Cellular responses and disease expression in oysters (Crassostrea virginica) exposed to suspended field - contaminated sediments

Exposure of oysters to water soluble fractions derived from field-contamina ted sediments (FCS) containing predominantly lower molecular weight organic aromatic compounds, has been previously demonstrated to enhance pre-existi ng infections caused by the protozoan parasite, Perkinsus marinus (Dermo), and the prevalence of experimentally induced infections. To further explore the role of pollution on the onset and progression of disease, effects of suspended FCS from an estuarine creek in Virginia, USA, dominated by higher molecular weight polycyclic aromatic hydrocarbons (PAHs) on cellular respo nses and Dermo disease expression in oysters (Crassostrea virginica) were e xamined. Sediments were collected from a PAH polluted estuarine creek in Vi rginia, USA. To test effects on cellular response, oysters from Maine were exposed daily to 0, 1.0, 1.5, or 2.0 g suspended FCS (corresponding to 0, 7 0.2, 105, or 140 mug PAHs, respectively) for 5, 10, 20, and 40 days. Hemocy te activities and plasma lipid, protein and lactate dehydrogenase (LDH) lev els were then measured. Exposure stimulated neutral red uptake, MTT reducti on, and H-3-leucine incorporation in oyster hemocytes at various exposure t imes, but did not affect the plasma protein, lipid and LDH levels. To test effects on Dermo expression, oysters from a Dermo enzootic area, with an in itial estimated infection prevalence of 39%, were exposed daily to 0, 1.0, 1.5, or 2.0 g suspended FCS (corresponding to 0, 75.0, 113, or 150 mug PAHs , respectively) for 30 days. Exposure enhanced disease expression in oyster s. However, no significant change was noted in any measured cellular or hum oral parameters. (C) 2001 Elsevier Science Ltd. All rights reserved.