Pseudogobius avicennia ( Herre, 1940 )

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 : 17-21

Pseudogobius avicennia ( Herre, 1940)

Avicennia snubnose goby

Figs 1 , 6–7 , Tables 1–5, 7

Vaimosa avicennia Herre, 1940: 17 , pl. 12 (Kranji River, Singapore).

Pseudogobius avicennia — Tan& Tan 1994: 356. 356 (Pulau Bintan, Indonesia); Larson in Randall & Lim 2000: 639 (South China Sea); Larson 2001: 202 (Kranji River, Singapore); Larson & Murdy 2001: 3601 (western central Pacific); Larson & Lim 2005: 140 (Sungei Simpang, Singapore); Larson et al. 2008: 143 ( Singapore); Chen et al. 2014a: 131 (Matang mangrove, Malaysia); Huang et al. 2014b: 112 ( Malaysia); Tran et al. 2013: 145 (Mekong Delta, Vietnam); Kottelat 2013: 422 (Kranji River, Singapore).

Material Examined. Holotype of Vaimosa avicennia, CAS 33006, 31.5 mm SL male, Kranji River, Singapore, A.W. Herre, 10 March 1937. THAILAND: QM I.39296, 1(30), Narathiwat Province, P. Sirimontaporn, 15 January 1984; NTM S.17893-001, 6(28–34.5), Chantaburi, Mahidolia Project, T. Wongratana ; USNM 316049, 1(25), Katumban, about 30 km from Bangkok on way to Samui Sankorn, T. Roberts, 11 July 1970; USNM 316043, 4(16– 28.5), roadside ditch 3 km from Tah Chalap, on road from Chantaburi city, Chantaburi Province, T. Roberts, 5 May 1970. VIETNAM: NTM S.17896-001, 2(17.5–20), Soc Tran, K. Shibukawa, 16 May 2012. INDONESIA: CMK 7276, 2(13.5–16.5), tidal creek about 500 m from sea, Sungai Lukit, Padang Island, Riau Province, M. Kottelat, 12 February 1991. SINGAPORE: CMK 8310, 2(27–31), Kranji mangroves near Sungei Buloh, D. Murphy and M. Kottelat, LOC 92-33, 8 April 1992; NTM S.18262-001, 1(26), Sungei Buloh mangroves, K. Lim, 30 January 1992; ZRC 39205, 1(22.5), mangrove pools on Pulau Buloh, Sungei Buloh Nature Park, K. Lim and party, 6 June 1995. BRUNEI: NTM S.12812-003, 1(17), in Nypa palm leaf axil, Kedalayan River, R. Hanley and S. Choy, RH 89-15, 7 April 1989; NTM S.14812-005, 1(35.5), Sungai Mataiang, Temburong District, H. Larson and party, HL 97-87, 30 August 1997; QM I.39297, 1(31.5), small stream, tidal influence via river, Kg Labu Estate, Temburong, S. Choy, 8 January 1992; USNM 383429, 12(9.5–27.5), mangroves, tributary of Sungei Brunei, Sungei Kalamasi, Muara District, L. Parenti and party, 16 August 1997.

Additional material (no data taken). INDONESIA: CMK 11539, 2, Sungei Seriam, Kalimantan Barat. MA- LAYSIA : ZRC 20628–34 , 6 , Malacca . BRUNEI: NTM S.14802-007, 8, Sungai Tutong, Lubok Api-api, H. Larson and party, 24 August 1997 ; NTM S.14786-006, 12, Sungai Dol Hakim, H. Larson and party, 17 August 1997 ; NTM S.14813-004, 11, Tanjung Bakaka, Pulau Berembang, H. Larson and party, 30 August 1997 . SINGAPORE: NTM S.13957-015, 1(26), Sungei Pandan, HL 93-47, H.K. Larson and party, 29 December 1993 ; ZRC 2099–996 , 6 , Senoko grassland ; ZRC 26511, 1 , Mandai Besar ; ZRC 27451–3 , 3 , Siglap Canal ; ZRC 29187, 1 , Sungei Buloh ; ZRC 27007–8 , 2 , Senoko ; ZRC 20891–2 , 2 , Senoko ; THAILAND: ANSP 87272 , 1 , Tachin River .

