Suspension feeding of anuran larvae at low concentrations of Chlorella algae (Amphibia, Anura).

Ingestion and filtering rates in larval Xenopus laevis, Bufo calamita, Rana temporia and Bufo bufo fed suspensions of Chlorella fusca were investigated. Concentrations were measured with a Coulter Counter. (1) For all species, filtration occurred at concentrations far below those reported by other authors for Rana sylvatica feeding on Chlorella pyrenoidosa. For Bufo bufo, only larvae near metamorphosis showed ingestion at low particle concentrations. Since buccopharyngeal ventilation continues even in the absence of food particles, this threshold feeding behaviour in the younger larvae must be due to different mechanisms to those found in Daphnia and Calanus studied by other authors: probably reduction of the buccal pumping rate and the mucus production of the filter apparatus. (2) For B. calamita, R. temporaria and X. laevis the highest suspension feeding efficiency was at early tadpole stages, corresponding with the high growth rate of these stages. (3) The life histories of the species provide the basis for understanding their different retention efficiencies and functional responses.