Recently it is discovered that chicken's pineal is a hematopoietic organ as well as its well known function as photosensory organ. The present work was conducted to study the effect of different waves lengthes (different colours) on pineal hematopoiesis. So one group of chickens was exposed to white light as control and compared with other three groups exposed to red, green and blue light respectively. The red light showed no variation on the level of erythropoiesis from that of the control. The extent of erythropoietic activity in chicken's pineal increased remarkably under the effect of blue light, however, the effect of green light was in contrary. There were no an important variations in the extent of granulopoiesis and the amount of lymphatic tissue in the treated chickens at the level of tissue sections. It is supposed that the chicken's pineal seems to be like other hematopoietic tissue in being seeded by ematopoietic precursors. Erythropoiesis and granulopoiesis were mostly localized in the pineal connective tissue capsule but erythropoiesis extended into the dura mater overlying the pineal. Some of the characteristic stages of erythropoiesis and granulopoiesis were recorded. The pineal hematopoiesis seemed to be pineal dependent and being one of the most striking features of pineal tissue in chickens. The variable effect of different colours of light on pineal hematopoiesis confirmed the paracrine action of pineal melatoninunder the control of retinal pathways.
Key words: Pineal organ. Hematopoiesis. Erythropoiesis.
Light colours. chicken.
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