Serous cutaneous glands in the South American horned frog Ceratophrys ornata (Leptodactylformes, Chthonobatrachia, Ceratophrydae): ultrastructural expression of poison biosynthesis and maturation.

Serous cutaneous glands are described in newly metamorphosed and juvenile specimens of the horned frog Ceratophrys ornata using light and trans- mission electron microscopy. We report patterns of bio- synthesis and maturation of the specific product of the gland secretory unit. The syncytial, secretory com- partment possesses a complex of endoplasmic reticulum (predominantly smooth endoplasmic reticulum after metamorphosis) and Golgi stacks. The serous product is weak in density and is contained in vesicles involved in repeating merging processes. During this maturation ac- tivity, secondary lysosomes are observed, which derive from autophagic processes (crinophagy) involving the se- cretory materials. Ceratophrys ornata, a species repre- sentative of the type genus of the family Ceratophrydae, belongs to the heterogeneous group of anurans that, pos- sibly as the result of convergence, all produce cutaneous poisons consisting of vesicles or faint density granules.