The Prevalence and Histological Appearance of Lip Papillomas in White Suckers ( Catostomus commersoni) from Two Sites in Central Ontario, Canada

Abstract

The white sucker, Catostomus commersoni (Lacapede), has been proposed as a sentinel species to monitor environmental health in the Great Lakes. In a population of white suckers spawning in the Ganaraska River, Lake Ontario (Port Hope, Ontario) there was an elevated prevalence of lip papillomas (46%), body papillomas (1.4%), and mucoid plaques (47%) compared to an inland reference population from the Squaw River, Little Bald Lake, Ontario (5%, 0%, and 0.5%, respectively). Multiple lip papillomas, and papillomas in apposition were prevalent in Ganaraska River suckers (17%) but rare in Squaw River suckers (1.2%). The prevalence of lip papillomas was not related to age or size, but papillomas at the Ganaraska site were up to 10 times larger than papillomas at the Squaw site. Relative papilloma prevalences at the two sites were correlated with relative concentrations of persistent contaminants (PCBs and OC compounds) in fish tissue. Histologically, lip and body papillomas were classified as benign hyperplasia and could be differentiated from normal tissue and mucoid plaques on the basis of biochemical (Protein Kinase C) activity. In laboratory experiments, mucoid plaques disappeared completely within 96 hours of antibiotic treatments (100% of treated suckers vs. 15% of untreated controls) and re-infection was not observed. These experiments indicate that mucoid plaques are not true neoplasms.