Toxic Properties of the Saliva of Cassis

Abstract

THE large gastropods of the genus Cassis feed on various achinoids1. Despite its toxic sharp spines, even the black sea urchin, Diadema antillarum, is the prey of the helmet conch, Cassis tuberosa. The feeding habits described by Schroeder2 show that C. tuberosa actively pursues the urchin and appears to overwhelm it physically, despite the phalanx of spines that Diadema brings to bear on any point of attack. Even for the tough-footed Cassis, this is a tour de force, since the microneedle points of the spines readily pierce the sole of the foot. One wonders whether the helmet is quite as reckless as first appears, or whether he is aided by tricks other than a headlong charge. Schroeder also reports “… its long proboscis may be seen greedily feeling among the spines for the urchin's body”. Cassis also everts his proboscis when he is broken from his shell, and then usually squirts a jet of clear fluid in different directions as he whips his proboscis about. This saliva is toxic to numerous marine organisms and conceivably could be used offensively as well as defensively. The work recorded here was undertaken to show the manner in which the poison acts on Diadema.