Microphysogobio nudiventris, Jiang & Gao, 2012

Jiang, Zhong-Guan & Gao, Er-Hu, 2012, Microphysogobio nudiventris, a new species of gudgeon (Teleostei: Cyprinidae) from the middle Chang-Jiang (Yangtze River) basin, Hubei Province, South China, Zootaxa 3586, pp. 211-221 : 212-215

Microphysogobio nudiventris sp. nov.

( Figs. 1 & 2)

Holotype. IHB 2011040304 , 64.7 mm SL, Du-He, a tributary flowing into Han-Jiang of Chang-Jiang basin, in Zhushan County, Hubei Province, South China, E Zhang & Z.G. Jiang, April, 2011.

Paratypes. IHB 201104076–7 , 2011040127 , 2011040131 , 2011040195 , 2011040303 , 2011040305–6 , 2011040311 , 2011040315–317 , 15 , 50.7–71.1 mm SL; other data same as holotype .

Diagnosis. Microphysogobio nudiventris belongs to the group of species with an incompletely scaled midventral region of the body. It, along with M. yaluensis , M. wulonghensis , and M. rapidus , differs from all other species of this group in having a scaleless midventral region of the body that extends more than two-thirds of the distance from the pectoral-fin insertion to the pelvic-fin insertion [vs. midway from the pectoral-fin insertion to the pelvic-fin insertion in M. linghensis , or to the pelvic-fin insertion in M. amurensis , M. chenhsienensis ( Fang 1938) , M. liaohensis (Qin 1987) , M. anudarini , M. chinssuensis and M. hsinglungshanensis ]. Microphysogobio nudiventris differs from M. yaluensis in having a slightly concave (vs. straight) distal edge of the dorsal fin, interorbital width greater (vs. less) than eye diameter, and a shorter snout with its length being less than (vs. greater than, or equal to) the postorbital head length, and from M. rapidus in having fewer perforated scales on the lateral line (35–37 vs. 39–41), fewer pectoral-fin rays (10–11 vs. 12–13), and a longer distance between the anus and analfin origin (14.1–17.7 vs. 8.2–13.1% SL). It differs from M. wulonghensis in having the two lateral lobes of the lower lip posteromedially disconnected (vs. connected), a heart-shaped median mental pad on the lower lip longitudinally bisected (vs. not bisected) by a groove, and more circumpeduncular scales (12 vs. 8–10).

Description. Morphometric data for type specimens are given in Table 1. See Figure 1 for general body appearance. Body small and slender, slightly compressed laterally. Lower surface of head and breast flat, abdomen rounded, caudal peduncle short and slightly compressed. Dorsal body profile rising sharply from tip of snout to dorsal-fin origin, greatly sloping along dorsal-fin base, then sloping gradually to caudal-fin base. Greatest body depth at dorsal-fin origin and least depth of caudal peduncle close to caudal-fin base. Anus located at anterior onethird of distance from pelvic-fin insertion to anal-fin origin.

Head short, length almost equal to body depth, roughly triangular in dorsal view. Snout slightly pointed, with a shallow groove across its tip in front of nostrils; snout length slightly less than postorbital part of head. Nostrils positioned closely; anterior one tubular, nearer to snout tip than to anterior margin of eye. Eye large, placed in dorsal half of head; interorbital space broad and flat, width greater than eye diameter. One pair of maxillary barbels rooted at extremity of upper lip, shorter than eye diameter, reaching beyond anterior margin of eye. Gill rakers rudimentary. Pharyngeal teeth in one row, with pointed, hooked and compressed tips.

Mouth inferior, horseshoe shaped. Lips thick, well developed, with globular papillae ( Fig. 2A). Papillae on median portion of upper lip arranged in one row and larger than all others; those on lateral portions in several rows. Median mental pad of lower lip heart-shaped, and longitudinally bisected by a groove into two elements of fleshly protuberances; two lateral lobes of lower lip covered with well-developed papillae, posteriorly disconnected from each other behind median mental pad and laterally connected with upper lip around corners of mouth. Upper and lower jaws with thin horny sheaths on their cutting margins ( Fig. 2A); width of cutting edge on upper jaw greater than half width of the mouth.

