FIELD OBSERVATIONS ON FEEDING OF THE LAND SNAIL HELIX ASPERSA MULLER |
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Authors: | IGLESIAS J; CASTILLEJO J |
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Institution: |
Department of Animal Biology, Faculty of Biology, University of Santiago de Compostela,
15706 Santiago de Compostela, Spain |
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Abstract: | Feeding of the land snail Helix aspersa (Müller) was observedat monthly
intervals. Three natural populations in Galicia (NW-Spain)were studied. At two sites only a few
plants constituted thebulk of the diet and in spring the snails' diet had the highestdiversity
(H'). In the third population feeding and distributionof Helix aspersa
(Müller) were observed in a small plotwith permanent patches of Urtica dioica.
Nearly one half offeeding snails fed upon Urtica dioica. Most of the other observations
wereon Mentha suaveolens, Ranunculus repens and Gramineae. The diversity
ofthe snails' diet showed seasonal variation with the maximumin the autumn months.
Comparison between the availability ofthe different plant species and their contribution to the
snails'diet showed that the snails did not eat at random; Urtica dioicawas eaten
much more than expected from its occurrence and grasseswere strongly under-represented in the
snails' diet. Temporalchanges of availability were significantly correlated with the
amountseaten in the case of Urtica, but not for the other food plants.The distribution of
the snails in the plot was significantlycorrelated with that of Urtica. Chemical analyses
of the foodplants revealed Urtica as the species with the higher protein,ash and calcium
contents. The strong preference of Helix aspersafor Urtica dioica could be
explained by the value of Urticaas food or by its suitability as habitat for the snails. The
largestproportions of green material in the snails' diet occurred inthe spring and juveniles
ate more green material than adultsin the three populations. (Received 16 March 1998; accepted 30 November 1998) |
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