| This is the study on morphology and development of thymus, head kidney andspleen in southem catfish (Silurus meridionalis) using histology histo-chemistryanatomy and electron microscope. The results show that the thymus, head kidney andspleen are main immune organs. And the order of maturation is thymus, head kidneyand spleen.Thymus of southern catfish locates on dorsal of the third gill arches, one pair andsymmetry distributing. At 36h after hatching, the thymus anlage appears; 5 dayspost-hatching(dph) 4-5um thymocytes can be observed in superficial layer of thymus.The thymocytes arranged dense outer and sparse inner at 6 dph; 7 dph, trabeculaeappeared at parenchyma in thymus. But the trabeculae are not obvious. 16 dph,thymus comprise of three regions, the outer, middle and inner. The outer comprises ofmucus cell, histo-epithelium, reticulation epithelium and a few lymphocytes. Themiddle comprises of lymphocyte abundance, epithelial reticular cell, macrophagic cell,tiny vascularity and trabeculae epeiric. The inner comprise of a few lymphocytes andmore epithelial reticular cells and increasing fibroblast. Blood vascularity is alsoample in inner region.Head kidney is the main lymphoid organ and endocrine organ, which belongs toreticulate lymphoid tissue. There is no nephron in head kidney of southern catfish.The outer layer of head kidney is wraped by thin mesothelial cells. Head kidneycontains three different regions: lymphocyte aggregate region, granulocyte aggregateregion and endocrine tissue region. In addition, there are artery, vena and amplesinusoid. After hatching, we can observe the globosity structure which looks like renalcorpuscle locating in the forepart of coelom. 2 dph, there are a few basophiliamesenchymal cell settling in prinephron. 6dph, basophilia lymphous mesenchymalcell proliferate remarkably in fore kidney and link together. 16dph, the pronephricbegin to disassemble. 28dph, renal corpuscle cells of fore kidney disassembledcompletely, but renal tubule can still be observed. 40dph, head kidney can be dividedinto lymphoid tissue and endocrine tissue. Head kidney come into being.Spleen of southern catfish looks dull red and locats near the stomach and thebending place of gut, dorsal to middle stomach or ventral to swim bladder. Spleen canbe divided into white plup, red plup, capsule and trabecula. The exterior of capsule issimple squamous epithelium. Trabecula comprises of elastic fiber, reticulocyte,fiberblast and smooth muscle cell. Trabeculae connect each other and form to reticulation. White plup comprises of periarterial lymphatic sheath and artery. Redplup contains splenic cord and splenic sinus, splenic cord and splenic sinus alternateeach other disturbuting in red plup. 4dph spleen anlage was observed. 6dph, the frontend of spleen anlage expanded and sublobe. The back end of spleen anlage proliferateand expand. The all shape looks like an apple at this time. 17dph, there are a fewbasophilia cell settling in spleen. 35dph, a lot of immature red cells existed in spleenand at the 70dph splenic histology structure can be seen such as matured spleen.In addition, Growth survival rates and immune organs of 6 day SilurMeridionalis juveniles feeding on LimnodriIu at different feeds and 6 different levelsfor 21 days were investigated. At head of 7d, feeds zooplankton is propitious toimmune organs developing. After 7d, feeds Limnodrilu is propitious to growth andimmune organs ontogeny. The results showed that the juveniles at 60% feedingquotiety growed faster than any other levels when the body length was less than 5centimeters and 50% feeding quotiety growed faster when more than 5 centimeters.The survival rates of group A,B,C,D,E and F were 56%,75%,89%,93%,94% and 91% respectively. The cannibal rate of A and B was 30% and 19% higherthan other groups. The cannibal rate of group E and F was lower, 4% and 4.5%respectively. Histology study of immune organs obseverd development lagging at lowfeedinglevel and edema can be seen at the same time. |
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