Boring food affects evolution of venom in snakes
doi:10.1038/nindia.2007.21 Published online 28 September 2007
What happens to sea snakes, who get to eat only fish as compared to their land cousins, who can chose from an à la carte menu of insects, lizards, frogs, toads, birds and rodents? Obviously, they get bored of this regulation diet. New research says such insipid diet makes for very poor evolution of their venom.
The study jointly conducted by scientists based in India, Australia, Singapore and USA shows how two varieties of sea snakes — the spine-bellied Lapemis curtus and the horned snake Acalyptophis peronii — have ceased to produce any interesting variety in their venom because they have had only fish eggs for breakfast, lunch and dinner since their great-great-great-grandfathers' times1.
"We constructed cDNA libraries from their venom glands and cloned them. Our data showed that despite their explosive evolutionary radiation, there is very little variation in the two main constituents of their venom — the three-finger toxin (3FTx) as well as the phospholipase A2 (PLA2) enzymes," says Susanta Pahari, one of the researchers at the Center for Post Graduate Studies, in Banagalore's Sri Bhagawan Mahaveer Jain College.
The team found that in A.edouxii, the 3FTx gene is activated by the deletion of a dinucleotide (TT) and this decelerates the evolution of the enzymes, unlike in other snake venoms. "As this unique sea snake feeds exclusively of fish eggs. We suggested that a shift in its diet may have resulted in the relaxation of selection pressures on these genes," he said.
The snake specimens were collected from Albatross Bay in Weipa, Queensland, Australia.
The authors of this work are from: Protein Science and Conservation Ecology Laboratories, Department of Biological Sciences, National University of Singapore; Department of Biochemistry & Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia; Deparment of Biochemistry, Medical college of Virginia, Virginia Commonwealth University, Richmond, USA; Center for Post Graduate Studies, Sri Bhagawan Mahaveer Jain College, Bangalore, India
- Pahari, S. et al. Expression pattern of three-finger toxin and phospholipase A2 genes in the venom glands of two sea snakes, Lapemis curtus and Acalyptophis peronii: comparison of evolution of these toxins in land snakes, sea kraits and sea snakes. BMC Evol. Biol. doi: 10.1186/1471-2148-7-175 (2007).