Rhinogobius vermiculatus, Chen & Kottelat, 2003

Chen, I-Shiung & Kottelat, Maurice, 2003, Three New Freshwater Gobies Of The Genus Rhinogobius (Teleostei: Gobiidae) From Northeastern Laos, Raffles Bulletin of Zoology 51 (1), pp. 87-95 : 91-94

Rhinogobius vermiculatus , new species

( Figs. 3 , 6 , 9)

Material examined. – Holotype – ZRC 46583, 39.0 mm SL, Laos: Houaphan Prov., Houay Tangoua, small stream entering Nam Xam in Ban Houtangoua , 20 o 09’24’’ N 104 o 32’50’’ E, coll. M. Kottelat et al., 5 May.1999.

Paratypes – ZRC 47676, 2 specimens, LARReC, uncat., 2 specimens, NMMBA 464, 2 specimens , CMK 15306, 10 specimens, 16.6 – 47.7 mm SL, same data as holotype . CMK 15321, 4 specimens, 29.5 – 34.1 mm SL, Laos: Houaphan Prov., Nam Hang, small stream on road from Xam Tai to Ban Tao , about 6 km from Xam Tai , 19 o 59’06’’N 104 o 40’30’’E, coll. M. Kottelat et al., 6 May.1999 .

Diagnosis. – Rhinogobius vermiculatus can be distinguished from all other species of the genus by the combination of the following characters: second dorsal fin rays modally I/ 9; anal fin rays I/7; pectoral fin rays modally 16; longitudinal scale series 32-34; vertebral counts 10 + 18 = 28; first dorsal

fin with rays III and IV longest; body with 6-7 dark brown blotches and female with 5 longitudinal dark brown lines. Opercle with vermiculate lines against brown background and branchiostegal membrane with small dark greyish brown spots in male; and caudal fin base with a dark brown mark.

Description. – Body cylindrical anteriorly and compressed posteriorly. Body proportions in Table 1. Head moderately large, and depressed in adult male. Eye large, dorsolateral. Snout pointed and longer in male. Bony interorbital quite narrow. Cheek very fleshy in male. Lips thick, and with projecting lateral side of upper lip (especially in male). Mouth oblique, maxillary extending to vertical through middle of orbit. Both jaws with 3-4 rows of conical teeth, outer rows enlarged. Tongue tip rounded, entire. Anterior nostril a short tube, posterior one merely a very shallow tube. Gill-opening extending to vertical through posterior extremity of preopercle. Isthmus broad. 10 + 18 = 28 (in 10 specimens).

Fins. D1 V-VII (mode VI); D2 I/8-9 (mode 9); A I/7; P 15- 18 (mode 16); V I/5+I/5 (frequency distribution in Table 2). D1 rays III and IV longest and somewhat filamentous in male, with D1 rear tip reaching 1st or 2nd branched rays of D2 when depressed in male, not extending to D2 origin in female. D2 and A rear tips not reaching procurrent rays of C. Origin of A inserted at vertical line between 2nd and 3rd branched rays of D2. P oblong, rear tip not extending to anus. V disc rounded, spinous rays with pointed membranous lobes. C elliptical with rounded rear edge.

Scales. Lateral body with moderately large ctenoid scales, anterior predorsal area naked, posterior predorsal region and belly scales cycloid, with 7-11 middle series of predorsal scales; scales in longitudinal series 32-34 (mode 33); transverse series 9-10; series between D1 origin and upper P origin 6-7 (frequency distribution in Table 2). Head including opercle, preopercle, and prepelvic area naked. Predorsal squamation with trifurcate anterior edge, anterior tip of middle series reaching vertical through middle of opercle; both tips of lateral squamation extending forward to above pore of posterior oculoscapular canal.

Head lateral-line system. Canals. Nasal extension of anterior oculoscapular canal with terminal pores located at middle between anterior and posterior nostril. Anterior interorbital sections of oculoscapular canal separated, with paired pores

. A single pore k in posterior interorbital region. Pore present at posteriodorsal edge of eye. Gap between anterior and posterior oculoscapular canals somewhat smaller than length of posterior oculoscapular canal. Preopercular canal present with pores r, and. Sensory papillae. Row a extending to vertical through middle of orbit. Length of row b slightly shorter than orbit. Rows c, d long, and row c reaching or slightly beyond vertical of pore a. A single cp papilla. Row f paired. Opercular rows ot and oi slightly separated. Other details in Fig. 5 .

Colouration in alcohol. – Body yellowish brown with 6-7 dark brown blotches; 5 longitudinal dark brown lines in female, indistinct markings except darker margins of lateral

b

Fig. 2. Rhinogobius nammaensis , (a) ZRC 46582, holotype, male, 43.0 mm SL, and (b) CMK 15370, female, 36.1 mm SL; Laos: Nam Ma basin.

scales in larger male. Predorsal region with several short, dark brown bars. Cheek with many irregular brown stripes or spots and a horizontal brownish black bar crossing anterior part, that of lower half near preopercle with few white rounded spots. Opercle with 8-10 white vermiculations on brown background on lower half in male, usually indistinct with 3-4 larger spots or plain in female. Snout with a pair of brownish black lines uniting at anterior tip. A brownish black line behind orbit along lateral section of anterior oculoscapular canal. A somewhat squarish, brownish grey blotch below eye. Branchiostegal membrane scattered with dark greyish spots (which may have been brownish red when fresh) in male, unmarked in female.

First dorsal fin membranes between three anterior rays with a black spot, rest of fin with 2-3 rows of dark brown spots in male, with 3-4 rows of dark spots in female. Caudal fin greyish with 4-6 vertical rows of dark brown spots in male, with 4-5 rows of greyish to dark brown spots in female. Caudal fin base with a vertical, dark brown curved bar. Anal fin greyish black on distal half with narrow white margin in male, uniform whitish in female. Pectoral fin with a conspicuous black spot on upper part of base, and a brown blotch on lower portion; basal region with a semicircular mark. Pelvic fin greyish near basal portion in male whitish in female.

Distribution. – Rhinogobius vermiculatus has been collected only in small forest streams, with stony substrate and rapid current of the Nan Xam basin, northeastern Laos. Its presence is expected in the same basin in Vietnam.

Etymology. – From the Latin, vermiculatus (vermiculated), refers to the coloration pattern on the opercle.

Remarks. – Rhinogobius vermiculatus is more similar to R. albimaculatus Chen. Kottelat & Miller, 1999 , than any other species of Rhinogobius . They share the similar development of predorsal scales. However, R. vermiculatus can be distinguished from R. albimaculatus by more pectoral fin rays (modally 16 vs. 15), more scales on longitudinal rows (modally 32-33 vs. 30), few large, vermiculated lines on opercle (vs. many tiny round spots on cheek and opercle); branchiostegal membrane with rounded dark greyish brown spots in male (vs. with white spots on a dark brown background).

Figures

Fig. 3. Rhinogobius vermiculatus, CMK 15306, paratypes, (a) male, 34.1 mm SL, and (b) female, 41.1 mm SL; Laos: Nam Hang.

Fig. 6. Rhinogobius vermiculatus, CMK 15306, 47.7 mm SL; head lateral-line system. Scale bar = 1 mm.

Fig. 5. Rhinogobius nammaensis, ZRC 46582, 43.0 mm SL; head lateral-line system. Scale bar = 1 mm.