Avoid predation or take risks in basic activities? Predator–prey relationship in subtropical streams between decapods and caddisflies

Abstract

The objective of the present study was to analyse the movement, feeding and case-building behaviours of Phylloicus in the presence and absence of a likely decapod predator, Aegla longirostri. We used aquaria divided by a perforated acrylic plate, with one side containing a Phylloicus and the other containing A. longirostri. Movement was quantified through the time spent in active movement, feeding was quantified through the amount of consumed leaves and the case-building was assessed by comparing the number of leaf discs selected of each plant species. The Phylloicus movement activity was affected by A. longirostri, being higher in the predator absence than in its presence. The caddisfly feeding behaviour was not affected by the presence of the crab. Phylloicus was selective in the choice of plant species for case-building; in the presence of the predator, harder discs were more often employed, whereas softer and less resistant discs were chosen in the absence of the predator. The anti-predator responses of caddisfly demonstrated that they are able to detect the presence of crabs and modify their activities, thereby increasing their chances of survival.