Histology and Ultrastructure of Head Kidney in the Southern Catfish,Silurus meridionalis Chen

The methods of anatomy,histology,histo-chemistry and electron microscope were applied to study the morphology of head kidney in the southern catfish,Silurus meridionalis Chen.The two parts of head kidney are separated;and they arent joined with kidney.Head kidney consists of blood vessels and three regions:lymphocyte-aggregate region,granulocyte-aggregate region and endocrine tissue region.Its blood vessels include arteries and veins of head kidney,posterior cardinal veins,and branches of posterior cardinal veins.The cells of lymphocyte-aggregate region assemble and reticulate.There are big lymphocyte,litter lymphocyte,plasma cell,monocyte,melano-macrophage and red cell.They are stained the darkest in three regions of head kidney.The granulocyte-aggregate region is stained half tint.The endocrine tissue region is stained very undertone.There are 2 kinds of cells in the endocrine tissue region:inter-renal tissue cell and super-renal tissue cell (chromaffin cell).The inter-renal tissue cells are abundant in mitochondria and smooth endoplasmic reticulum,and a few secretive granules.The super-renal tissue cells distribute around posterior cardinal veins,portal veins and their branches,or in their walls.There are abundant smooth endoplasmic reticulum and secretive granules in the super-renal tissue cells.Some secretive vesicles have electronic dense granules.The head kidney of the southern catfish is an organ of making blood,immunity and endocrine.Its super-renal tissues cells and inter-renal tissues cells are concentrate in the head kidney,which can enhance the function of endocrine and adjust the southern catfish to moving quickly and to hunt other fish for food.