Date of Award
Campus Access Thesis
Master of Science (MS)
In 1983 large numbers of the sea urchin Diadema antillarum unexplainably began showing signs of illness and dying in the Caribbean, and over the next year they came close to extinction, making it one of the worst mass mortality events on record. Present evidence suggests a water-borne pathogen as the etiological agent. Decades later Diadema densities remain low, and its near extinction has been a major factor in transforming living coral reefs in the Caribbean to barren algae-covered rock. In the ensuing decades, no solid explanation has been found to the questions: what killed Diadema; why did Diadema succumb while other species of urchins on the same reefs did not; and why has Diadema still not recovered? A recent hypothesis posited by our lab as to Diadema’s vulnerability was directed at possible compromised immunity in Diadema, and experimental results found a significantly impaired humoral response to a key component of gram-negative bacteria. Here flow cytometry was used to examine the cellular arm of invertebrate immunity. Cytotoxicity and phagocytosis assays were performed as a measure of the cellular immune responses of cells from Diadema and two other species of sea urchins not affected by the die-off. Despite previous findings of an impaired humoral response, this study found no apparent difference in the cellular phagocytic response of Diadema compared to the other urchin species studied.
DeFilippo, John P., "A Comparison of Phagocytosis in Three Caribbean Sea Urchins: Investigating the Role of Compromised Immunity in a Marine Invertebrate Mass Mortality" (2021). Graduate Masters Theses. 667.