Conus species

Conotoxins are the venoms of the marine cone snails. The >500 Conus species produce >10,000 different toxins. All are cysteine-rich peptides of 10-30 amino... 

Conus Species Feeding lypes, Taxonomic Considerations... 

Figure 4. Worm-hunting and snail-hunting Conus, (a) The ver-mivorous species Conus brunneus about to sting its polychaete worm prey, (b) The molluscivorous species Conus dalli stinging the snail prey, Columhella. Both Conus species were collected in the Gulf of California. Photographs by Alex Kerstitch.

Between 6 and 10 homologous peptides have been extensively characterized for each toxin class. Although uj- and a-conotoxins have been isolated from several fish-hunting Conus species, x-conotoxins have so far been isolated only from C. geographus venom. 

Evolution is tireless in the development of natural toxins. A vast number of variations are possible with even a small number of amino acids in peptides, and peptides make up only one of a broad array of toxic compounds. For example, the predatory marine snail genus Conus is estimated to include at least 500 different species. Each species kills or paralyzes its prey with a venom that contains 50-200 different peptides or proteins. Furthermore, there is little duplication of peptides among Conus species. Other animals with useful toxins include snakes, frogs, spiders, bees, wasps, and scorpions. Plant species with toxic (or therapeutic) substances are too numerous to mention here they are referred to in many chapters of this book. 

Defensive uses of the venom of cone snails have not been well documented. In a few instances, human fatalities have resulted from the stings of these animals it can be argued that this is the result of defensive maneuvers of the snail. However, most Conus species are not sufficiently aggressive to display such behavior. Nevertheless, these animals should not be handled by nonexperts and all precautions must be taken when handling live cone snails. 

One of the most representative examples of venomous animals is constituted by the Conus marine snails [2]. Of the approximately 500 Conus species, about 40-100 prey primarily on Qsh (Qsh-hunting species), and these species use two parallel physiological mechanisms requiring multiple neurotoxins to immobilize Qsh rapidly [3] neuromuscular block and excitotoxic shock. Fishhunting Conus snails use a harpoon-like device to inject their venom in their preys. The venom contains a cocktail of neurotoxins that will cause a double-phase paralytic process (Table 5.1), with an initial phase characterized by a fast paralysis with tetanus and a second phase characterized by a Qaccid paralysis. Finally, the Qsh will be engulfed by the snail. 

As indicated, co-conotoxins are found in almost aU fish-hunting Conus species examined up to now. The most thoroughly studied are the venoms from C. geographus, C. magus, and C. striatus. Several of these peptides have been purified, sequenced, and synthesized (with similar potency as the natural toxins) and they have become important tools for the identification and characterization of the different subtypes of voltage-dependent Ca channels found in neuronal tissues. 

Welcometo ConoServer. Database oftoxins isolated from Conus species, http //www.marinespecies.org/index.php WoRMS. World Register of Marine Species, http / / docmd. com / z iconotide /... 

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