Fish hunting cone snails

In the fish-hunting cone snail venoms, a- and w-conotoxins are ubiquitously distributed. As noted above, z-conotoxins have only been found in one species. Conus geographus. In addition to these three well-characterized classes, however, a fourth class of paralytic conotoxins has been found. In contrast to the a-, z-, and... 

Contryphans, H-Gly-Cys-Hyp-D-Trp-Xaa-Trp-Cys-NH2, unusual peptides containing a distinctive post-translational modification in form of D-Trp or D-Leu isolated from venoms of fish-hunting cone snails. 

Schulz, J.R., Norton, A.G., and Gilly W.F. (2004) The projectile tooth of a fishing-hunting cone snail Conus catus injects venom into fish prey using a high-speed ballistic mechanism. Biol. Bull., 207, 77-79. 

Peptide neurotoxins from fish-hunting cone snails. Science 230 1338-1343. 

Figure 1. Diagram of the venom duct of Conus. The venom is produced in the venom duct, apparently expelled from the duct into the proboscis by contraction of the venom bulb. Simultaneously, a harpoon-like tooth is transferred from the radula sac to the proboscis. When injection takes place, the venom is pushed through the hollow tooth and flows into the prey through a hole at the tip of the tooth. Typically, fish-hunting cones will strike at a fish only once and grasp the tooth after injection has occurred, effectively harpooning their prey while injecting the paralytic venom. In contrast, snail-hunting cones will usually sting their prey several times before total paralysis occurs. (Reprinted with permission from the Second Revised Edition of Ref. 8. Copyright 1988 Darwin Press, Inc.)...

A hunting cone snail (Conus textile). Currently, more than 2,000 species are known. They occur in every ocean in the World. From the phylogenetic viewpoint, cone snails have a strikingly broad spectrum of prey. This stretches from other snails via worms to fish. Each species has its own toxins, consisting of diverse cocktails of up to 200 (from a pool of ca. 50,000) different neuroactive peptides, some of which can also be dangerous to humans. 

Conotoxins are small (10-30 amino acids), disulphide-rich, conformationally constrained peptides produced by marine mollusks such as cone snails. The fish-hunting snails, in particular Conus geographus, have been extensively studied. Depending upon the arrangement of disulphide bonds and the number of residues between cysteines, five or more classes of conotoxin can be structurally identified ... 

Examples of marine species using venoms for hunting are too numerous to list here but one which caught my imagination was the piscivorous sea snail Conus purpurascens or purple cone. How can a snail survive by catching fish given the relative speed (or lack of it) of the two animals The answer is that the snail possesses... 

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