Feeding clusters and olfaction in the mangrove snail Terebralia palustris (Linnaeus) (Potamididae : Gastropoda)

Large numbers of the snail Terebralia palustris (Linnaeus) (Potamididae; Ga stropoda) are frequently observed feeding in a cluster on a single fallen m angrove leaf, yet none are present on leaves nearby. Consequently, we inves tigated the food-finding ability of T. palustris in a Kenyan mangrove fores t using field experiments. We estimated the attractive effect of different cues and analysed the paths (video-recorded) of snails when approaching a f ood-related odour, This intertidal snail can potentially use both air-borne and water-borne odours to locate food. T. palustris is attracted to conspecifics feeding on leaves, while intact l eaves as well as non-feeding snails are not attractive. Moreover, the guidi ng stimulus appears to be compounds released when the leaves are damaged. T . palustris also seems able to discriminate between different food items; i t is more strongly attracted to green mangrove leaves than senescent or fal len ones or mangrove propagules, probably because green leaves release a gr eater amount of attractive cues. Feeding snails thus recruit more snails to feed on the same leaf. The ecolo gical implications of this behaviour are discussed: a large number of snail s on the same leaf counteracts the ability of crabs to remove the leaf bein g eaten by the snails. (C) 2001 Elsevier Science B.V. All rights reserved.