Serous cutaneous glands of ArgentinePhyllomedusaWagler 1830 (Anura Hylidae): secretory polymorphism and adaptive plasticity

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Abstract
An ultrastructural study has been carried out on the cutaneous serous glands in the Argentine hylids Phyllomedusa sauvagei Boulenger 1882 and P. hypochondrialis Boulenger 1882. Both species possess type I serous units, which are representative of the usual serous glands in anurans, and type II units, peculiar to the genus Phyllomedusa Wagler 1830. Type I secretory units were further characterized as type Ia and Ib, on account of the morphology of their specific products. Type Ia secretory materials consist of spheroidal granules (4–6 μm in diameter), which are compact in P. sauvagei and provided with a mesh-like substructure in P. hypochondrialis. Type Ib serous deposits in P. sauvagei are also granules, which exhibit variable density, irregular shape, and are usually larger (up to 15 μm in diameter), whereas in P. hypochondrialis they are even wider vesicles (up to 20 μm), holding a finely dispersed material. No intermediate forms were detected between these features, and therefore the type I secretory units of these species produce two morphological subclasses of serous products. Type II glands display consistent ultrastructural features in both species. They have been described in the past as wax glands, since they produce lipids which the frogs spread over the body surface. The adaptive value of wax glands is reconsidered in this paper, using ultrastructural criteria. Type II glands share the fundamental traits of anuran serous glands; as sites for production of substances relevant to regulation of water loss through the body surface, they represent an example of the adaptive plasticity of the serous secretory units in anuran skin.

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