Agukoy | Text and photos by NMP Zoology Division, National Museum of the Philippines

Agukoy (Fiddler Crab)

Do you notice the small crabs on mudflats in the mangrove forest known as fiddlers (Agukoy)?

They have colorful bodies and claws that seem to wave at us. Having eyes mounted on long stalks which enable them to see their surroundings and sensitive hairs, the slightest movement of intruders will make them immediately retreat to their burrows or cover themselves with mud or sand on the spot. They cannot swim and prefer to breathe air. At high tide, they hide in burrows which they plug with a ball of sand to trap the air inside.

The male fiddler has one huge colorful pincer that is as large as its body. It is not used for hunting food but for attracting females and for intimidating rival males. To attract females, the male waves its large pincer in a manner unique to his species – that is, with a rhythm and style. Female fiddler is attracted to the male that waves faster. But, if there is a rival male, a pincer fight will solve the issue which will lead to the amputation of the others’ pincer. But worry not, because in time, the male with the amputated pincer will be able to grow a new one. When a male fiddler succeeds in persuading the female to mate with him, they retire into his burrow where the female may remain there until the eggs hatch into free-swimming larvae. These larvae drift with the plankton until they develop and change into tiny fiddler crabs.

Fiddler crabs play a vital role because their feeding and burrowing helps keep marshes clean and helps them to grow. They aid in the aeration of sediments circulated from the burrows they made.

Similar to other species found in mangrove areas and shores, fiddler crabs’ existence are at stake due to anthropogenic activities and pollution. Let’s avoid collecting fiddler crabs in our shores and beaches. Fiddler crabs play a significant role in maintaining the balance of our ecosystem.

Text and photos by NMP Zoology Division, National Museum of the Philippines

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