Correlations between metal uptake in the soft tissue of Perna perna and gill filament pathology after exposure to mercury

The accumulation of metal in soft tissues, filtration rate and gill filament morphology are correlated in the southern African rock mussel, Perna perna, during exposure to mercury (24 days) and recovery (24 days). The amount of Hg in soft tissues increased from 0.13 to 87.5 μg/g dry weight after 24 days exposure, and declined to 13 μg/g during recovery. Mean filtration rate fell from 3979 to 1818 ml/h/g dry weight by day 2, but recovered slightly through days 4 and 8 (3037 ml/h/g), with a higher average rate (5030 ml/h/g) being maintained over the 24–48 days recovery period. The initial decline in filtration coincided with epithelial cell deterioration presented as interstitial oedema, neural and epithelial cell degeneration and reduced ciliation. Between days 8 and 24, cilia regenerated and there was a general improvement in cell morphology. Gill filament morphology returned to near normal during the metal-free recovery period. The usefulness of P. perna as an indicator of pollution is discussed.