When the sun really starts to sizzle, most animals tough it out in the shade. But the Australian green-striped burrowing frog, Cyclorana alboguttata, avoids the sun and lethal dehydration altogether by retreating into the ground and undertaking a `summer hibernation', or aestivation, for up to nine months. Long hibernations often cause havoc with mammals' muscles, which atrophy through misuse, however previous research on the green-striped burrowing frog showed that their leg muscles weren't affected by a three month aestivation. But, since the frogs are in the ground for up to nine months, Beth Symonds and her colleagues from the University of Queensland and Coventry University wanted to know if the frogs' muscles were still unaffected after a full aestivation. They chose to scrutinise the structure and the contractions of two frog `thigh' muscles: the sartorius,which is a mostly fast twitch muscle at the front of the leg; and the iliofibularis, a slow twitch muscle found at the back of the leg().
The team found that while the cross-sectional area of the iliofibularis and sartorius muscle fibre density decreased after aestivation, no other properties of the muscles such as muscle mass or the proportion of slow and fast fibres changed. Examining the muscles' contractions, they found that muscle contraction speed slowed down in the slower-twitch iliofibularis only,but despite these small changes the muscles still produced the same amount of power, showing that that they resisted atrophy during their subterranean break. The next challenge will be to work out how the frogs manage this feat.
