Responses of mud snails and periwinkles to environmental odors and disaccharide mimics of fish odor

Abstract

Estuarine snails, periwinkles (Littoraria irorata), and mud snails (Ilyanassa obsoleta) were tested for behavioral responses to aqueous extracts of tissue macerates, odors of living intact organisms, and to disaccharides derived from heparin. Extracts included salt-marsh cordgrass (Spartina alterniflora), pink shrimp (Penaeus duorarum), crushed periwinkles, and crushed mud snails. Odors included live periwinkles, mud snails, stone crab (Menippe mercenaria), striped hermit crab (Clibanarius vittatus), tulip snail (Fasciolaria hunteria), and mummichog (Fundulus heteroclitus). Responses were determined upon contact by snails of a ring of solution in the bottom of an otherwise dry bowl and by presenting snails in seawater with 25 μl of solution on a cotton swab. In each test, the response of 30 individuals was determined. Behaviors were recorded as fed, alarm, and no response. The strongest alarm response (>80% of all snails tested) in both snails was elicited by crushed mud snails. The strongest feeding response was to shrimp and periwinkle extract for mud snails (>70%), and salt-marsh cordgrass extract attracted periwinkles. High percentages of mud snails and periwinkles fled in response to the odors of intact snail predators, stone crabs, tulip snails, and mummichogs. Mud snails and periwinkles did not flee in response to nonpredator odors, including each other's odor, as well as that of hermit crabs, shrimp, and marsh cordgrass. Heparin disaccharides were tested because other studies reported that biological activity of predatory fish odor is due to similar disaccharides originating from fish mucus. Mud snail responses to disaccharides indicate that they respond to the same kinds of molecules as crustacean larvae and that the modified amine on the disaccharide is essential for activity. The Q-tip assay is appropriate for bioassay-directed purification of alarm signals originating in fish body odor.