Pseudogobius masago ( Tomiyama, 1936 )

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 : 44-47

Pseudogobius masago ( Tomiyama, 1936)

Masago snubnose goby

Figs 1 , 16–17 , Tables 1–5, 14

Gobius ornatus masago Tomiyama, 1936: 73 , fig. 26 (coast of Tiba-Ken, Japan).

Acentrogobius masago —Dotu 1958 (not seen; cited in Takagi 1966); Kikuchi & Yamashita 1992: 78 (Shioirihama mudflat, Amakusa).

Pseudogobius masago — Sakai et al. 2001: 115–116 (Tanegashima Island, Okinawa Island; Miyagi Prefecture); Senou et al. 2004: 234 ( Japan); Tran et al. 2013: 145 (Mekong Delta, Vietnam); Chen & Fang 1999: 229 (Taiwan); Zhou & Gao 2011: 292 (Taiwan); Chen et al. 2014b: 317 (Kinmen Island, Taiwan); Huang et al. 2014b: 96 (Taiwan); Hammer et al. 2021: 2 ( Japan and Vietnam [distinct mitochondrial DNA lineage]).

Material Examined. JAPAN: Holotype of Gobius ornatus masago, ZUMT 30228, 1(22), coast of Chiba-ken . Paratype of Gobius ornatus masago, ZUMT 34047, 1(19.5), coast of Chiba-ken. YCM 6937 , 24 (9–15), Iida River, Kashima county , Saga Prefecture, 13 September 1979 ; NTM S.18263-001, 49(17–22), Tamagawa River, 2 kilometres from mouth, Kawasaki , Kanagawa Prefecture, K. Shibukawa, 24 May 2014 ; NTM S.17899-001, 10(18–22), Tamagawa River, 2 kilometres from mouth, Kawasaki , Kanagawa Prefecture, K. Shibukawa, 24 May 2014 . VIET- NAM: ROM 105373 , 7 (13–19), mangrove channel about 10 km E of Haiphong Institute of Oceanology, Red River drainage, Haiphong , R. Winterbottom and P . T. Dinh , 29 February 2000 ; ROM 105374 , 4 (14–19.5), Haiphong city market , R. Winterbottom and party, 24 February 2000 .

Additional material (no data taken). JAPAN: S.17898-001, 34, Tamagawa River , 2 kilometres from mouth, Kawasaki, Kanagawa Prefecture, K. Shibukawa, 24 May 2014 . VIETNAM: NTM S.17897-001, 3, Phu Quoc Island , Kien Giang, K. Shibukawa and party, 26 November 2011 . SINGAPORE: NTM S.15344-017, 1, Sungei Buloh, HL 97-89, H.K. Larson and party, 5 September 1997 ; ZRC 27449, 1 , canal at Siglap, K. Lim and P.G. Lee, 25 September 1992 ; ZRC 48457, 5 , Pasir Ris Park mangroves, Z. Jaafar and Y. Yatiman, 20 April 2002 .

Diagnosis. A small Pseudogobius with second dorsal rays I,6–8; anal rays I,6–8; pectoral rays 14–17; 15–16 segmented caudal rays in 9/7 pattern; lateral scales 24–27; TRB 7–8; predorsal scales 7–10; opercle with at least two rows of cycloid scales, cheek naked; shoulder girdle smooth; tongue blunt; upper jaw teeth similar between sexes, in 2–4 rows, very small, sharp and close-set, outer row teeth larger; head and body whitish to yellowish brown, scale margins edged with brown, small single or paired brownish spots or small blotches along mid-side of body with posteriormost spot at hypural crease, extending upward onto caudal fin as oval or rounded blotch; known from estuarine habitats of East Asia and South-east Asia.

Description. Based on 21 specimens, 12.5–22 mm SL. An asterisk indicates the counts of the 22 mm SL holotype of Gobius ornatus masago .

First dorsal VI*; second dorsal I,6*–8 (usually I,7); anal I,6–8 (usually 7*); pectoral rays 14–17 (usually 16; 15 in holotype); segmented caudal rays 15–16, in 9/7 pattern (8/ 7 in one); branched caudal rays 7/6–8/6, modally 7/6; 9/9 procurrent rays (in 1); lateral scale count 24–27 (usually 25); TRB 7*–8 (modally 8); predorsal scale count 7–10 (modally 8, 9 in holotype).

Body slender and slim, compressed. Body depth at anal origin 15.1–19.3% SL (mean 16.5%). Head wider than deep, but not greatly so, HL 22.6–29.6% SL (mean 26.0%). Depth at posterior preopercular margin 52.9–63.6% HL (mean 58.3%). Width at posterior preopercular margin 62.5–75.6% HL (mean 67.9%). Mouth small, subterminal, slightly oblique, upper jaw slightly in advance of lower; jaws reaching to vertical through mid-eye in males and to anterior half of eye in females; upper jaw 26.8–41.7% HL (mean 32.5%); lips relatively thin, lower lip fleshier than upper and fused to chin anteriorly. Eyes lateral, high on head, top forming part of dorsal profile, 26.5–33.3% HL (mean 28.8%). Snout rounded, may be slightly inflated, 22.0–27.8% HL (mean 24.4%). Interorbital moderately narrow, 11.4–19.4% HL (mean 14.6%). Caudal peduncle long and compressed, length 24.1–30.8% SL (mean 27.9%). Caudal peduncle depth 9.4–27.1% SL (mean 15.9%).

