الملخص الإنجليزي
Green turtles, Cheionia mydas, are considered to be endangered marine animals. They usually come to Omani beaches for nesting all around the year and abundantly in the . period from May to September. This study aims to provide a staging scheme and to demonstrate the morphological changes of the developing limbs of green turtles embryos, besides a general proteomic patterning profiles of those limbs. One hundred and twenty six freshly laid green turtle eggs were collected from Ras Al-Hadd reserve in Oman and were brought to SQU Biology Department laboratories. They were incubated at 30 °C. The eggs were opened in progressive manner till the hatching day. For each opening day, three embryos were collected for staging; scanning electron microscopy (SEM), transmission electron microscopy (TEM) and general protein analysis. A staging scheme of 19 developmental stages was provided from day 6 of incubation to the hatching day (day 50) in reference to Miller's staging system (1985) for marine turtles. The stable incubation temperature (30 °C# 0.05 °C) supported the uniform staging system in all embryos. The growth rate of embryos in this study was found to be faster than Miller's staging scheme. The limbs were seen for the first time in day 10 of incubation as buds with apical ectoderinal ridge (AER). In gross features, the skeletal development appears as condensation of cartilage formation in proximodistal direction. The five digits are enclosed in hard keratinized webbed skin. The ossification and skin pigmentation are the common preceding growth features. They are seen first in the forelimbs. AER persists in the limbs from day 10 and regressed in day 17 of incubation. The electron micrographs revealed the development of the skin, muscle, cartilage, bone and blood vessels of the limbs. The SEM, showed the skin pores which are associated with mucus droplets and micro-ridges presence. The pipping and hatchlings express both states the ossified and the cartilaginous digits. A prominent protein band of 66.2- 67 kDa appeared in polyacrylamide electrophoresis gel in Day 14 forelimb and diminished significantly in the following stages. In conclusion the staging of the limb development in green turtles seems to be slower when compared to the most common studied models of vertebrate's limb, such as chick and mouse.
