Fish Diseases and Management

2.2.9 Haemoporetic tissue

Haemopoietic tissue is located in the stroma of the spleen and the interstitium of the kidney and to a lesser extent found to be associated with periportal areas, intestinal submucosa and specialised lymphoid organ. It concerns with production of RBC, which is present in animal tissue.  RBC level is maintained or retained by haemopoietic tissue.

Types of Haemopoietic tissue

1) Renal haemopoietic tissue- The anterior kidney is mainly haemopoietic in nature. The corpuscles of stannius and the interrenal tissue are embedded within the haemopoietic tissue. Another cellular structure found throughout the teleost haemopietic tissue but not in higher vertebrates is the melanomacrophage centre.

2) Splenic haemopoietic tissue- Spleen is the only lymph node like organ to be found in the teleost fish. Main elements of the spleen are the ellipsoids, the pulp and the melanomacrophage centres.

3) Thymus haemopoietic tissue- The thymus is a paired organ, an ovoid pad of paired lymphoid tissue situated subcutaneously in the dorsal commissure of the operculum. Thymus is thought to be the site of immunocompetent T cell maturation.