Morphology and defensive structures in the predator-prey interaction: an experimental study ofParabroteas sarsi(Copepoda, Calanoida) with different cladoceran prey

摘要

Parabroteas sarsiis a predaceous calanoid copepod commonly found in South Andes lakes. Feeding experiments were carried out in order to estimate the predation rates and attack patterns on different cladoceran prey. Predation rates were related with prey sizes. The smallest prey,Bosmina longirostris, was ingested up to 5 prey pred−1h−1while the largest,Daphnia middendorffiana, only at 0.12 prey pred−1h−1. The functional response ofP. sarsidiffered when confronted with different prey although in all cases, the number of kills increased with prey density. A saturation of ingestion rates at high prey densities was only observed forB. longirostrisandCeriodaphnia dubiajuveniles. Remains seldom appeared at the end of the experiments, implying that the predator consumed prey totally. Yet, in all experiments carried out withDaphnia ambiguaandD. middendorffiana, remains, including soft parts, were found. Direct observations of attack and of number and types of remains showed interference of handling by tail, helmet, and size of t