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Some aquatic taxa (fishes, snakes) exhibit a puzzling form of sexual dimorphism: males have a more rugose body surface than do conspecific females. As a first step towards understanding the biological significance of this phenomenon, the nature and correlates (sex, size, body condition, season, and latitude) of scale rugosity was quantified in preserved museum specimens of four species of sea snakes (Family Hydrophiidae): Astrotia stokesii, Emydocephalus annulatus, Hydrophis elegans, and Lapemis hardwickii. Males are more rugose than conspecific females in all four taxa, on ventral as well as dorsal scales. The position of rugosities on the body differs among species. For example, rugosities are found over the entire body in E. annulatus, but are concentrated anteriorly in L. hardwickii and posteriorly in H. elegans. Females possess rugosities that are similar to those of conspecific males, but smaller (in female E. annulatus, they are visible only with scanning electron microscopy analysis). The degree of male rugosity varies seasonally in at least two species (E. annulatus, L. hardwickii), being most pronounced during the winter breeding season. Thus, the transition from terrestrial to aquatic life in proteroglyphous snakes has been accompanied both by an increase in overall rugosity, and by a seasonally labile sex-specific elaboration of this trait. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89, 343–354.

Sea snakes of Sri Lanka are among the most venomous snakes in the island although they have not received much attention in the last few decades. According to data from other countries, they may be more toxic than highly venomous land snakes in the island. Most sea snake species found around Sri Lanka are gentle and inoffensive and will only bite when provoked, but certain species like Astrotia stokesii and Enhydrina schistosa are known to be much more aggressive. We report a case of fatal sea snake envenoming in Sri Lanka. DOI: http://dx.doi.org/10.4038/cmj.v57i4.5089 Ceylon Medical Journal 2012; 57 : 174-175

Offshore reefs of the North West Shelf of Australia support the most diverse and abundant sea snake communities in the world. Ashmore Reef (12° 17′S, 123° 02′ E) is the regional centre of diversity hosting 17 species, including two endemics (Rasmussen et al. 2011; Elfes et al. 2013). However, over the last decade the diversity and abundance of sea snakes at Ashmore Reef have declined drastically. In 2010, only two species (Aipysurus laevis, Astrotia stokesii) were observed and at least five species are now presumed locally extinct (Lukoschek et al. 2013). Here we report on a 2013 survey of Ashmore Reef where, despite extensive boatbased searches over nine days and SCUBA-surveys encompassing 12 ha of reef and lagoonal habitat, no sea snakes were encountered. Identifying the causes of sea snake declines at Ashmore Reef is hampered by a lack of distributional data. To address this, we recorded sea snakes at four previously unsurveyed North West Shelf shoals, namely Echuca, Eugene McDermott, Heywood, and Vulcan, which occur approximately 150–200 km SSE of Ashmore (Fig. 1). Three species were observed (Fig. 1): Aipysurus laevis at Heywood, EugeneMcDermott and Vulcan (one individual at each); Emydocephalus annulatus at Echuca (two individuals) and Heyward (one individual); and the Australasian endemic Aipysurus duboisii at Vulcan (two individuals). These shoals are permanently subtidal (20 m+deep) of consolidated low-relief coral and calcareous algae interspersed with extensive rubble fields. Snakes were seen feeding or resting at 20–25 m or ascending/descending. All three species were also sighted at Hibernia Reef (~30 km NE of Ashmore). Given local extinctions at Ashmore and the demonstrated potential for introgressive hybridisation among Aipysurus spp. in the Timor Sea (Sanders et al. 2014)

Sea-snakes were collected from research trawlers and commercial prawn trawlers in the Gulf of Carpentaria during the period from April 1976 to December 1991. The data were analysed on the basis of CPUE (catch per unit effort) for depth, latitude and season. The research trawlers, operating in the eastern Gulf of Carpentaria, and the commercial prawn trawlers, operating in the south-western Gulf of Carpentaria, caught sea-snakes at a rate of 0.028 and 0.026 sea-snakes per metre of headrope length per hour, respectively. Lapemis hardwickii was the sea-snake most commonly caught by the research trawlers-53% of all snakes-and Hydrophis elegans was the sea-snake most commonly caught by commercial trawlers-25% of all snakes. Depth was the most significant factor affecting CPUE, with more than 70% of all sea-snakes being caught in waters less than 15 m deep. When catches of all species were combined, a significant interaction (P

