Seasonality of Freeze Tolerance in a Subarctic Population of the Wood Frog, Rana sylvatica

Table 1

Somatic and physiological characteristics of wood frogs sampled in winter and spring.

	Winter	Spring	t	P
Body mass (g)	7.2 ± 0.5	11.1 ± 0.5	5.20	0.0002
Snout-ischium length (cm)	4.3 ± 0.1	4.9 ± 0.1	3.87	0.002
Body water content (g g^−1)	3.91 ± 0.05	4.03 ± 0.10	0.86	0.417
Coelomic fat body (mg)	1.5 ± 0.8	4.5 ± 1.6	1.64	0.126
Muscle glycogen (𝜇mol g^−1)	533 ± 42	508 ± 97	0.24	0.812
Hepatosomatic index	22.4 ± 0.9	8.0 ± 1.4	9.07	<0.0001
Liver glycogen
Concentration (𝜇mol g^−1)	3549 ± 88	1500 ± 404	4.96	0.003
Total reserve (𝜇mol)	1170 ± 97	294 ± 97	6.24	<0.0001
Richness (𝜇mol g^−1 frog)	794 ± 33	128 ± 37	13.20	<0.0001
Plasma
Glucose (𝜇mol mL^−1)	7.2 ± 1.3	7.1 ± 1.6	0.01	0.991
Urea (𝜇mol mL^−1)	105.8 ± 9.7	8.6 ± 1.4	9.92	<0.0001
Osmolality (mosmol kg^−1)	419 ± 9	187 ± 2	25.51	<0.0001
𝑛	8	7

Note: Values are mean ± SEM. Comparison between winter and spring groups was made using unpaired Student’s t-test. Data from winter frogs were initially reported in Costanzo et al. [10].