Water is a precious resource that is expected to become more scarce in the years to come. It’s likely that animals will have to work harder to find the water they need, and their supplies will be unreliable. New work reported in the Proceedings of the Royal Society B: Biological Sciences has found that muscles could act as a supply for animals that need water but can’t locate any. The research is by scientists from Arizona State University and the Centre d'Etudes Biologiques de Chizé in France.
"We know about the importance of fat reserves to fuel the energetic costs of reproduction. But what about water? Our study shows that during reproduction, muscle metabolism is linked to the water requirements of developing offspring. Fat is only about ten percent water, whereas muscle is closer to 75 percent, so burning muscle will release extra water," explained lead investigator George Brusch IV, a doctoral candidate at Arizona State University. "From an evolutionary perspective, the concept of capital breeding -- or using stored resources to fuel reproduction -- is currently restricted to energetic needs. We propose that this should extend to a broader, multi-resource strategy that also includes water allocation."
For this work, the scientists studied the effects of water scarcity on a snake that reproduces during Australia’s dry season, the female Children's python. Pregnant pythons were paired with non-productive females of a similar size, and for three weeks, only half of the pairs got water. Reproductive females don’t eat while pregnant and only use internal resources to get by. In those animals, muscles can provide the body with water when there’s none around.
"Female Children's pythons can change how they use internal resources based on limitations in the environment," explained Brusch. "Understanding exactly how animals cope with resource restrictions will help scientists predict whether the animals might be impacted by future climate change, where, in many regions, rain is expected to be less reliable," added Brusch.
The researchers assessed a variety of metabolic markers and reproductive effects on the experimental groups. Animals without water access used more muscle than fat to get their water, and laid about the same number of eggs. Those eggs, however, had thinner shells and weighed less.
A steady source of clean water is critical to the survival of most animals, something that’s only more important during pregnancy. The authors have suggested that this is a mechanism other animals might be using.
"Our enhanced knowledge regarding the relationship between hydration and reproductive investment will also enable us to better understand global responses to water limitations and change the way scientists approach reproductive investment in ecological contexts, which, in the past, frequently ignore water and focus solely on energetic resources," said Brusch.