Morphology of the Cutaneous Poison and Mucous Glands in Amphibians with Particular Emphasis on Caecilians (Siphonops annulatus)

Caecilians (order Gymnophiona) are apodan, snake-like amphibians, usually with fossorial habits, constituting one of the most unknown groups of terrestrial vertebrates. As in orders Anura (frogs, tree frogs and toads) and Caudata (salamanders and newts), the caecilian skin is rich in mucous glands, responsible for body lubrication, and poison glands, producing varied toxins used in defence against predators and microorganisms. Whereas in anurans and caudatans skin gland morphology has been well studied, caecilian poison glands remain poorly elucidated. Here we characterised the skin gland morphology of the caecilian Siphonops annulatus, emphasising the poison glands in comparison to those of anurans and salamanders. We showed that S. annulatus glands are similar to those of salamanders, consisting of several syncytial compartments full of granules composed of protein material but showing some differentiated apical compartments containing mucus. An unusual structure resembling a mucous gland is frequently observed in lateral/apical position, apparently connected to the main duct. We conclude that the morphology of skin poison glands in caecilians is more similar to salamander glands when compared to anuran glands that show a much-simplified structure.

Some Breast Malformations

The breast or milk gland is the largest skin gland, characteristic of the female gender, which is called the whole mammalian genus. It is located on the ventral side of the chest at the border of the bone and cartilage of the fourth rib. Breast is a genetic apocrine skin gland. The female infant’s breast does not differ from the male infant’s breast. One and the other immediately after birth excrete secretion under the influence of prolactin hormone. Until the beginning of puberty, men’s and women’s breasts are developing equally, and then men’s breasts are generally no longer developing while women breasts, under the influence of female sex hormones, develop and its development ends during pregnancy and breastfeeding

Some Breast Malformations

The breast or milk gland is the largest skin gland, characteristic of the female gender, which is called the whole mammalian genus. It is located on the ventral side of the chest at the border of the bone and cartilage of the fourth rib. Breast is a genetic apocrine skin gland. The female infant’s breast does not differ from the male infant’s breast. One and the other immediately after birth excrete secretion under the influence of prolactin hormone. Until the beginning of puberty, men’s and women’s breasts are developing equally, and then men’s breasts are generally no longer developing while women breasts, under the influence of female sex hormones, develop and its development ends during pregnancy and breastfeeding

Gland composition in sexually dimorphic skin structures of two species of Hylid frogs: Plectrohyla guatemalensis and Ptychohyla hypomykter

Secondary sexual characters form a diverse group of traits widely spread in amphibians. Within anurans, the Hylini tribe represents an interesting group to examine the evolution of this type of characters because it has different skin structure modifications, including ventrolateral glands, nuptial pads, and unique swollen upper lips. We analysed the skin gland composition in the upper lip of Plectrohyla guatemalensis and the ventrolateral gland of Ptychohyla hypomykter (Hylidae: Hylinae: Hylini). Each of these species is characterized by a different type of sexually dimorphic skin gland; specialized mucous glands (SMGs) in Pl. guatemalensis and specialized serous glands (SSGs) in Pt. hypomykter. The SMGs conform to the general type of sexually dimorphic skin glands in amphibians, whereas SSGs are very rare. Because SMGs are likely involved in the production of sexual pheromones, their distinctive location and their co-occurrence with other secondary sexual characters like long and pointed maxillary and premaxillary teeth in Pl. guatemalensis suggests that the system used for their delivery may be a distinguishing behavioral feature in this species. The presence of both types of glands in Pt. hypomykter (SMGs in nuptial pads, and SSGs in ventrolateral glands) suggests a different or, at least, a complementary role of these two types of glands during reproduction.