The giant triton snail (Charonia tritonis) is one of the few natural predators of the adult Crown-of-Thorns starfish (COTS), a corallivore that has been damaging to many reefs in the Indo-Pacific. Charonia species have large salivary glands (SGs) that are suspected to produce either a venom and/or sulphuric acid which can immobilize their prey and neutralize the intrinsic toxic properties of COTS. To date, there is little information on the types of toxins produced by tritons. In this paper, the predatory behaviour of the C. tritonis is described. Then, the C. tritonis SG, which itself is made up of an anterior lobe (AL) and posterior lobe (PL), was analyzed using an integrated transcriptomics and proteomics approach, to identify putative toxin-and feeding-related proteins. A de novo transcriptome database and in silico protein analysis predicts that ~3800 proteins have features consistent with being secreted. A gland-specific proteomics analysis confirmed the presence of numerous SG-AL and SG-PL proteins, including those with similarity to cysteine-rich venom proteins. Sulfuric acid biosynthesis enzymes were identified, specific to the SG-PL. Our analysis of the C. tritonis SG (AL and PL) has provided a deeper insight into the biomolecular toolkit used for predation and feeding by C. tritonis. If a generalist predator evolves to a more a specialist diet, it is assumed that it would be accompanied by modifications of characters that permit greater efficiency in capturing specific prey species. These likely include foraging behaviors and search strategies with fine-tuned chemosensory systems, physiological processes associated with digestion and waste removal, and other features involved with prey capture 1 . Among predatory taxa the evolution of a specialized diet is likely to be strongly linked to the evolution of venoms used to subdue prey. Although the evolution of many of these characters may be difficult to trace for a species that has evolved a restricted diet, the evolution of venoms can be inferred from analyses of expression of genes encoding venom and digestion components 2, 3 . Marine organisms from a broad range of phyla, from bacteria and algae to invertebrates and vertebrates, are known to produce toxins with high chemical diversity, divergence of which is likely driven by speciation and diet 4-6 . Some examples include tetrodotoxins produced by bacteria found in the saliva of the blue-ringed octopus and puffer fish 7, 8 , potent pore-forming toxins produced by cnidarians 9 , okadaic acid produced by bacteria in marine sponges 10 , and saponins (steroidal and triterpenoid) that are produced by echinoderms 11 . Venoms, and in particular specific toxins, play multiple roles from foraging to defense and intraspecific conflict 12 . Although there are many species of predatory marine snails, studies of venom toxins have been restricted to species within the superfamily Conoidea 13 . These venomous marine cone snails synthesize a remarkable diversity of pharmacologically active small peptides (conotoxins) to enable prey capture, self-defense and intra-specific competition 14-16 . The potency and selective profiles of the conotoxins vary depending on species targets that may include various subtypes of voltage-and ligand-gated ion channels, G protein-coupled receptors and neurotransmitter transporters 17 . Gastropods of the superfamily Tonnoidea are effective predators and thought to capture prey through envenomation 18 . Within the Tonnoidea, several species in the Cassidae family of snails are specialist predators of echinoderms. The large paired and mono-lobed salivary gland (SG) of Cassidae family snails are known to be toxic and inject a strong acid or venomous saliva into their prey to paralyse them before consumption [19] [20] [21] . For example, Cassidae helmet shell snails secrete an acidic saliva to soften the body wall of their preferred prey, sea urchin 22, 23 , Published: xx xx xxxx OPEN www.nature.com/scientificreports/ 2 Scientific RepoRts | 7: 6000 |
Output: Multiomics analysis of the giant triton snail salivary gland, a crown- of-thorns starfish predator OPEN