Morphological re-evaluation of the parotoid glands of Bufo ictericus (Amphibia, Anura, Bufonidae)

Multicellular glands in the amphibian integument represent a significant evolutionary advance over those of fishes. Bufonids have parotoid glands, symmetrically disposed in a post-orbital position. Their secretion may contribute to protection against predators and parasites. This study provides a re-evaluation of the morphology of the Bufo ictericus parotoid glands. The parotoid gland integument of the medial surface shows rounded depressions with small pores that connect with the duct openings of the larger granular glands. Under light microscopic evaluation the integument is constituted by typical epidermis, supported by dermis subdivided into a spongious dermis, a reticular dermis, and a compact dermis. The Eberth-Katschenko layer is identified as a basophilic material scattered throughout the superficial spongious dermis. The parotoid gland is an integument region, in which three exocrine glandular types occur: mixed glands, smaller granular glands and larger granular glands. The mixed gland is formed by mucous and serous cells while the small granular glands contain a homogene acidophilic intake. The larger granular glands produce a basophilic and alcianophilic material, and are responsible for the macroscopic protuberances designed as parotoid glands. Thus, the end product released by the parotoid glands is a mix of secretions produced by the three glands.