Pseudogobius Popta, 1922

Larson, Helen K. & Hammer, Michael P., 2021, A revision of the gobiid fish genus Pseudogobius (Teleostei, Gobiidae, Tridentigerinae), with description of seven new species from Australia and South-east Asia, Zootaxa 4961 (1), pp. 1-85 : 7-10

Pseudogobius Popta, 1922

Pseudogobius Popta, 1922: 36 (type species Gobius javanicus Bleeker, 1856: 88 , by subsequent designation by Larson, 2001: 200).

Pseudogobius Koumans, 1931: 101 , 102 (first published as a synonym, made available by Aurich, 1938: 158 [ICZN Code art. 11.6.1]. Type species: Gobius javanicus Bleeker, 1856: 88 ).

Lizagobius Whitley, 1933: 93 (as subgenus of Ellogobius Whitley, 1933: 92 ; type species Mugilogobius galwayi McCulloch and Waite, 1918: 50 , pl. 3, fig. 1, by original designation and monotypy).

Diagnosis. Distinguished from other tridentigerines by the following combination of characters. Second dorsal fin rays I,6–9; anal fin rays I,6–9; second dorsal and anal fin rays modally equal in number; pectoral rays 14–17; segmented caudal rays 16, often in 9/7 pattern; 24–30 scales in lateral series; predorsal scales 6–11, usually with large scale present close behind eyes; opercle always at least partly scaled; cheek naked or with 1–3 scales just behind eye; no fine villi on head; posterior portion of oculoscapular canal absent, no preopercular pores; papillae on head in longitudinal pattern, cheek papillae in rows a, c and cp larger and more widely spaced than those in rows b and d ( Fig. 2 ); gill opening restricted to under opercle at most; pectoral girdle smooth or with low flange, without distinct fleshy lobes or flaps; tongue tip blunt to rounded; intestine and stomach coiled in corkscrew manner about each other; lower jaw usually inferior, with blunt, rounded to inflated snout that may overhang upper lip; jaws usually short with thin to almost absent lips; teeth shape and arrangement usually differing between sexes; genital papilla elongate and flattened in male and short and rounded in female.

Pterygiophore formula 3-12210; vertebrae 9–10+15–16, usually 10+16; two epurals; 2 pre-anal pterygiophores (rarely 3); first few neural spines slender, pointed; metapterygoid short and wide, may be expanded dorsally but not forming bridge to quadrate; palatine short and broad, only reaching partly down pterygoid, which is always much shorter than palatine ( Fig. 3 ); fifth ceratobranchial slender to broad, flattened and porous with thin fine teeth and low ridge or flange on back; no to five gill rakers ossified; top of scapula above foramen may be ossified.

Key to species of Pseudogobius

(adult specimens of both sexes required for best results)

1 Strongly sexually dichromatic, males with dense black line along mid-side of body extending from above opercle to caudal fin base, distinct black spot on upper part of base of caudal fin, females with black line faded and replaced by series of thin elongate blotches, dense black spot on caudal fin present but may be obscured by neighbouring dark blotches; small fish when mature (largest 19.5 mm SL)......................................... P. rhizophora n. sp. (estuarine; northern Australia)

- Not strongly sexually dichromatic, males without dense black line along mid-side of body, distinct black spot on upper part of base of caudal fin may be present in both sexes; size variable when mature (from 18-37 mm SL)...................... 2

2 Dorsal rays I,8–9 (usually I,8); anal rays I,7–9 (usually I,8); predorsal scales 8–11 (usually 10); lateral scales 26–30 (usually 28); mouth relatively large (reaching under mid-eye), lips fleshy; upper and lower jaw teeth conical, usually pointed (not sharp), without symphyseal canine teeth in lower jaw; adults large, up to 61 mm SL (mean 37 mm SL).............................................................. P. olorum ( Sauvage, 1880) (estuarine to freshwater; south-western Australia)

- Dorsal and anal rays I,7 (rarely I,8, if so, then predorsal scales 6–9, rarely 10); lateral scales 22–28; mouth may not reach to below mid-eye; lips usually thin, especially lower lip; teeth conical to compressed, symphyseal canine teeth may be present in lower jaw; adult size variable, up to 40 mm SL............................................................. 3

