Accelerometry predicts muscle ultrastructure and flight capabilities in a wild bird

Abstract

Muscle ultrastructure is closely linked with athletic performance in humans and lab animals, and presumably plays an important role in the movement ecology of wild animals. Movement is critical for wild animals to forage, escape predators, and reproduce. However, little evidence directly links muscle condition to locomotion in the wild. We used GPS-accelerometers to examine flight behaviour and muscle biopsies in breeding black-legged kittiwakes (Rissa tridactyla) to assess muscle ultrastructure. Biopsied kittiwakes showed similar reproductive success and subsequent over-winter survival to non-biopsied kittiwakes, suggesting that our study method did not greatly impact foraging ability. Muscle fibre diameter was negatively associated with wing beat frequency, suggesting that larger muscle fibres facilitate powered flight. Number of nuclei per fibre was positively associated with average airspeed, likely because higher power output needed by faster-flying birds required plasticity for muscle fibre recruitment. These results suggest the potential for flight behaviour to predict muscle ultrastructure.

Skeletal muscle and metabolic flexibility in response to changing energy demands in wild birds

“…Besides thermally induced remodeling in avian muscle, the number of nuclei per fiber is positively associated with flight velocity in black-legged kittiwakes, likely because higher power output needed by faster-flying birds required plasticity for muscle fiber recruitment (Lalla et al, 2020). The number of nuclei per muscle fiber increases with muscle training, even preceding hypertrophic muscle growth (Bruusgaard et al, 2010), supporting our hypothesis that a higher number of nuclei per fiber is associated with faster flight speeds.…”