Conférence de madame Victoria McCready
Queen’s University Belfast Marine Laboratory au Royaume-Uni
Midi conférence NÉMO
Vendredi 27 février à midi
Salle Mohamed El-Sabh (P-210)
"Orientation of substrata and putative predators have marked consequences for jellyfish (Aurelia aurita) polyp settlement"
Scyphozoan jellyfish (e.g. Aurelia aurita) have a benthic polyp life stage that requires hard substratum for settlement. Coastal urbanisation may provide the polyp life stage with additional settlement opportunities compared to space limited natural habitats, contributing towards localised jellyfish blooms. To test whether jellyfish polyp settlement was influenced by the orientation of man-made structures, acrylic settlement plates (reflecting materials used widely in aquaculture) were positioned in vertical, upward facing and downward facing orientations within a circular experimental tank. Following the introduction of A.aurita planulae larvae, highest densities of polyps were found on vertical and upward facing orientations and lowest on the underside of settlement plates. These findings are contrary to previous studies, where planulae were found to settle predominately on the underside of substrata. Possible drivers of these differences are explored with respect to experimental design during controlled settlement experiments.
Furthermore, we investigated A.aurita planulae settlement when presented with high and low densities of putative benthic competitors (i.e. macroalgae and mussels), with dead mussel shells used as structural mimics (i.e. secondary controls). Settlement was lower in high-density live mussel treatments suggesting that such species might decrease the numbers of planulae larvae through ingestion.
Dernier ajout: jeudi 26 février 2015