Hydrophis Latreille

Rasmussen, Arne Redsted, Elmberg, Johan, Gravlund, Peter & Ineich, Ivan, 2011, Sea snakes (Serpentes: subfamilies Hydrophiinae and Laticaudinae) in Vietnam: a comprehensive checklist and an updated identification key, Zootaxa 2894, pp. 1-20 : 5-8

Hydrophis Latreille

Remarks: The genus Hydrophis is diverse and includes 36 species ( Rasmussen & Ineich, 2000; Rasmussen et al., 2001; Rasmussen et al., 2007), 13 of which have been found in Vietnamese waters.

Hydrophis atriceps Günther : ( Smith, 1926; Bourret, 1934, 1936; Shuntov, 1962; Pickwell, 1972; Harding & Welch, 1980; Tran & Nguyên, 1980; Kharin, 1984b; Tran & Nguyên, 1995; Nguyên & Hó, 1996; Kharin, 2006; Nguyên et al., 2009).

Diagnostic characters: Head small. Body slender anteriorly and long. More than 31 scale rows around midtail. Scale rows around neck 25–30; scale rows around body 39–49; ventrals 320–455. Maxillary teeth behind fangs 5–6. Colouration: Anterior part of body dark or black with pale yellowish oval spots on the sides or spots merging into bands. Posterior part of the body greyish white above, whitish below, with dark bands that may extend down the sides to form complete bands. Head dark or black. Size: 120 cm. General distribution: Singapore, Gulf of Thailand, South China Sea, Philippines, Indonesia and Arafura Sea ( Smith, 1926; David & Ineich, 1999). Remarks: H. atriceps has been regarded as a subspecies of H. fasciatus ; now most authors recognise H. atriceps as a valid species ( Cogger et al., 1983), thus excluding the allopatric H. fasciatus .

Hydrophis belcheri (Gray) : ( Rasmussen et al., 2007).

Diagnostic characters: Normally only one supralabial (the fourth) bordering the eye, but rarely two (third and fourth or fourth and fifth). Scale rows around neck 24–27; scale rows around body 32–37; ventrals 278–313. Maxillary teeth behind fangs 7–8, rarely 6 or 9. Colouration: Body yellow or greyish above, yellow-whitish below, with 52–70 dark or black bands. Head dark with flecks of olive or yellowish markings on prefrontal and around eye. Size: 94 cm. General distribution: Gulf of Thailand, Vietnam, Indonesia and New Guinea ( McCarthy & Warrell, 1991; David & Ineich, 1999; Rasmussen et al., 2007; Nguyên et al., 2009).

Hydrophis brookii Günther : ( Smith, 1926; Bourret, 1934, 1936; Minton, 1975; Harding & Welch, 1980; Tran & Nguyên, 1980; Kharin, 1984b; Welch, 1988; Golay et al., 1993; Tran & Nguyên, 1995; Nguyên & Hó, 1996; Dotsenko, 1999; Nguyên et al., 2005; Kharin, 2006; Nguyên et al., 2009).

Diagnostic characters: Head small, body long and slender anteriorly. Scale rows around neck 25–31; scale rows around body 37–45; ventrals 328–414. Maxillary teeth behind fangs 4–5. Colouration: Body bluish white with 60 to 80 dark or black bands. Anteriorly these completely encircle the body, but posteriorly they narrow on the sides and may be incomplete below. Head blackish, with a yellow horseshoe mark on the upper side. Size: 104 cm. General distribution: Indo-Malayan Archipelago, South China Sea and North Coast of Borneo and Java ( David & Ineich, 1999).

Hydrophis caerulescens (Shaw) : ( Smith, 1926; Bourret, 1934, 1936; Kharin, 1984b; Tran & Nguyên, 1995; Nguyên & Hó, 1996; Kharin, 2004a; Nguyên et al., 2005; Kharin, 2006; Nguyên et al., 2009).

Diagnostic characters: The only sea snake with more than 13 maxillary teeth (i.e. 14–18) behind the poison fangs. Scale rows around neck 31–43; scale rows around body 38–54; ventrals 253–334. Colouration: Body bluish-grey above, greyish below, with 40–60 dark or black bands, which are broader than the interspaces between them. With age the bands become indistinct and the body almost uniformly greyish blue. Size: 82 cm. General distribution: Pakistan, India, Andaman Sea, Indo-Malayan Archipelago, South China Sea, Indonesia, Arafura Sea and Gulf of Carpentaria ( Australia) ( David & Ineich, 1999).

