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Morphological and biochemical study of the accessory glands in the parotoid glands of toads

par Boskovits, Nikoletta
Promoteur Roelants, Kim
Co-Promoteur Jared, Carlos
Publication Non publié, 2024-08-30

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Résumé :

Amphibians have skin glands scattered throughout the body, called mucous and poison glands, which play a key role, particularly in relation to chemical defence against predators and microorganisms. In toads (Bufonidae), poison glands are concentrated behind the eyes, forming a pair of protuberances, known as parotoid macroglands. Internally, the parotoids are made up of a group of large poison glands arranged side by side, forming a honeycomb-shaped structure. Each parotoid secretory unit connects to the surface of the skin through an epithelial duct obstructed, in its innermost portion, by a plug. Around the duct there are clusters of mucous glands which are morphologically distinct from other mucous glands found in the skin. Due to their unique location in the parotoid and characteristic arrangement around the duct of each secretory unit, these mucous glands are known as accessory glands. This study aims at the morphological and biochemical characterisation of the accessory glands of Rhinella icterica toad. We found that the cells in these glands are of two types; big, prismatic, peptide producing cells and small, mucous and lipids producing cells. For the first time, the secretion of accessory glands was isolated and peptides were biochemically discovered in it. Finally, we conclude that the most probable scenarios regarding the glands’ function are: 1) participation as a poison component, 2) development of the epithelial plug, 3) protection from bacteria or fungi and 4) repair of the epithelial plug after its rupture.