Research press release





今回、Alan Wilsonたちの研究グループは、移動性のヌーの筋繊維の効率を調べた。Wilsonたちは、動作センサーと環境センサーの付いたGPS追跡首輪を用いて、ボツワナ北部の高温乾燥環境に生息するオグロヌー(Connochaetes taurinus)が、5日間水を飲まずに80キロメートル移動したことを明らかにした。オグロヌーの筋繊維は、エネルギーの3分の2を仕事量に変換し、熱として消費されたのは残りの3分の1のみであり、同じような大きさの動物(ウシなど)や小型動物(ウサギなど)よりも相当に効率が良いことが報告されている。このように、オグロヌーは筋肉の効率が良いため熱産生量が最小限に抑えられており、このことから、頻繁に息を吐いても失われる水分量が少なく、そのために水を飲む頻度が低いことが示唆される。

Efficient muscle fibres allow wildebeest to travel long distances without overheating, reports a paper published online this week in Nature. These findings represent the first direct energetic measurements of muscle fibres of large mammals, and suggest how animals living in desert environments can cope with seasonal and local variations in rainfall, food, and climate.

An animal’s capacity for long-distance travel is dependent on their energy utilization and heat production when moving. Large animals are more efficient at travelling large distances overland than smaller species, but the efficiency of individual muscle fibres is less understood. In mice, it is known that a third of the energy is translated into movement while the other two-thirds are expended as heat. The direct study of living muscle fibres is difficult, even for small animals, and it hasn’t been attempted for anything larger than a rabbit.

Alan Wilson and colleagues have now studied the efficiency of muscle fibres for the migrating wildebeest. The authors used GPS tracking collars with movement and environmental sensors to show that blue wildebeest living in a hot arid environment in Northern Botswana could travel up to 80km over five days without drinking. They report that wildebeest muscle fibres convert two thirds of energy into work, and waste only a third as heat — substantially more efficient than both comparably sized animals such as cows and small animals such as rabbits. This muscle efficiency minimizes heat produced by the wildebeest, which suggests that they lose less water through frequent exhaling and so need to drink less frequently.

doi: 10.1038/s41586-018-0602-4

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