Serous Glands in the Skin of the Tungara Frog, Engystomops pustulosus (Cope, 1864) (Anura, Leptodactylidae): Degenerated Secretory Units are Selectively Removed by Macrophages

Abstract

The cutaneous apparatus of Engystomops pustulosus (Cope, 1864) (the Tungara frog) includes serous glands that show impressive patterns of degeneration in their syncytial secretory units, and thus represent suitable organ models to investigate the role of macrophages in renewal processes of multicellular structures. The present case report exploits this chance and highlights that: (a) degenerating glands pertain to the Ia line of the polymorphic serous gland assortment in Tungara skin; (b) resident macrophages migrate from spongy dermis and remove syncytium debris; (c) secretory syncytium collapse results from impairment of the equilibrium between serous product manufacturing/storage and merocrine release into the dermal environment; (d) Intercalated tract (or gland neck) and myoepithelium (included its ortho-sympathetic nerve supply), are neither involved in degeneration nor affected by macrophage response. According to present evidence and current literature, it is concluded that the scavenger activity of macrophages prepares secretory unit renewal, performed by stem cells from the neck. In addition, gland functional rehabilitation may rely on effectiveness of the preexisting neuromuscular apparatus to achieve secretory bulk release onto the cutaneous surface.