Development of rapid diagnostic techniques for idiopathic blindness in the American lobster, Homarus americanus, from eastern Long Island Sound

Idiopathic blindness is a condition that afflicts approximately 50% of the lobsters, Homarus americanus H. Milne-Edwards, 1837, in Long Island Sound (LIS). The condition occurs in lobsters from LIS and Narragansett Bay, but has lower prevalence levels in the Gulf of Maine. Grossly, the condition presents as patches of cloudy, gray-colored regions in the eyes of afflicted animals. Histologically, the ommatidia show signs of altered pigment distribution, necrosis of the optic nerves and rhabdoms, and hemocyte infiltration through the protective basement membrane separating the ommatidia from the optic nerves. Severe lesions show areas with necrotic ommatidia and nearly complete loss of the underlying associated optic nerves. We assessed a rapid, nondestructive, diagnostic technique for determining blindness in lobsters. We compared the use of an otolaryngoscope (o-scope) with stereomicroscopy on live, frozen, and histologically-fixed eyes. Live lobsters from Narragansett Bay, Rhode Island, and off southern Massachusetts were assessed with the o-scope. Right eyes were analyzed via standard histological procedures. Left eyes were frozen and stored at –80 °C, and later thawed and reassessed for blindness. The o-scope had good sensitivity and specificity in diagnosing blindness in the laboratory with good inter-observer comparisons among trained staff. Initial results indicate that the etiological agent of idiopathic blindness is present throughout a large portion of the sound, and that lobsters are probably continually exposed to it. The use of the o-scope as a diagnostic tool will help us better understand the distribution of idiopathic blindness in lobsters from the New England region.