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[15] [16] The free-swimming tiny zoea larvae can float and take advantage of water currents. They have a spine, which probably reduces the rate of predation by larger animals. The zoea of most species must find food, but some crabs provide enough yolk in the eggs that the larval stages can continue to live off the yolk.
Only a few land crabs, including certain Geosesarma species, have direct development (the mother carries the eggs until they have become tiny, fully developed crabs), and these do not need access to water to breed. [5] [6] Many crabs belonging to the family Potamidae, which contains mostly freshwater crabs, have developed a semiterrestrial (for ...
The colonisation of fresh water has required crabs to alter their water balance; freshwater crabs can reabsorb salt from their urine, and have various adaptations to reduce the loss of water. [4] In addition to their gills, freshwater crabs have a "pseudolung" in their gill chamber that allows them to breathe in air. [4]
Coconut crabs live alone in burrows and rock crevices, depending on the local terrain. They dig their own burrows in sand or loose soil. During the day, the animal stays hidden to reduce water loss from heat. The coconut crabs' burrows contain very fine yet strong fibres of the coconut husk which the animal uses as bedding. [43]
This suggests that C. maenas is unable to cross deeper water. [25] Females can produce up to 185,000 eggs, and larvae develop offshore in several stages before their final moult to juvenile crabs in the intertidal zone. [26] Young crabs live among seaweeds and seagrasses, such as Posidonia oceanica, until they reach adulthood. [27]
Eggs carried by the female's pleopods are fertilized through indirect sperm transfer. [14] They can carry 7,957 to 9,456 eggs, holding them for up to 5 weeks. [15] Oyster crab females begin producing one batch of eggs the first year and after the second or third year, they can increase to two batches. [15] Once the eggs have developed into free ...
The carapace of G. ruricola grows in width at a rate of about 1 in (25 mm) per year, with the crabs reaching maturity after 5 years, and living for up to 10 years in total. [6] G. ruricola crabs have a number of adaptations to terrestrial life, mostly regarding water conservation. They are nocturnal, to prevent the hot sun from drying them out.
Horseshoe crabs primarily live at the water's bottom but they can swim if needed. In the modern day, their distribution is limited, only found along the east coasts of North America and South Asia. Horseshoe crabs are often caught for their blood, which contains Limulus amebocyte lysate, a chemical used to detect bacterial endotoxins.