Venom of the Annulated Sea Snake : A Biochemically Simple but Genetically Complex Weapon.

Given that the venom system in sea snakes has a role in enhancing their secondary adaption to the marine environment, it follows that elucidating the diversity and function of venom toxins will help to understand the adaptive radiation of sea snakes. We performed proteomic and de novo NGS analyses to explore the diversity of venom toxins in the annulated sea snake () and estimated the adaptive molecular evolution of the toxin-coding unigenes and the toxicity of the major components. We found three-finger toxins (3-FTxs), phospholipase A (PLA) and cysteine-rich secretory protein (CRISP) in the venom proteome and 59 toxin-coding unigenes belonging to 24 protein families in the venom-gland transcriptome; 3-FTx and PLA were the most abundant families. Nearly half of the toxin-coding unigenes had undergone positive selection. The short- (i.p. 0.09 μg/g) and long-chain neurotoxin (i.p. 0.14 μg/g) presented fairly high toxicity, whereas both basic and acidic PLAs expressed low toxicity. The toxicity of venom was largely determined by the 3-FTxs. Our data show the venom is used by as a biochemically simple but genetically complex weapon and venom evolution in is presumably driven by natural selection to deal with fast-moving prey and enemies in the marine environment.