Consumption and preference of selected food types by two freshwater gastropod species
Lombardo, Paola; Cooke, G. Dennis
published: Dec 9, 2002
ArtNo. ESP141015504007, Price: 29.00 €
Snails are considered to be primarily algivores, and may consume macrophytes only upon plant senescence and death. However, allegedly algivorous gastropods also consume leaf litter, and occasionally even living plant tissue. Periphyton, living plant, and detritus consumption by snails have seldom been compared directly. Two common pulmonate species, Physa spp. (Physidae) and Helisoma trivolvis (Planorbidae) were offered living macrophytes, decomposing maple leaves, and periphyton grown on glass tiles, either singly or together. Both species fed on all food types when offered singly, indicating trophic generalism. Preference within trophic spectra was inferred from all-items conditions. Both snail species preferred periphyton (especially Physa) and maple leaves (especially H. trivolvis), and rejected macrophytes, though some plant tissue was consumed by H. trivolvis. Plant biomass decreased in all conditions except in all-items Physa aquaria. Feeding preference may be related to snail body size. Nutrient (phosphorus) concentration increased in snail presence. Snail action on trophic resources may be dual, with reduction in food biomass accompanied by nutrient enrichment of the water column. Both species, especially Physa, may enhance macrophyte productivity when other food resources are abundant.