AUTOMATIC ACQUISITION OF GRAZING ACTIVITY IN LIMPETS

Department of Zoology and Genetics, University of Florence, Florence, Italy

Littoral gastropods and chitons that graze algal films on rocky shores represent valid biological models for the analysis of resource exploitation in the intertidal zone, typically characterised by physical constraints and by intense inter- and intra-specific competition phenomena. Limpets in general and Patella caerulea in particular are good prototypes for understanding herbivorous foraging in reference to energy maximisation and time minimisation strategies. In order to construct objective mathematical models first of all it is necessary to obtain simple parameters describing foraging and identify related currency.

We have developed a sonographic technique that permits to acquire and automatically store on computer every single grazing event, simply deriving the sounds produced by the radular activity on the substrate. This technique encompasses an instrument consisting of three electronic devices:

1. Rasping detecting device (RD). Placed on limpet's shell is the transducer of the mechanical vibrations produced by the radula scraping the algae from the rocks.
2. Amplifying, filtering and digital-encoding device (AFD). An eight-channel 'black-box' that clears the analog signal and codes it in digital.
3. Acquisition and storing device (AS). Placed on the computer, this device acquires and stores the signal.