Blue Land Crab

This blue land crab with its asymmetrical claws sits guarding a den 200 yards from a Costa Rican beach. A den such as this requires constant tending to ensure the bottom reaches the underlying water table and fills with 1-2 liters of water, allowing the crab to stay moist. Blue land crabs cannot swim but return to the water, risking drowning, to release fertilized eggs into the salty water after carrying them in a sac on the female’s back for two months. This annual migration follows spring rains as well as the lunar cycle – females release their eggs within two days of a full moon. While the chances of survival for these eggs are minuscule, those that reach adulthood will have undergone 60 molts for their carapace (back) to reach 4.3 inches, and males may see their larger claw reach up to 5.9 inches long!

information from: http://www.sms.si.edu/IRLspec/Cardis_guanhu.htm

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