The genus Paraheterotyphlum is upheld, the type species, australe Johnston and Mawson, 1948, is redescribed from the type material and compared with specimens collected from the following sea snakes from Australian waters: Pelamis platurus, Hydrophis elegans, Aipysurus laevis, Astrotia stokesii, Disteira kingii. These specimens were also compared with specimens from Laticauda semifasciata and colubrina from Taiwan waters.Two species are differentiated: P. australe and P. ophiophagos Schmidt and Kuntz, 1973 mainly by the larger and more distinct interlocking facets on the lips of the latter species. Third and fourth stage larvae, probably of P. australe are described and the distribution and affinities of these species is discussed.

A case of a near-fatal sea snake bite, believed to the the first such case in Australia, is presented. The two-year-old girl victim became unconscious and apnoeic soon after envenomation by an Astrotia stokesii, and required artificial ventilation for 22 hours. She regained consciousness 4 1/2 hours after the administration of antivenom. The recovery phase was marked by hallucinations and tonic spasms. The patient made a full recovery before discharge from hospital. Language: en

From the venom of a sea snake Astrotia stokesii three neurotoxic components, toxins Astrotia stokesii a, b and c were isolated in 40, 15 and 5% yield by weight respectively of the whole venom. Their LD50 values for 20g mice were 0.13, 0.096 and 0.098 microgram/g body wt. respectively and accounted for almost all the lethal activity of the venom. Their amino acid sequences were determined. Astrotia stokesii a was composed of 60 amino acid residues with nine half-cystine residues and was quite homologous to other sea-snake short-chain neurotoxins in its amino acid sequence. Toxins Astrotia stokesii b and c were composed of 70 and 72 amino acid residues respectively with 10 half-cystine residues. They are the first long-chain neurotoxins with high activity isolated from sea-snake venoms. The C-terminal carboxy groups of toxins b and c were found to be amidated; the amidation is known for some polypeptides, but is novel for a protein. The amide group may make a hydrogen-bond with glutamic acid-39, which replaces a lysine that has so far been found invariably in long-chain neutrotoxins. Astrotia stokesii b and c are also novel in having phenylalanine-25 and isoleucine- or valine-42. The ordinary Tyr-Glu pair, which is observed in X-ray structure [Low, Preston, Sato, Rosen, Searl, Rudko & Richardson (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 2991-2994] and n.m.r.study [Inagaki, Tatsumi, Miyazawa, Hori & Tamiya (1977) Abstr. Int. Congr. Pure Appl. Chem. 26th, p. 336] on erabutoxins may be replaced by a hydrophobic pair. Detailed evidence for the amino acid sequences of the proteins has been deposited as Supplementary Publication SUP 5009o (30 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7B1, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1978) 169, 5.

The main neurotoxic components, toxins Hydrophis ornatus a and Hydrophis lapemoides a, were isolated from the venoms of the sea snakes Hydrophis ornatus and Hydrophis lapemoides respectively. The amino acid sequence of toxin Hydrophis ornatus a was deduced to be identical with that of toxin Astrotia stokesii a [Maeda & Tamiya (1978) Biochem. J. 175, 507-517] on the basis of identity of the tryptic peptide ‘map’ and the amino acid composition of each peptide. The amino acid sequence of toxin Hydrophis lapemoides a was determined mainly on the basis of identity of the amino acid compositions, mobilities on paper electrophoresis and migration positions on paper chromatography of the tryptic peptides with those of other sea-snake toxins whose sequences are known. Both toxins Hydrophis ornatus a and Hydrophis lapemoides a consisted of 60 amino acid residues and there were six amino acid replacements between them. The taxonomy of sea snakes in the Hydrophis ornatus complex has long been confused, and the above snakes were originally assigned to taxa that proved to be inconsistent with the relationships indicated by the neurotoxin amino acid sequences obtained. A subsequent re-examination of the specimens revealed an error in the original identifications and demonstrated the value of the protein amino acid sequences in systematic and phylogenetic studies. The isolation procedure and results of amino acid analysis of the tryptic peptides have been deposited as Supplementary Publication SUP 50121 (8 pages) with the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies may be obtained as indicated in Biochem. J. (1983) 209, 5.

