Responses of basophilic cells of the digestive gland of mussels to petroleum hydrocarbon exposure

A stereological study was conducted on the digestive gland of mussels Mytilus galloprovincialis Lmk., exposed to the water accomodated fraction of 2 crude oils and a commercial lubricant oil (3 hfferent concentrations of each). Mussels were sampled after 21, 35, 77 and 91 d exposures, and the volume density (VD) of basophllic cells was determined in paraffin sections by a point-counting method. Exposure to petroleum hydrocarbons resulted in a significant dose-dependent increase in basophilic cell volume density. This was due to the presence of higher numbers of basophilic cells per digestive tubule, while the size of basophlic cells remained apparently unchanged. Results are interpreted in terms of an enhanced epithelia] cell regeneration that might be linked to fundamental digestive processes. Indeed, a significant positive linear correlation exists between basophilic cell VD and the percentage of disintegrating tubules.