Serous gland polymorphism in the skin of Phyllomedusa hypochondrialis azurea (Anura, Hylidae): response by different gland types to norepinephrine stimulation

Abstract

Stimulation by norepinephrine in physiological concentration was used on the dorsal skin of the Argentine tree-frog Phyllomedusa hypochondrialis azurea to trigger contraction of myoepithelial cells encircling the serous glands and provoke secretory release. This hylid species possesses two kinds of serous cutaneous glands, producing secretory granules or vesicles (type Ia and Ib serous units, respectively), along with serous-derived glands which synthesise lipids and store them in complex aggregates (type II units). Structural and ultrastructural observations on myoepithelia, secretory units and gland products collected in saline after discharge, revealed consistent but different responses in the three types investigated. Type Ia glands reacted intensely to treatment, with both contractile and secretory responses, type Ib glands were only mildly affected in their myoepithelia and glands of type II were not affected at all. According to data available in the literature, these findings suggest that: (a) the dense (type Ia) granules are expelled as a phasic response through bulk (holocrine) discharge, (b) the secretory (type Ib) vesicles are released as a tonic response through a merocrine mechanism and (c) lipid (type II) aggregates are exuded as a secretory component of a complex behavioural response which tends to reduce transcutaneous water loss. Furthermore, these findings indicate that the use of pharmacological modulation of myoepithelial activity allows selective collection of skin products in species characterised by serous gland polymorphism.

Comparative analysis of the integument of different tree frog species from Ololygon and Scinax genera (Anura: Hylidae)

“…In addition, apocrine glands with heterogeneous content occurred in the integument of all species of Scinaxinae. Nevertheless, in O. angrensis, the secretory product contained peculiar basophilic granules with dense cores intermingled with acidophilic cytoplasm, and their histological features resembled those of type Ia glands described for Pithecopus azureus (Cope, 1862) (former Phyllomedusa azurea) (Nosi et al 2002).…”

“…Nevertheless, various subtypes of serous glands with high morphological variability have been reported (Goniakowska-Witalinska and Kubiczek 1998, Delfino et al 1999, Warburg et al 2000, Nosi et al 2002, Brunetti et al 2012, Moreno-Gómez et al 2014.…”

Investigation of dorsal/ventral skin and the parotoid region of Lyciasalamandra billae and Lyciasalamandra luschani basoglui (Urodela: Salamandridae)

“…In R. icterica, two types of glands, mucous and venom, were detected by de Brito-Gitirana & Azevedo (2005). However, other authors (Warburg et al 2000;Nosi et al 2002) reported different types of dermal glands, such as lipid (wax) and mixed (seromucous gland). Bingöl Ozakpinar & Murathanoglu (2011) observed three types of skin glands; serous, mucous and mixed glands in the dorsal and ventral parts of Triturus karelinii (Strauch, 1870).…”

The morphology of the dorsal and ventral skin of Triturus karelinii (Caudata: Salamandridae)

“…By light microscopy analysis, three serous gland types (I, II and III), which consist of different appearances and sizes of granules, were observed. Several morphological studies dealing with serous gland polymorphism in the amphibian skin have been reported (Delfino et al 1998(Delfino et al , 1999Nosi et al 2002). Delfino et al (1998) suggested that this polymorphism has been related to the secretory state of the glandular cells or different types of skin glands.…”

“…On the basis of structural, ultrastructural and histochemical properties, the amphibian skin possesses two types of cutaneous glands: mucous and granular (serous or venom) glands (Toledo & Jared 1995). Additionally, the presence of two types of skin glands in certain amphibian species has been described by some authors: lipid (or wax) (Warburg et al 2000;Nosi et al 2002) and mixed glands (Seki et al 1995;Staub & Paladin 1997;Tsurada et al 2002). Furthermore, the secretions of the dermal glands are source of proteins, peptides, biogenic amines, alkaloids, steroids and lipids (Daly et al 1987;Bevins & Zasloff 1990;Warburg et al 2000).…”