Saurogobio gracilicaudatus Yao & Yang
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publication ID |
https://doi.org/ 10.11646/zootaxa.3847.2.8 |
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publication LSID |
lsid:zoobank.org:pub:5C18E9A1-9D8D-4715-86F6-8714FF2CE3AE |
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DOI |
https://doi.org/10.5281/zenodo.5619169 |
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persistent identifier |
https://treatment.plazi.org/id/AA26345B-FFFA-FFE3-FF2C-F9247F51FD02 |
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treatment provided by |
Plazi |
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scientific name |
Saurogobio gracilicaudatus Yao & Yang |
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Saurogobio gracilicaudatus Yao & Yang View in CoL in Luo, Yue & Chen 1977
( Fig. 2 View FIGURE 2 )
Saurogobio gracilicaudatus Yao & Yang in Luo, Yue & Chen, 1977: 542 (Yichang, and Guanghua [now Laohekou] in Hubei Province); Yue in Chen, 1998: 385 (Yichang, Laohekou, and Danjiangkou in Hubei Province, and Taoyuan in Hunan Province).
Examined material. South China: Hubei Province: IHB 63VII 2598, 632745-8, 5 specimens, 83.1–133.4 mm SL, Chang-Jiang at Yichang City; IHB 592749, 1 specimen, 143.2 mm SL, Han-Jiang of middle Chang-Jiang basin at Laohekou City; these six specimens are syntypes. IHB uncatalogued, 8 specimens, 100.3–116.0 mm SL, mainstream of middle Chang-Jiang at Wuhan. Hunan Province: IHB 2012120223-7, 5 specimens, 100.3–116.0 mm SL, Xiang-Jiang of Dongting Lake system in lower Chang-Jiang basin, Xiangyin County.
Diagnosis. Saurogobio gracilicaudatus is easily distinguished from all congeners by having a slightly crenulated (vs. non-crenulated) median part of the rostral cap; numerous, brush-like and conical (vs. globular, if present) papillae scattered over lips, and a smaller (vs. larger), non-papillated (vs. papillated), protruded (vs. nonprotruded) central pad of the lower lip anteriorly free (vs. not free) ( Fig. 1 View FIGURE 1 A).
Description. Morphometric data for examined specimens including the types are given in Table 1 View TABLE 1 . See Figure 1 View FIGURE 1 A for ventral view of head, and Figure 2 View FIGURE 2 for general body appearance. Body slender, dorsally rounded and ventrally flattened in cross-section anterior to pelvic-fin insertion, becoming increasingly circular in cross-section from pelvic-fin insertion to anal-fin origin and ovoid in cross-section posterior to anal-fin origin. Greatest body depth at dorsal-fin origin, evenly decreasing in depth toward caudal-fin base; least caudal-peduncle depth near to caudal-fin base. Dorsal profile of body slightly convex anterior to dorsal-fin origin, from there to caudal-fin base slightly concave. Ventral profile flattened from snout tip to anal-fin origin, from there to caudal-fin base concave. Anus located at anterior one-third of distance between pelvic-fin insertion and anal-fin origin.
Head slightly depressed, wider than deep, twice as long as deep, longer than body depth. Snout pointed in lateral view, longer than postorbital portion of head, with shallow transverse notch across tip anterior to nostrils. Nostrils nearer to anterior edge of eye than to snout tip. Eye moderate, horizontally ovoid, and dorsolaterally positioned in middle of head. Interorbital space slightly concave, wider than eye diameter. Pair of maxillary barbels rooted at corners of mouth, longer than or nearly equal to eye diameter.
Mouth inferior and horseshoe-shaped. Rostral cap well-developed, non-papillose with slightly crenulated median part, partially overhanging median portion of upper lip, separated from upper lip by groove, and laterally continuous with lower lip around corners of mouth. Lips thick, well-developed, and densely covered with brushlike, conical papillae. Distal edge and inner surface of upper lip completely papillated; papillae scarcely scattered over external surface of lateral portion of upper lip. Lower lip modified into two lateral lobes and a central pad; lateral lobe expanded as wing-shaped, triangular flap completely covered with papillae, anteromedially discontinuous from its counterpart anterior to central pad, but posteromedially continuous with its counterpart posterior central pad, and posterolateraly confluent with upper lip around corner of mouth; central pad smooth, protruded, anteriorly free and posteriorly continuous with lateral lobes. Anterior fold of lower lip (typical for all other congeners) absent or greatly reduced. Postlabial groove prolonged, extending anteromedially to meet with its counterpart. Upper and lower jaws completely enclosed by lips.
Dorsal fin with 1 simple or unbranched and 8 1/2 (20) branched rays, last one split to base; longest ray shorter than head; origin anterior to pelvic-fin insertion, nearer to snout tip than to caudal-fin base; distal margin somewhat concave. Pectoral fin with 1 simple and 14 (1), 15 (11) or 16 (8) branched rays, longest one shorter than head; inserted closer to snout tip than to pelvic-fin insertion; tip of adpressed fin extending beyond dorsal-fin origin, not reaching pelvic-fin insertion. Pelvic fin with 1 simple and 7 (20) branched rays; inserted below fourth or fifth branched dorsal-fin ray, about halfway from pectoral-fin insertion to anal-fin origin; tip of adpressed fin not extending to caudal-fin base; axillary lobe at pelvic-fin base. Anal fin with 3 simple and 6 1/2 (5) branched rays, last one split to base; origin nearer to caudal-fin base than to pelvic-fin insertion; distal margin slightly concave; tip of adpressed fin extending far short of ventral origin of procurrent rays of caudal fin. Caudal fin deeply forked with two pointed lobes; lower lobe slightly larger and longer than upper one.
