Litter shredding in a desert oasis by the snail Melanopsis praemorsa |
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Authors: | Heller Joseph Abotbol Avi |
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Affiliation: | (1) Department of Evolution, Systematics and Ecology, The Hebrew University, Jerusalem, 91904, Israel;(2) En Gedi Field School, En Gedi, Israel |
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Abstract: | The freshwater snail Melanopsis praemorsa is veryabundant inoases of the Judean Desert. To determine its role as littershredder, experiments were carried out in Nahal Arugot. Boxeswereplaced in the stream (29 °C), each containing 1 g ofdrywillow leaves together with one snail; or six snails.With one snail per box, dry leaf weight after two daysdeclined to72% of the initial dry weight, after twelve days to 58% andaftereighteen days to only 40%. During this period thesnails in the experiment increased by 12% in shell-height, by20%in snail weight (including the shell), by 33% in live freshbiomass. Each snail consumed about 10 mg litter per day.With six snails per box, dry leaf weight after two daysdeclined to62% of the initial dry weight and after twenty days to only15%.In natural populations where density was 44 snails per quadrat(of25 × 25 cm), 1 g of dry leaves was reduced to 25%theinitial weight within three days. Overall plant cover along a600 × 10 m stretch of the stream was found to be45%, ofwhich 65% was willow. During one year about 1 kg litter wasshedper m2 willow; by extrapolation, this would be about1800 kglitter throughout the stretch. Much of this vast amount oflitteris consumed by the snails, who thereby reduce summer dammingof theoasis. Our study suggests that M. praemorsa, a generalistfeeder, may be a major litter shredder in certain desert oasisecosystems. |
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Keywords: | snails shredding desert oases willow litter Melanopsis |
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