Effect of mercuric chloride on the ultrastructure of bladder epithelial cells in crayfish, Astacus leptodactylus

The induced stress by pollutants such as heavy metal, is caused cellular responses leading to ultrastructural changes. The ultrastructural alternations of epithelial cells in the bladder of crayfish (Astacus leptodactylus) to study the effect of mercuric chloride treatments were conducted. Eighty specimen of crayfish were collected from the Anzali wetland and every 20 of them were divided into four treatments with concentration of 0, 5, 15 and 20 ppb of mercury chloride. After one week of exposure period, their green gland were removed and fixed into glutaraldehyde for TEM study. There was no losses during experiment in 0 and 5 ppb treatments, whereas 20% and 100% of death were recorded in 15 and 20 treatments, respectively. Results did not show any ultrastructural alternation in the epithelial cells of bladder at 0 dose. In 5 ppb treatment, observed ultrastructural alternations were the complexity of basal membrane cells, swelling and deformation mitochondria and the significant increase in the number and size of vacuoles. In 15 ppb dose in addition to mentioned alterations, degeneration of mitochondrial crystals, increasing excessive deformity of vacuoles and in general, necrosis of cells were observed. The results showed that the green gland of crayfish could be the main site of detoxification and removal of the entered mercury in hemolymph. Due to its high accumulation in bladder can cause ultrastructural alterations and damages by disturbing mechanism of waste discharging and specially osmoregulation would cause death in this aquatic organism.