Lateral line complete; 44 (7), 45 (10) or 46 (3) perforated scales. Scale rows above lateral line 6 1/2 (20), and below 3 1/2 (20). Circumpeduncular scales 12 (20). Predorsal scales 13 (5), 14 (8) or 15 (7). Gas bladder reduced; anterior chamber enveloped in bony capsule, and posterior chamber very small, stick-like. One row of pharyngeal teeth (IHB 2012120223, 97.7 mm SL); tooth pattern 5-5, with hooked and pointed tips. Scales missing on anterior two-thirds or more of chest and abdomen between pectoral- and pelvic-fin insertions.
Coloration in preservative. Top of head black; infraorbitals and operculum grayish or light brown; all other portions of check, and ventral surface of head yellow-white. Each scale on back and flank with dark chromatophores along exposed portion of its posterior edge forming a faint, dusky, crescentic mark. Dorsal and caudal fins dusky, and all other fins white.
Distribution and conservation status. Saurogobio gracilicaudatus is currently known from the middle Chang-Jiang basin ( Fig. 3 View FIGURE 3 ). It was initially described from the main stream of the middle Chang-Jiang at Yichang City, and the Han-Jiang of the middle Chang-Jiang basin at Guanghua County (presently Laohekou City), Hubei Province. Chen (1990) reported on the occurrence of this species in Hubei Province where it was also found in the main stream of the Chang-Jiang at Three Gorges, and Donghu Lake linked to the middle Chang-Jiang at Wuhan. Yue in Chen et al. (1998) documented A. gracilicaudatus from the main stream of the middle Chang-Jiang at Yichang City and the Han-Jiang (a tributary of the middle Chang-Jiang basin) at Danjiangkou and Laohekou cities, Hubei Province, and the Yuan-Jiang (a tributary of the Dongting Lake system in the middle Chang-Jiang basin) at Taoyuan County, Hunan Province, South China. Our specimens are from the Xiang-Jiang (a tributary of the Dongting Lake system in the middle Chang-Jiang basin) at Xiangyin County, Hunan Province, South China.
Despite the persistence of A. gracilicaudatus in the middle Chang-Jiang basin, its known occurrence has continually declined during the past half-century or more. As a result of the construction of the Gezhouba Dam and Three Gorges Dam in the early 80s and the late 90s of the last century, respectively, at Yichang City across the main stream of the middle Chang-Jiang, this benthic, rheophilic species has disappeared; it live in reservoirs. It has not been found in Donghu Lake since the early 60’s of the last century when the lake, whose outlet joins the Chang- Jiang through Qinshan canal, was controlled by a sluice gate. Evidently, this species has declined in its geographic range and population size due to habitat alteration brought about by anthropogenic activities. According to the IUCN Red list guidelines ( IUCN, 2012), it is herein classified as a vulnerable species.
TABLE 1. Morphometric data of Saurogobio gracilicaudatus (n = 20).
| In percentage of SL | Range | Mean | SD |
|---|---|---|---|
| Body depth | 13.1–17.4 | 14.6 | 1.23 |
| Pre-dorsal length | 37.3–43.7 | 41.1 | 1.88 |
| Dorsal-fin base length | 13.8–16.3 | 15.0 | 0.79 |
| Dorsal-fin length | 17.1–21.1 | 18.6 | 0.97 |
| Pre-anal length | 71.4–76.7 | 74.9 | 1.23 |
| Anal-fin base length | 7.1–8.9 | 8.1 | 0.50 |
| Anal-fin length | 9.7–14.7 | 12.5 | 1.13 |
| Pre-pectoral length | 22.4–25.8 | 24.9 | 0.93 |
| Pectoral-fin base length | 5.0–7.2 | 6.2 | 0.59 |
| Pectoral-fin length | 16.1–21.0 | 19.3 | 1.17 |
| Pre-pelvic length | 47.3–50.4 | 48.7 | 0.71 |
| Pelvic-fin base length | 3.0–4.5 | 3.9 | 0.38 |
| Pelvic-fin length | 11.3–14.3 | 13.2 | 0.90 |
| Caudal-peduncle length | 11.4–14.0 | 12.7 | 0.72 |
| Caudal-peduncle depth | 4.6–6.6 | 5.3 | 0.43 |
| Head length | 22.6–27.2 | 25.4 | 0.93 |
| In percentage of HL | |||
| Head depth | 34.7–50.5 | 46.1 | 3.09 |
| Head width | 44.6–61.9 | 50.4 | 4.21 |
| Snout length | 44.5–52.4 | 48.1 | 2.02 |
| Eye diameter | 15.5–22.0 | 18.5 | 1.96 |
| Interorbital width | 21.7–27.9 | 25.1 | 1.58 |
| Mouth width | 19.2–31.8 | 22.0 | 2.76 |
| IHB |
Institute of Hydrobiology, Chinese Academy of Sciences |
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