alterations in the corpuscles of stannius of euphorbia royleana treated catfish, heteropneustes fossilis

background: we aimed to evaluate effect of euphorbia royleana exposure on histocytology of corpuscles of stannius in fish, heteropneustes fossilis. methods: fish were subjected to 2.47 mg/l and 0.618 mg/l of e. royleana for short-term and long-term exposure, respectively. blood samples were collected on 24, 48, 72 and 96 h in short-term and after 7, 14, 21, and 28 d in long-term experiment and analyzed for serum calcium levels. corpuscles of stannius were fixed on these intervals. results: serum calcium levels of h. fossilis decline progressively from 48 h until 96 h following the e. royleana exposures. serum calcium levels decreased on 7 d. this decrease continued until close of the experiment. after 96 h treatment, af–positive cells of cs exhibit increased granulation. nuclear volume of these cells exhibited no change throughout short-term treatment. increased nuclear volume of af– negative cells of cs is noticed at 96 h. nuclear volume of af-positive cells decreases after 14 d and onwards. the af–positive cells exhibit increased granulation following 21 d exposure. after 28 d these changes are intensified and few degenerating cells have been encountered. af–negative cells of cs increase in their nuclear volume 21 d onwards. conclusion: the botanical pesticide induced severe changes in the corpuscles of stannius of catfish. this gland controls the calcium level in fish and thus the use of e. royleana should not be done near water reservoirs.