Chemical Camouflaging and Behavioral Defenses Against a Predatory Seastar by Three Species of Gastropods From the Surfgrassphyllospadixcommunity

In Phyllospadix beds of central California, the gastropods Lacuna marmorata, Alia carinata, and Notoacmea paleacea occur in abundance with the predatory seastar Leptasterias hexactis. All three gastropods have defensive adaptations that reduce the frequency of predation by this seastar. 2. Lacuna responds to waterborne chemicals ("scent") emanating from distant Leptasterias by rotating the shell through an arc of 360°, waving its cephalic tentacles, and increasing general activity. Upon contact with the predator, Lacuna flees by falling off the Phyllospadix blade. 3. Alia does not respond vigorously to the scent of distant specimens of Leptasterias. Upon contact with Leptasterias, Alia rears up on the posterior portion of the foot and then begins to run away. If contact with the seastar persists, the snail strikes at the seastar's tube feet with its proboscis. 4. N. paleacea does not give a behavioral defensive response to Leptasterias. Rather, this stenotopic limpet may be chemically camouflaged, and this camouflage, together with the limpet's precisely fitting shell, may reduce predation by Leptasterias. Notoacmea paleacea eats Phyllospadix, and at least one specific chemical from the plant, a sulphated flavonoid pigment, also is found in the shell of this limpet. Due to the presence of specific, host-plant chemicals in the shell of N. paleacea, Leptasterias may fail to detect the limpet against the chemical background of the host plant. 5. Lacuna is the most frequently consumed prey of Leptasterias in the Phyllospadix beds, yet 89% of the 75 encounters observed between Lacuna and Leptasterias in the field resulted in the successful escape of the prey. The defensive adaptations of Alia and N. paleacea seem to be even more effective, since these gastropods are consumed only rarely by Leptasterias.