Histopathological alterations in gills of freshwater prawn, Macrobrachium dayanum (Crustacea - Decapoda) after acute and sub-acute exposure of lead nitrate

Lead is a nonessential “grey listed” heavy metal, used in fuels, ceramics, paints and glass wares in industries and vehicles. After taking entry in aquatic ecosystem it becomes toxic and cause serious problem to plants and animals. Haematological, neurological, nephrological and histopathological effects of lead are well known. Fresh water prawn, Macrobrachium dayanum, a potential animal for freshwater aquaculture, subjected to acute and sub-acute concentration of lead nitrate (116.46 mg/l; 96h LC50 and 29.12 mg/l; 25% of 96h LC50) showed severe histopathological alterations in gills after 24, 48, 72 and 96h and 10, 20 and 30 day exposure. Chief alterations during acute exposure were thickening of gill plates, reduction in inter lameller spaces, cuticular irruption, inflammation and necrosis where as clumping of gill plates, hyperplasia, hypertrophied haemocytes with nuclear pycnosis and leakage of haemocytes in inter-lameller spaces as well as deposition of broken tissue debris near gill base were observed during sub-acute exposure. The severity of histopathological alterations was found duration dependant. Present study reveals that histological bio- markers provides complete information regarding heavy metal toxicity particularly lead to these economically important fresh water prawns, which can themselves serve as bio-indicator of worsening status of surface aquatic bodies.