Onset of chromatophore-stimulating activity by the hypothalamus and adenohyphysis in Hyla regilla and Ambystoma tigrinum

Abstract

Infundibular and adenohypophysial analagen were homoplastically transplanted to subcutaneous tissue of larvae previously hypophysectomized at the tailbud stage. Results indicate that at the stages employed in this study differentiation of the grafts proceeded at a rate reflected by the stage of development of the donor. The onset of chromatophore-stimulating activity by hypothalamic grafts from tailbud embryos of the Pacific Treefrog, Hyla regilla, occurred at post-tailbud stages 20 and 21 (Eakin's series). Adenohypophysial grafts, on the other hand, evoked initial responses in the host melanophores at young larval stages 23 and 24. Similarly in the Tiger Salamander, Ambystoma tigrinum melanostictum, initial pigment responses by hypothalamic and adenohypophysial grafts occurred at post-tailbud stages 37 and 38 and larval stages 39 and 40 (Harrison's series), respectively. By triturating individual grafts the chromatophorotropin was detected approximately one stage prior to the initial release.