Factors affecting the microdistribution of Gammarus pulex (Amphipoda): an experimental study |
| |
Authors: | JONATHAN ADAMS JOHN GEE PAUL GREENWOOD SIMON McKELVEY RICHARD PERRY |
| |
Institution: | Department of Zoology, Univcrsily of Newcastle upon Tyne;Department of Zoology, University College of Wales, Aberystwyth;Department of Adult and Continuing Education, University of Durham |
| |
Abstract: | SUMMARY. 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 that the assortative mechanism is stimulated by current avoidance rather than food searching. 2. In uniformly mixed substrate, G. pulex tend to 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. |
| |
Keywords: | |
|
|