M. nudiventris M. kiatingensis (n = 9) Characters Paratypes (n = 15) Holotype Range Mean SD Range Mean SD

SL (mm) 64.7 50.7–71.1 57.8 6.08 54.1–88.8 65.5 12.65

In percentage of SL

Body depth 20.8 18.0–22.5 20.3 1.35 14.3–18.4 16.4 1.46

Predorsal length 41.5 37.1–47.5 43.7 2.37 39.5–44.7 42.8 1.60

Dorsal-fin base length 15.2 14.0–15.9 14.8 0.52 12.9–14.2 13.5 0.45

Dorsal-fin length 21.0 18.6–22.1 20.4 1.08 19.2–23.2 21.2 1.37

Preanal length 74.8 73.4–79.2 75.8 1.51 73.1–80.5 75.7 2.53

Anal-fin base length 9.9 7.7–10.1 8.9 0.72 6.5–9.7 8.1 1.23

Anal-fin length 12.3 12.1–15.2 13.6 1.03 11.7–14.5 13.5 1.02

Prepectoral length 19.9 18.9–23.8 21.5 1.37 21.2–24.0 22.5 0.95

Pectoral-fin base length 6.7 5.7–7.4 6.4 0.56 5.2–6.5 5.9 0.46

Pectoral-fin length 23.8 21.1–26.4 23.7 1.48 17.0–25.0 21.2 2.32

Prepelvic length 47.3 47.3–53.1 50.2 1.73 46.6–50.9 48.5 1.18

Pelvic-fin base length 5.3 4.7–6.1 5.4 0.35 4.2–5.9 5.0 0.63

Pelvic-fin length 16.7 13.3–17.3 15.2 1.40 12.6–17.8 16.0 1.73

Caudal-peduncle length 19.9 14.4–19.9 17.1 1.51 16.9–19.6 17.8 0.94

Caudal-peduncle depth 8.7 7.9–10.0 9.0 0.56 6.7–8.5 8.0 0.60

Head length 22.3 20.2–23.3 21.6 0.83 19.8–23.4 22.2 1.37

In percentage of HL

Head depth 71.0 63.9–73.2 68.8 2.54 56.7–62.9 59.0 2.20

Head width 76.1 73.9–84.5 76.9 2.73 58.6–70.8 64.2 3.40

Snout length 28.6 28.6–37.3 32.2 2.45 37.7–49.3 42.3 4.08

Eye diameter 27.7 23.3–28.8 26.3 1.39 22.0–32.0 26.7 3.19

Interorbital width 27.9 27.9–41.1 35.6 2.90 18.5–36.4 28.0 5.46

Mouth width 28.9 25.6–34.4 28.6 2.03 24.2–32.0 27.2 2.30

Maxillary barbel length 11.6 11.5–18.0 14.8 1.87 17.8–24.4 21.4 2.18

Fins flexible, without spinous rays. Dorsal fin with 3 simple and 7 (16) branched rays; distal margin slightly concave, origin far anterior to vertical through pelvic-fin insertion and nearer to snout tip than to caudal-fin base. Pectoral fin with 1 simple and 10 (5) or 11 (11) branched rays; inserted posterior to vertical through posteriormost point of operculum; tip of adpressed fin not extending to pelvic-fin insertion. Pelvic fin with 1 simple and 7 (16) branched rays, inserted below third or fourth branched dorsal-fin ray; tip of adpressed fin reaching beyond midway to anal-fin origin. Anal fin with 3 simple and 6 (16) branched rays; origin almost equidistant from pelvic-fin insertion and caudal-fin base. Caudal fin slightly emarginated, its lobes pointed.

Lateral line complete, almost straight, slightly curving ventrally at level of dorsal fin. Lateral-line perforated scales 35 (7), 36 (5), or 37 (4). Scale rows above lateral line 3.5 (16) and below 2 (16). Predorsal scales 10 (9) or 11 (7), and circumpeduncular scales 12 (16). Midventral region of body scaleless on anterior two-thirds of distance between pectoral-fin insertion and pelvic-fin insertion or more. Vertebrae 4+33 (9) -34 (7).

Coloration in preservative. Head blackish dorsally and dorsolaterally above level of ventral orbital margin, shading to grayish-white below, becoming yellow on ventral surface. Ground body color white and grey dorsally, yellow-white ventrally. A longitudinal dark brown stripe extending along lateral line with 8 or 9 indistinct black blotches; dorsal body and flank above longitudinal stripe densely covered with dark-grey irregular spots, spots more sparse below longitudinal stripe. Five black crossbars on back of body; first placed posterior to head, indistinct; second and third at dorsal-fin origin and posterior end of dorsal-fin base, respectively; forth at vertical though anal-fin origin; fifth at dorsal origin of procurrent caudal-fin rays. Each scale with a crescentic mark formed by black chromatophores. All fins grey and white with irregular spots scattered along branched rays; dorsal and caudal fins with more spots.

Distribution. Known only from the Du-He, a tributary flowing into the Han-Jiang of the middle Chang-Jiang basin, in Zhushan County, Hubei Province, South China ( Fig. 3).

Etymology. The specific epithet, here used as a noun, is a combination of the Latin nudus (naked) and ventris (belly), in allusion to the scalesless midventral region of the body which extends slightly more than two-thirds of the distance between the pectoral- and pelvic-fin insertions.