The effect of environmental factors on the activity ofGammarus pseudolimnaeus (Amphipoda)
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- Dudley Williams, D. & Moore, K.A. Hydrobiologia (1982) 96: 137. doi:10.1007/BF02185429
Various environmental parameters which may affect the activity ofGammarus pseudolimnaeus were examined in the laboratory. The animals' responses were monitored automatically using an ultraviolet beam interruption technique. The basic diel activity pattern in the fall showed high rates of drifting at night but in the summer showed uniform drift throughout the light/dark cycle. Upstream activity was greater in the summer when it compensated approximately 11% of the number of animals drifting downstream. A large-sized gravel substrate (31.5 mm diameter) produced significantly lower night-time drift than either a medium-sized gravel (11.0 mm diameter) or a small-sized gravel (3.4 mm diameter). Animals drifted more at current speeds of 5 to 15 cm/s than at 20 to 25 cm/s. The introduction of rainbow trout to the tanks in the day or night caused almost total cessation of drift and upstream activity within minutes. Trials with fish water suggested that the amphipods detect some form of labile exudate produced by the fishes. Additions of toxicants, in the form of sulphuric acid and NaCl, produced changes in activity levels before lethal concentrations were reached.