The effects of xenobiotics on fish tissues: morphological studies.

Current applications of light and electron microscopy to investigations of changes in various tissues from fish exposed to xenobiotics have been reviewed. Emphasis has been placed on two types of contaminants, petroleum hydrocarbons and chlorobiphenyls, as examples of important xenobiotics found in the marine environment. Although the data are fragmentary because of the small number of studies, they clearly contribute new and valuable information to an understanding of the impact of these contaminants on the olfactory organ, liver, lens, and intestine from several species of fish. The morphological aspects of damage to the olfactory organs of fish exposed to petroleum hydrocarbons included hyperplasia and attenuation of the chemosensory cilia. In the liver of fish exposed to chlorobiphenyls, one of the most evident cellular anomalies was whorls of smooth endoplasmic reticulum. The rough endoplasmic reticulum appeared proliferated and its cisternae were dilated. Changes in th amount of lipid stored in the hepatocytes have been observed in fish exposed to both petroleum hydrocarbons and chlorobiphenyls. Some hydrocarbons affected eye tissues. Structural alterations that occurred during hydration of lens fiber cells and cataract formation were elucidated. A synopsis of the morphological changes in the intestine of fish exposed to petroleum hydrocarbons alone, chlorobiphenyls alone, and the combined contaminants is presented. All three groups of contaminant-exposed fish have subcellular inclusions that are distinctly abnormal. Recommendations for future studies include the need for further characterization of the range of normal tissue structure, comparative studies of additional species, and multiple contaminant exposures.

The comparative ultrastructure of the egg membrane and associated pore structures in the starry flounder, Platichthys stellatus (Pallas), and pink salmon, Oncorhynchus gorbuscha (Walbaum).

Eggs of the starry flounder (Platichthys stellatus) and pink salmon (Oncorhynchus gorbuscha) were examined by scanning and transmission electron microscopy to determine differences in egg membrane structure with reference to contrasting ecological conditions in which the eggs normally develop. The egg membrane of the starry flounder constitutes 0.22--0.50% of the egg's diameter. The zona radiata is composed of 6 continuous horizontal lamellae, covered by a thin triple layered border, and pierced by numerous regularly spaced pore canals. The micropyle canal measures 8 microns at the opening and tapers to 3.6 microns as it penetrates the membrane. In contrast, the thicker membrane of the pink salmon egg forms 0.80--1.0% of the egg's diameter, is composed of numerous short discontinuous lamellae which are pierced by pore canals, and is covered by a coating of irregular thickness. The 15--16 micron micropyle opening is surrounded by an area of protrusions, and the funnel-shaped canal tapers to 2 microns at its terminal aperture. Contrasting environmental conditions during embryogenesis of these two species may be reflected by the thin membrane and simple lamellar structure in the pelagic egg of the starry flounder, and the thick membrane and complex lamellar structure in the demersal egg of the pink salmon.