Metaxas, A. Department of Biology, Woods Hole Oceanographic Institution,

I examined changes in the vertical distribution and swimming patterns of 4-armed larvae in the sea urchin Echinometra lucunter around food patches of a range of microalgal densities. I reared larvae in high and low rations of a single- and mixed-species diet of microalgae. In plexiglass cylinders, I inserted a food patch that consisted of 0, 2500, 5000 or 10000 microalgal cells/ml in experimental haloclines. Tracking of swimming paths showed that larvae swam into or through the patches of low density, and to positions just below the patches of intermediate and high density, within a few minutes. The number of larvae that were within or above the patch at the end of the experiment decreased with increasing within-patch algal density, but this pattern varied with dietary conditioning. The greater number of algal cells in digestive tracts of larvae from treatments with than without a patch confirmed that larvae fed on the cells in the patch. This study showed that invertebrate larvae are able to alter their swimming behaviour and take advantage of the presence of a food patch. Larvae with such an ability can increase their chances for survival and eventual recruitment to the benthos.
Day: Thursday, Feb. 4
Time: 09:45 - 10:00am
Location: Eldorado Hotel
Code: SS26TH0945E