MORPHOGENESIS OF THE DIGITAL PAD LAMELLAE IN THE EMBRYO OF THE LIZARDANOLIS-LINEATOPUS

The present study in the embryo of the lizard Anolis lineatopus descri bes the modality of cell proliferation responsible for the morphogenes is of the digital pad lamellae and of the epidermal stratification. Af ter tritiated thymidine and 5-bromodeoxy-uridine administration, autor adiographic and immunocytochemical methods have been used. The lamella e originate as long, slightly slanted, undulations of the epidermis of fingers and toes. At an early stage, the epidermis consists of an out er periderm and a basal layer. Cell hypertrophy, and the prevalent cel l proliferation in the longer side of the undulation with respect to t he shorter side, generate the surface of the outer lamella. Under the peridermis, a shedding complex, composed by clear and oberhautchen lay ers, is formed and later determines the first intraepidermal shed. The first subperidermal layer derived from the basal layer is a clear lay er and the first shed epidermis in the embryo is represented by peride rm and clear layer. The heavily granulated clear layer in Anolis linea topus represents the first epidermal layer produced in the embryonic e pidermis, and is connected with the process of shedding. The spinulae of the underlying oberhautchen in the outer scale surface become long setae which grow toward the upper clear layer. Under the shedding comp lex a beta-layer is produced. Autoradiographical study shows that the radioactivity stays in the basal layer for about 4 days before cells m ove to upper layers. At 6-8 days post-injection labelled cells are vis ible in the differentiated clear, oberhautchen and beta-layers. Under the beta-layer differentiating mesos cells are visible before the embr yo hatches.