Integumentary structure and its relationship to wiping behaviour in the common Indian tree frog, Polypedates maculatus

Abstract

With 2 plates in the text) Skin of the Indian tree frog, Polyprdutes maculatus (Rhacophoridae), was studied in the context of self-wiping behaviour which functions to expel and distribute cutaneous secretions recently shown to retard evaporative water loss. The secretions contain both mucus and lipids and are derived from a common gland considered to be homologous with characteristic anuran mucous glands. The glands are bipotcnt and secrete both mucus and lipoid products which are evidently mixed within the glandular lumen. Another type of gland resembling characteristic anuriin serous (or granular) glands is found in dorsal but not ventral skin, whereas the lipid-secreting mucous glands are found in skin associated with all body surfaces. There is no distinct, lipid-secreting gland present in the skin of this species other than the mucous glands. These histochemical data complement the earlier finding that resistance to evaporative water loss in this species is relatively small compared with phyllomedusine .watetproof frogs which also exhibit wiping behaviour associated with secretion of lipids. Thus, wiping behaviour may have evolved in association with mucous secretions before dominant lipoid secretions resulted from strong selection for water conservation.

Cutaneous glands in the Australian hylid Litoria caerulea (Amphibia, Hylidae)

“…Their dimensions were 74×93 µm in adult L. caerulea as compared to 125 µm in adult Xenopus (Fujikura et al 1988), and 190 µm in adult Bufo (Moon et al 1988). Recently, mucous glands (41-74 µm) described in an Indian tree frog, were found to contain lipids (Lillywhite et al 1997). The serous glands have a small cavity filled with granules of various sizes, shapes and electron densities, as seen only by TEM, reported in Rana (Bovbjerg 1963) and in Bombina (Obert and Schneider 1978).…”

“…Others, arboreal phyllomedusine anurans from South America, African hyperoliids and the rhacophorid Chiromantis, remain exposed to harsh ambient conditions. In some of these arboreal frogs, lipidcontaining glands have been demonstrated in their skin (Blaylock et al 1976;McClanahan and Shoemaker 1987;Lillywhite et al 1997;Delfino et al 1998). About 30% of the cutaneous glands in four Phyllomedusa species are alveolar and secrete lipids (Blaylock et al 1976).…”

The evolution of milk secretion and its ancient origins

“…Certainly, some extant frogs secrete lipids as a means of reducing water loss across the skin (Lillywhite et al, 1997;Lillywhite, 2006), and secreted lipids applied to eggs could have had an impact on egg moisture loss (Oftedal, 2002a). However, much more research is required to understand the differences and similarities of secretory mechanisms.…”

The effect of substrate diameter and incline on locomotion in an arboreal frog

“…Species of the genus Phyllomedusa are of special interest given their known ability to move across branches of narrow diameter and the fine motor control they appear to have over their fingers, allowing them to perform a precision grip (Burton, 1998;Herrel et al, 2008). Moreover, many of these arboreal species are known to use their forelimbs in contexts other than locomotion yet requiring great dexterity such as prey capture and manipulation (Gray et al, 1997;Sustaita et al, 2013), nest building (Kenny, 1966;Biju, 2009), and the wiping behaviour where frogs spread lipids over their body (Lillywhite et al, 1997;Barbeau and Lillywhite, 2005). In the present study, we focused on the effects of substrate diameter and incline on the kinematics of the forelimb in a fine branch specialist, Phyllomedusa azurea.…”