Journal of Comparative Physiology B

, Volume 181, Issue 6, pp 781–792

Skin ice nucleators and glycerol in the freezing-tolerant frog Litoria ewingii

  • Kalinka M. J. Rexer-Huber
  • Phillip J. Bishop
  • David A. Wharton
Original Paper

DOI: 10.1007/s00360-011-0561-7

Cite this article as:
Rexer-Huber, K.M.J., Bishop, P.J. & Wharton, D.A. J Comp Physiol B (2011) 181: 781. doi:10.1007/s00360-011-0561-7


The brown tree frog (Litoria ewingii) is the only known Southern Hemisphere vertebrate that can survive full-body freezing. Freezing challenges living organisms in many ways, with ice formation in the body producing a suite of physical and metabolic stresses which can damage cells and tissues. The present study looked at two mechanisms that address some of these stresses: cryoprotectants and ice nucleating agents (INAs). Skin secretions from L. ewingii were sampled along with microhabitat substrate and tested for the presence of INAs, which help control ice formation in the body. L. ewingii plasma was tested for seasonal and freezing-induced changes in both glucose and glycerol, which may have a cryoprotective role in freezing-tolerant frogs. Glycerol levels increased on freezing and decreased on thawing, while glucose levels did not change on freezing but increased on thawing. This suggests that glycerol may be acting as a cryoprotectant, although levels are low compared to other frogs. A clear seasonal change was seen in INA activity, with greater activity in winter than in summer. While potent INAs came from the microhabitat substrate, this work has shown for the first time that skin secretions also contain active INAs.


Brown tree frog Cryoprotectant Freezing tolerance INA Glucose Glycerol 



Ice nucleating agent


Keyhole cardiac puncture


Snout-vent length


Body temperature


Crystallization temperature


Circulator temperature

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Kalinka M. J. Rexer-Huber
    • 1
  • Phillip J. Bishop
    • 1
  • David A. Wharton
    • 1
  1. 1.Department of ZoologyUniversity of OtagoDunedinNew Zealand