The present work is concerned with the effect of different concentrations of two heavy metals; lead and cadmium on
Caelatura aegyptiaca (a Bivalve clam). This effect was indicated by assessing the mortality rates after 10 days exposure to certain concentrations, LC50 values, accumulation levels in ctenidia and foot tissues and their histopathological changes in the latter tissues due to the above exposure. The mortality rate was proportional to the concentrations of lead and cadmium in the test aquaria. The accumulated levels were higher in the ctenidia than in the muscle tissues and increased with raising the concentrations of the meta1 salts. The behavior of treated species during the experiment was
abnormal indicating loss of equilibrium during swimming. Histological examinations of the ctenidia & muscles of the
treated clam have revealed various degrees of histopathological changes.