3 Opercle nearly always with ctenoid scales at least dorsally; predorsal scales mostly ctenoid (on sides at least); first dorsal fin tall and pointed, crossed by two broad black stripes ending in black spot or blotch posteriorly; distinct broad black bar extends obliquely from eye to ventral margin of preopercle; upper jaw teeth conical and pointed in males, small, sharp and close-set in females................................... P. melanosticta ( Day, 1876) (estuarine to freshwater; Indo-west Pacific)

- Opercle always with cycloid scales; predorsal scales usually cycloid (may be ctenoid on side of nape); first dorsal fin rounded, not pointed and crossed by two distinct dark stripes with black blotch posteriorly; if black bar present on cheek then short and and may be diffuse; upper jaw teeth in males conical and pointed or blunt and flattened............................. 4

4 Single distinct round black spot (may be ocellated, surrounded by yellow when alive) on upper base of caudal fin, most distinct in males; fleshy suborbital curved ventrally below eye at centre of jaw, partly covering upper lip, curve deepest in adult males, giving distinctive look to head; caudal fin dark with submarginal black line and translucent margin; females with black spot on caudal fin base but fin barred and with less pronounced, or no black submarginal line; breeding males with greatly inflated cheeks and dark bodies; outer row of upper jaw teeth often with compressed tips, blunt to pointed and pair of symphyseal caniniform teeth present; lower jaw teeth in females minute, usually hidden by flesh of gum..................................................................................... P. avicennia ( Herre, 1940) (estuarine; South-east Asia)

- No single distinct black ocellated round spot on base of caudal fin, although dark brown to black spots may be present, often paired; suborbital not curved ventrally below eye in centre of jaw, partly covering upper lip; caudal fin plain, spotted or banded but not dark with submarginal black line and translucent margin; breeding males lack greatly inflated cheeks and dark bodies; outer row of upper jaw teeth often with compressed tips, blunt to pointed; lower jaw teeth in females smaller than those of males but visible, symphyseal caniniform teeth not present in some species............................................ 5

5 First dorsal fin plain, without blackish spot posteriorly; male and female very similar in colour pattern; body slender, BDA 15–19% of SL, usually about 16–17%; fish small, adult females attaining 22 mm SL and males smaller, reaching only 18.5 mm SL ................................................................................................. 6

- First dorsal fin with one or two dark stripes and usually with blackish or blue spot posteriorly; body stout or slender, BDA 17–26% of SL, usually 20–21%; fish larger, maximum size of adult females usually greater than 22 mm SL and males up to 34.5 mm SL......................................................................................... 7

6 First dorsal fin translucent, male and female almost identical in colour pattern; no conspicuous brown spots or markings other than diffuse yellowish brown patches on dorsum (body with small brownish spots and speckles when preserved); cheek with diffuse greyish bar when live; body slender, BDA 16.4–18.8% of SL, usually about 17%; fish very small, adult females attaining 18 mm SL.................................................. P. minimus ( Hora, 1923) (brackish; South Asia)

- First dorsal fin translucent to plain pale brownish; body pale with 3–4 small brown paired spots along mid-side and fine brown reticulate pattern on dorsum (visible when alive or preserved); cheek with brown bar or angular blotch below eye; body relatively slender, BDA 15–19% of SL, usually about 16%; adults may reach 22 mm SL.................................................................. P. masago ( Tomiyama, 1936) (estuarine to freshwater; East Asia, South-east Asia)

7 Side of head with distinctive oblique wedge-shaped brown bar from posteroventral edge of eye reaching back to angular dark blotch on lower part of opercle (entire mark looks like large oblique tear when alive); first dorsal fin rounded, diffusely mottled with pale grey to pale brown, with distinctive blue-edged black spot at rear of fin............................................................................... P. tiajiangensis Chen, Huang and Huang, 2014 (estuarine; East Asia).

