Effect of various temperature and light intensity regimes on daphnia magna swimming behaviour

Abstract

© SGEM 2019. The biology and ecology of Daphnia (Crustacea: Cladocera) is dependent on a number of biotic and abiotic factors. One of the ways Daphnia adapts to changes in environmental conditions is their swimming behavior. In this study, we assessed the effect of temperature and light intensity on the swimming activity of Daphnia magna in laboratory experiments using computerized video analysis in real time by the hardware-software system “TrackTox”. In experiments we simulated different levels of temperature (14.5 ± 0.2, 20.9 ± 0.6, 25.7 ± 0.4 °C) and illumination (2156 ± 60, 4123 ± 62, 6059 ± 6 lux) and studied how the swimming parameters of animals changes. For each level, the observation time was 30 minutes for one replication. In experiments with different levels of temperature and illumination, the swimming activity of daphnids was different. Increase in the temperature from 14.5 to 25.7 °C, the median swimming speed of animals increased 1.6 times from 0.18 to 0.29 cm/s. The distance travelled by one Daphnia per minute at 14.5 °C was 14.03 cm, and at 20.9 and 25.7 °C it was 48 and 33% higher, respectively. Increase in the level of illumination from 2156 to 4123 lux, the swimming speed of daphnids did not change and was 0.30 cm/s. With an increase in the level of illumination from 4123 to 6059 lux, there was a significant increase in speed by 1.3 times to 0.39 cm/s. In addition, the distance travelled by daphnia increased from 23.07 to 25.00 and 27.16 cm, respectively. Daphnia in all experiments (except for the low temperature variant) showed negative phototaxis, most of the time they were at the bottom of the container. In the group with a temperature of 14.5 °C daphnids were mainly located in the surface zone.