Spatial organization of foraging activity in Siphonaria lessoni from The SW Atlantic, Argentina

Abstract

Siphonaria lessoni is the only gastropod species living in the upper littoral rocky shore in Northern Argentina. S. lessoni do not show homing behaviour. Excursions occur during splash of wave action or rain. Movements are shown by a zig-zag of mucus trails on vertical walls. On horizontal surfaces of tidal pools where a thin layer of sand is retained above the rocky substratum, S. lessoni moves leaving a zig-zag trail visible because they sweep the sand. In order to answer if this pattern of movement is a response to quartzose rock, rugose surfaces, or a intrinsic limpet behaviour, a series of aquarium observations were performed. Individuals of adult S. lessoni were placed in an aquarium after allowing a microalgal film to grow on the walls. The limpets started to move and graze in a zig-zag pattern of increasing amplitude of radular bites from one to fifteen as a general rule. The final result is the almost complete depletion of the algae film of the aquarium wall. We conclude that the zig-zag pattern of movement and grazing is an intrinsic behaviour which is not related to microenvironmental heterogeneity and allows the limpets to explore and cover a wider surface area. This behaviour would be linked with the lack of homing in the species.