Sinocyclocheilus gracilicaudatus Zhao and Zhang
Wang, Dan, Zhao, Yahui, Yang, Junxing & Zhang, Chunguang, 2014, A new cavefish species from Southwest China, Sinocyclocheilus gracilicaudatus sp. nov. (Teleostei: Cypriniformes: Cyprinidae), Zootaxa 3768 (5), pp. 583-590: 584-589
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|Sinocyclocheilus gracilicaudatus Zhao and Zhang|
Figure 1View FIGURE 1
Holotype: ASIZB 186399, 94.7mm standard length ( SL), Zhujiang (Pearl) River Basin, Donglei Cave, Mulun town, Huanjiang County, Guangxi Zhuang Autonomous Region, China; 2009; collected by M. Y. Tian
Paratype: ASIZB 186400, 79.0mm SL, ASIZB 186401 (preserved in collection of South China Agricultural University) 60.8mm SL, same data as for holotype.
Diagnosis. The new species can be distinguished from other known congeners by the following combination of characteristics: body normal shape; eyes present, normal; well scaled excluding head; lateral-line curved, scales 59–64; half-hard dorsal-fin spine; 8 gill rakers; 8 predorsal vertebrae; caudal peduncle length 21.3–22.7 % of SL; caudal peduncle depth 10.5 –12.0% SL.
Description. General body characters are shown in Figure 1View FIGURE 1. Meristic features and proportional measurements as percentages of standard length are listed in Table 1.
Body moderately elongate and compressed. Dorsal profile convex from snout to dorsal fin, greatest body depth at dorsal fin insertion, and being slightly concave from end of dorsal-fin base to caudal fin. Ventral profile concave, tapering gradually toward anal fin.
Head compressed. Two pairs of nostrils, anterior and posterior nostrils neighbored, front edge of anterior nostril midway from snout tip to front edge of eye; anterior-nostril possessing a rim with a fleshy flap forming a small tube. Mouth curved and slightly sub-inferior. Two pairs of barbels; insertion of maxillary barbel in front of anterior nostril, barbel long, extending to middle part of operculum; rictal barbel long, reaching posterior margin of operculum. Eye present and well developed, round, anterior and posterior edge of orbit at one third and half distance between snout tip to posterior margin of operculum, respectively. Cranial sensory canals developed, superaorbital and infraorbital canals connected. Gill opening large. Gill rakers triangular, well developed, 8 on first gill arch, 2 and 6 on epibranchial and ceratobranchial respectively. Pharyngeal teeth in three rows with counts of 1,3,4-4,3,1 (one specimens checked), pharyngeal teeth at outer row strong and well developed, with curved and pointed tip.
Pectoral-fin insertion under posterior margin of operculum, pectoral fin not reaching pelvic fin insertion. Pelvic-fin insertion opposite dorsal-fin insertion; pelvic fin long, reaching four fifths of distance from pelvic-fin insertion to anus. Dorsal-fin a little closer to caudal fin base than to snout tip, last unbranched ray hard at base, softening toward tip, and with serrations along posterior edge. Anal-fin origin directly posterior to anus, reaching midway between anal-fin insertion to caudal fin base. Caudal-fin bifurcate.
Lateral-line complete and curved, descending to above pectoral-fin rays from posterior margin of operculum and ascending to body midline above anal-fin base where extends to end of caudal peduncle. Scales small. Lateralline scales larger than other scales. Lateral-line scale rows 59–64; scale rows above lateral line 22–24; scale rows below lateral line 13; circumpeduncular scale rows 38. Predorsal scales irregularly arranged and difficult to count accurately.
Coloration in alcohol.—Specimens were fixed in 10 % formalin and then preserved in 75 % alcohol. Dorsum dark grayish, abdomen light yellowish; no spots or blotches on body, head or fins; ventral aspect of caudal peduncle with very light black strip along midline from top of anus to base of caudal fin. Pectoral, dorsal and caudal fins grayish; anal-fin light grayish; pelvic-fin whitish.
