Rhinogbius variolatus, Chen & Kottelat, 2005

Chen, I-Shiung & Kottelat, Maurice, 2005, Four new freshwater gobies of the genus Rhinogobius (Teleostei: Gobiidae) from northern Vietnam, Journal of Natural History 39 (17), pp. 1407-1429 : 1417-1422

Rhinogbius variolatus new species

( Figures 4 , 8 , 12 )

Material examined

Holotype: ZRC 49202, 26.8 mm SL, Vietnam: Quang Ninh Province, Cam Pha District , small coastal stream, at about km 10 on road from Mong Duong to Tien Yen, 21 ° 059380N, 107 ° 21920E, coll. M. Kottelat et al., 5 October 1998 . Paratypes: CMK 14982, three specimens , ZRC 49203, two specimens, 20.5–27.6 mm SL, same data as holotype . CMK 14951, one specimen, 20.2 mm SL, Vietnam, Quang Ninh Province, Ba Che District, Ba Che River 4 km up-river of Ba Che city, 21 ° 169340N, 107 ° 149540E, coll. M. Kottelat et al., 4 October 1998 .

Diagnosis

Rhingobius variolatus is distinguished from all congeners by the unique combination of the following features: cheek and opercle with two rows of longitudinally arranged black spots in male, none in female; branchiostegal membrane without distinct mark in male; body with two major longitudinal rows of brownish black spots on lower half of lateral trunk in male; pectoral fin whitish, base with two conspicuous black spots in male; caudal fin base with a median black spot; second dorsal fin rays modally eight; anal fin rays modally seven; pectoral fin rays 15; longitudinal scale rows 26–27; predorsal median series 8–11; and vertebrae modally 27.

Description

Body cylindrical anteriorly and compressed posteriorly. Body proportions in Table I. Head moderately large, slightly depressed anteriorly. Eye large, lips thick. Mouth oblique, rear edge reaching beyond vertical of anterior margin of pupil in male, not reaching vertical of anterior margin in female. Both jaws with three to four rows of conical teeth, and outer rows enlarged. Tongue margin rounded. Anterior nostril a short tube and posterior one a round hole. Gill opening extending to vertical through middle of opercle. Isthmus broad. 10+16217526227 vertebrae (mode 27).

Fins. D1 VI; D2 I/7–8 (mode 8); A I/7–8 (mode 7); P 15–16 (mode 15); V I/5+I/5 (frequency distribution in Table II). D1 rays about equal, III, IV longest, rear tip not extending to origin of D 2 in both sexes. A origin inserted below second branched ray of D2. P large, rear margin almost extending to vertical of anus in male; never reaching it in female. V disc rounded, spinous rays with pointed membranous lobe. C elliptical, rear edge rounded.

Scales. Body with rather large ctenoid scales, anterior part of predorsal area naked; scales on posterior predorsal region and belly cycloid; scales in longitudinal series 26–27 (mode 26); transverse series seven to eight (mode seven); predorsal median series 8–11; series between first dorsal and upper pectoral fin origin seven to eight (mode seven) (frequency distribution in Table III). Head including opercle, preopercle, and prepelvic areas naked. Predorsal squamation with slightly trifurcate anterior edge, anterior extension of median series reaching beyond the vertical of pores H.

Head lateral-line system. Canals: nasal extension of anterior oculoscapular canal with terminal pores S slightly in front of posterior nostril. Anterior interorbital section of oculoscapular canal separated, with paired pores l. A single pore K in posterior interorbital region. Pore v present at posterior edge of eye. Gap between anterior and posterior oculoscapular canals larger than the length of posterior oculoscapular canal. Preopercular canal usually with three pores c, d, E but few males lack pore c.

Sensory papillae: row a extending to midline of orbit. Length of row b much smaller than orbit. Row c, d long, not reaching vertical of pore a. A single cp papilla. Row f paired. Opercular rows ot and oi well separated.

Coloration in alcohol. Head and body light yellowish brown. Body without distinct dark blotches. Two major longitudinal rows of brownish black spots on lower half of lateral trunk in male, but indistinct merely with darker brown margins of scale pockets. Dorsal side of snout with a pair of brown lines united at tip of snout. A longitudinal brown stripe behind orbit. Cheek and opercle with two rows of longitudinally arranged black spots in male, none in female. A somewhat indistinct longitudinal thin brown line on middle of cheek. Branchiostegal membrane without distinct marks, uniformly light yellowish in both sexes.

First dorsal fin with light margin and a dark spot in front of third spinous ray in male, none in female. Second dorsal fin with two basal rows of blackish brown spots and greyish distal region in male, whitish with three rows of longitudinal brown spots in female. Pectoral fin whitish, base with two conspicuous black spots in male, a single brown spot in female. Caudal fin with three to five vertical rows of greyish brown lines and spots, base with a median black spot. Pelvic fin pale white.

Distribution

Rhinogobius variolatus is presently known only from the Ba Che drainage and an unnamed creek north of Cam Pha ( Figure 1 ). It was collected in a small, shallow coastal stream with a gravel to boulder substratum, and from the Ba Che river, which in the rainy season was flowing swift, turbid water over large boulders.

Etymology

From the latin variola (‘‘spotted disease’’, smallpox), allusion to the spots on the cheek and opercle. An adjective (feminine: variolata; neuter: variolatum).

Remarks

Rhinogobius variolatus has more similarities with R. linshuienesis Chen et al., 2002 (a species endemic to Hainan island) than with any other congener in southern China and Vietnam. They can be distinguished by the following features: (1) scale counts: R. variolatus has fewer longitudinal scales than R. linshuiensis (26–27 versus 29–30); (2) male coloration pattern: cheek with two rows of black spots in R. variolatus versus a single row of red spots in R. linshuiensis ; caudal fin base with a single median black spot in R. variolatus versus with two separated, greyish brown spots in R. linshuiensis .

Figures

Figure 1. Distribution of Rhinogobius boa (white triangles), R. sulcatus (diamond), R. variolatus (squares), and R. virgigena (black triangle) in north-eastern Vietnam. A, Mong Cai; B, Tien Yen; C, Ba Che; D, Mong Duong.

Figure 4. Head lateral-line system of Rhinogobius variolatus, paratype, CMK 14982, 25.9 mm SL. Scale bar: 1 mm.

Figure 8. Rhinogobius variolatus, holotype, ZRC 49202, 26.8 mm SL, cephalic colour pattern of male. Scale bar: 1 mm.

Figure 12. Rhinogobius variolatus. (A) Male, holotype, ZRC 49202, 26.8 mm SL; (B) female, paratype, ZRC 49203, 27.6 mm SL.