Unusual gait of the rabbits jumping – Explained

An international team of researchers was interested in rabbit movement. She went so far as to dig through their genome to better understand their jumping movements and above all the strange approach of the jumper Alfort.

Alforta jumpers, real balancers

Rabbits, hares or even kangaroos move by performing coordinated jumps. If the complex muscular process is fairly clear, the underlying molecular and genetic phenomena have remained poorly understood to date. For this reason, the authors of the new study were published March 25, 2021 in the journal Plos genetics they were interested in Alfort jumpers, an extremely special breed of domestic rabbits. “At a slow speed, during the swinging phase, they raise their hind limbs excessively, explain to biologists in their study. At higher speeds, the movements of the hind limbs, instead of synchronizing, show a slight lag and jumping rabbits never perform a jump. This poor coordination significantly impairs movement efficiency, and therefore individuals of this strain adjust their movement behavior for longer and / or faster movements by lifting the hind limbs off the ground and moving only when supported by the front limbs.In particular, these animals are bipedal on their front legs! In some of these rabbits the lack of synchronization is weak and they can still move normally. However, others walk only on their front limbs. This “breed” of rabbits, probably incapable of surviving in the wild, it was kept for studies, especially on movement problems.

Credit: Carneiro M et al., 2021, PLOS Genetics

Mutation involved

To better target the genes involved during rabbit movement, the researchers therefore crossed Alfort jumpers with another breed, called the “New Zealand rabbit”, over two generations. By observing the movements of young rabbits that are the result of these crosses and analyzing their genome, the scientists finally understood the secret of this movement and the Alfort jumper problem. The results highlight the discovery of a mutation in a gene called RORB for RAR related orfhan receptor B. The latter encodes the synthesis of a protein that is usually ubiquitous in the nervous system of rabbits, “especially in the posterior horn of the spinal cord“, the study emphasizes. The mutation leads to a decrease in the number of neurons in the spinal cord capable of creating RORBs that are necessary for the proper regulation of nervous activity. The result is … Alfort jumpers.”Our results show that the RORB function is necessary to perform skipped locomotion in rabbits.“, the researchers conclude.

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