Serous cutaneous glands of Argentine Phyllomedusa Wagler 1830 (Anura Hylidae): secretory polymorphism and adaptive plasticity

An ultrastructural study has been carried out on the cutaneous serous gland s in the Argentine hylids Phyllomedusa sauvagei Boulenger 1882 and P. hypoc hondrialis 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 we re 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 mu m in diameter), which are compact in P. sauvagei and prov ided with a mesh-like substructure in P, hypochondrialis. Type Ib serous de posits in P. sauvagei are also granules, which exhibit variable density, ir regular shape, and are usually larger (up to 15 mu m in diameter), whereas in P. hypochondrialis they are even wider vesicles (up to 20 mu m), holding a finely dispersed material. No intermediate forms were detected between t hese features, and therefore the type I secretory units of these species pr oduce two morphological subclasses of serous products. Type II glands displ ay consistent ultrastructural features in both species. They have been desc ribed 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 reconside red in this paper, using ultrastructural criteria. Type II glands share the fundamental traits of anuran serous glands; as sites for production of sub stances relevant to regulation of water loss through the body surface, they represent an example of the adaptive plasticity of the serous secretory un its in anuran skin.