Pseudogobiopsis tigrellus ( Nichols, 1951 )

Larson, Helen K., 2009, Review Of The Gobiid Fish Genera Eugnathogobius And Pseudogobiopsis (Gobioidei: Gobiidae: Gobionellinae), With Descriptions Of Three New Species, Raffles Bulletin of Zoology 57 (1), pp. 127-181 : 167-169

Pseudogobiopsis tigrellus ( Nichols, 1951)

( Fig. 31 ; Plate 2C; Tables 13–16, 20)

Gobius tigrellus Nichols, 1951: 3 , Fig. 2 (Bernhard Camp, Idenburg River, West New Guinea). – Larson 2001: 71–72, Fig. 68 (as incertae sedis).

Ctenogobius tigrellus – Allen 1996: 19.

Material Examined. Holotype, AMNH 18574 , 1 (21.5), 75 m altitude, Bernhard Camp, Idenburg River [tributary of Mamberamo River], West New Guinea, W. B. Richardson, Apr.1939 . Paratypes, AMNH 15096 , 9 (16–22), same data as holotype . WAM P.31752- 001, 6(21.0–25.5), Furu Creek , Mamberamo River, West Papua, 0.1–1.0 m, G . R. Allen, 4 Sep.2000 ; WAM P.31754-003, 1(24.5), Dabra, Tiri Creek , Mamberamo River, West Papua, 0.1–1.0 m, G . R. Allen, 7 Sep.2000 .

Description. – Based on eight specimens, 21.0– 25.5 mm SL; osteological information from x-rays of type specimens. An asterisk indicates the counts of the holotype.

First dorsal VI*; second dorsal I,7*; anal I,6–7* (modally I,6), pectoral rays 14*–16 (modally 15), segmented caudal rays 17*; caudal ray pattern 9/8; branched caudal rays 14–15, in 7/7 pattern (broken in holotype); longitudinal scale count 23–25 (24 in holotype); TRB 7–8*; predorsal scale count 2–9 (1 in holotype); circumpeduncular scales 12*. Gill rakers on outer face of first arch 2+6 (in 1), 2+7 (in 1). Vertebrae 10+16 (in 9), 10+15 (1). Neural spine of second vertebra slightly expanded at tip (in 2), or all pointed (in 1). Two epurals (in 7); nearly fused in two. One to three (modally 2) anal pterygiophores before haemal spine of first caudal vertebra (in 9).

Body slender, compressed. Body depth at anal fin origin 17.1–18.6% (mean 17.9%) of SL. Head slightly depressed, wider than deep, but not greatly so, HL 25.8–31.6% (mean 28.7%) of SL. Depth at posterior preopercular margin 51.5– 61.3% (mean 58.4%) of HL. Width at posterior preopercular margin 58.8–75.8% (mean 69.3%) of HL. Mouth subterminal, very slightly oblique, forming an angle of about 12° with body axis; jaws reach to below just past middle of eye in males and to below front half of eye in females. Lips fleshy, smooth. Upper jaw 34.3–47.2% (mean 35.0% in females, 44.2% in males) of HL. Eyes dorsolateral, forming part of dorsal profile, 25.0–29.9% (mean 27.7%) of HL. Snout short, rounded to slightly pointed, 25.4–30.8% (mean 27.7%) of HL. Interorbital narrow, 8.3–13.3% (mean 10.2%) of HL. Caudal peduncle slender, compressed, length 25.6–30.8% (mean 28.5%) of SL. Caudal peduncle depth 11.4–13.5% (mean 12.0%) of SL.

First dorsal fin triangular in males, triangular to slightly rounded in females, tips of spines free; spines slightly longer in males than females; fin barely reaches second dorsal origin when depressed. First dorsal spine always longest, spine length 12.2–16.7% (mean 14.2% in females, 15.7% in males) of SL. In females, second dorsal fin short and triangular, anterior rays longest, posteriormost rays fall well short of caudal fin base when depressed; in males second dorsal fin triangular, anterior rays tall but posteriormost rays longer (about twice height of anteriormost ray), elongate and reaching to caudal fin base in two largest male specimens. Anal fin rounded, posteriormost rays longest, especially in males, but always falling short of reaching caudal fin base. Pectoral fin slender, pointed, central rays longest, 20.0–29.4% (mean 26.2%) of SL; rays all branched. Pelvic fins oval, reaching to anus, 22.8–28.6% (mean 25.9%) of SL; frenum Plate 2.

A. Pseudogobiopsis festivus , new species, captive specimen from Bako National Park, Sarawak. Photograph by Peter Ng.

B. Pseudogobiopsis oligactis , captive specimen from Andaman coast, Thailand. Photograph by Gerhard Ott.

C. Pseudogobiopsis tigrellus , captive male specimen from Furu Creek, Mamberamo River, West Papua (one of WAM P.31752-001). Photograph by Gerry Allen.

fleshy, especially around pelvic spines. Caudal fin oval to slightly pointed, 12.2–16.7% (mean 14.7%) of SL.