Diagnosis. A moderate-sized Pseudogobius with second dorsal rays I,7; anal rays I,7; pectoral rays 14–17; 6 segmented caudal rays in 9/7 pattern; lateral scales 25–28; TRB 6–8½; predorsal scales 8–10; opercle with 2–4 rows of cycloid scales, cheek scaleless; shoulder girdle smooth; tongue short and mostly fused to floor of mouth; teeth similar in both sexes (though males have 2–3 curved symphyseal canines behind anterior tooth rows), with upper jaw teeth in two rows, teeth in outer row pointed, bluntly rounded to flattened, small, closely spaced, evenly sized, teeth usually absent from side of jaw; fish yellowish brown with five dark brown blotches along side and distinctive yellow-edged black spot on upper part of the caudal fin in both sexes; a sexually dimorphic species, with adult males having inflated cheeks and nape, more prominent eyes, a strongly curved suborbital, larger jaws and relatively plain dark body colour; known from mangroves and lower estuaries of rivers and streams in South-east Asia.

Description. Based on 23 specimens, 13.5–35.5 mm SL. An asterisk indicates the counts of the 31.5 mm SL male holotype of Vaimosa avicennia .

First dorsal VI*; second dorsal always I,7*; anal always I,7*; pectoral rays 14–17, modally 16 (15*); segmented caudal rays 16*, in 9/7 pattern; branched caudal rays 7/7–8/8; unsegmented (procurrent) caudal rays 7/7 or 8/8; lateral scale count 25–28* (modally 26); TRB 6–8½ (modally 8*); TRF 8–10* (modally 9½); predorsal scales 8–10* (modally 9).

Body compressed; head rounded, HL 24.4–29.6% SL (mean 26.4%). Head depth at posterior preopercular margin 54.3–63.8% HL (mean 60.8%). Head wider than deep, especially in males (which have inflated cheeks and nape), width at posterior preopercular margin 68.2–76.6% HL (mean 73.7%). Adult males develop inflated cheeks while large males also have an inflated nape and slightly more slender body (mean body depth of 18.2% of SL versus 19.2% in females), giving them a “fat-headed” appearance. Mouth subterminal, very slightly oblique, jaws small in females, larger in males, jaws usually reaching to vertical below mid-eye and to rear edge of eye in mature males; upper jaw 26.2–51.5% HL (mean 46.6% in males, 31% in females); lips thin, upper lip thicker than lower, lower lip broadly fused to chin. Fleshy suborbital curved ventrally below eye in centre of jaw, partly covering upper lip, curve deepest in adult males, giving a distinctive “sneer”. Eyes lateral, high on head, top may form part of dorsal profile, 21.8–32.7% HL (mean 28.0%); eyes in adult males more prominent, partly due to slightly concave interorbital and inflated nape behind eyes. Snout rounded to steep and blunt, may be slightly inflated (snout may be steep in adult males), 26.5–29.9% HL (mean 29.5%). Interorbital moderate, 14.1–22.4% HL (mean 22.2%). Body depth at anus 15.8–18.9% SL (mean 18.9%). Caudal peduncle compressed, length 25.5–29.7% SL (mean 24.4%). Caudal peduncle depth 10.9–14.3% SL (mean 13.2%).

First dorsal fin triangular to rounded, second and third spines longest, usually equal, third spine longest otherwise. In males, depressed first dorsal fin just reaching to first element of second dorsal fin, fin 17.1–22.0% of SL (mean 19.1%), fin falling short of second dorsal fin in females. Second dorsal spine length 13.9–16.9% of SL (mean 15.2%); third dorsal spine length 13.4–18.0% (mean 15.6%); spines always longer in males. Second dorsal and anal fin heights moderate, fins slightly pointed posteriorly, with posteriormost rays longest, when depressed just falling short of caudal fin base in males, falling well short in females. Pectoral fin rounded, central rays longest, extending to vertical just short of anus, 17.6–21.8 % SL (mean 19.7%). Pelvic fins short, rounded, not reaching anus, 15.8–19.4% SL (mean 17.6%). Caudal fin broad, rounded posteriorly, 24.6–31.7% SL (mean 28.8%).

