Snails and Their Trails: the Multiple Functions of Trail-Following in Gastropods

Biol. Rev. (2013), pp. 000–000. doi: 10.1111/brv.12023

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Snails and their trails: the multiple functions of trail-following in gastropods

Terence P. T. Ng1 , Sara H. Saltin2 , Mark S. Davies3 , Kerstin Johannesson2 , Richard Stafford4 and Gray A. Williams1,∗

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The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Hong Kong SAR, China Department of Biological and Environmental Sciences-Tj¨ rn¨, University of Gothenburg, SE-452 96 Str¨mstad, Sweden a o o 3 Faculty of Applied Sciences, University of Sunderland, Sunderland SR1 3SD, UK 4 Institute of Biomedical and Environmental Science and Technology (iBEST), University of Bedfordshire, Luton LU1 3JU, UK

ABSTRACT Snails are highly unusual among multicellular animals in that they move on a layer of costly mucus, leaving behind a trail that can be followed and utilized for various purposes by themselves or by other animals. Here we review more than 40 years of experimental and theoretical research to try to understand the ecological and evolutionary rationales for trail-following in gastropods. Data from over 30 genera are currently available, representing a broad taxonomic range living in both aquatic and terrestrial environments. The emerging picture is that the production of mucus trails, which initially was an adaptation to facilitate locomotion and/or habitat extension, has evolved to facilitate a multitude of additional functions. Trail-following supports homing behaviours, and provides simple mechanisms for self-organisation in groups of snails, promoting aggregation and thus relieving desiccation and predation pressures. In gastropods that copulate, trail-following is an important component in mate-searching, either as an alternative, or in addition to the release of water- or air-borne pheromones. In some species, this includes a capacity of males not only to identify trails of conspecifics but also to discriminate between trails laid by females and...