Water economy in the casque‐headed tree‐frog Corythomantis greeningi (Hylidae): role of behaviour, skin, and skull skin co‐ossification

Abstract

The Brazilian tree-frog Corythomantis greeningi inhabits the Caatinga, a semi-arid habitat. This species exhibits putative adaptations to a dry environment, including a¯at head, co-ossi®cation of the cranial skin, and phragmotic behaviour (retreat to crevices using the head to seal the entrance). Real frogs were compared with agar models to study water balance under simulated Caatinga conditions and to investigate the ability of C. greeningi to ®nd small water sources. The bene®ts of skin co-ossi®cation were also studied by comparing agar models with and without nail polish on the head. Tree-frogs repeatedly preferred a humid test tube out of 10 possible choices, and adopted phragmotic behaviour inside it. In both agar models and tree-frogs, total water evaporation increased with body size, but relative water loss was higher in smaller individuals. The presence of nail polish on agar models barely reduced water loss, suggesting that cranial skin co-ossi®cation has a small role in water economy. Although both models and tree-frogs evaporated about 90% more water when exposed than when phragmotic, tree-frogs evaporated about 50% less water than agar models at any test condition. We conclude that reduced skin permeability, phragmotic behaviour and a keen capacity to identify humid crevices, explain the success of this species in a semi-arid habitat.

Water relations of tetrapod integument

“…The presence of osteoderms or 'co-ossified' regions in skin where bone tissue occurs in the dermis is potentially significant for regional enhancement of R s , and this subject has been given limited attention principally in amphibians (Seibert et al, 1974;Ruibal and Shoemaker, 1984;De Andrade and Abe, 1997;Navas et al, 2002;Jared et al, 2005). The integument of co-ossified regions of skin contains collagen fibres with reduced presence of blood vessels and mucous glands.…”

Predação de ovos de Corythomantis greeningi Boulenger, 1896 (Anura, Hylidae) por Solenopsis invicta Buren, 1972 (Formicidae: Myrmicinae)

“…Registros de predação de ovos de anuros por formigas desse gênero foram citados para Physalaemus cuvieri (Sazima, 1972) e P. aff. gracilis (Lingnau e Di-Bernardo, 2006 (Jared et al, 1999;Navas et al, 2002;Juncá et al, 2008) e ajuda de especialistas.…”

“…Possui cabeça bem ossifi cada, em formato de capacete ou escudo que tem a função de tampa em fendas rochosas, servindo de proteção contra predadores; ocupam ambientes como bromeliáceas, ocos de arvores e frestas de rochas (Jared et al, 1999;Navas et al, 2002). Esta espécie tem sua reprodução bem marcada na época chuvosa, ocupando ambientes aquáticos temporários, lóticos e rasos.…”

Thermal Ecology Of Pleurodema thaul (Amphibia: Leptodactylidae)

“…In fact, the effectiveness of basking behaviour is severely constrained in most anurans due to their limited ability to control evaporative water loss (Carey 1978;Navas et al 2002). Therefore, in contrast to lizards, amphibians are rarely observed in sunny patches (e.g.…”