Predatory Behavior and Prey Selectivity of the Pelagic Water Mite Piona constricta

Abstract

Predation by the pelagic water mite Piona constricta on the various components of the zooplankton community of Heney Lake, Quebec, Canada, was investigated through both direct observation and several series of feeding experiments. On encountering a prey item, the mite seized the organism with its four pairs of legs and pair of palps and tore a hole in the body wall with its chelicerae. The soft body tissues of the prey were predigested and the liquid nutriment was then drawn into the mouth. Pionid adults ate an average of 10–15 prey∙mite⁻¹∙d⁻¹ and selected prey items as follows: Bosmina > Daphnia, Ceriodaphnia > Chydorus >> Diaphanosoma, Diaptomus > Mesocyclops. The nymphs ate only 2–3 prey∙mite⁻¹∙d⁻¹ with Bosmina and Chydorus as the preferred items. The other cladocerans and the copepods were only rarely eaten. The pattern of prey selection for the adults and nymphs appeared to depend primarily on the escape response of the prey (their ability to detect an approaching mite and flee the area before being grabbed). Prey size and carapace thickness were of secondary importance.Key words: water mites, Piona constricta; zooplankton, predator–prey interactions