Pseudogobius minimus ( Hora, 1923 )

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 : 53-56

Pseudogobius minimus ( Hora, 1923)

Miniature snubnose goby

Figs 1 , 20–21 , Tables 1–5, 16

Ctenogobius minima Hora, 1923: 749 , fig. 30 (Nalbano Island, Rambha Bay, off Balugoan, between Cherria Island and the mainland, off Kalidai, north-east of Nalbano, near Manikpatna, Serua Nadi, Domkuda and Samal Islands, near Nalbano, off Balugoan, west of Satpara, Mahosa, on Barhampur Island, Serua Nadi, Barkul Point, Chilka Lake, India).— Das 2003: 373 ( India, Orissa, Chilka Lake).

Stigmatogobius minima — Menon & Yazdani 1968: 154 (Chilka Lake); Talwar & Jhingran 1991: 948 (Chilka Lake, Orissa); Mohanty et al. 2015: 12 (Chilika Lake).

Material Examined. Syntype of Ctenogobius minima, ZSI 10177, 16 mm SL female, between Cherria and Manikpatna, Chilika [Chilka] Lake, India, Chilka Survey, 20 July 1914. LACM 38301-8 , 15 (14.5–18) , salt plant 2–3 km SE of Korangi Creek , Sind, Pakistan, CCS79-12, 22 January 1979; CAS-SU 47840 , 4 (15.5–18) , Sundarbans , Lower Bengal, Uttarbhag, India, A.W. Herre, 11 April 1937; ROM 39312, 1 (15.5) , low tide at Korangi Beach, Pakistan, SH-83, S.M. Hoda, 15 January 1979 .

Diagnosis. A small slender Pseudogobius with second dorsal rays I,7; anal rays I,7; pectoral rays 15; 15–16 segmented caudal rays, usually in 9/7 pattern; lateral scales 25–26; TRB 8; predorsal scales 8–9; opercle with 1–2 rows of cycloid scales, cheek naked; shoulder girdle smooth edge; tongue blunt; upper jaw teeth very small, straight and sharp; body whitish to pale yellowish with scattered small brown spots, scales of dorsum with brown margins, narrow black line or spot at mid-base of caudal fin and two brown spots above and below midline, with ventral spot always smaller (live colour yellow-brown); known only from a few coastal lagoons in South Asia.

Description. Based on 12 specimens, 14.5–18 mm SL. An asterisk indicates the counts of the 16 mm SL ZSI female syntype ( Fig. 21D ).

First dorsal VI*; second dorsal I,7*; anal I,7*; pectoral rays 15*; segmented caudal rays 8/7–9/7; branched caudal rays 7/6*; lateral scale count 25*–26; TRB 8*; predorsal scale count 8–9*. Gill rakers on first arch 1+5 (in 1) or 2+6 (in 1).

Body slender, compressed, with a “small-headed” appearance. Head slightly wider than deep, HL 23.9–28.8% SL (mean 25.3%). Depth at posterior preopercular margin 60.5–66.7 HL (mean 63.3%). Width at posterior preopercular margin 66.7–77.5% HL (mean 70.4%). Mouth small, subterminal, very slightly oblique, jaws reaching to vertical below anterior half of eye in females and nearly to mid-eye in males (very little difference); upper jaw 28.3–35.0% HL (mean 31.2%); lips thin, lower lip broadly fused to chin anteriorly. Eyes lateral, high on head, 26.2– 30.4% HL (mean 28.5%). Snout short, rounded, 20.9–28.9% HL (mean 24.2%). Interorbital narrow, 11.1–17.4% HL (mean 13.4%). Body depth at anal origin 16.4–18.8% SL (mean 17.4%). Caudal peduncle long, compressed, length 25.6–29.1% SL (mean 27.8%). Caudal peduncle depth 6.2–12.8% SL (mean 11.1%).

First dorsal fin low, rounded, second or third spines longest. Appressed first dorsal fin falling short of second dorsal in both sexes. Second dorsal spine length 14.4–15.3% SL (mean 14.9%). Third dorsal spine length 12.2– 15.8% SL (mean 14.5%). Second dorsal and anal fins low, rounded posteriorly, posteriormost rays falling well short of caudal fin base when appressed. Pectoral fin rounded, with central rays longest, extending back to vertical just above anus in large specimens, 17.7–25.0 % SL (mean 21.2%). Pelvic fins oval, rounded posteriorly, barely reaching to anus, 18.9–23.1% SL (mean 20.9%). Caudal fin slender, rounded posteriorly, 25.0–32.0% SL (mean 28.9%).

Anterior nostril in short tube, oriented down over upper lip. Posterior nostril rounded, with very low rim, placed very close to eye at mid-level. Gill opening extending forward to under opercle. Gill rakers on outer face of first arch very short stout stubs. Shoulder girdle with smooth hard edge. Tongue tip blunt. Upper jaw teeth very small, straight and sharp, in 2–3 evenly sized rows. Lower jaw teeth in 2–3 rows, but teeth smaller and blunter.

