A recent research published in Cell, concludes that the ability to walk originated much earlier than what was thought previously. According to the study the first sea fish that developed the ability to walk did not venture out of the oceans and stayed put in deep waters. According to the study these creatures did not use their evolution to their advantage. The study was based on a genetic analysis of the brain cells of the little skate fish (Leucoraja erinacea), as it is one of the most primitive vertebrates (animals with a backbone). The study infers that the brain systems controlling the movement of this skate fish are very similar as of mammals and hence these sea creatures were the first to learn the behaviour similar to walking. Scientists recorded a video of little skate fish embryos making movements that mimic walking along the bottom of a fish tank.
According to the study, the walking motions of the little skate fish might go back to more than 400 million years. Previously it was believed that the network of nerves that was needed for walking were unique to land animals that evolved from fishes around 380 million years ago. However, through this research, it was found that the skate fish and basal sharks already have these networks in place. Little skate fish are the last common ancestors of sharks and mammals and their genetic history of utmost importance. Genes preserved through the time of elephant shark and the catshark were compared by scientists, and the RNA sequencing showed that the genetic blueprints for controlling limbs, muscles and bending and straightening of limbs could be a possible link between little skate and mammals. Jurassic Era ‘Fish Lizard’ Ichthyosaur’s Fossil Which Lived Alongside Dinosaurs Found In India
Watch the walking motion of the little skate fish (Leucoraja erinacea)
The little skate fish also presents a simpler way to study how these motor neurons work inside the brain. The little skate fish doesn’t have legs but two sets of fins – a large pectoral fin and smaller pelvic fin. It uses the large pectoral fins for swimming and the smaller pelvic fins allow it to walk along the bottom of the ocean. The alternating left-and-right motion that the little skate employs is known as ambulatory motion and hence makes it a very apt subject for studying the origins of walking. This will help scientist collect important information about the process of walking and how motor neuron diseases can be treated. It is difficult to study this in mammals because their brain is much more advanced and there are many things going on in their brains at one time. The little skate fish also provides a simpler model to study the circuits used in walking as they use only six muscles instead of the hundreds that mammals use for walking.