Date Awarded


Document Type


Degree Name

Master of Science (M.Sc.)


Virginia Institute of Marine Science


In 1999 a mass mortality of the American lobster (Homarus americanus) occurred in western Long Island Sound (WLIS). Although the etiology remains unknown, warm bottom water temperature, hypoxia, heavy metal poisoning, and pesticides have been suggested as casual factors. Subsequently, lobsters from WLIS have continued to display symptoms of morbidity that include lethargy and cloudy grey eyes, caused by idiopathic lesions. The effects of these lesions on lobster vision are unknown. We therefore used electoretinography (ERG) to document changes in visual function in lobsters obtained from WLIS, while simultaneously using histology to quantify the extent of damage. Of the lobsters collected from WLIS, seventy three percent showed damage to photoreceptors and optic nerve fibers including necrosis of the optic nerve, breakdown of the rhabdom, and hemocyte infiltration through the basement membrane into the ommatidia. Animals with more than 15% of photoreceptors exhibiting histological damage also exhibited markedly reduced responses to 10 ms flashes of a broad-spectrum white light. Specifically, the maximum voltage (Vmax) response was significantly lower and occurred at a lower light intensity as compared to responses from lobsters without idiopathic lesions. Lobsters from outside WLIS did not show such reduced changes to their vision. Lobsters from WLIS still appear to be subjected to an unknown stressor with an idiopathic etiology that is causing significant functional damage to their visual system.



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