Detection of micronuclei in gill cells and haemocytes of mussels exposed to benzo[a]pyrene.

Mediterranean mussels were exposed to benzo[a]pyrene for 2 days at doses which had previously caused the formation of specific adducts in gill DNA. Micronuclei and other nuclear abnormalities were detected in gill cells and haemocytes in order to ascertain the induction of cytogenetic damage in two different target cells in parallel. A number of procedural details were examined initially to improve the quality of slides obtained from mussel cells. Adequate cytological preparations were obtained when gill cells and haemocytes were suspended, respectively, in Alsever and sea water with EDTA, cytospun and fixed with absolute methanol. In the exposed mussels, micronuclei significantly increased in both the large gill cells (the main cell type) and the agranular haemocytes. Granular haemocytes, cells present in variable proportions between individual mussels, did not show cytogenetic damage except at the highest B[a]P doses. In the same slides, steady levels of binucleated cells were detected, whereas the incidence of other nuclear abnormalities was significantly higher in the exposed compared with control mussels. Precise knowledge of the replication kinetics of gill cells and haemocytes is still lacking.