Experimental study of swimming behaviours of Daphnia Magna

Abstract

Daphnia are commonly used as model organisms for ecological, evolutionary, and ecotoxicological research due to their high sensitivity to changes in environmental conditions. Although there are numerous studies with the use of Daphnia, but most of these studies use mortality and immobilisation as endpoints to determine toxicity. These endpoints may not be enough to evaluate the early and chronic effect of certain toxicants and environmental conditions. Therefore, to evaluate these effects, sensitive biomarkers such as swimming behaviour should be used instead. In this project, the swimming stroke cycle of Daphnia was first analysed closely via a frame-by-frame analysis to gain a deeper insight into their swimming stroke cycle. Next, sensitive and quantifiable parameters were provided to describe the swimming behaviour of Daphnia. The swimming behaviour of Daphnia were then observed in various environmental conditions. Environmental conditions were either altered by the addition of various concentrations of fertilizer or adjustment in population density. The results showed that the introduction of fertilizer would cause an increase in increase in swimming activity at the beginning. However, it was observed that fertilizers would eventually cause an inhibition in the swimming abilities of Daphnia. In addition, it can also be observed that Daphnia possess some form of adaptation mechanism when placed in an environment with altered population density. Since the results from this project shows that fertilizer inhibits the swimming abilities of Daphnia, it should be considered hazardous to zooplanktons.