Anterior nostril in short tube, oriented down over upper lip. Posterior nostril oval, with very low rim, placed at mid-level of eye. Gill opening usually extending forward to under mid-opercle. Shoulder girdle smooth, one specimen with low bony edge. Tongue very short, tip blunt to rounded, mostly fused to floor of mouth. Upper jaw teeth in two rows, teeth in outer row pointed, bluntly rounded to flattened, small, closely spaced, evenly sized, absent from sides of jaw; inner row very small, close-set and pointed. Lower jaw curved, with raised symphysis; teeth in two rows, very small, difficult to find in females (hidden by flesh of gum), teeth conical, with pointed tips and two to three curved symphyseal canines behind anterior tooth rows in males; sides of jaw usually without teeth in both sexes (some females with blunt-tipped small teeth at side near front of jaw).

Body scales ctenoid to pectoral fin base, cycloid scales on predorsal and pectoral fin base (pectoral base sometimes with only two to no scales); opercle with 2–4 rows of cycloid scales; belly scales cycloid on posterior half at least, often ctenoid scales anteriorly. Lateral canals, pores and sensory papillae pattern as in Fig. 6 .

Coloration of preserved material. Females and immature males: Head and body whitish to pale yellowish brown, with light to dark brown markings. Head with grey to light brown snout (snout may have small dark spots and short vermiculate lines), nape with irregular dark brown mottling and spotting, most nape scales with dark brown spot near rear of each scale. Side of head with one broad brown bar from front of eye to end on jaw close to anterior nostril; second brown bar (often diffuse or broken-up) from ventral edge of eye and ending just before corner of mouth, and third horizontal brown bar from lower rear edge of eye to rear edge of preopercle and often continuing onto opercle where it becomes indistinct. Cheek and opercle with variable scattered dark brown mottling and irregular small spots; may be small dark spot near upper rear corner of opercle. Lips plain grey, not distinctly outlined. Underside of head plain whitish with dusky grey speckling or patch on chin.

Side of body with mid-lateral series of five dark brown rectangular blotches, anteriormost blotch usually small, almost square and difficult to distinguish from the other dark brown spots and blotches nearby; posteriormost blotch on mid-base of caudal fin; these five blotches joined along side by dark brown lines above and below each blotch; dark lines occasionally broken into rows of elongate spots. Remainder of body with scattered small dark brown spots and blotches, which may form irregular rows or pairs of markings. Dorsum with six dark brown blotches or small saddles, beginning at nape just before first dorsal fin; scales on dorsum usually with thin dark margins. Breast and belly plain whitish. Peritoneum dark brown dorsally, abruptly becoming pale at sides of abdomen. Four dark brown to blackish blotches along ventral midline, two above anal fin and two on caudal peduncle. Posteriormost mid-lateral rectangular blotch usually partly joined by dark brown markings on scaly base of caudal fin.

First dorsal fin transparent to translucent dusky brownish, usually rays darker than membrane, may be scattered with small dark spots; indistinct irregular darker brown basal band becoming darker toward rear of fin. Second dorsal fin transparent with about four rows of dark brown small spots on rays, markings fading or elongating toward rear of fin; indistinct submarginal greyish stripe may be present. Anal fin translucent, with dark fin rays, may be concentrated into short streaks toward centre or base of fin. Caudal fin transparent with large dark brown to blackish pale-edged round spot just at upper fin base, with similarly coloured curved band from lower base of fin ending at point just below large round spot; rest of fin with about five curved brown broad lines or rows of brown spots; immature males with whole caudal fin grey but still showing the spots and rows or lines. Pectoral fin base plain brownish with brown to dark brown square blotch or bar on uppermost part, extending onto fin itself and may coalesce with streaks on fin rays. Pectoral fin transparent to greyish, with white curved patch along ray bases; rays with scattered brown streaks mostly on upper part of fin. Pelvic fins almost translucent white.

Mature males: Head and nape colour similar to females but spots and bars from eye diffuse and indistinct, but for first dark bar from eye to jaw. Underside of head brown to dark brown, especially branchiostegal rays and isthmus. Breast brown to dark brown, pale just before pelvic fin base. Pectoral fin base plain brown to dark brown with broad white lunate patch across bases of fin rays. Body colouring similar to that in females but rectangular dark brown mid-lateral blotches and all other dark markings much paler, fading into background colour.

