The strategy used by some piscivorous cone snails to capture their prey: the effects of their venoms on vertebrates and on isolated neuromuscular preparations

Three piscivorous Conus species, C, ermineus, C. censor and C. catus were a cclimatized in aquaria. The study of their strategy to capture the prey and details of their radula's morphology revealed that all of them used a 'hoo k and line' strategy which consists of immobilizing the prey rapidly before engulfing it. The venoms from these piscivorous species clearly elicit, wh en injected into fish, an excitotoxic shock characterized by a sudden tetan us of the prey. In mammals, the venoms induce both flaccid paralysis via i. p. injection and seizures via i.c.v. injection. Intracellular recordings fr om frog nerve-muscle preparations revealed that the venoms from these Conus species first caused spontaneous synaptic potentials which in turn trigger ed muscle action potentials. Such spontaneous activity is due to an increas ed nerve terminal excitability. In addition, the venoms suppressed neuromus cular transmission probably by blocking postsynaptic nicotinic acetylcholin e receptors. No direct effect of these Conus venoms was observed on the mem brane of skeletal muscle fibres. In conclusion, C. ermineus, C. censor and C. catus, which have not securely tethered their prey used a mixture of tox ins which target both pre-and postsynaptic elements of the neuromuscular ju nction and which produce rapid immobilization of their prey. (C) 1999 Elsev ier Science Ltd. All rights reserved.