In vitro cross-neutralization of venoms of nine species of sea snake was studied, using mice and immunodiffusion patterns as indicators. Tiger snake antivenene was more effective than sea-snake antivenene against all species. Both antivenenes neutralized all venoms tested— Aipysurus laevis , Astrotia stokesii , Enhydrina schistosa , Hydrophis cyanocinctus , H. elegans , H. major , H. spiralis , Lapemis hardwickii , Laticauda semifasciata and Notechis scutatus . Immunodiffusion patterns did not always reflect the in vivo observations. The significance of the results in indicating the choice of an antivenene for treatment of sea snake envenomation is discussed.

The 270-MHz proton NMR spectra of the unique long neurotoxins bearing Phe-25, Astrotia stokesii b (As b) and Astrotia stokesii c (As c) from Astrotia stokesii, and Acanthophis antarcticus b (Aa b) from Acanthophis antarcticus, have been analyzed. The aromatic proton resonances of Phe-25 in As b and Aa b were assigned on the basis of the nuclear Overhauser effects observed on irradiation of slowly exchanging amide protons. Phe-25 was found to be involved in hydrophobic interactions with Ile/Val-42, Ala-46 and Ile-58 in As b and As c, and with Ala-46 and Val-58 in Aa b. These hydrophobic interactions, instead of the hydrogen bond between Tyr-25 and Glu-42 found in other neurotoxins, appear to be important for maintenance of the biologically active tertiary structure. The pH dependency of the chemical shift and intensity of the Trp-72 N-1 proton resonance of As b indicates that the indole ring is not fully exposed to the solvent and that the extra tail segment of this long neurotoxin interacts with the main part of the molecule.

The venom of sea snakes, family Hydrophiidae, is among the most potent of all known snake toxins. Although various signs and symptoms accompany sea snake envenomation, paralysis and respiratory depression are the most prominent. Crude sea snake venom and purified toxins characteristically exhibit neuromuscular activity. Purified neurotoxins have been isolated from Laticauda semifasciata (Tamiya and Arai, 1966), Laticauda laticaudata and Laticauda colubrina (Sato et al., 1969), Lapemis hardwickii (Tu and Hong, 1971), Enhydrina schistosa (Karlsson et al., 1972), and Hydrophis cyanocinctus (Liu et al., 1973). Recently, during an expedition of the Research Vessel Alpha Helix to Ashmore Reef, venom was collected from several species which are more rarely encountered. A preliminary report indicated the neurotoxic activity of crude venom from each of Astrotia stokesii, Aipysurus laevis, Hydrophis elegans, and Hydrophis beleheri collected during that expedition (Barber et al., 1974). Our present report includes additional data regarding the crude venoms of A. stokesii, A. laevis, and H elegans.

An intensive search for marine snakes was carried out in the course of a five week cruise among the Philippine Islands in August and September of 1975. The Visayan Sea was by far the most productive area found, especially near the Gigante Islands. In this area it appears that 12 species are sympatric on shoals of 5-20 meters depth. A 13th species (Cerberus), a mangrove form, is found nearby. Two hydrophiid species, Hydrophis ornatus and Laticauda semifasciata are numerically dominant on the offshore shoals; the former is nocturnal and the latter diurnal. In the mangroves the nocturnal colubrid Cerberus rhynchops and the acrochordid Acrochordus granulatus were common. Laticauda colubrina was a nocturnal shallow water reef and mangrove form. No snakes were found in shallow coastal waters of the Sulu Sea which appear superficially to be suitable habitat. Two individuals of Astrotia stokesii caught at the Gigante Islands represent the first record of this species in the Philippines. * * *