Eggs-Only Diet: Its Implications for the Toxin Profile Changes and Ecology of the Marbled Sea Snake ( Aipysurus eydouxii)
Received: 03 May 2004 Accepted: 16 August 2004 DOI:
Cite this article as: Li, M., Fry, B. & Kini, R.M. J Mol Evol (2005) 60: 81. doi:10.1007/s00239-004-0138-0 Abstract
Studies so far have correlated the variation in the composition of snake venoms with the target prey population and snake’s diet. Here we present the first example of an alternative evolutionary link between venom composition and dietary adaptation of snakes. We describe a dinucleotide deletion in the only three finger toxin gene expressed in the sea snake
Aipysurus eydouxii (Marbled Sea Snake) venom and how it may have been the result of a significant change in dietary habits. The deletion leads to a frame shift and truncation with an accompanying loss of neurotoxicity. Due to the remarkable streamlining of sea snake venoms, a mutation of a single toxin can have dramatic effects on the whole venom, in this case likely explaining the 50- to 100-fold decrease in venom toxicity in comparison to that of other species in the same genus. This is a secondary result of the adaptation of A. eydouxii to a new dietary habit — feeding exclusively on fish eggs and, thus, the snake no longer using its venom for prey capture. This was parallel to greatly atrophied venom glands and loss of effective fangs. It is interesting to note that a potent venom was not maintained for use in defense, thus reinforcing that the primary use of snake venom is for prey capture. Keywords Sea snake Venom gland Pseudogene Three-finger toxin Neurotoxin Aipysurus eydouxii
Nucleotide sequence data reported here have been deposited in the GenBank database under accession number AY559317.
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