First dorsal fin mostly plain dusky grey to dark brown, paler toward margin, with small dark brown to blackish spot at rear of fin between fifth and sixth spines. Second dorsal fin plain dusky grey to dark brown with broad transparent margin. Anal fin plain brown to dark brown, may have narrow transparent margin (may be absent). Pectoral fin with white lunate patch across base of rays, fin dusky in middle, becoming transparent toward rear half of fin. Pelvic fin plain dusky grey to dark brown, including frenum. Caudal fin with distinct round dark brown to blackish spot on upper base, rest of fin plain dark brown, with asymmetric translucent margin extending from mid-upper part of fin to posteriormost edge.

Coloration of fresh material. Based on photographs in Larson and Lim (2005), Tran et al. (2013) and photographs of freshly dead specimens ( Fig. 7 ).

Females. The colour pattern is essentially the same as in preserved specimens, but the background colour is golden brown to yellowish and all markings are darker, with the round spot on the upper caudal fin has a bright yellow surround dorsoposteriorly. Caudal fin whitish to yellowish in between the dark rows and spots. Cheek, opercle and anterior half of pectoral fin base may show pale blue to greenish blue iridescence among the scattered melanophores. Iris is red-gold, with thin gold edge to pupil.

Males. Head and body light brown to pinkish brown, with brown to yellowish brown markings as for preserved specimens. Underside of head, branchiostegal membranes, breast and pectoral fin base blackish. Belly pinkish to orange white. Four blocks of blackish internal pigment visible above mid-ventral line of anal fin and caudal peduncle. First dorsal fin yellowish brown becoming darker posteriorly, with dull yellow margin and bright blue black-rimmed round spot between fifth and sixth spines. Second dorsal fin blackish with yellow-brown spotting and speckles on ventral half and broad pale yellow margin, separated from rest of fin by narrow band of dull blue. Anal fin with dark grey rays, membrane anteriorly and basally with blue to whitish blue pigment, and dark orange streaks between rays along middle of fin. Pectoral fin transparent with curved whitish band crossing bases of rays, orange patch near upper base of fin, rest of fin with dusky brown fine speckling. Pelvic fins blackish with whitish base, margin of disc whitish. Caudal fin dusky brown to blackish, banded with about three indistinct rows of darker spots, black spot on upper caudal fin base, and broad creamy yellow margin to rear of fin, separated from rest of fin by narrow black band.

Comparisons. This is a sexually dimorphic species, with the adult males being most distinctive with their inflated head, more prominent eyes, a strongly curved suborbital and relatively plain dark body colour. The yellowsurrounded black spot on the upper part of the caudal fin in both sexes is distinctive. Females and immature males with indistinct pigmentation could be confused with P. poicilosoma , which usually has 15 pectoral rays (versus usually 16 in P. avicennia ), and has a pair of dark spots at the base of the caudal fin (versus a single conspicuous black spot on the upper caudal base in P. avicennia ; if a lower dark spot is present it is smaller and more diffuse).

Distribution. Known from Thailand, Malaysia, Singapore, Brunei and Indonesia (west of Lydekker’s Line).

Ecology. This species is found in mangroves and lower estuaries of rivers and streams, at depths of 0–2 m; nearly always associated with mangroves [its etymology reflects its association with the mangrove genus Avicennia].

Figures

FIGURE 1A. Distribution maps of species in the genus Pseudogobius, based upon material examined and inspected (circles) with the type localities indicated (squares).

FIGURE 6. Sensory pores and papilla rows in Pseudogobius avicennia, 29 mm SL female, ZRC 20628-34, Malacca, Malaysia. Drawing by HKL.

FIGURE 7. Pseudogobius avicennia, South-east Asia, (A) fresh male, Vietnam, CTU-P02316, photo by K. Shibukawa (courtesy FIMSEA Working Group); (B) fresh female, Vietnam, CTU-P01271, photo by K. Shibukawa (courtesy FIMSEA Working Group); (C) preserved male, 26 mm SL male, NTM S.13957-015, Singapore; (D) preserved female, 26 mm SL, NTM S.18262- 001, Singapore, photos by MPH; (E) preserved holotype of Vaimosa avicennia, 31.5 mm SL male, CAS-SU 33006, Kranji River, Singapore, photo courtesy CAS Department of Ichthyology.