the major lymphoid tissues in teleost fish are the kidneys, thymus, spleen and mucosa-associatedlymphoid tissue including the skin, gills and intestine. the head of kidney (pronephros) is an importanthaematopoietic organ and has morphological similarities with the bone marrow in higher vertebrates. in thisstudy, during 12 months from august 2002 to july 2003, 120 grass carp (10 fish/month) were...