Morphology of the parotoid macroglands in Phyllomedusa leaf frogs

Abstract

The parotoid macroglands of toads (bufonids) and leaf frogs (hylids) are used in passive defence against predators. The parotoids release poison when the amphibian is bitten by a predator. Despite the apparent similarity, the anatomical and histological structure of these macroglands in hylids is poorly studied when compared with those of bufonids. In this paper, we focused on the morphology of the macroglands of P. distincta, a leaf frog endemic to the Brazilian Atlantic rainforest, comparing their structure with those of bufonids. In addition, we compared the macrogland morphology of P. distincta with those from major clades of Phyllomedusa. All results revealed a macrogland morphology in leaf frogs distinct from that of toads, suggesting that the term parotoid should be used only for those of bufonids.

Morphological Changes in Skin Glands During Development inRhinella Arenarum(Anura: Bufonidae)

“…As the basal bufonid Rhaebo guttatus also presents a complex parotoid macrogland composed of highly packed glands (Jared et al, ; Mailho‐Fontana et al, ), parotoids in bufonids seem to be a specialized macrogland different from parotoids of other groups. For instance, parotoids of hylids do not share the same complex arrangement as those of bufonids, and their secretion products are of a different chemical nature (Antoniazzi et al, ). Another example of a macrogland consisting of a complex arrangement of glands is the femoral gland of some mantelline frogs, which consists of circularly arranged granular glands that secrete their products into a central external depression (Vences et al, ).…”

“…Our study of the ontogeny of the postorbital/supratympanic region showed that these diverse types of glands differentiate from similar syncytial glands, suggesting that the differentiation of the glands occurs during postmetamorphic development. A particular characteristic of the parotoid gland of bufonids is the presence of differentiated mucous glands around the duct of the large glands (Jared et al, ; Antoniazzi et al, ); in R. arenarum , these mucous glands were only observed around the duct of the central glands. Glands surrounding the ducts differ from the other mucous glands of the body, both in their function and their morphological characteristics.…”

“…The skin of extant adult amphibians consists of an epidermis and an underlying dermis with two types of glands, considered synapomorphies of Lissamphibia: mucous glands, usually associated with respiration and water balance, and granular (also known as serous or venom) glands, related to defense mechanisms (Duellman and Trueb, ). Granular glands synthesize a wide variety of chemical compounds, e.g., proteins, lipids, catecholamines, alkaloids, or glycoconjugates, depending on the group of amphibians (Toledo and Jared, ; Jared et al, ; Antoniazzi et al, ; Ferraro, Topa and Hermida, ). Among anurans, true toads belonging to the family Bufonidae produce highly toxic skin secretions, which are composed of cardiotonic steroids, called bufadienolides, and biogenic amines like catecholamines, with a powerful vasopressor action in vertebrates (Toledo and Jared, ; Maciel et al, ; Cunha‐Filho et al, ; Sciani et al, ).…”

Ultrastructural Evidence of Serous Gland Polymorphism in the Skin of the Tungara Frog Engystomops pustulosus (Anura Leptodactylidae)

“…Occurrence of three serous gland types is unusual in anuran skin, where no more than two different types were previously reported. Actually, three syncytial gland types have been also described in leaf frogs of the genus Phyllomedusa (Delfino et al, ; Nosi et al, ), but this variety includes secretory units specialized in producing skin wax (Blaylock et al, ; Antoniazzi et al, ) that therefore represent a serous‐derived rather than a proper serous type (Delfino et al, ).…”

Passive and active defense in toads: The parotoid macroglands inRhinella marinaandRhaebo guttatus

“…Therefore, it is the predator who causes its own poisoning, which can often be lethal (Sakate and Lucas de Oliveira, ; Jared and Antoniazzi, ; Jared et al, ). Predator's self‐poisoning is characteristic of amphibian defense, which is classified as a “passive defense” (Jared and Antoniazzi, ; Antoniazzi et al, ), as opposed to “active defense” presented, for example, by the snakes, who attack the aggressor and inject their venom through glands compressed by surrounding muscles (Kochva, ; Pough et al, ; Jared et al, ).…”