Rabbits that do handstands reveal why some animals can hop
The Alfort jumper rabbit has a mutation in a gene known as RORB that prevents it from hopping like most other breeds.
Researchers have found the gene behind hopping animals' bouncing gait – by studying a breed of rabbit that doesn't hop at all.
The sauteur d'Alfort, also known as the Alfort jumper rabbit, has a rather acrobatic way of moving. Over short distances, particularly when it's moving slowly, the rabbit will walk more or less as normal, though its back feet will hit the floor one after another, rather than at the same time.
But when it wants to travel further or faster, it lifts its back feet above its head in an agile handstand, and walks on its front paws. So why doesn't this breed of rabbit bounce, like most breeds?
Experiments on the breed in 1943 showed that this strange locomotion was due to a recessive gene, and was not a learned behaviour. So, the team, at the Universidade do Porto and Uppsala University, wanted to find out what gene was responsible for the difference.
They bred Alfort jumper rabbits with another breed and compared their offsprings' genomes and jumping abilities. They found that the ability to hop correctly depended on whether or not the rabbit had a functioning copy of the gene called RAR-related orphan receptor beta, or RORB. The rabbits with a specific mutation in this gene couldn't jump, and instead walked on their front paws.
The RORB gene encodes for a protein found in many places in the rabbit nervous system. Rabbits with the mutation had far fewer neurons in their spinal cord that produced this protein.
Previous studies have looked at the impact of the RORB gene in other animals. A 2017 study published in Neuron showed that mice without the gene walked with a high-legged step described as a 'duck gait'.
The team say that the study also advances our understanding of the different ways that vertebrates can walk.
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