Giant claw ‘helps fiddler crabs to stay cool, attract females’
Monday 20 November, 2017

Giant claw ‘helps fiddler crabs to stay cool, attract females’

Published On: Tue, Sep 6th, 2011 | Marine Biology | By BioNews

Ever wondered why fiddler crabs have such a ridiculously large claw? Well, it has emerged that the oversized limb has dual functions.

Scientists from the University of Texas, US, have found that in addition to having a role in mating displays and in fighting off competitors, the huge claw helps them in staying cool.

In other words, the claw aids in thermoregulation.

Only male crabs possess assymetrical claw, while females have two normal-sized claws.

Dr Zachary Darnell and Assistant Professor Pablo Munguia tested a bunch of Gulf coast fiddler crabs (Uca Panacea) – both those who still had their major claws and those who had lost theirs.

When they shone lights on the crabs to heat them up, they found that those who had the major claws were able to cool themselves down far more effectively than their peers without claws.

“The major claw likely functions like a heat sink, with heat being transferred from the body to the claw and dissipated into the surrounding air through convective heat transfer,” said Dr Darnell.

The results are the first evidence to show how the enlarged structure benefits both reproduction and survival.

“With the large claw acting as a heat sink male fiddler crabs can remain on the surface longer, foraging and performing the waving display,” Dr Darnell told BBC Nature.

The researchers also suggested that this previously unknown benefit could help offset the energy cost of growing such a large sexual ornament.

The study was recently published in the American Naturalist journal.

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