Examining the relationship between sexual dimorphism in skin anatomy and body size in the white-lipped treefrog, Litoria infrafrenata (Anura: Hylidae)

Abstract

Amphibians transport water, oxygen, carbon dioxide and various ions (e.g. sodium and potassium) across their skin. This cutaneous permeability is thought to affect their ability to respond to environmental change and to play a role in global population declines. Sexual dimorphism of skin anatomy has been accepted in some species, but rejected in others. The species in which such dimorphism has been detected have all been sexually dimorphic in body size, with males that are smaller and have thinner skin. It is unclear whether this difference in skin thickness manifests a functional difference or if it is related to body size alone. Skin thickness (epidermis, spongy dermis, compact dermis and total thickness) was examined in males and females of the white-lipped treefrog ( Litoria infrafrenata ). Although the skin of males is absolutely thinner than that of females, this difference is explained by body size differences between the sexes. Overall, we conclude that skin thickness in male and female L. infrafrenata correlates with body size dimorphism and suggest that future studies on amphibian skin anatomy include measures of body size, test the ecological significance of sexually dimorphic skin anatomy and better document the prevalence of sexually dimorphic amphibian skin anatomy.

Temperature and mass scaling affect cutaneous and pulmonary respiratory performance in a diving frog

“…for the cutaneous-respiration scaling coefficient observed in this study. Furthermore, X. laevis skin thickness appears to increase with body size, based on prior studies showing that females have both larger body mass and thicker skin than males (Greven et al 1995;VanBuren et al 2018). Based on these findings, a combination of SA:V and skin-thickness scaling relationships can likely account for the lower-than-expected mass-scaling exponent for cutaneous respiration observed in this study.…”

“…1995; VanBuren et al . 2018). A prior study observed a mass‐scaling exponent of 1.08 for X. laevis whole‐body respiration, but frogs were taken out of their normal aquatic environment for measurements of oxygen consumption, possibly forcing them to rely more heavily than normal on pulmonary respiration (Hillman & Withers 1979).…”

“…Previous authors have demonstrated that withinspecies metabolic mass scaling relationships exhibit a wide range of exponents (here defined as parameter "b" in models), possibly due to differential reliance on specific physiological systems (reviewed by Glazier 2005Glazier , 2014a. For example, X. laevis is a diving frog that relies heavily on cutaneous respiration (gas exchange through the skin; Hutchison et al 1968), which is temperature dependent and may be limited by the organism's surface area to volume ratio (SA:V; predicted scaling exponent of 2/3) or increased skin thickness in larger frogs (Rubner 1883; Greven et al 1995;VanBuren et al 2018). A prior study observed a mass-scaling exponent of 1.08 for X. laevis whole-body respiration, but frogs were taken out of their normal aquatic environment for measurements of oxygen consumption, possibly forcing them to rely more heavily than normal on pulmonary respiration (Hillman & Withers 1979).…”

Description of a new halophilic tiger beetle in the genus Eunota (Coleoptera, Cicindelidae, Cicindelini) identified using morphology, phylogenetics and biogeography

“…Tiger beetles are one of the most studied groups of non-pest insects [ 1 , 2 ] and have been used as models organisms in conservation biology and biodiversity assessments [ 3 , 4 ]. Most of the fauna of North America had been described by the mid-1800s and by the latter half of the 1900s it appeared as if nearly all of the diversity had been discovered and named [ 5 ]. Species delineations had been based nearly exclusively on morphological characters for the vast majority of taxa, with lesser reliance on ecological or other characters.…”

“…Species delineations had been based nearly exclusively on morphological characters for the vast majority of taxa, with lesser reliance on ecological or other characters. However, in recent years, taxa have been delineated and described through the integration of traditional morphology, molecular data and/or life history [ 5 – 9 ]. This has led to the discovery of ‘cryptic species’; that is, species that are distinct evolutionary units, but had gone undetected due to physical similarity with closely related species.…”