RESUMO
Objective After an experimental exposure to low dosage of Cd 2+(39*!?mol/L) for 30 days,the changes of Cd 2+ on ultrastructure of the hepatopancreas cells of the freshwater crab (Sinopotamon yangtsekiense♂)at three different times were studied. Methods Sixty freshwater crabs(♂)were divided into two groups:control(n=30) and test(n=30)groups.The test(n=30) group was exposed to low dosage of Cd 2+(39*!?mol/L)while the control crabs were in water without cadmium.During the 5*!d,15*!d,30*!d,the ultrastructure of the hepatopancreas cells was observed by using transmission electro-microscopy(TEM). Results In the course of the experiment,the nuclear membrane changed from spreading all over the place to disintegrated,and the penetration of the mitochondrial outer membrane and inner membrane was changed.The mitochondria showed swelling and vacuolating.Mitochondrial cristae partly disintegrated,then fully disintegrated.Besides,the Cd 2+ exposure affected the gross form and the structure of the rough endoplasmic reticulum(RER).At first,the RER became the different sized vesicles,then,the ribosomes on the little vesicles began to fall,and finally,the RER turned to the concentric round lamellar structures.But the smooth endoplasmic reticulum(SER)increased markedly.In addition,the numbers and types of lysosome were increased in the mean time and some lysosomes became void vesicles,the autophagosomes or the myeloid bodies(MD).The microvilli showed partly falling and vacuolating.Conclusion After the cadmium treatment the detoxification mechanism of the freshwater crab's hepatopancreas cells lost,the structural and functional integrality of the mostly organelles,such as the nucleous,the mitochondria and the rough endoplasmic reticulum,were destroyed,so that the normal physiological function of hepatopancreas cells was affected.