Christmas Island Red Crabs
Gecarcoidea natalis (Pocock, 1888)The Christmas Island red crab is by far the most obvious of the 14 species of land crabs found on Christmas Island. It is estimated that 120 million of these bright red land crabs live in their preferred shady sites all over the island.
Physical Characteristics of Christmas Island Red Crabs
Bright red is the common colour but there are the occasional orange specimens and more rarely some purple animals. They are a big crab. An adult body shell (or carapace) may measure up to 116mm across. The Christmas Island red crabs' carapace is round shouldered and encloses their lungs and gills. Their claws are usually of equal size unless one is a regrowing claw. Males grow larger overall than females, while females have a much broader abdomen and usually have smaller claws than males. However young Christmas Island red crabs all have the characteristic narrow abdomen of the male. The broader abdomen on the female Christmas Island red crab only becomes apparent in the third year of growth.Christmas Island red crabs grow slowly, reaching about 40mm in carapace width after 4-5 years. They are sexually mature at this age and begin to participate in the breeding migrations.
The Christmas Island red crabs moult their shells regularly during their early growth phases to match their increasing body size. Moulting usually takes place in the protected moist environment of their burrows. Mature Christmas Island red crabs probably moult only once a year, as their growth rate slows.
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