The role of defensive ecological interactions in the evolution of conotoxins

Venoms comprise of complex mixtures of peptides evolved for predation and defensive purposes. Remarkably, some carnivorous cone snails can inject two distinct venoms in response to predatory or defensive stimuli, providing a unique opportunity to study separately how different ecological pressures contribute to toxin diversification. Here, we report the extraordinary defensive strategy of the Rhizoconus subgenus of cone snails. The defensive venom from this worm-hunting subgenus is unusually simple, almost exclusively composed of αD-conotoxins instead of the ubiquitous αA-conotoxins found in the more complex defensive venom of mollusc- and fish-hunting cone snails. A similarly compartmentalised venom gland as those observed in the other dietary groups facilitates the deployment of this defensive venom. Transcriptomic analysis of a C. vexillum venom gland revealed the αD-conotoxins as the major transcripts, with lower amounts of 15 known and 4 new conotoxin superfamilies also detected wi...