UTTAR PRADESH JOURNAL OF ZOOLOGY

Lead (Pb), a non-essential “Grey listed” heavy metal is a serious threat to aquatic flora and fauna. The haematological, nephrological, histopathological and neurological effects of lead are well known in vertebrates. Present study aims to investigate effect of lead on morphology of haemocytes, a important component of immune system of freshwater prawn, Macrobrachium dayanum. Prawns, collected at “Gulala-Ghat” from river Gomti, Lucknow, subjected to acute and sub-acute concentrations of lead nitrate (116.46 mg/l, 96h LC₅₀; 29.12 mg/l, 25% of 96h LC₅₀) showed morphological changes in haemocytes after 24, 48, 72 and 96h in acute exposure and after 10, 20 and 30 days in sub-acute exposure. The chief morphological changes like surface blebbing, vacuolization, cytoplasmic darkening, fragmentation of nuclear material, cone formation, nuclear pycnosis and breaking of plasma membrane were noticed after acute exposure (116.46 mg/litre). Black granular depositions, nuclear pycnosis and fragmentation of nuclear material; pseudopodial projections, blackening of the plasma membrane, achromatia were observed after sub-acute exposure (29.12 mg/litre). These changes were pronounced in prohaemocytes, granulocytes, plasmatocytes and spindle cells. The severity of morphological changes was dose- and duration-dependent. The present study found a positive correlation between heavy metal lead exposure and morphological changes in haemocyte morphology leading to severe immune dysfunction in freshwater prawn M. dayanum. This parameter can be used as bio-marker in health monitoring of prawns as well as environmental monitoring without sacrificing the animal.