Ancestors of two venomous front-fanged snakes arrived in Australia by SEA, study reveals

From spiders to snakes, Australia is known for its range of incredible, yet deadly wildlife.

Now, a new study has revealed the surprising origin of two of Australia’s most dangerous snakes – the tiger snake and the brown snake.

While most other Australian reptiles arrived by land, researchers from the University of Adelaide claim that these snakes actually arrived by sea.

The timeline of their arrival remains unclear, but the researchers hope their findings will help to shed light on these deadly species. 

Tiger snakes are large and highly venomous, with distinctive black and yellow bands, much like a tiger.

‘Although generally shy and preferring escape over conflict, a cornered tiger snake will put on an impressive threat display by holding its forebody in a tense, loose curve with the head slightly raised and pointed at the offender,’ The Australian Museum explained.

‘It will hiss loudly as it inflates and deflates its body, and if provoked further will lash out and bite forcefully.’

Meanwhile, brown snakes are smaller in size, yet even more deadly.

‘This species has the unfortunate distinction of causing more deaths from snake bite than any other species of snake in Australia,’ The Australian Museum added. 

In the study, the researchers analysed the genomes of the two front-fanged snake species (known as elapids), and compared them to marine and semi-marine elapid sea snakes, and Asian elapids.

Their analysis revealed that the ancestor of the Australian elapids had a number of genes that were not present in the Asian elapids.

Professor David Adelson, an author of the study, said: ‘While we know all marine and semi-marine sea snakes descended from a common Australian land-based ancestor, the origin of Australian elapids has been debated for some time.

‘Some believe their ancestors travelled by land, whereas others hold the more contentious view that a marine or semi-marine ancestor swam here.

Tiger snakes are large and highly venomous, with distinctive black and yellow bands, much like a tiger

‘In our research we found a number of genes that were present in the ancestor of all Australian elapids but could not be traced to a snake ancestor; instead they could be traced to similar transposable gene sequences found in marine life, including fish, sea squirts, sea urchins, bivalves, and turtles.

‘This indicates the marine environment transferred the new genetic material into the snakes and offers new support to the argument that the first Australian elapids swam to our shores.

‘They must have previously acquired the new genetic material during an ancestral period when they were adapted to marine life.’

In particular, the researchers found 14 distinct transfer events, in which new genetic material had been transferred from other marine organisms.

Meanwhile, eight genes were found to be uniquely present in the marine and semi-marine sea snake genomes.

‘This is the first time that jumping genes have been used to confirm the evolutionary history of any animal species, and this research definitively proved that the common ancestor of all Australian elapids adapted to a marine environment,’ Professor Adelson added.

‘It may also have made it easier for the subsequent land to marine transition of sea snakes.’