These findings support the vascular depression hypothesis, which has important implications for the understanding and management of late-life depression.
Adult chironomids feed readily on materials containing sucrose and glucose, and the addition of dyes is an easy way of demonstrating that food passes through the gut. Male and female flies are shown to make very different use of the food they take in. Males show no change in longevity but extend their flight time for an average of 160% over unfed males. Females, by contrast, show no detectable increase in flight time, but increase longevity by about 40%. Sexual dimorphism in the use of food seems appropriate to the roles of the sexes. We infer that males improve their swarming performance while females may benefit from increased longevity both in gaining time to find suitable mates and in the distance dispersed after mating. Males, and to a less extent females, are found on aphid infested trees near fresh water, and the suggested biological value of feeding is in sustaining the swarming flight especially for the males. Trichoptera adults are found feeding on aphid infested trees and the earlier findings that adult Trichoptera feed are confirmed.
1. The tnierodistribution of Gammarus species is size assortative: larger animals are associated with larger substrate particles. Using an artificial stream with scrubbed substrate we investigate the hypothesis thai the assortative mechanism is stimulated by current avoidance rather than food searching.2. In uniformly mixed substrate, G. pulex tend lo move upstream, but in patchy substrate they are found in a predictable substrate grade. There is no discrimination between patches by different size classes of G". pulex in static water. The size assortative field pattern can only be reproduced under flow conditions in the laboratory. It occurs in the absence of food and irrespective of the sequence or location of substrate patches.3. As density increases. G. pulex are displaced from the optimal patches but move into the open stream rather than into the cover of alternative patch types. 4. We discuss the significance of these results and suggest that some earlier models explaining mechanisms for microdistribution patterns tnay have been unnecessarily complex. Contrasts between natural and simulated stream situations and their experimental advantages are noted.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.