Impacts of oxygen on Tetrahymena thermophila in microcosms: Dispersal, demography, morphology, and behaviour

Details

Supervisors

Schtickzelle, Nicolas

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

Habitat fragmentation is currently the most significant threat to biodiversity. Understanding its impacts might lead us toward better conservation policies. Microcosms of Tetrahymena thermophila (a motile unicellular eukaryote living in freshwater environments) proved to be a useful tool to study habitat fragmentation and its impacts on dispersal, one of the key components of metapopulation persistence. As previous unpublished results suggested that, in these microcosms, a lower dissolved oxygen availability could impact negatively the dispersal of T. thermophila, and as its natural environment is expected to decrease in dissolved oxygen under the climate change scenario, it is interesting to study the impacts of dissolved oxygen availability on several traits of T. thermophila (dispersal, demography, morphology, and movement behaviour). One experiment in the long term was carried out to test the influence of multiple oxygen availabilities on demography, morphology and behaviour. It showed that a higher oxygen availability was linked to a “live fast die young” pace of life and that higher trajectory linearity could be its main strategy to try to flee harsher conditions associated with lower oxygen availability. A second experiment, coupled with a model, parameterized with its trajectory data to simulate it as if cells made no decisions, was carried out to test the impact of oxygen on dispersal, morphology and behaviour in the short term. It showed that oxygen had no major influence. However, as it gave different results than the model, this suggests that, either the variation in the real experiment concealed the effects, or that cells made dispersal decisions that led to a different outcome. Once more, trajectory linearity proved to be one of the most important factors, but for dispersal. Fleeing harsher conditions might therefore be preferred for T. thermophila compared to a sit and wait strategy. The new dispersal system created in this experiment in order to follow the whole dispersal process gave promising results, even though it still needs improvements.