A comparative study of the functional response of four species of carnivorous stoneflies

Abstract

SUMMARY 1. Comparisons were made of the functional responses of mature larvae of Perlodes microcephalus, Isoperla grammatica, Dinocras cephalotes and Perla bipunctata. Experiments were performed in stream tanks with natural substrata and glass bottoms, so that feeding could be observed above and below the substratum. There was one stonefly per tank and one of 10 prey densities between 20 and 200 larvae of either Chironomus sp. or Baetis rhodani per tank. Consumed prey were replaced in a first set of experiments but not in a second set. Additional experiments assessed intraspecific interference between larvae of each predator species (two to five predators per tank). 2. The number of prey eaten increased curvilinearly with prey density. The relationship was described by two models, a Type II instantaneous model and its integrated equivalent, for experiments with and without prey replacement, respectively. Handling time did not change significantly with prey density, and was the same for experiments with and without prey replacement. Estimates of attack rate were similar for the two models, but varied between prey type and predator species. Handling time varied considerably but was normally distributed for each prey type and predator species. Mean handling time varied for Chironomus from 39 s for Isoperla, which rarely ate a whole larva, to 57 s for Perlodes and for Baetis from 116 s for Perlodes to 167 s for Perla. All predators were more efficient at capturing Baetis, but the longer handling time for Baetis ensured that more Chironomus were eaten. It was concluded that these variations in attack rate and handling time were related to activity and growth differences between the predator species, and that experiments with and without prey replacement could both be relevant to the field, depending on how the predators searched for food. 3. In the interference experiments, mean handling time did not change with increasing predator density, but attack rate decreased curvilinearly, the decrease varying from negligible for Isoperla to marked for Perlodes. Prey capture decreased with decreasing attack rate. Therefore, interference reduced prey consumption, but this effect was negligible for Isoperla and increasingly severe in the order Dinocras, Perla and Perlodes.

Comparative Study of Functional Response of Common Hemipteran Bugs of East Calcutta Wetlands, India

“…Similar observations were made for the belostomatids but not for the notonectids under field conditions (personal observation). In contrast to this the mutual interference of other predatory aquatic insects like stoneflies, caddisflies feeding on chironomid larvae increased with predator density thus exhibiting a uniform or random dispersal pattern (ELLIOT, 2003a(ELLIOT, , 2003b(ELLIOT, , 2005.…”

“…The mutual interference constants for the species were different and reflected the degree of suppression of prey consumption due to presence of other conspecific predators. In another sense this is an indicator of aggregation from the part of the predator individuals that target the same patch of prey (ELLIOT, 2003a). For the mosquito larvae the spatial distribution in the habitats can vary from random to clumped and was rarely uniform.…”

“…The difference in the levels of intraspecific interference also provides an idea about the spatial distribution of predators in the field (ELLIOT, 2003a(ELLIOT, , 2003b.…”

Spatial Distribution and Diversity of Macroinvertebrates on the Stony Shore of a Subarctic Lake

“…in the family Perlodidae were the most abundant carnivores in the littoral and their aggressive behaviour probably ensured that the larvae kept well apart whilst searching for food. Aggressive interference has been documented in other carnivorous stoneflies (ELLIOTT, 2003), and the spatial distribution of the very aggressive perlodid, Perlodes microcephalus (PICTET), was random to near regular in a stony stream (ELLIOTT, 2002). Such a distribution may be typical of these aggressive carnivorous insects.…”

Modelling the predation effects of invasive crayfish,Procambarus clarkii(Girard, 1852), on invasive zebra mussel,Dreissena polymorpha(Pallas, 1771), under laboratory conditions

“…The shape of the functional response curve is dependent on several characteristics such as the encounter rate between prey and predator, capture efficiency and handling time; these characteristics may differ within a species as a consequence of predator or prey size, interference among predators or presence of alternative prey (Safina 1990;Tripet & Perrin 1994;Elliott 2003).…”