Decapod Crabs

Reproduction and Development

Decapod crabs are built like a folded-up lobster. The abdomen, which is equivalent to a tail, is folded up tightly underneath its body to form an abdominal flap.

When you turn a crab over and look underneath, you can tell a crab's sex by looking at its abdominal flap. A male crab has a small triangular flap, while a female crab has a broad oval-shaped abdominal flap.

When a male and female crab mate, many female decapod crabs can store the male sperm until her eggs are ready to be released. When the eggs are released, the stored sperm flows over them and they become fertilised.

The female crab holds the fertilised eggs in a big spongy mass between its abdominal flap and the body. The eggs are cemented to the pleopods, which are small legs, creating the "berried" appearance.

To keep the eggs healthy, the female crab continually "waves" water over the eggs with the pleopods.

When the eggs hatch into zoea larvae, they drift away in the ocean currents as plankton. As the juvenile crab grows in size, it goes through a series of moults, each larval stage changing form and function as it grows in a process called metamorphosis.

At each moult more segments are added to the end (posterior), and the feathered limbs are replaced by the clawed limbs. The megalops stage more closely resembles the adult decapod crab.

Crabs

Tubercled Crab
Reef Crab
Smooth-handed Crab
Variegated Shore Crab
Red Bait Crab
Sowrie Crab
Mudflat Sentinal Crab
Smooth Shore Crab
Seaweed-decorator Crab
Crab reproduction
Crab parasitism

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