London, July 29 (ANI): A team of scientists has identified some of the metabolic changes that occur to transform tens of millions of red crabs from inactive, antisocial creatures into an unstoppable sea of individuals capable of walking for several days on end, thus making one of the most spectacular animal migrations on Earth.

"This (migration) requires a major physiological change," said Steve Morris of the University of Bristol, UK, who led the study.

"If they are made to walk for 5 minutes in the dry season they build up high levels of lactic acid, yet when the rains come they'll walk a kilometre a day quite easily," he added.

The red land crab, Gecarcoidea natalis, is unique to Christmas Island, which is located in the Indian Ocean, south of Indonesia.

Their migration usually occurs at the start of the wet season, and is timed so that females can release their eggs into the sea at the turn of high tide during the last quarter of the moon.

Previous studies have shown that injecting crustacean hyperglycaemic hormone (CHH) into crabs boosts blood sugar levels, suggesting that it is roughly analogous to insulin in humans, triggering the breakdown of glycogen into glucose to be used as fuel when required.

To find out whether this hormone played a role in the migration of red crabs, Morris and colleagues measured concentrations of CHH in the crabs' eyestalk glands and blood during the wet and dry seasons.

They found that there was an increase in CHH in the crabs immediately before dawn during the wet season but not during the dry season.

"We've shown the level of this hormone goes up and is important in encouraging the release of glucose for muscle activity during the migration," said Morris.

However, it is unclear whether this is the direct trigger for the migration, or if another mechanism is at work too. (ANI)