Vol. 51 No. 7, 2012

Cutaneous Resistance to Evaporative Water Loss in Taiwanese Arboreal Rhacophorid Frog

Jian-Nan Liu^1,2,* and Ping-Chun Lucy Hou¹

¹Department of Life Sciences, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan
²Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, A227 Russell Labs, 1630 Linden Dr., Madison, WI 53706, USA

Jian-Nan Liu and Ping-Chun Lucy Hou (2012) In this study, we investigated whether arboreal rhacophorid amphibians in humid subtropical Taiwan exhibit significant cutaneous resistance (R_c) to evaporative water loss (CWL).  Animals from 7 arboreal rhacophorid and 3 non-arboreal amphibian species were injected with a neuromuscular blocking agent to eliminate pulmonary water loss, and their rates of CWL were measured gravimetrically in a wind tunnel at a wind speed of approximately 1.0 m/s.  For each individual, we used a same-sized 3% agar replica to determine its boundary layer resistance, which allowed us to calculate R_c.  Our results showed that all 7 arboreal species exhibited a detectable R_c that ranged 1.2-3.3 s/cm, and rates of CWL of arboreal species were 1/2-1/5 those of non-arboreal species.  We further tested whether arboreal species actively adjusted their Rc in response to an increase in CWL associated with a high wind speed.  Rates of total evaporative water loss (EWL) and Rc of physically restricted animals were measured at wind speeds of 0.6 cm/s and 1.0 m/s.  Results showed that the R_c of arboreal rhacophorid species did not significantly differ between the 2 wind speeds despite substantially increased rates of EWL at the high wind speed.  A comparison between the CWL of paralyzed frogs and the EWL of restricted frogs showed that the ratio of pulmonary water loss to total EWL in Taiwanese amphibians is very low and can be neglected. 

Key words: Cutaneous resistance, Rhacophoridae, Subtropical, Tree frog, Wind speed.

*Correspondence: Tel: 886-2-27871594.  Fax: 886-2-27858059.  E-mail:jnliu@gate.sinica.edu.tw