ABSTRACT
Venonous activity, defined as the capacity of injecting poisonous chemicals, is Known in only 2 classes of Echinoderms, Asteroidea and Echinoidea : in the starfish Acanthaster planci and some of the most primitive sea-urchins venom is injected by spines, with poisonous bags at the tip in Echinothuriidae, and merely covered with very irritating mucus in Acanthaster and Diadematidae ; in other Echinoidea venom is injected by globiferous pedicellariae. We discovered that those of Toxopneustes, dangerous for man, and venomous spines of Asthenosoma, Diadema and Echinothrix are completely harmless for starfishes. On the contrary, in temperate and cold littoral waters of the Northern Hemisphere, globiferous pedicellariae react only to contact with predatory starfishes and can often Kill them, according to our experiments. Venomous activity is directed against major predators of sea-urchins in the ecosystem, fishes in warm waters of the Indo-Pacific, and starfishes on both sides of the Northern Atlantic and Pacific Oceans, where we discovered, beside neurotoxic action, a necrotic action on starfishes. We observed, on the other hand, that some starfishes which prey upon sea-urchins -such as Harthasterias glacialis and Luidia ciliaris -have developed resistance against the venom of Paracentrotus lividus, at least in some geographical areas. Peculiar ecological conditions explain how the preyspecies can nonetheless survive. Some hypotheses are made about the possible influence of starfishes on the present distribution of Echinoidea.