- Side of head with two or three short dark vertical to oblique bars and blotches that do not reach back to opercle (markings may be diffuse); first dorsal fin usually triangular, with rows of dark spots and streaks as well as black or blue spot at rear of fin;. ................................................................................................... 8

8 One or two cycloid scales on cheek close behind eye; body without diagonal dark bar extending from dorsum (short diffuse bar may be present under first dorsal fin)..................................................................... 9

- No cycloid scales on cheek close behind eye; body may have a narrow blackish vertical to oblique bar, sometimes indistinct, extending from rear of first dorsal fin forward and down to lower side.......................................... 11

9 Body with 3–4 dark grey to blackish vertical bars along side, narrow blackish vertical bar (sometimes indistinct), extends from rear of first dorsal fin forward and down to lower side of body; diffuse brownish to dark grey spots along side of body................................................................... P. cinctus n. sp. (estuarine; northern Australia)

- Body without diffuse vertical bars, about 5–6 elongate blackish blotches along mid-side of body and additional dark spots on sides and dorsum.................................................................................... 10

10 Caudal fin translucent to dusky grey small dark spots near base but not forming distinct lines; at caudal fin base, posteriormost mid-lateral blackish mark fuses with blackish blotch at midbase of fin or may form an irregular vertical bar; scale margins on body narrowly outlined with dark brown (may form network pattern)...... P. jeffi n. sp. (estuarine; north-eastern Australia)

- Caudal fin translucent with 5–6 rows of small dark spots forming distinct dark lines; caudal fin base with two blackish spots which may form an irregular vertical bar or may fuse with mid-lateral dark blotch; scale margins on body outlined with dark brown (may form distinct network pattern) … P. hoesei n. sp. (freshwater to estuarine; New Guinea, north-eastern Australia)

11 Teeth in both sexes stout and conical, may be curved, with slightly pointed to almost blunt tips; teeth in inner rows very small, close-set and sharp, no symphyseal canines present; predorsal scales 7–10, usually 8.................................................................................. P. eos n. sp. (estuarine to freshwater; south-eastern Australia)

- Teeth sexually dimorphic, may be conical, pointed, slightly flattened or compressed in males, symphyseal canines may be present, females with very small blunt-tipped compressed teeth or teeth reduced and concealed within flesh of jaw; predorsal scales 6–8, usually 7....................................................................................... 12

12 Body without blackish vertical bar, caudal fin plain translucent with two brown spots at base, may fuse with posteriormost brown blotch on mid-side; about 5–6 elongate or X-shaped small brown blotches along mid-side of body (blotches may be paired); first dorsal fin translucent with broad diffuse brown band across most of fin............................................................................................ P. aquilonius n. sp. (estuarine; northern Australia)

- Body with oblique to vertical blackish bar extending down from first dorsal fin; colour pattern not as above............ 13

13 Single vertical blackish line crosses first dorsal fin, no black spot at rear of fin, caudal fin plain, transparent, though some males may have a few rows of small brown spots near base of fin; yellow blotch or half-moon shape around distinct dark spots at fin base of caudal fin when alive....................................... P. verticalis n. sp. (estuarine; South-east Asia)

- Two or three blackish stripes cross first dorsal, with distinct rounded to irregular black spot at rear of fin; yellow blotch at base of caudal fin may be present when live, fin plain transparent to greyish or with rows of small dark spots............... 14

14 Caudal fin base with two small blackish spots which may form an irregular vertical bar and bright yellow half-moon blotch at base of caudal fin when alive, fin plain, transparent; outer row teeth in upper jaw very small, compressed (close-set in females, evenly spaced in males) with blunt to slightly pointed tips................................................................................ P. fulvicaudus Huang, Shao and Chen, 2014 (estuarine; South-east Asia, northern Australia)

- Caudal fin base with two well-separated blackish spots, fin transparent to greyish with 5–6 curving rows of small dark spots; outer teeth in upper jaw usually widely spaced, conical to slightly flattened, with slightly pointed tips, lower jaw with 2–3 curved symphyseal canines behind anterior tooth rows in males................................................................................... P. poicilosoma (Bleeker, 1849) (estuarine; East Asia, South Asia, South-east Asia)

Figures

FIGURE 2. Sensory pores and papilla rows in Pseudogobius poicilosoma, with papilla rows labelled as according to Sanzo (1911), 34 mm SL male, WAM P.30806-003, Maratua Island, Kalimantan Timur, Indonesia. Drawing by HKL.

FIGURE 3. Suspensorium in Pseudogobius poicilosoma, 31 mm male, NTM S.11125-029, Sanur Beach mangroves, Bali, Indonesia. Drawing by HKL (black indicates cartilage).