The Skin of the Tadpole of the Common Toad, Bufo bufo bufo (L.), during Metamorphosis
- 1During metamorphosis, the epidermis of the toad tadpole changes from a single-layered to a multi-layered epithelium, and epidermal cells, initially heavily pigmented, lose the pigment granules. Melanophores occur among the epidermal cells at the beginning of the process, but later come to lie internal to the bases of the cells of the stratum gerniinativum.
- 2The corium is initially a dense condensation of connective tissue. Following invasion by fibroblasts (hind limb 3-jointed) it differentiates into two layers, the strata spongiosum and compactum.
- 3At the beginning of metamorphosis epidermal glands are unicellular. Multicellular glands appear when the anal canal is resorbing. Order of appearance and distribution follow a definite pattern. The development of the two types of gland found is described.
- 4The toad tadpole has a functional sixth branchial arch with a hemibranch on the posterior wall of the branchial cavity.
- 5Blood vessels reach the skin at the stage when the anal canal is resorbing, but the rete subcutanea begins to form only at the 3-leg, 12 mm. tail stage. Later, capillaries from the rete subcutanea pierce the stratum compactum and the rete subepidermale is formed (4-leg, 5 mm. tail). Finally, epidermal capillaries arise from the rete subepidermale.
- 6There is close correspondence between the stages of vascularization of the skin and the response of toad tadpoles to injection with post-pituitary extracts.
- 7Developmental processes in the skin of the trunk region are initiated in the field of the occipito-vertebral artery.