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 transmission electron microscopy. We report patterns of biosynthesis and maturation of the specific product of the gland secretory unit. The syncytial, secretory compartment 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 activity, secondary lysosomes are observed, which derive from autophagic processes (crinophagy) involving the secretory materials. Ceratophrys ornata, a species representative of the type genus of the family Ceratophrydae, belongs to the heterogeneous group of anurans that, possibly as the result of convergence, all produce cutaneous poisons consisting of vesicles or faint density granules.