THE INFLUENCE OF INGESTIVE CONDITIONING ON FOOD CHOICES IN THE LAND SNAIL HELIX-ASPERSA MULLER (GASTROPODA, PULMONATA, STYLOMMATOPHORA)

An experiment of food choice in one-day-old naive land snail Helix aspersa Muller was carried out, involving three phases. First, a training period on a monophagous diet of leaf discs of Taraxacum officinale or Urtica dioica was given for 1, 5, 10, 15 or 30 days. The area of leaf discs consumed by each snail during this stage was assessed. In the intermediate phase, the animals were not fed for 24 hours. Finally, food choice was tested over 24 hours, when animals could eat leaf discs of each species of plant used for training. A coefficient of food preference for Urtica dioica was calculated (UPC = area of Urtica leaf disc consumed/area of Urtica and Taraxacum discs of leaves consumed for 24 hours). The length of the training phase did not reduce the percentage of individuals preferring the plant previously consumed. On the contrary, after 15 days of monophagous diet, animals formerly fed on Urtica showed a coefficient of food preference for Urtica significantly higher than Taraxacum fed animals, and after 30 days of training this phenomenon was more pronounced. Thus, during the choice test, snails ate more of the previously eaten plant leaf. Our experiment highlighted the feeding behaviour plasticity of H. aspersa. The significant correlation between the area of Urtica eaten during the training phase and the coefficient of food preference for Urtica is discussed.