Accessory Kidney of Threadfin Bream <i>Nemipterus japonicus</i> and Their Relation to Gonad Maturation

Abstract

This study determined the structure of intramuscular organ embedded in the flesh of Threadfin bream Nemipterus japonicus and their relation to gonad maturation. Small pieces of this organ tissue (approximately 0.5 cm 3 ) were divided into sections one for histological studies and other for ultrastructure with electron microscope. This study revealed the presence of a new organ embedded in the flesh of Nemipterus japonicus (collected from the Suez Gulf, Egypt) at the end of abdominal cavity at the beginning of caudal part of the body. Both sexes have the same structure located in this region of fish. This structure showed the same histological organization and ultrastructure like kidney such as proximal segment, distal segment and renal corpuscle. There was a relationship between this new organ and sex & gonad maturation of Nemipterus japonicus. In females, this organ is small and unchangeable in size and weight. However, in males it is different; the degree of development of new organ followed that of the testes. So, this new organ is called a globiform accessory kidney.