The ability of crabs to pull the large muscles within its claws through small joints when molting out of an old shell holds the promise of a better understanding of muscle atrophy in humans, said Colorado State University researcher Don Mykles, who was recently awarded a three-year, $473,000 grant from the National Science Foundation to conduct research in the area.
Crabs are able to induce atrophy, a reduction of muscle mass, solely in the muscles within their claws, said Mykles, a biology professor in Colorado State’s College of Natural Sciences. Once the claw muscles are reduced by about one-third from their regular size, the crab is then able to pull the muscles through small joints that connect the appendage to its body. It takes about three weeks as the animal prepares to molt. It takes another three weeks after molting for the muscle to grow back. Myostatin, a protein that controls muscle growth and prevents muscles from growing too large, plays a crucial role in this process, Mykles said.
"This grant is just the beginning of understanding how myostatin works," Mykles said. "Imagine if we could manipulate the myostatin by blocking it. We can increase growth of crabs and lobsters and improve food quality. The hunt is on for compounds that block myostatin."
Mykles has discovered in crabs the presence of myostatin, which previously had only been found in mammals, birds and fish. Mykles theorizes that crabs use myostatin to reduce the size of muscles within the claws and are able to localize the myostatin to only its claws as other muscles within crabs’ body do not show signs of atrophy during molting.
When a crab’s shell becomes too small for its growing body, a molting hormone is secreted by a gland within the crab’s body. This triggers synthesis of a new shell, regeneration of legs and atrophy of the claw muscle.
"Our data indicate that myostatin is a critical link between molting hormone and skeletal muscle atrophy," Mykles said.
Mykles, who has researched crabs and lobsters for 33 years, said a better understanding of myostatin’s effect on muscles could lead to advancements in several areas, including aquaculture.
When it comes to human applications, Mykles said a myostatin blocker could possibly be administered to humans who are bedridden and fighting muscle atrophy to prevent muscle mass from breaking down.