Three types of serous products were detected in the syncytial cutaneous glands of the leptodactylid tungara frog, Engystomops pustulosus: type Ia, granules with wide halos and variable density cores; type Ib, high density granules without halos; and type II, vesicles containing a finely dispersed product. Ultrastructural evidence revealed that these products were manufactured by different serous gland types and excluded that they represented different steps in the secretory cycle of a single gland type. Indeed, secretory maturation affecting the products released by the Golgi apparatus proceeded through different mechanisms: confluence (vesicles), interactions between syncytium and secretory product (type Ib granules), and a combination of both processes (type Ia granules). In conclusion, this investigation of secretory maturation was shown to be a suitable approach for the identification of serous gland polymorphism and demonstrated that the tungara frog belongs to the minority of anuran species characterized by this peculiar morpho-functional trait.
Keywords: anurans; serous cutaneous glands; ultrastructure.
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