Rhinogobius virgigena, 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 : 1423-1428

Rhinogobius virgigena new species

( Figures 5 , 9 , 13 )

Material examined

Holotype: ZRC 49204, 28.0 mm SL, Vietnam: Quang Ninh Province, Ba Che District, tributary of Ba Che River , about 11 km from Ba Che on road to Tien Yen, 21 ° 179100N, 107 ° 209020E, coll. M. Kottelat et al., 5 October 1998 . Paratypes: CMK 14975, two specimens , ZRC 49205, two specimens, 24.6–28.2 mm SL, same data as holotype .

Diagnosis

Rhingobius virgigena is distinguished from all congeners by the unique combination of the following features: cheek with a long, conspicuous brownish black stripe extending forwards to upper lip, followed posteriorly by a short brownish black bar in male; branchiostegal membrane deep grey in male with 9–12 round light spots; body with four to five small dark brown blotches in posteror part of lateral trunk; scales pockets with darker brown margin; pectoral fin base with one thin brownish black line in male; caudal fin base with a median black spot; second dorsal fin rays modally eight; anal fin rays eight; pectoral fin rays 16; longitudinal scale rows 30–31; predorsal median series 10–12; and vertebrae 26.

Description. Body rather slender, cylindrical anteriorly, compressed posteriorly. Body proportions in Table I. Head moderately large, slightly depressed anteriorly. Eye large, lips thick. Mouth oblique, rear edge reaching beyond vertical through anterior margin of pupil in male, merely extending beyond vertical of anterior margin of orbit in female. Both jaws with three to four rows of conical teeth, outer rows enlarged. Tongue margin rounded. Anterior nostril a short tube, posterior one a round hole. Gill opening extending to vertical through rear margin of preopercle. Isthmus broad. 10+16526 vertebrae.

Fins. D1 VI; D2 I/8–9 (mode 8); A I/8; P 16; 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 quite long and large, rear margin extending beyond vertical of anus in both sexes. V disc long and elliptical, spinous rays with pointed membranous lobe. C elliptical, rear edge rounded.

Scales. Body with moderately large ctenoid scales, anterior part of predorsal area naked; scales on posterior predorsal region and belly cycloid; scales in longitudinal series 30–31 (mode 31); transverse series eight to nine (mode nine); predorsal median series 10–12 (mode 11); series between 1st dorsal and upper pectoral fin origin six to seven (mode six) (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 vertical of pores H.

Head lateral-line system. Canals: nasal extension of anterior oculoscapular canal with terminal pores S 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 slightly smaller than the length of posterior oculoscapular canal. Preopercular canal with three pores c, d, E.

Sensory papillae: row a not reaching midline of orbit. Length of row b smaller than orbit. Row c, d long, not reaching the 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 with four to five small dark brown blotches in posterior part of lateral trunk in both sexes. Scales pockets with darker brown margin. Dorsal side of snout with a pair of brown lines united at tip of snout. A longitudinal brown stripe behind orbit. A dark brown mark below orbit in both sexes. Cheek with a long, conspicuous brownish black stripe extending forward to upper lip, posteriorly with a short brownish black bar in male; marking missing in female. Nape with a few deep brown marks or bars. A longitudinal brown line on middle from lower margin of eye to posterior point of opercle. Branchiostegal membrane deep grey in male, with 9–12 round or oblong light spots (orange in life), uniformly light yellow in female.

First dorsal fin pale white with dark spots in front of second spinous ray in male, none in female. Second dorsal fin pale white with two rows of blackish brown spots and greyish distal region in male, with three rows of longitudinal brown spots in female. Anal fin greyish with light margin. Pectoral fin whitish, fin base with one thin brownish black line in male, with one broader brown spot in female. Caudal fin with six to seven vertical rows of greyish brown spots, base with a median black spot. Pelvic fin pale white.

Distribution

Rhinogobius virgigena is presently known only from the type locality, in Ba Che drainage, northern Vietnam. It was collected together with R. variolatus .

Etymology

Virgigena, from the latin virga (coloured band on cloth) and gena (cheek). A noun in apposition.

Remarks

Rhinogobius virgigena is more similar to Rhinogobius duospilus ( Herre, 1935a) (a species endemic to Hong Kong) than to any other species in southern China. However, they can be distinguished by the following combinations of features: (1) body shape: rather slender body with lower body depth in R. virgigena (body depth in anal fin origin 12.1–12.4% (average 12.2%) versus 13.4–15.8% (average 15.1%) in male); (2) vertebral counts: R. virgigena with lower vertebrae count than R. duospilus (26 versus 27); and (3) coloration pattern in male: cheek with a rather long black stripe extending forward on upper lip and a short black bar in R. virgigena versus three conspicuous deep brown stripes in R. duospilus ; pectoral fin base with a thin black line in R. virgigena versus two blackish brown spots in R. duospilus .

Discussion

Although different degrees of head canal reduction have been seen in the Chinese species of genus Rhinogobius Gill, 1859 (Chen and Miller 1998; Chen and Fang 1999), even some species with complete reduction of head canal, almost all the Vietnamese species seem to represent the normal canal status of typical Rhinogobius canal development except the new species, R. variolatus , with some specimens as canal reduction of preopercular canal in male. However, very conspicuous coloration pattern, body shape, even some meristic features have been well distinguished from all nominal allopatric or sympatric species in Vietnam. Another five valid, endemic species seen in the Mekong basin also represent normal status of head canal development with different counts of vertebrae and other features ( Chen, Kottelat and Miller 1999; Chen and Kottelat 2000, 2003).

An artificial key to all nominal Rhinogobius species with longitudinal infraorbital neuromast organs from northern Vietnam

1. Pectoral fin base with a vertically greyish brown curve, pectoral fin ray counts more than 17................. R. leavelli – Pectoral fin base lacking vertical dark blotch; pectoral fin ray modally 15–16.. 2

2. Cheek with several densely set round dark spots as pupil size.. R. honghensis – Cheek unlike such pattern of marks.............. 3

3. Pectoral fin base with one thin, longitudinal dark line in male. R. virgigena n. sp. – Pectoral fin base always with two dark spots or marks in both sexes.... 4 4. Cheek with many oblique dark stripes in male...... R. sulcatus n. sp. – Cheek with round spots at least in lower part but lacking such stripes in male. 5

5. Cheek with two longitudinal rows of round black spots in male; LR usually 26–27;

VC modally 26............... R. variolatus n. sp.

– Cheek merely with two small greyish spots on lower region in male; LR usually 30–31; VC modally 27............. R. boa n. sp.

Figures

Figure 5. Head lateral-line system of Rhinogobius virgigena, holotype, ZRC 49204, 28.0 mm SL. Scale bar: 1 mm.

Figure 9. Rhinogobius virgigena, holotype, ZRC 49204, 28.0 mm SL, cephalic colour pattern of male. Scale bar: 1 mm.

Figure 13. Rhinogobius virgigena. (A) Male, holotype, ZRC 49204, 28.0 mm SL; (B) female, paratype, ZRC 49205, 28.2 mm SL.