Journal of Ecophysiology & Occupational Health

Gafrarium divaricatum were exposed to the chronic concentrations of xylene (4.25 and 8.50 mg/l), benzene (4.35 and 8.70 mg/l) and gear oil-WSF (1 and 2%) for 30 days. Gill of the control clam comprised a pair of demibranchs dividing the pallial cavity into inhalant and exhalent chambers. Each demibranch was formed of two lamellae which were held together by connective tissue junctions. The lamellae were made up of ciliary filaments through which pass branchial blood vessels. The filament, tubular structure made up of epithelial cells, showed a pair of chitinous rods and 3 sets of cilia -lateral cilia, latero-frontal cilia and frontal cilia. Histopathological alterations in gills of clams exposed to varying concentration of the pollutants included widening of ostial spaces, vacuolization of basal part of filaments, sloughing off ciliary portions and skeletal rods of gill filaments. Lysis of epithelial cells and epithelial layer, complete degeneration of gill filaments and development of necrotic tissue, change in regular tubular shape of filaments, loss of inter-filamental junctions, invasion of hemocytes and widening of inter-filamental space were also observed. However, the histo-pathological damage in gills were most severe in clams exposed to higher concentration of xylene.