Salinity Fluctuation’s Effect on Dendraster excentricus Developmental Defects

Abstract

Preliminary studies suggest that salinity concentrations affect the developmental defect known as exogastrulation in the sand dollar Dendraster excentricus. Gastrulation is a very important morphological change as the vegetal plate of an embryo buckles inward to form the archenteron, which eventually forms the larval gut. However, successful gastrulation isn’t always the case and defects arise. A defect known as exogastrulation occurs when exposed to particular pollutants. A calcium deficient environment is one of those stimuli that can induce exogastrulation. In this study, embryos were exposed to varying salinity and calcium conditions and the archenteron lengths were measured near the end of the gastrulation process. The blastocoel and cell layer volumes were also collected to determine if the blastocoel was expanding at the same rate that the cell layer was expanding at. It was hypothesized that the rate of expansion would be a causing factor for whether an organism underwent successful gastrulation or exogastrulated. The results suggest that salinity does not have an effect on the sensitivity to the exogastrulation defect.