cone

$Venomous Cone Snails Cone snails are the world's most venomous molluscs, and the :>500 species in the genus Conus have evolved tens of thousands of different peptide toxins that are used to paralyze prey by blocking nerve and muscle activity. These toxins are injected from an extensible proboscis through a hollow, barbed tubular tooth that serves as a syringe needle. Nearly all cones snails show a high degree of specificity for certain prey types -- worms, other molluscs or fish. Only Conus californicus, a species found from San Francisco to Cabo San Lucas, is known to prey on all three of these groups (See October, 2005, Biological Bulletin). Snails that prey on fish tend to have toxins that are harmful to humans, and some toxins are being developed as human pharmaceuticals for treatment of chronic pain. A variety of cone snails grouped into their preferred prey types. Only C. californicus hunts all three. Conus californicus in the act of hunting. The hollow tooth is held near the tip of the extended proboscis and fired into the victim like a bullet. The siphon is used for breathing. Photo of tooth by E. Urban; close-up of head by W. Gilly; living snail by T. Anderson. Joseph Schulz and Alex Norton captured the fist images of the explosive injection of the Conus tooth using high-speed video methods. They found that the entire process from detecting the prey to stunning it takes only a fraction of a second -- and that the actual flight time of the tooth was only ~0.001 second. The source of this explosive power is unknown. (http://www.biolbull.org/cgi/content/full/207/2/77 and http://www.mbl.edu/BiologicalBulletin/VIDEO/schulz/). For a review of this work see http://sciencenow.sciencemag.org/cgi/content/full/2004/1019/2. Whereas most laboratories working on cone snail toxins are focused on identifying new toxins, we have opted to investigate the biological mechanisms by which the toxins are manufactured and processed prior to use. This work has turned up several unexpected levels of complexity. For exampe, different snails of the same species can utilize different toxins, even though they inhabit the same area. Joseph Schulz in collaboration with Dr. Jonathan Sweedler's lab at the University of Illinois , Urbana , showed that individual specimens of Conus striatus, a well studied fish-hunter, utilized different complements of toxins. Reasons for this selectivity or how toxins are selected are unknown. For a review of this work see http://jeb.biologists.org/cgi/content/full/208/15/ii$ shapeimage_2_link_0