Hydrophis cyanocinctus Daudin : ( Smith, 1926; Bourret, 1934, 1936; Shuntov, 1962; Pickwell, 1972; Harding & Welch, 1980; Tran & Nguyên, 1980; Kharin, 1984b; Golay et al., 1993; Tran & Nguyên, 1995; Nguyên & Hó, 1996; Dotsenko, 1999; Nguyên et al., 2005; Kharin, 2006; Nguyên et al., 2009).

Diagnostic characters: Scale rows around neck 27–35, rarely 25; scale rows around body 37–47; ventrals 279–390. Maxillary teeth behind fangs 5–8. Colouration: Very variable, especially the bands. Body pale yellow green or greyish above, whitish below. Dark bluish or black bands, which may be: a) encircling the body and broadest above, b) encircling the body and of rather uniform width, or c) broadest above and narrowing out to disappear laterally. On the posterior part of the body the bands are dorsally always broader than the interspaces between them. With age the banding pattern fades. Size: 275 cm. General distribution: From the Arabian Gulf in the west to Japan in the east ( David & Ineich, 1999) Remarks: One of the largest species of sea snake, approaching 3 m.

Hydrophis gracilis (Shaw) : ( Smith, 1926; Bourret, 1934, 1936; Shuntov, 1962; Harding & Welch, 1980; Tran & Nguyên, 1980; Kharin, 1984b; Golay et al., 1993; Tran & Nguyên, 1995; Nguyên & Hó, 1996; Dotsenko, 1999; Nguyên et al., 2005; Kharin, 2006; Nguyên et al., 2009).

Diagnostic characters: Ventrals entire anteriorly, more or less completely divided by a longitudinal furrow posteriorly. Head small. Body slender anteriorly. Scale rows around neck 17–23; scale rows around body 30–43; ventrals 215–350. Maxillary teeth behind fangs 5–6. Colouration: Anterior part of body black, with whitish lateral patches (formed by dark bands merging dorsally) or complete pale transverse bands. Posterior part of the body with more unbroken alternating black and whitish bands. With age the bands disappear and the body becomes uniformly greyish. Size: 122 cm. General distribution: From Arabian Gulf to South China Sea and Indonesia, Arafura Sea to Gulf of Papua (New Guinea) ( David & Ineich, 1999). Smith (1926) defined two subspecies with H. g. microcephalus occurring in the middle of the range of the typical form (Natuna and Java Seas).

Hydrophis klossi Boulenger : ( Kharin, 2004b, 2006).

Diagnostic characters: Head small. Body slender anteriorly. Scale rows around neck 22–25, rarely 27; scale rows around body 30–37, rarely 39; ventrals 360–415. Maxillary teeth behind fangs 5–6. Colouration: Body greyish yellow with 50–75 dark or black bands, which are broader than their interspaces dorsally. Head greyish black, sometimes with an indistinct pale horseshoe-shaped mark above. Size: 142 cm. General distribution: Straits of Malacca, the Gulf of Thailand, Cambodia and southern Vietnam ( David & Ineich, 1999; Kharin, 2004b).

Hydrophis lamberti Smith : ( Kharin, 2006; Rasmussen et al., 2007; Nguyên et al., 2009).

Diagnostic characters: Scale rows around neck 37–45; scale rows around body 45–56; ventrals 258–306. Maxillary teeth behind fangs 9–12. Colouration: Body whitish or pale grey above, paler below. Large rounded dorsal bands anteriorly, posteriorly gradually becoming narrower and separated by broader interspaces. Bands broader above, narrow and faintly coloured laterally. Size: 122 cm. General distribution: Singapore, Gulf of Thailand, Vietnam and Philippines ( Rasmussen, 1989; David & Ineich, 1999). Remarks: Has been included in H. ornatus by some authors (e. g. Smith, 1926), but is very distinct in its colour pattern.

Hydrophis melanocephalus Gray : ( Kharin, 2006; Rasmussen et al., 2007; Nguyên et al., 2009).

Diagnostic characters: Head small, body slender anteriorly. Scale rows around neck 23–27; scale rows around body 33–41; ventrals 289–358. Maxillary teeth behind fangs 6–8. Colouration: Body greyish yellow above, yellowish or white below, with 40–55 black bands, about as broad as their interspaces, usually broadest above and below. Head blackish, sometimes with yellow spots. Size: 123 cm. General distribution: Vietnam, China, Taiwan, Japan, and Philippines ( David & Ineich, 1999; Kharin, 2006). Remarks: Has been confused with H. coggeri in the Australian region ( Kharin, 1984a).

