Distastefulness as a defense mechanism in<i>Aplysia brasiliana</i>(Mollusca: Gastropoda)

Abstract

The biochemical literature on the toxicity of various species of Aplysia is reviewed to indicate that Aplysia are probably not toxic to predators under natural conditions. The possibility that Aplysia avoid prrdation by being distasteful is examined by offering various portions of Aplysia brasiliana and pieces of fish to sea gulls. Gulls are shown to find all parts of Aplysia more distasteful than fish, even fish soaked in a mixture of Aplysia blood, mucus, and ink. Ink gland, gill, and epidermal portions are shown to be significantly more distasteful than other portions, even the midgut and opaline glands, sites of compounds which can be toxic when injected. Distastefulness as a mechanism for avoiding predation and the possible function of the ink gland are discussed in light of these findings and current literature.