Keywords: 
• Litopenaeus vannamei /
• hypoxia /
• mitochondria /
• ultrastructure

Abstract: The mitochondrial ultrastructures in the tissues of muscle and gill of two varieties Zhengda and A6410 of the white-leg shrimp Litopenaeus vannamei under hypoxia were observed by transmission electron microscopy（ TEM） for comparison. Observations showed that the two shrimp varieties of L. vannamei had homogeneous mitochondrial ultrastructures in the tissues of muscle and gill with smooth and intact inner and outer membranes and slender and homogeneously distributed inner cristae. However,placed under hypoxia for 12 h,the Zhengda shrimps did not show homogeneous mitochondrial ultrastructures in the muscle tissue; their mitochondrial membranes were distorted and enlarged; the number of cristae and the matrix volume were obviously decreased; the structure was not intact,with loose muscle fibers and fractured dissolved myofilaments. The mitochondria in the muscle of A6410 were slightly swelled,the outer and inner membranes had partial lesions,the inner cristae dissolved,and parts of myofilaments loosened and fractured. The outer membranes of mitochondria in the gill of the Zhengda shrimps were distorted,and the inner cristae were blurred and arranged in disorder,giving medullary deformation and serious cavitation. The mitochondrial cristae and the matrix in the gill of A6410 were partially reduced,showing slight cavitation. The high hypoxia tolerance variety A6410 showed obviously less mitochondrial damages in the tissues of muscle and gill than the variety Zhengda. It is concluded that different tissues of both the shrimp varieties displayed different levels of sensitivity to hypoxia,and that hypoxia tolerance was closely correlated with mitochondrial ultrastructure.