title: Survival and metabolism of Rana arvalis during freezing.
abstract: Freeze tolerance and changes in metabolism during freezing were investigated in the moor frog (Rana arvalis) under laboratory conditions. The data show for the first time a well-developed freeze tolerance in juveniles of a European frog capable of surviving a freezing exposure of about 72 h with a final body temperature of -3 degrees C. A biochemical analysis showed an increase in liver and muscle glucose in response to freezing (respectively, 14-fold and 4-fold between 4 and -1 degrees C). Lactate accumulation was only observed in the liver (4.1+/-0.8 against 16.6+/-2.4 micromol g(-1) fresh weight (FW) between 4 and -1 degrees C). The quantification of the respiratory metabolism of frozen frogs showed that the aerobic metabolism persists under freezing conditions (1.4+/-0.7 microl O(2) g(-1) FW h(-1) at -4 degrees C) and decreases with body temperature. After thawing, the oxygen consumption rose rapidly during the first hour (6-fold to 16-fold) and continued to increase for 24 h, but at a lower rate. In early winter, juvenile R. arvalis held in an outdoor enclosure were observed to emerge from ponds and hibernate in the upper soil and litter layers. Temperature recordings in the substratum of the enclosure suggested that the hibernacula of these juvenile frogs provided sheltering from sub-zero air temperatures and reduced the time spent in a frozen state corresponding well with the observed freeze tolerance of the juveniles. This study strongly suggests that freeze tolerance of R. arvalis is an adaptive trait necessary for winter survival.
authors.affiliation: Ecologie des Hydrosystème Fluviaux (U.M.R. CNRS 5023), Université Claude Bernard Lyon1, Université de Lyon, Bât. Darwin C, 69622 Villeurbanne Cedex, France. yann.voituron@univ-lyon1.fr
authors.forename: Yann
authors.initials: Y
authors.lastname: Voituron
authors.forename: Louise
authors.initials: L
authors.lastname: Paaschburg
authors.forename: Martin
authors.initials: M
authors.lastname: Holmstrup
authors.forename: Hervé
authors.initials: H
authors.lastname: Barré
authors.forename: Hans
authors.initials: H
authors.lastname: Ramløv
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D001831:Body Temperature; D004734:Energy Metabolism / Q000502:physiology*; D005615:Freezing; D005947:Glucose / Q000032:analysis; D019344:Lactic Acid / Q000032:analysis; D010101:Oxygen Consumption / Q000502:physiology; D011898:Ranidae / Q000502:physiology*; D013997:Time Factors
chemical_list: D019344:Lactic Acid; D005947:Glucose