The status of taxonomy and venom in sea snakes

The status of taxonomy and venom in sea snakesArne R Rasmussen1, Kate L Sanders21 The Royal Danish Academy of Fine Arts, School of Architecture, Design & Conservation, Copenhagen, Denmark2 School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia 5000, AustraliaSea snakes form two aquatic groups of snakes with a flat vertically paddle-form tail (sea kraits and viviparous sea snakes). Sea snakes belong to the same family Elapidae, which also includes the terrestrial mambas, cobra, kraits, taipan and brown snake. All elapids are characterized by the anterior position of the poison-fangs on the maxillary bone (proteroglyphous). Globally there are some 70 species of sea snake found in the tropical and subtropical waters of the Indian Ocean and the Pacific Ocean. Most species are found in the Indo-Malayan Archipelago, the China Sea, Indonesia, and the Australian region. Substantial morphological and molecular evidence has been found for recognizing two major clades within the viviparous sea snakes: An ‘Aipysurus’ lineage comprises ten species in the genera Aipysurus and Emydocephalus that are mostly restricted to the Australo-Papuan region, and a much more speciose ‘Hydrophis’ lineage contains about 50 species, many of which have very wide distributions across the Indo-Pacific. The Aipysurus group has experienced a relatively stable taxonomic history, and mitochondrial phylogenies of sampled taxa are well resolved. In contrast, Hydrophis group species have until recently been classified in 10–16 genera and/or subgenera, reflecting their confusing patterns of phenotypic diversity. The viviparous sea snakes are estimated (based on fossil calibratedmolecular clocks) to have a divergence times from terrestrial elapids at around 7.8 million years before present, the Aipysurus group was separated from the other viviparous sea snakes at around 5.8 million years before present and in the Hydrophis lineage the Hydrophis group was separated from the three semi-marine lineages at around 4.4 million years before present. The venoms of sea snakes are rather simple, typically containing a-neurotoxins and phospholipases A2 (PLA2s), and in terms of lethality are known to be more potent than the venoms from terrestrial snakes.