Body scales ctenoid to pectoral fin base, cycloid scales on predorsal extending up to behind eyes in most specimens (entire predorsal naked in one), with scale closest to eye sometimes larger than others; pectoral fin base naked; opercle with 1–3 rows of cycloid scales; breast naked or with embedded cycloid scales; belly scales cycloid, scales may be scattered with naked midline. Sensory papillae and lateral canal pores as in Fig. 20 ; note that rows b and d are relatively long compared to those in congeners.

Coloration of preserved material. Description taken mostly from LACM specimens (which retain some pigmentation) ( Fig. 21C ). Body whitish to pale yellowish brown, with scattered small brown spots (placed toward base of each scale); scale margins of dorsum narrowly outlined with darker brown; spots on sides largest and more irregular along mid to lower half of body and in some specimens these spots form about two diffuse rows of very short streaks. Head pale brownish dorsally, becoming paler on sides; underside of head unpigmented; indistinct broad brown bar running from eye to end just above lower edge of preopercle. Breast and belly unpigmented. Pectoral fin base pale with diffuse brown blotch on upper quarter. Five blackish narrow blotches along ventral midline, two above anal fin and two on caudal peduncle and one across bases of ventral procurrent rays. In front of mid-base of caudal fin, a narrow partly internal black line or elongate spot. Bases of upper procurrent rays with brown blotch. Two brown spots on caudal fin at base, upper spot placed just above midline, and lower spot usually smaller than upper and always placed slightly more ventrally from mid-line.

First dorsal fin transparent with scattered pale brown speckling, mostly on anterior half of fin. Second dorsal fin transparent with pale brown spots and short streaks covering most of membrane. Anal fin plain translucent. Caudal fin transparent with diffuse pale brown pigment on most of fin, lower portion partly unpigmented. Pectoral and pelvic fins transparent with slight dusting of pale brown speckles along fin rays (may be very faint).

Based on HKL’s notes, the ZSIC syntype had similar speckled body colour, with an almost <shaped brown mark on the caudal base and lower part of the fin; its head had a broad brownish bar from eye to ventral edge of the preopercle and much thinner brown line from eye to middle of upper jaw.

Coloration of fresh material. Based on photos by Beta Mahatvaraj of male and female captive fish from Pulicat Lake, Tamil Nadu, India ( Fig. 21 ). Head and body pale silvery grey with small indistinct yellowish brown saddles, blotches and spots on dorsal half of body and faint grey short bars along mid-side. Ventral half of body with series of short silvery white bars and spots. Base of caudal fin with dull yellow narrow bar and blotch extending out onto lower middle of fin. Head with brownish bar from front of eye to middle of upper jaw and diffuse dark grey bar from lower edge of eye toward ventral margin of preopercle. Opercle with iridescent greenish area in centre. Iris orange-brown. Fins mostly transparent in female; in male, dorsal fins faint grey with darker submarginal stripe and caudal fin rays yellowish grey.

Comparisons. This is a very small, slender species with small head and relatively plain coloration (no diagnostic spots or markings). It is unlike any species other than P. masago from Japan, which has a series of paired small brown spots along the side of the body (versus only scattered fine dark speckles and spots on upper part of body in P. minimus ).

Distribution. So far known only from Chilika and Pulicat lakes and the Sundarbans, India, and Sind, Pakistan.

Ecology. Coastal brackish lagoons, known from brackish lakes and salt pans. Pulicat Lake is heavily fished, with limited habitat suitable for Pseudogobius (HKL pers. obs. 2018). May co-occur with P. melanosticta .

Remarks. Possible syntypes are contained in RMNH 12060, from Madras, but this material was not available. Talwar and Jhingran’s record of this species from Godavari estuary, Andhra Pradesh, is based on their tentative placement of Stigmatogobius yanamensis Rao as a synonym (which it is not). We have amended the ending of minima , as it is an adjective and should agree with the gender of Pseudogobius (masculine).

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 20. Sensory pores and papilla rows in Pseudogobius minimus, 16 mm SL female, one of LACM 38301-8, Sind, Pakistan. Drawing by HKL.

FIGURE 21. Pseudogobius minimus, South Asia, (A) captive male, Pulicat Lake, Coromandel Coast, India, photo by B. Mahatvaraj; (B) captive female, Pulicat Lake, Coromandel Coast, India, photo by B. Mahatvaraj; (C) preserved male (top) and female, LACM 38301-8, Korangi Creek, Pakistan; (D) preserved syntype of Ctenogobius minima, 16 mm SL female, ZSI 10177, between Cherria and Manikpatna, Chilika Lake, India, photos by MPH.