The life-extending effects of diet restriction are well documented. One evolutionary model that accounts for this widespread conservation is the resource allocation model, where the selected individuals are those that can delay reproduction during periods of resource limitation. In this study, we use closely related species of a model organism, Daphnia, with widely divergent lifespans to addres...

1. The various types of eye movement exhibited by the cyclopean eye of Daphnia pulex were studied using high speed motion photography. 2. This rudimentary eye, which consists of only 22 ommatidia, can move through approximately 150 degrees in the sagittal plane and 60 degrees in the horizontal plane. 3. Four classes of eye movement were found: (1) a high speed tremor at 16 Hz with an amplitude ...

Non-native species introductions are widespread and can affect ecosystem functioning by altering the structure of food webs. Invading plants often modify habitat structure, which may affect the suitability of vegetation as refuge and could thus impact predator-prey dynamics. Yet little is known about how the replacement of native by non-native vegetation affects predator-prey dynamics. We hypot...

A key challenge for ecological and ecotoxicological risk assessment is to predict the of organisms when exposed simultaneously multiple stressors in sub-lethal concentrations. Here, we assessed whether concentrations an anthropogenic stressors, heavy metal copper (Cu), mediates impacts a natural threat species, predation risk, among six distinct Daphnia pulex clones. We investigated interaction...

THE gregarines of Gammarus pulex L. have long been known, in fact they were some of the earliest of these Sporozoa to be observed (Text-figs. 1-3). However,.so far, no adequate description has been given of the gametes and spores which are the most important stages from the systematic point of view. Lady Muriel Percy, who worked in this Department from 1925 to 1929, helped in the investigation ...