New research by University of Liverpool scientists and international collaborators has revealed how the water shrew evolved to survive for long periods underwater without breathing.
The water shrew, known as the world's smallest diving mammal, lives in wetland habitats such as streams, ponds, and swims underwater to catch grubs. Although it has no webbed legs, the spiky hair on its back leg helps it swim. Its capacity to stay for long periods underwater when compared with other animals searching for food underwater has long remained a mystery for scientists.
According to scientists, the confusing thing about this animal is its ability to stay long underwater, unlike other mammals, which can't because of their low body oxygen stores coupled with the highest rates of oxygen use and loss of body heat.
The team's new study, published in the journal eLife, sampled DNA from 71 different shrews and mole species all belonging to a large group of related, insect-eating mammals called Eulipotyphla, in order to map the evolution of the oxygen-binding protein myoglobin and reconstruct the origins of diving lifestyles within the group.
Their analysis showed that the protein saw three transitions that gave the shrews their exceptional ability to underwater foraging.
"Our research did what past studies couldn't do, and resolved the century-old controversy about the evolutionary origins of this unlikely specialized lifestyle among shrews and slightly larger moles in one of the most diverse and species-rich order of mammals," Dr. Michael Berenbrink, who was a co-lead author on the study, said in a report posted on the university's website.
"It is an example of the value of long-term, low cost international research collaboration that utilizes museum collections and field work to build up comprehensive data sets over many years," Berenbrink said.