FEATURES
Arabian Gulf Sea Snake (Hydrophis lapemoides) in Abu Dhabi, UAE by Rima Jabado.
be found in America, Africa, Europe, Asia, and some Pacific Islands and comprises of only nonvenomous snakes. That said, they are counted amongst their number as some of the biggest snakes in the world. They don’t have fangs to inject venom, but instead kill their prey by constriction. They have rows of sharp teeth in their upper and lower jaws with which to hold prey, they then squeeze the life out them until they are ready to eat. Pythonidae – Python Snakes: Just like the Boidae family, the Pythonidae family also comprises large nonvenomous snakes, which kill their prey by constriction. To most people it’s very easy to be confused between pythons and boas. While some of them have a very similar look and have almost the same feeding habits, on a closer inspection there are a number of unique characteristic features that set them apart. AQUATIC SNAKES There are in effect Five Families (or Radiations) of Aquatic or Sea Snakes: Marine Hydropiines – True Sea Snakes: The largest group of Sea Snakes are the marine Hydrophiines or True Sea Snakes. There are approximately 60 species of Hydrophiine Sea Snakes covering 16 genera (genus).They evolved originally from Australian Terrestrial Elapids. Conversely and rather confusingly, Australian and Melanesian Terrestrial Elapids also belong to the Subfamily Hydrophiinae. Thus, the subfamily Hydrophiinae includes all Australian and Melanesian Terrestrial Elapids, as well as all True Sea Snakes. The subfamily Hydrophiinae also includes the 58
DIVERS FOR THE ENVIRONMENT | MARCH 2017
genus Laticauda or Sea Kraits. The remaining “old world” elapids found in Asia and Africa, such as cobras and mambas, belong to the subfamily Elapinae. Together, the Hydrophiinae and Elapinae make up the Elapidae family. All very confusing isn’t it? Suffice to say, the largest grouping of Sea Snakes originates from the Southern hemisphere but then extended their coverage in our oceans and seas. In the main, all Elapidae and Hydropiine are venomous, however there are one or two which have a weaker venom. For example, Turtle-headed Sea Snakes (Genus emydocephalus) feed exclusively on fish eggs, thus, do not need a strong venom to subdue or immobilise their prey. The venom of Turtleheaded Sea Snakes is far less toxic than the venom of other species, including Sea Snake species which are closely related to Turtleheaded Sea Snakes. Laticauda – Sea Kraits: The genus Laticauda, or Sea Kraits, comprise of approximately seven species, six of which are marine. Sea Kraits also evolved from Terrestrial Elapids, however, they evolved separately from the Marine Hydrophiines. In fact, the genus Laticauda evolved much earlier than the Marine Hydrophiines. The exact date when this lineage evolved is also uncertain, however, it is likely that they evolved around 15-20 million years ago. Acrochordidae – File Snakes: The family Acrochordidae or File Snakes is the oldest of the Sea Snake lineage, having evolved over 40 million years ago. There are three extant
species in this family and two of these species are marine. File Snakes are not venomous and they give birth to live young. Homalopsidae – Mangrove or Mud Snakes: The family Homalopsidae comprises of 34 species of aquatic or semi-aquatic snakes. Approximately 10 species occur in aquatic habitats such as mud flats, mangroves and estuaries across Southeast Asia and into Northern Australia, however only three species are fully marine. This family belongs to the superfamily Colubroidae and evolved some 15-25 million years ago. Homalopsids are venomous but they are rear-fanged. They also give birth to live young. Natricinae – Salt Marsh Snakes: The Natricinae also belong to the superfamily Colubroidea and are confined almost entirely to salt marsh environments. Three species occur in marine habitats and they are confined to temperate and subtropical North America. They are not venomous. It is thought within the scientific community that the marine Natricine species might be in the early stages of evolving further adaptations to pure marine rather than aquatic environments. PHYSIOLOGY Size: Sea Snakes are only moderately large compared to some of their terrestrial cousins and rarely exceed 2 metres in length, often with peculiarly small heads for their body size. There are however two species of open water Sea Snake that have been known to grow up to three metres.