Swimming behaviour in Monoporeia affinis (Crustacea : Amphipoda) - dependence on temperature and population density

Swimming speed and swimming activity of the nocturnally active benthic amph ipod Monoporeia affinis were measured in water temperatures from 3 to 18 de greesC and different population densities in the laboratory. Swimming speed increased with increasing temperature. Increasing water temperature reduce d the percentage of active animals in the population, as measured by a "fre eze frame" technique. At 7 and 10 degreesC a higher percentage of the popul ation was active in higher animal densities. In ail tested conditions swimm ing activity was highest at about 1 h after light-off and lowest shortly be fore the predicted time of right-on. The consequences of the documented beh avioural responses to environmental stimuli are discussed in relation to po pulation dynamics. (C) 2001 Elsevier Science B.V. All rights reserved.