Hydrophis ornatus (Gray) : ( Smith, 1926; Bourret, 1934, 1936; Shuntov, 1962; Pickwell, 1972; Harding & Welch, 1980; Tran & Nguyên, 1980; Kharin, 1984b; Gasperetti, 1988; Golay et al., 1993; Tran & Nguyên, 1995; Nguyên & Hó, 1996; Dotsenko, 1999; Nguyên et al., 2005; Kharin, 2006; Rasmussen et al., 2007; Nguyên et al., 2009).

Diagnostic characters: Scale rows around neck 34–41; scale rows around body 42–54; ventrals 235–294. Maxillary teeth behind fangs 9–13. Colouration: Body pale grey above, whitish below. Broad dark greyish bands, interspaces narrow and almost equidistant anteriorly. Head olive-green or greyish above. Size: 115 cm. General distribution: From the Arabian Gulf in the west to Japan, Philippines, Indonesia and New Caledonia ( Rasmussen, 1989; Ineich & Rasmussen, 1997; David & Ineich, 1999), and the Australian region ( H. ornatus ocellatus ) ( Smith, 1926).

Hydrophis pachycercos Fischer : ( Rasmussen et al., 2007).

Diagnostic characters: Scale rows around neck 26–31; scale rows around body 39–45; ventrals 247–297. Maxillary teeth behind fangs 7–8. Colouration: Body pale yellow above, white below, with pale brown transverse bands fading on the upper part of the flanks. Head white below, black/dark above with pale supralabials and a pale ring around the eyes. Size: 111 cm. General distribution: South China Sea (one specimen at the Natural History Museum, London, collected in “E. Ind. Archipelago”)( Rasmussen et al., 2007). Remarks: Recently resurrected from H. belcheri ( Rasmussen et al., 2007) .

Hydrophis parviceps Smith: (Smith, 1935 ; Taylor, 1963; Kharin, 1984b; Nguyên & Hó, 1996; Nguyên et al., 2005; Kharin, 2006; Rasmussen et al., 2007; Nguyên et al., 2009).

Diagnostic characters: Head small, body slender anteriorly. Scale rows around neck 19–21; scale rows around body 31–34; ventrals 329–348. Maxillary teeth behind fangs 6–7. Colouration: Body olivaceous above, greyish below, with 65–70 blackish bands. Head black with no or only a few faint paler marks. Size: 125 cm. General distribution: Southern Vietnam ( Smith, 1935; Taylor, 1963) Remarks: Only two specimens known previously; one caught in 1929 and one in 1960, both from the coast of southern Vietnam ( Smith, 1935; Taylor, 1963). Four additional specimens were collected during the fishing vessel survey in 2001 SW of Ham Tan. The species is endemic to Vietnam.

Hydrophis spiralis (Shaw) : ( Dotsenko, 1999).

Diagnostic characters: Scale rows around neck 25–31; scale rows around body 33–38; ventrals 295–362. Maxillary teeth behind fangs 6–7. Colouration: Body yellow above, pale yellow below, with black bands. Interspaces broader than bands, at least posteriorly. Head yellow/dark above, paler below. Size: 275 cm. General distribution: From the Arabian Gulf in the west to Vietnam in the east, Indonesia and New Caledonia ( Ineich & Rasmussen, 1997; David & Ineich, 1999; Dotsenko, 1999).

Hydrophis torquatus diadema Günther : ( Bourret, 1934; Warrell, 1994; Ineich, 1996; Nguyên & Hó, 1996; Nguyên et al., 2005; Nguyên et al., 2009). Despite mentioned by many authors the species is not yet confirmed from Vietnamese waters.

Diagnostic characters: Scale rows around neck 29–37; scale rows around body 35–49; ventrals 230–340. Maxillary teeth behind fangs 8–10. Colouration: Body grey or whitish above, yellow or whitish below, with black bands, which are often incomplete below. Bands fade and disappear with age, leaving the back more or less uniform grey. Head black with a yellowish band across the snout and along sides. Size: 104 cm. General distribution: Straits of Malacca, Borneo, Gulf of Thailand, Tonle Sap lake in Cambodia, and possibly China ( Smith, 1926; Ineich, 1996; David & Ineich, 1999) Remarks: Three subspecies are defined, each with a very limited range ( Smith, 1926). The one found closest to Vietnamese waters is H. torquatus diadema ( Smith, 1926; Ineich, 1996).