Effects Of Oil On Digestive Cells In Mussels - Quantitative Alterations In Cellular And Lysosomal Structure

Structural changes were observed in the digestive tubule epithelial cells of Mytilus edulis following long-term exposure to the water accommodated fraction (WAF) of North Sea crude oil (30 μg · l−1 total oil derived aromatic hydrocarbons). The changes observed involved a reduction in the height of the digestive cells beyond that demonstrated in a normal feeding cycle. In addition there was a loss of the normal synchrony of the digestive cells to a point where nearly all the tubules exhibited an appearance similar to that which is usually termed ‘reconstituting’. These alterations were quantified using an image analysis technique and the mean height of the digestive cells used as an index of digestive function or state. Long-term exposure also induced a radical alteration of the structure of secondary lysosomes within the digestive cells, resulting in the formation of large lysosomes, believed to be autolysosomes. Stereological analyses showed that these lysosomes are reduced in numbers and greatly increased in volume in comparison with controls. There is a concomitant increase in surface area of lysosomes per unit volume of digestive cell compared with control conditions. These alterations are indicative of fundamental changes in secondary lysosomal function involving an autophagic response to oil derived hydrocarbons. which would contribute to the reduction of digestive cell cytoplasm. These cellular alterations are discussed in terms of their use as indices of cell injury, in response to oil.

Mixed-Function Oxygenases And Xenobiotic Detoxication-Toxication Systems In Bivalve Mollusks

Components of a xenobiotic detoxication/toxication system involving mixed function oxygenases are present inMytilus edulis. Our paper critically reviews the recent literature on this topic which reported the apparent absence of such a system in bivalve molluscs and attempts to reconcile this viewpoint with our own findings on NADPH neotetrazolium reductase, glucose-6-phosphate dehydrogenase, aldrin epoxidation and other reports of the presence of mixed function oxygenases. New experimental data are presented which indicate that some elements of the detoxication/toxication system inM. edulis can be induced by aromatic hydrocarbons derived from crude oil. This includes a brief review of the results of long-term experiments in which mussels were exposed to low concentrations of the water accommodated fraction of North Sea crude oil (7.7–68 µg 1−1) in which general stress responses such as reduced physiological scope for growth, cytotoxic damage to lysosomal integrity and cellular damage are considered as characteristics of the general stress syndrome induced by the toxic action of the xenobiotics. In addition, induction in the blood cells of microsomal NADPH neotetrazolium reductase (associated with mixed function oxygenases) and the NADPH generating enzyme glucose-6-phosphate dehydrogenase are considered to be specific biological responses to the presence of aromatic hydrocarbons. The consequences of this detoxication/toxication system forMytilus edulis are discussed in terms of the formation of toxic electrophilic intermediate metabolites which are highly reactive and can combine with DNA, RNA and proteins with subsequent damage to these cellular constituents. Implications for neoplasms associated with the blood cells are also discussed. Finally, in view of the increased use of mussel species in pollutant monitoring programmes, the induction phenomenon which is associated with microsomal enzymes in the blood cells is considered as a possible tool for the detection of the biological effects of environmental contamination by low concentrations of certain groups of organic xenobiotics.

The effect of pollution of intertidal sediments on the viability of calanoid copepod eggs

Calanoid copepod eggs have been extracted from intertidal sediments and hatched in the laboratory. Although most of the eggs which hatched did so within < 7 days, the hatching of some continued over a more prolonged period (> 20 days). This indicates that there were a significant number of diapausing or delayed hatching eggs. The species of calanoids present include some of which are known to produce diapausing eggs. Hatching of nauplii from incubated sediment samples was slower than from the extracted eggs indicating dormancy induced by the effects of burial in the sediment. Viability of the eggs has been related to chronic industrial or urban pollution as indicated by polycyclic aromatic hydrocarbon levels. These hatchings were conducted simultaneously with those for cleaner locations. The viability of eggs was significantly depressed in the more heavily polluted sites. An oil spill arising from the grounding of the "Sea Empress" at Milford Haven, UK, in February 1996 has provided a comparison of the impact of an acute situation with these chronic effects. An immediate drastic reduction in viability was followed by a recovery in the year following the spill. The data have provided no evidence for differences in the response to pollution between diapausing and subitaneous eggs.