An Investigation into Neoplasia in the Brown Bullhead Catfish Ameiurus nebulosus
Open Access
- Author:
- Grazio, James Lee
- Graduate Program:
- Wildlife and Fisheries Science
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 24, 2015
- Committee Members:
- Jay Richard Stauffer Jr., Dissertation Advisor/Co-Advisor
David Andrew Miller, Committee Member
Michael Rutter, Committee Member
Timothy Lee King, Committee Member - Keywords:
- Brown Bullhead
Ameiurus
neoplasm
tumor
carcinogen
contaminant
PAH - Abstract:
- Brown Bullhead (Ameiurus nebulosus) are often used as bioindicators of environmental contamination. Neoplasms and other lesions in this species are thought to reflect the presence of pollutants in the sediment of aquatic ecosystems. The basis for the bioindicator status of the species is tenuous, however, and has been challenged. My study sought to better understand the background distribution and prevalence of neoplasia in Brown Bullhead and the relationship between this disease and exposure to contaminated sediment. I conducted surveys of Brown Bullhead populations in Lake Erie and inland northwestern Pennsylvania and found evidence of liver and/or orocutaneous neoplasms at every site. When critical covariates such as age were accounted for via logistic regression, Lake Erie populations were found to have a significantly greater likelihood of both liver and orocutaneous neoplasms than were inland Pennsylvania populations. I investigated the relationship between sediment contaminants and neoplasia by exposing Brown Bullhead (N=66) to sediment containing either “low” or “high” concentrations of metals and Polycyclic Aromatic Hydrocarbons using a laboratory microcosm experiment. None of the specimens developed grossly visible internal or orocutaneous proliferative lesions. A single specimen in the “low” contaminant condition was found to have a hepatic neoplasm following 556d of exposure but no hepatic lesions were found in specimens exposed to higher levels of contaminants. There were no significant differences among treatments in terms of biomarkers of early-stage carcinogenesis including DNA adduct formation and the development of microscopic pre-neoplastic lesions. These results, combined with a reexamination of key foundational literature, do not support the use of Brown Bullhead as bioindicators of environmental contamination.