No mental fraenum, chin smooth to slightly raised. Anterior nostril tubular, placed just behind upper lip, tube short, oriented upward. Posterior nostril oval, placed close to anterior margin of eye, above level of centre of eye. Gill opening extends forward to under opercle. Inner edge of shoulder girdle smooth. Gill rakers on outer face of first arch very short and stubby, longest rakers near angle of arch. Tongue tip blunt to slightly concave. Teeth in upper jaw in three or four rows, outer row teeth largest and stoutest (in males especially); all teeth small, sharp and conical; largest tooth at mid-side of jaw. Lower jaw small and sharp, in broad band of three to five rows across front of jaw; side of jaw with two rows of slightly more upright sharp teeth; outermost row of teeth across front of jaw largest, stoutest and more curved.

Predorsal scales small, cycloid; arrangement variable (one fish with scales right up to behind eyes, others have scales up to above rear margin of preopercle at least on the side, with only a few scales on midline). Operculum with one to several cycloid scales, usually partly embedded. Cheek, pectoral base and prepelvic area naked. Belly midline broadly naked. Side of body covered with ctenoid scales; scales on midbody slightly larger than others.

Head pores as for Pseudogobiopsis oligactis , with three preopercular pores ( Fig. 31 ).

Sensory papillae pattern with cheek rows a, c and cp composed of few large, widely spaced papillae; rows b and d of small, closely spaced papillae ( Fig. 31 ). Two s rows on snout, of one papilla each, just behind upper lip, other papillae close together by posterior nostril. Mandibular papillae widely spaced, with mental f row consisting of one papilla on each side of symphysis.

Colouration of fresh material. – Based on scans of colour slides of captive male and female by Gerry Allen (Plate 2C). Head and body translucent pearly grey, with 12–14 black to blackish narrow vertical bars along side of body and posterior half of head, dorsum with short blackish lines and blotches partly following scale margins, predorsal region with irregular black blotches and lines; side of body dusted with orange and pink-gold speckles, most noticeable in between vertical black bars. Side of head with two oblique black lines crossing cheek from ventral edge of eye; opercle with vertical black bar posteriorly (continuation of anteriormost vertical bar on nape) and two black blotches anteriorly (ventralmost is a blotch in male and oblique line in female, a continuation of dorsalmost oblique line from eye). Interorbital and snout with irregular blackish lines and spots and intensification of the orange and pink-gold speckles. Iris silvery, becoming pale golden dorsally, and speckled with brown. Tips of lips dull yellowish with dusky blotches extending from snout tip.

Dorsal fins translucent yellowish-white with black markings. In male, first dorsal fin with 5–6 irregular lines, becoming vermiculate and broken posteriorly, fin margin narrowly dense black, post-margin region plain yellowish white. In female, first dorsal fin similar but with four blackish irregular lines and broad blackish margin and dense black double spot at rear of fin. Second dorsal fin pattern in males similar to that of first dorsal fin but fin margin more diffusely blackish and irregular lines more oblique and broken, especially on posterior half of fin; in females, second dorsal fin similar to first dorsal fin in that fewer dark lines present. Caudal fin transparent, rays yellowish, rear margin of fin slightly dusky, 8–10 vertical blackish lines crossing fin, basalmost line broadest and most intense, forming narrow blotch (within line) at mid-base of fin; ventralmost quarter of fin unmarked. Anal fin plain whitish yellow. Pectoral fin transparent. Pelvic fins transparent, dusted lightly with melanophores.

Colouration of preserved material. – Preserved colour is basically the same as live colour, with background colour yellowish white and brown to dark brown body markings, scale margins on upper half of body thinly outlined with fine dark speckling, dorsal fin markings black to dark brown, caudal fin barring dark brown.

Comparisons. – The species resembles Pseudogobiopsis oligactis in possessing the posterior portion of the oculoscapular canal above the preopercle; the two species are more similar to each other than other species of the genus. Its strongly barred colour pattern is distinctive, and is unlike that of any other related species.

Distribution. – Known only from the Mamberamo River system of West Papua.

Ecology. – The species has been found only in “… small, clear, relatively fast-flowing rainforest (mostly closed-canopy forest) creeks. The fish were invariably found away from the main flow, around the edge of small pools to about 10 cm depth. They were seen solitary or in loose groups of 2–4 individuals, generally resting on sand or rock substrate” (Jerry Allen, in litt.)

Remarks. – The holotype and nine paratypes have been dehydrated at some stage and are not in the best condition, so that at first it was difficult to be sure as to what genus they actually belonged ( Larson, 2001). The capture of fresh specimens by Jerry Allen provided the key to the identity of this species.

Figures

Fig. 31. Pseudogobiopsis tigrellus, 25.2 mm SL male, WAM P.31752-001, Mamberamo River, West Papua, showing headpore and papillae pattern. Scale bar = 1 mm.

Fig. 2. One of the 10 trees from PAUP analyses; preferred tree on which classification is based (CI = 0.4935, RI = 0.6929).