Cryoprotectants and extreme freeze tolerance in a subarctic population of the wood frog.
PLoS One
; 10(2): e0117234, 2015.
Article
en En
| MEDLINE
| ID: mdl-25688861
Wood frogs (Rana sylvatica) exhibit marked geographic variation in freeze tolerance, with subarctic populations tolerating experimental freezing to temperatures at least 10-13 degrees Celsius below the lethal limits for conspecifics from more temperate locales. We determined how seasonal responses enhance the cryoprotectant system in these northern frogs, and also investigated their physiological responses to somatic freezing at extreme temperatures. Alaskan frogs collected in late summer had plasma urea levels near 10 µmol ml-1, but this level rose during preparation for winter to 85.5 ± 2.9 µmol ml-1 (mean ± SEM) in frogs that remained fully hydrated, and to 186.9 ± 12.4 µmol ml-1 in frogs held under a restricted moisture regime. An osmolality gap indicated that the plasma of winter-conditioned frogs contained an as yet unidentified osmolyte(s) that contributed about 75 mOsmol kg-1 to total osmotic pressure. Experimental freezing to -8°C, either directly or following three cycles of freezing/thawing between -4 and 0°C, or -16°C increased the liver's synthesis of glucose and, to a lesser extent, urea. Concomitantly, organs shed up to one-half (skeletal muscle) or two-thirds (liver) of their water, with cryoprotectant in the remaining fluid reaching concentrations as high as 0.2 and 2.1 M, respectively. Freeze/thaw cycling, which was readily survived by winter-conditioned frogs, greatly increased hepatic glycogenolysis and delivery of glucose (but not urea) to skeletal muscle. We conclude that cryoprotectant accrual in anticipation of and in response to freezing have been greatly enhanced and contribute to extreme freeze tolerance in northern R. sylvatica.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Ranidae
/
Crioprotectores
/
Congelación
Límite:
Animals
Idioma:
En
Revista:
PLoS One
Asunto de la revista:
CIENCIA
/
MEDICINA
Año:
2015
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Estados Unidos