view of body. Body slender, strongly compressed laterally, with greatest depth at dorsal-fin origin. Dorsal profile of head rising progressively from tip of snout to nape, from there to caudal-fin base nearly straight. Ventral profile of head slightly concave; ventral profile of body almost straight or slightly concave. Lateral line nearly complete, extending along mid-lateral body to terminate in median caudal-fin rays. Cheek and trunk covered with some minute scales.

Head short, compressed laterally, longer than maximum body depth. Snout slightly obtuse in lateral view, slightly shorter than postorbital head. Eye small, dorsolateral, in upper half of head; diameter less than interorbital width. Mouth inferior, with opening laterally extended to vertical through anterior margin of nostril. Button-like structures in gular region absent; no median incisions in lower lip. Two rostral barbels at tip of snout. Maxillary barbel in corner of mouth, not reaching to level of anterior margin of eye. Simple suborbital spine ventral to anterior margin of eye, not or just reaching posterior margin of eye.

Fin rays flexible. Dorsal fin with 4 unbranched and 8 branched rays; distal margin slightly concave; origin slightly posterior to pelvic-fin insertion and closer to caudal-fin base than to tip of snout. Pectoral fin with 1 unbranched and 10-11 branched rays, not extending to midway from pectoral-fin to pelvic-fin insertion. Pelvic fin with 1 unbranched and 7 branched rays, not extending to halfway to anal-fin origin or not reaching anus; vent closer to anal-fin origin than to pelvic-fin insertion. Anal fin with 3 unbranched and 5 branched rays, not reaching caudal-fin base; distal margin slightly concave; origin closer to pelvic-fin insertion than to caudal-fin base. Caudal fin emarginate or shallowly forked, length of median fin rays 1.3-1.5 times in length of upper lobe; caudal-fin lobes rounded; upper and lower ones almost equal in length and shape.

Colouration.

In freshly-caught specimens, ground colour of head and body brownish-yellow; darker in upper half of head, but lighter in lower half of head and ventral side of body. A continuous or discontinuous orange stripe along mid-line of dorsum from nape to caudal-fin base, becoming more conspicuous towards caudal-fin base. Anterior to orange stripe, a short orange stripe present between eye and anterior margin of nape. A dark grey stripe on basal portion of dorsal fin and one stripe on dorsal fin. A dark grey band at caudal-fin base. Some irregular black stripes on caudal fin with hyaline distal edge. Distinct stripes absent from other fins. Specimens stored in formalin with ground colour of head and body pale brown. Discontinuous or continuous white line along dorsal mid-line of body also faded.

Geographical distribution and habitat.

Leptobotia brachycephala is known only from the Ou-Jiang and Qu-Jiang, two coastal rivers of southern Zhejiang Province, China (Fig. 3 ). Type specimens were caught in fast-flowing clear water with mixed substrate including pebbles, gravels and boulders (Fig. 5 ). Syntopic species included Sarcocheilichthys parvus Nichols, 1930, Acrossocheilus wenchowensis Wang, 1935, Cobitis sinensis Sauvage & Dabry de Thiersant, 1874 and Rhinogobius giurinus (Rutter, 1897).

Explanation of name.

The specific epithet is a Latin version of the Greek words βραχύς (short) and κεφαλά (head), with reference to the short head; to be treated as a noun in apposition.

Genetic comparisons.

A total of 50 unique haplotypes were detected amongst the 103 cyt b sequences of species of Leptobotia (Table 3 ). The fragment contained 784 conserved sites, 276 variable sites, 233 parsimony informative sites and 43 singleton sites. The average frequency of four nucleotides of L. citrauratea was A = 27.8%, T = 27.8%, C = 30.3% and G = 14.1%. The intraspecific genetic distance, calculated for sampled species of Leptobotia with more than one haplotype, varied from 0.1% to 0.8%. Leptobotia citrauratea is separated from other congeneric species by high genetic divergences of 2.9% to 10.5%; its intraspecific genetic distance was 0.4%. The genetic distance of L. brachycephala versus congeneric species ranged from 2.9% to 10.6%; its intraspecific genetic distance was 0.1% (Table 4 ).

In the Bayesian 50% majority consensus tree, samples of L. brachycephala formed a well-supported (100% pp) lineage and so did those of both L. citrauratea and L. elongata . L. citrauratea was distantly allied to L. elongata , but robustly supported by 100% pp to be sister to L. brachycephala (Fig. 6 ).

Comparative morphometrics.

In the Principal Component Analysis of specimens of L. citrauratea from Dongting Lake and the Gan-Jiang and L. brachycephala from the Ou-Jiang and Qu-Jiang, the first three components explained 91.60% of the total variance, of which 64.58%, 19.61% and 7.41% were explained, respectively by PC 1, PC 2 and PC 3 (Table 5 ). In the scatterplot of PC 2 and PC 3 loadings (Fig. 7 ), specimens of L. citrauratea and L. brachycephala constituted two distinct clusters separated on the PC 2 axis. Six characters with main loading on this axis were caudal-peduncle length, anal-fin length, dorsal-fin length, upper caudal-lobe length, pectoral-fin length and vent to anal-fin distance. Except for the last character, all of them exhibited differences in the morphometric comparisons. Table 2 and Fig. 2 show the main morphological characters.

Figures

Figure 1. Lateral (upper) and dorsal (lower) view of L. citrauratea for freshly-caught specimens a IHB 2017100265, topotype, 53.0 mm SL, China, Hunan Province, Yiyang City, Nanxian County, Dongting Lake b IHB 2017056850, 38.1 mm SL, China, Jiangxi Province, Nanchang City, Gan-Jiang c AMNH 8402, holotype, 50 mm SL, China, Hunan Province, Dungting (presently Dongting) Lake (photos by Department of Ichthyology, American Museum of Natural History).

Figure 2. Relationship between body depth and SL (a), between head length and SL (b), between caudal-peduncle length and SL (c) and between pectoral-fin length and SL (d) for two closely-related species: L. brachycephala (gray triangle) and L. citrauratea (light blue diamond).

Figure 3. Collection localities of L. brachycephala (dark blue star) and L. citrauratea (light green dot).

Figure 4. Lateral (upper) and dorsal (lower) view of body for L. brachycephala: a IHB 201909037510, holotype, 63.9 mm SL, China, Zhejiang Province, Lishui City, Qingtian County, Ou-Jiang, kept in formalin preservative after capture b IHB 2017056867, paratype, 62.5 mm SL, freshly collected from Qu-Jiang at Kecheng District, Quzhou City, Zhejiang Province.

Figure 5. Type locality of L. brachycephala: fast-flowing clear water with mixed substrate including pebbles, gravels and boulders.

Figure 6. Bayesian Inference tree inferred from the cyt b gene for 13 analysed species of Leptobotia. Nodal numbers are posterior probability values greater than 50 %

Figure 7. Scatter plot of the principal components II and principal components III, extracted from morphometric data of L. brachycephala: Ou-Jiang (plus symbol). L. citrauratea: Dongting Lake (black circle) and Gan-Jiang (white diamond).