Hypseleotris guentheri, (BLEEKER, 1875)

HYPSELEOTRIS GUENTHERI ( BLEEKER, 1875) View in CoL

( FIGS 1–4, 7; TABLES 4, 5)

Material examined: Holotype: BMNH 2003.8 .7.1, female (61.4 mm SL); not Oualan (Kosrae, Caroline Islands) but Ovalau ( Fiji) (see discussion above).

Others: MNHN-IC-2005-1896, one male (28 mm SL); Vanuatu, Santo , rivière salée, 16 Jul. 2005; Keith et al. coll. MNHN-IC-2009-0827, Vanuatu, Santo, Trou bleu, 20 Sept. 2006; Keith & Lord coll. MNHN-IC-2014-2795, two of three males (34.0– 36.7 mm SL); Tube 3, Vanuatu, Malekula , Mapes River 30 Jan. 2010; Keith et al. coll. MNHN-IC-2007-0109; Tube 4, Vanuatu, Santo , Peavot, Peavohori River, 21 Nov. 2006; Keith & Lord coll. MNHN-IC-1996-443, two females (59.0– 62.7 mm SL); New Caledonia, Paraoua , 21 Sept 1991; Pedcal coll. MNHN-IC-2009-0895, two males, two females (32.5–41.6 mm SL); Samoa, Upolu , Palilua River, 24 July 2008; Keith, Gerbeaux et al. coll. MNHN-IC-A-3708, one female (77 mm SL); New Caledonia, 1881; Bougier coll.

Description: The ray and scale counts are given in Table 4 and selected morphometrics in Table 5. The body is compressed laterally. The body depth at anus is 18–21% SL for males and 19–24 for females, at first dorsal fin 18–22% SL for males and 1 8–2 6% for females. The caudal peduncle depth is 11–14% SL. No variation in depth with sex or size in the samples studied. Pre-dorsal length 38–41% SL and preanal length 57–60% SL. Size: up to 8 cm SL.

The head is 25–28% SL, rounded dorsally with a broad interorbital, the snout is pointed. The mouth (terminal) and jaw length 6–7% SL are small; jaws oblique with several rows of conical teeth, 13–17 on first upper outer raw (the biggest in front are usually curved), 6–12 on the first lower outer row. Posterior end of maxillary ending below or just before posterior nostril before eye. Anterior nostril at the end of a short tube above upper lip; posterior nostril a simple pore in front of eye. Eye diameter 6–8% SL and interorbital length 6–8% SL.

Dorsal fins VI–I,8, with no filamentous rays. The first dorsal fin is with second, third, fourth and fifth rays longer. Anal fin I,9–10 (usually 10) directly opposite to the second dorsal fin. The caudal fin is with 11 branched rays and its posterior margin is straight or slightly rounded. Pelvic fins separate, I,5. Pectoral fins 13–14 (usually 13). Lateral scales 28–29, with ctenoid scales on flanks and caudal peduncle. Pre-dorsal scales cycloid anteriorly from snout, adjacent to anterior nostril, to D1. Ctenoid scales on operculum, on base of pectoral fins and on belly extending to anus. Cheek with cycloid and ctenoid scales. Scales in transverse back series 9–10 (usually 9), in transverse forward 10–11, in pre-dorsal 16–18 and in zigzag usually 6–7, interorbital scales 2–3. Vertebrae 25. Gill opening extending to below posterior preopercular margin.

Males have a more elongated second dorsal fin (26– 33 vs. 23–27% SL) and anal fin (30–36 vs. 23–27% SL) than females and a higher first dorsal fin. Males with a slightly triangular urogenital papilla with a small angular lateral extension on each side on the distal part. The females have a rectangular or chalice-shaped bulbous urogenital papilla with crenulated outer edges around distal opening.

Cephalic sensory pore system as described by Akihito et al. (1988) with oculoscapular canal nasal to post-temporal with the pores C’, D, E’, K’, L’; preopercular canal long with the pores M’, N, O, P’.

Colour in preservation: Male and female usually similar except for fins. Background of body brown on the back, beige on the flanks; belly whitish to greyish. A dark blotch on pectoral fin base and on caudal fin base. Top and middle of head dark brown, inferior part clear whitish to greyish. A broad dark stripe from snout and eye, across upper part of preoperculum and operculum, below midline ending at base of caudal fin. Males: First dorsal fin generally greyish with a basal white band, and another one at the tip. Second dorsal fin with several rows of ovoid white spots. Anal and caudal fins hyaline or finely spotted. Females ( Fig. 7C): Fins hyaline.