Distribution. Known only from a subterranean river of a cave in the town of Mulun, Huanjiang County, Guangxi Zhuang Autonomous Region, China. The subterranean river drains to the Longjiang River, a tributary of the Pearl River System ( Fig. 2View FIGURE 2).
Etymology. The name gracilicaudatus is a noun in apposition, derived from gracilis meaning slender and caudatus meaning tail, in reference to the narrow caudal peduncle and caudal fin.
Discussion. Following the list of species of Sinocyclocheilus in Zhao et al. (2006), the new species can be distinguished from all other known species except for Sinocyclocheilus donglanensis , by having developed eyes, completely scaled body with a normal body shape, half-hard dorsal fin spine, curved lateral line with 59–63 lateralline scales, relatively short pectoral fin, 8 gill rakers and 8 predorsal vertebrae. Sinocyclocheilus gracilicaudatus is most similar to S. donglanensis . These two species are easily distinguished. Sinocyclocheilus gracilicaudatus has a more slender and longer caudal peduncle length (21.3–22.7 % vs. 16.8–20.4 % of SL) and narrower caudal peduncle depth (10.5 –12.0% vs. 12.5–15.5 % of SL) relative to S. donglanensis ( Fig. 3View FIGURE 3, Table 1). Interestingly, compared to S. donglanensis , Sinocyclocheilus gracilicaudatus has smaller eyes (eye diameter 5.8–8.3 % vs. 6.5–10.9 % of SL), but longer barbels (maxilla barbel length 16.6–24.3 % vs. 11.1–21.1 % of SL and rectal barbel length 19.5–21.6 % vs. 11.3–21.1 % of SL) ( Fig. 4View FIGURE 4, 5View FIGURE 5; Table 1). Moreover, principle component analysis (PCA) of morphometric characters also reveals the two species differing primarily on the basis of three additional characters, including length of the maxilla and rictal barbels and length of the lower jaw ( Fig. 6View FIGURE 6, Table 2).
PC I PC II
Standard length 0.2807 - 0.0107 Body depth 0.3278 0.1061 Predorsal length 0.2849 0.0087 Distance from head end to dorsal fin insertion (dorsal view) 0.319 - 0.0048 Sinocyclocheilus gracilicaudatus is also distributed allopatrically from S. donglanensis . The former species occurs only in a cave and the subterranean river of the Longjiang River system, a tributary of the Pearl River system. Whereas Sinocyclocheilus donglanensis occurs in the Hongshuihe River system, another tributary of the Pearl River system.
Based on morphology and DNA sequences, the genus Sinocyclocheilus could be divided into four clades, given the appellations “ jii ”, “ angularis ”, “ cyphotergous ”, and “ tingi ” (names of clades from species names representative of each clade.) Species of each clade have similar characteristics across each clade and they each have their own unique distributions with only very narrow overlap between the distributions of clades angularis and cyphotergous ( Zhao & Zhang, 2009) . Species of the “ jii ” clade have soft dorsal fin spines. Species of the “ angularis ” clade have a horn-like structure on the nape. Most species of the “ tingi ” clade have more than 70 lateral-line scale rows. Given the number of lateral-line scales (59–63), the new species is hypothesized to belong to the “ cyphotergous ” clade, although it does not have typical dorsal protuberance similar to a humpback ( Romero, et al., 2009; Zhao & Zhang, 2009). The distribution of the new species is also in the range of the “ cyphotergous ” clade.
Comparative materials. Sinocyclocheilus donglanensis : ASIZB 94976, holotype, 98.1mm SL, ASIZB 74217, 74218, 94747, 94748 (4 specimens), paratypes, 53.2–123.9mm SL, Zhujiang River basin: Hongshuihe River, Gongping Village, Taiping Town, Donglan County, Guangxi Zhuang Autonomous Region, China; 7 Oct 2002, by C. G. Zhang and K. Watanabe.
|N Min Max Mean SD Holotype|
|5 53.2 123.9 82.6 28.4|
|Width between posterior nostrils|
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