Seasonal changes in the content of fatty acids in the skeletal muscles of the long-tailed ground squirrel <I>Urocitellus undulatus</I>

Seasonal changes in the fatty acid composition in four skeletal muscles of the true hibernant Yakut long-tailed ground squirrel Urocitellus undulatus were studied. Measurements were taken on animals of four experimental groups: summer active, autumn active, winter dormant, and winter active. An increase in the total amount of fatty acids was found in winter in the quadriceps muscle of the thigh (m. vastus lateralis), the triceps muscle of the forearm (m. triceps), and the psoas muscle (m. psoas). In all muscles, including m. gastrocnemius, a decrease in the total amount of saturated fatty acids was observed in winter. An increase in the total amount of monounsaturated fatty acids in winter hibernating animals occurred in the quadriceps femoris muscle, triceps muscle of the forearm, and in the psoas muscle. In winter active animals, the total content of polyunsaturated fatty acids in the quadriceps femoris and psoas muscles increased. A significant decrease in palmitic acid content in sleeping and winter active ground squirrels compared to summer and autumn animals was found in all muscles studied. The amount of palmitoleic acid significantly increased in sleeping animals in the quadriceps femoris and psoas muscles. In the triceps muscle of the forearm. the amount of palmitoleic acid increased in autumn active and winter dormant individuals. The amount of oleic acid was increased in all muscles of winter hibernating animals relative to active autumn animals. The content of linoleic acid significantly increased in winter active ground squirrels in all muscles except the gastrocnemius. In the autumn period the amount of dihomo-gamma-linolenic acid also increased in all muscles, with a significant decrease in its content in winter sleeping and winter active animals to the level of summer (seasonal) control. The results obtained indicate that most changes in fatty acid composition have the same direction in all four studied skeletal muscles of the long-tailed ground squirrel. Possible roles of seasonal changes in fatty acid composition and the participation of fatty acids in biochemical processes in the muscle tissue of the long-tailed ground squirrel are discussed.