Colour in life: Breeding males are often more brightly coloured than females which are usually with lighter fins and body. Males ( Fig. 7A): Head and body greenish brown to beige, white on underside of head. Belly whitish. A golden to blackish spot on operculum. A broad dark stripe from lower lip, snout and eye, across upper part of preoperculum and operculum, below midline ending at base of caudal fin. Pectoral fin base with a dark bar dorsally. First dorsal fin variable but usually blackish with a median yellow to whitish stripe, and several orange to yellow spots at the basal part. Second dorsal fin with 5–6 rows of orange to yellow spots between rays, tip of fin bluish-white. Anal fin with a basal bluish stripe, rest of fin dark and tip bluish-white. Caudal fin usually hyaline or with small black spots forming bands. Pectoral fins hyaline. Females ( Fig. 7B): Head and body light brown to yellowish. Fins hyaline. A golden to blackish spot on operculum. A broad dark stripe from snout and eye, across upper part of preoperculum and operculum, below midline ending at base of caudal fin.

Ecology: Hypseleotris guentheri occurs in coastal streams from estuaries to lower parts of rivers and ponds, usually in bank vegetation where the current is slow (pH 8.0–8.4, 290–305 µS/cm and 25–28 °C) ( Keith et al., 2010, 2013). As a free swimming species it is a predator, feeding on zooplankton and small invertebrates. Often aggregated in small schools, it is territorial. Hypseleotris guentheri is thought to be amphidromous.

Distribution: The species is known from Vanuatu, New Caledonia, Samoa and Fiji ( Fig. 4).

Comparison: Hypseleotris guentheri differs from the other species sequenced in having a significant percentage of divergence in the ND2 gene from 4% to 18.5% ( Table 3). Moreover, it differs from H. cyprinoides in having a more prominent stripe on the side of the body and by a combination of characters including more scales in lateral series (usually 28–29 vs. usually 26–27), in pre-dorsal series (16–18 vs. 14–16), a smaller body depth at first dorsal fin in males (18–22 vs. 23–27% SL) and at anus (18–25 vs. 24–30% SL). It differs from H. everetti by fewer pectoral fin rays (13 vs. 14–15), more scales in lateral series (28–29 vs. 26–27), a smaller head length (25–28 vs. 29–33% SL), a smaller pre-dorsal length (38–41 vs. 40–46% SL), a smaller body depth at anus in males (18–21 vs. 28–35% SL) and females (19–25 vs. 24–30% SL), a smaller body depth at first dorsal fin in males (18–22 vs. 28–35% SL) and females (18–26 vs. 26–29% SL), and a smaller caudal peduncle depth (11–14 vs. 14–17% SL). It differs from H. ebneri in having fewer scales in pre-dorsal series (16–18 vs. 18–19), a smaller head length (25–28 vs. 29–31% SL), a smaller pre-dorsal length (38–41 vs. 42–45% SL), and a smaller body depth at first dorsal fin in males (18–22 vs. 25% SL). It differs from H. alexis in having more scales in lateral series (usually 28–29 vs. usually 27–28), more scales in transverse forward series (10–11 vs. 9–10), more scales in transverse back series (9–10 vs. 8–9), and a smaller head length (25–28 vs. 27–31% SL). It differs from H. compressa in having 13–14 pectoral fin rays vs. 14–15, D2 I8 vs. usually I9, more scales in lateral series (usually 28–29 vs. usually 26–28), fewer scales in transverse forward series (10–11 vs. 12–14), more scales in pre-dorsal series (16–18 vs. 14–15) and in interorbital (2–3 vs. 0), a smaller head length (25–28 vs. 29–33% SL), a smaller body depth at first dorsal fin in males (18–22 vs. 28–35% SL) and females (18–26 vs. 24–35), and a smaller body depth at anus (18–25 vs. 24–36% SL). It differs from H. moncktoni in having more scales in transverse back series (9–10 vs. 8), fewer scales in pre-dorsal series (16–18 vs. 19), a smaller body depth at first dorsal fin in females (18–25 vs. 27% SL), a smaller body depth at anus in females (19–24 vs. 26% SL), and a smaller caudal peduncle depth (11–14 vs. 15% SL).