First dorsal fin rounded, second or third spines longest (usually second). Appressed first dorsal fin 14.9–19.3% SL (mean 16.4%), fin falling short of second dorsal fin in both sexes. Second dorsal spine length 11.2–15.1% SL (mean 13.2%). Third dorsal spine length 12.0–14.1% SL (mean 13.0%). Second dorsal and anal fin heights moderate, fins rounded posteriorly with posteriormost rays longest, rays falling well short of caudal fin base when appressed. Pectoral fin oval to rounded, central rays longest, extending back to vertical just above anus, 20.0–24.4% SL (mean 22.4%). Pelvic fins rounded, just reaching anus, 18.5–25.6% SL (mean 22.0%). Caudal fin broad, rounded posteriorly, 26.0–35.2% SL (mean 29.6%).

Anterior nostril in very short tube, oriented over upper lip. Posterior nostril round, with very low rim, placed at mid-level of eye. Gill opening extending forward to just under opercle (reaching mid-opercle in one). Shoulder girdle smooth. Tongue tip blunt. Upper jaw teeth in 2–4 rows, very small, sharp and close-set; outer row teeth larger. Lower jaw teeth in 2–3 rows, small, sharp and close-set.

Body scales ctenoid to below first dorsal fin; predorsal scales cycloid, reaching close to behind interorbital and anteriormost scale largest; opercle with at least two rows of large cycloid scales; breast usually naked, sides may be scaled (specimens from Vietnam with 1–2 large scales on breast); belly scales cycloid on posterior half at least, midline or entire belly naked; pectoral base naked. Lateral canals, pores and sensory papillae pattern as in Fig. 16 .

Coloration of preserved material. Head and body whitish to pale yellowish brown, with scale margins outlined with brown ( Fig. 17 ). Marginal pigment slightly darkened where scales intersect, forming small spots amid the network. Dorsum with series of faint brownish blotches from nape to caudal base. Mid-side of body with row of small single or paired dark brown spots or short elongate blotches; posteriormost spot at middle of caudal fin base and extending upward onto fin as oval or rounded dark brown blotch. Top of head, snout, upper part of cheek and opercle dusky brownish; lower half of head whitish with dark brown bar from lower edge of eye extending obliquely back behind jaws and ending on lower edge of preopercle. Underside of head, breast and belly whitish.

First dorsal fin in males plain dusky grey, darkening a little posteriorly (but not forming spot), fin in females transparent at base, rest of fin pale greyish. Second dorsal fin plain dusky grey in males, with broad translucent margin, fin darkening dorsoposteriorly; in females, fin translucent with pale greyish patches and grey margin. Anal fin in males same as second dorsal fin; translucent in females. Pectoral fin transparent with fine brown speckling along rays. Pelvic fins translucent. Caudal fin transparent with 3–5 indistinct vertical rows of fine brown speckles and 1–2 distinct brown spots above and below hypural crease.

Coloration of fresh material. Based on photos of live fish by Taiga Kunishima in Senou et al. (2004: 234), and of fresh-dead fish in Tran et al. (2011: 145) (see also Fig. 17 ). Head and body translucent whitish to pale whitish brown, with scale margins on upper half of body outlined at least partly with red-brown to dark brown and scattered white or yellowish white short lines and spots on upper half of body. Dorsum with several indistinct darker blotches. Mid-side of body with row of small blackish to dark brown blotches and spots; posteriormost blotch anterior to caudal base elongate, with posterior end forming small rounded mark on base of caudal fin. Four dark grey to blackish internal spots along ventral midline starting at anal fin and ending on caudal peduncle near caudal fin base. Side of head with diffuse dark brown bar from eye to upper lip and two similar oblique diffuse brown bars from eye across preopercle and towards opercle. Dorsal fins translucent with indistinct greyish brown spots and fin margins.

Comparisons. This is a small, slender species with a long caudal peduncle and a plain-coloured first dorsal fin in both sexes. The low rounded dusky grey first dorsal fin is shared with the more robust and larger (when adult) P. taijiangensis , which has a blue spot at the rear of the fin.

Distribution. Recorded from Japan, Hong Kong, China, Taiwan ( Chen & Fang 1999), Vietnam and Singapore; does not appear to extend far onto Sunda Shelf habitats.

Ecology. Found in intertidal estuarine habitats and river mouths, mudflats and mangroves. Kikuchi & Yamashita (1992) found that this small species apparently spawned in May and August and fed mostly on copepods and amphipods. Co-occurs with several Pseudogobius , especially P. pocilosoma .

Remarks. This species was originally described as a new form of Gobius ornatus ; the name was subsequently used as a full species by Akihito (1984) and thus meets the criteria of availability with original author and date.

The Okinawa population is Red-Listed as a threatened local population by the Japanese Environmental Agency ( Sakai et al. 2001), but has not yet been assessed for the IUCN Red List.

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 16. Pseudogobius masago, sensory papillae and pores, 21 mm SL female, NTM S.17898-001, Tanagawa River, Japan. Drawing by HKL.

FIGURE 17. Pseudogobius masago, East Asia and South-east Asia, (A) captive male, Pak Nai, New Territories, Hong Kong, photo copyright H.T. Cheng; (B) and (C) preserved topotypic male (upper) and female, NTM S.17899-001, from Tama-Gawa River, Kawasakai, Japan. Photos by MPH.