The first type is due to the direct toxic effects of petroleum 

 hydrocarbons and associated heavy metals on cells. These compounds 

 may produce a variety of histopathological lesions in the affected 

 organ systems. There are several reports that exposure to sublethal 

 concentrations of oil in laboratory or field studies resulted in epi- 

 thelial sloughing and discharge of mucus glands in the gills of teleost 

 fish (Blanton and Robinson, 1973; Gardner, 1975; Hawkes, 1977; McKeown 

 and March, 1978). McCain et al. (1978) reported severe hepatocellular 

 lipid vacuolization in English sole Parophrys ventulus following exposure 

 for four months to experimentally oiled (Alaskan North Slope crude oil) 

 sediments. Rainbow trout fed Prudhoe Bay crude oil-contaminated food 

 showed several histopathological changes in the liver (Hawkes, 1977). 

 These included glycogen depletion, proliferation of the endoplasmic 

 reticulum and focal necrosis with connective tissue infiltration in 

 necrotic regions. We have described a wide variety of histopathological 

 lesions to embryos and fry of the killifish Fundulus heteroclitus exposed 

 chronically during embryonic development to the water-soluble fraction 

 of No. 2 fuel oil (Ernst et al. , 1977). In a recent laboratory study 

 of the effects of water soluble fractions of crude oil on marine fish, 

 one of us (Eurell and Haensly, 1981) observed a variety of histopatho- 

 logic changes in liver and gill tissues. 



Little research has been published on the histopathological effects 

 of petroleum in benthic marine invertebrates. However lesions similar 

 to those described in fish can be expected in the analogous organs of 

 marine invertebrates. 



Although crude oil contains known carcinogens such as benzo[a]pyrene 

 and 7,12-dimethylbenz[a]anthracene, petroleum- induced cancer has not been 

 unequivocally demonstrated in any marine species (Neff, 1979). However, 

 there are several reports of increased incidence of cancer-like lesions 

 in natural populations of marine invertebrates and fish from hydrocarbon 

 polluted sites (See recent symposium volumes edited by Dawe et al. , 1976 

 and Kraybill et al. , 1977). 



The second type of histopathological lesion resulting from chronic 

 exposure to sublethal concentrations of oil is caused by elevated suscep- 

 tibility of contaminated animals to bacterial, virus or parasite infection. 

 This increased susceptibility may result from damage to protective epi- 

 thelia in the affected animals or to deleterious effects of the pollutant 

 hydrocarbons on the immune system of the animal (Hodgins et al. , 1977; 

 Sinderman, 1979). Marine animals which have been subjected to chronic 

 sublethal oil pollution stress can be expected to exhibit an elevated 

 incidence of disease in comparison to non-contaminated animals. 



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