Secondary palate development in the domestic duck (Khaki Campbell). An electron microscopic, histochemical, autoradiographic and biochemical study.

Prenatal development of the secondary palate in duck was studied using light and electron microscopic, histochemical, autoradiographic and biochemical techniques. The secondary palate of duck develops between Days 7-12 of incubation (HH 25-37). During this period the palatal shelves grow horizontally toward one another but, unlike those in mammals and the alligator, they never fuse, and a physiological cleft persists between them. In contrast to both chick, where the MEE differentiates to orthokeratinisation, and quail, where the MEE becomes parakeratinised, the MEE of duck differentiates to a non-keratinised stratified type. A continuation of DNA synthesis in the MEE, unchanged levels of cyclic AMP in the palatal tissues and an absence of programmed cell death in the MEE during duck palatogenesis distinguish it from the mammalian palate morphogenesis. Also, although the morphogenesis of palate in duck, chick and quail is similar, the cytodifferentiation of their MEE is different.