Meeting Abstract
P3.57 Jan. 6 Morphological plasticity of skeletal muscles of working Greenland dogs in response to seasonal changes of temperature, food supply, and exercise GERTH, N.; SUM, S.; JACKSON, S.; STARCK, J.M.*; Univ. Munich, Germany; Univ. Athens, Georgia; Univ. Stellenbosch, South Africa; Univ. Munich, Germany starck@uni-muenchen.de
Greenland sled dogs experience seasonal changes in temperature, food supply, and exercise. During winter they work as sled dogs and feed every day. Throughout the mild arctic summer the dogs are chained to rocks without exercise and with intermittent food supply (2 � 5 days feed intervals). During summer 2005 and winter 2005/2006 we studied phenotypic flexibility in a team of 14 Greenland dogs at Qeqertarsuaq, Disko Island, Greenland (69�15� N, 53�32� W). We used transcutaneous ultrasonography to record the thickness of selected muscles of the locomotor apparatus. The thickness of the combined M. trapezius and M. supraspinatus (on scapula), the combined M. biceps femoris and M. vastus lateralis (hindleg) revealed significant differences between summer and winter condition. During summer, muscle thickness on the scapula of standing dogs was 2.24 � 0.2 cm and differed significantly from muscle thickness during winter (2.71 � 0.2 cm). The values of muscle thickness on the hind leg differed significantly between summer (1.43 � 0.16 cm) and winter condition (2.30 � 0.19 cm). We took microbiopsy samples from M. quadriceps femoris to explore possible structural differences of muscles of dogs in summer and winter condition by light- and electron microscopy. Muscle fibers from dogs in summer condition are characterized by a serious depletion of myofilamental structures from sarcomeres when compared to fibers obtained from dogs in winter condition. Muscle fibers also differ in the amount of lipid droplets within and between dogs, and between seasons. No muscle damage was observed throughout the seasons. Ongoing studies consider the fiber type distribution, capillarization, density of vascular transport vesicles, and morphometry of diffusion distances.
