Red-fingered marsh crab fact sheet | Field of Mars EEC

What is a red-fingered marsh crab?

The red-fingered marsh crab is an crustacean that lives in the intertidal zone of the mangrove forest, often in great numbers. The intertidal zone is the area between high and low tides.

Red-fingered marsh crabs get their name from the bright red-orange tips on the claws of the adult crabs. They are from the order Decapoda which means they have 10 legs. The 2 legs at the front of the crab have been modified into the claws that display the red tips.

Their scientific name is  Parasesarma erthrodactyla.

A red-fingered marsh crab

Red-fingered marsh crabs use their large claws for feeding and defence.

Crabs have ten legs including the two front claws

What do red-fingered marsh crabs look like?

The body of a red-fingered marsh crab is around 3 centimetres wide when fully grown. The males have bright green shells and their characteristic red tipped pincer-like claws. The red-fingered marsh crab has short eye stalks meaning that the eyes sit just above the shell. Length of eye stalks helps scientists to distinguish the red-fingered marsh crab from another common species found in the mangroves, the semaphore crab.

The claws of red-fingered marsh crabs have bright red tips.

Red-fingered marsh crabs have short eye stalks.

Where do red-fingered marsh crabs live?

Red-fingered marsh crabs live on the mangrove forest floor. They construct burrows in the muddy intertidal zone. The burrows provide safety from predators during low tide. Crabs will often be seen scurrying sideways into the nearest burrow when threatened.

Red-fingered marsh crabs live in the mud of mangrove forests.

Red-fingered marsh crabs live in mangrove forests like this one in Lane Cove National Park.

What do red-fingered marsh crabs eat?

Red-fingered marsh crabs play a vital role in the recycling of nutrients in the mangrove ecosystem, much in the same way as worms do in terrestrial environments. Terrestrial means land.

Red-fingered marsh crabs are omnivorous meaning they eat both plant and animal material such as mangrove leaves, insects, small fish and other crabs. They use their big claws to help break down the food prior to eating.

Red-fingered marsh crabs eat mangrove leaves and insects.

What eats red-fingered marsh crabs?

Red-fingered marsh crabs are an important part of the food web in the mangrove ecosystem. Common predators include fish during high tide and shore birds during low tide.

How are red-fingered marsh crabs adapted to their environment?

Red-fingered marsh crabs use their large claws for feeding and defence.

Red-fingered marsh crabs are well adapted to living on land during low tide. Their hard exoskeleton helps store water which is flushed over their gills allowing them to breathe when they are out of the water. The exoskeleton also prevents the crabs from drying out and provides protection from any predators.

The bright green colour of the exoskeleton may be a camouflage as it resembles the seeds from nearby mangroves.

An ability to move quickly sideways and retreat down a burrow is an effective behaviour of red-fingered marsh crabs for escaping predators. Their flat bodies allow them to hide in small crevices.

Claws and an exoskeleton provide protection for red-fingered marsh crabs.

Red-fingered marsh crabs retreat to burrows when threatened.

Flat bodies allows red-fingered marsh crabs to hide in crevices.

Related fact sheets

More invertebrate and environment fact sheets

• Mangrove forest fact sheet – habitat overview where red-fingered marsh crabs live.
• Crustaceans fact sheet – broader crustacean group including crabs, slaters and other isopods.
• Semaphore crab - Another crab that lives in mangrove forests.
• Pill bugs fact sheet – land-living crustaceans that also help recycle nutrients in damp environments.

Learn with us