Scylla serrata
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Scylla serrata (often called mud crab or mangrove crab, although both terms are highly ambiguous, as well as black crab) is an economically important crab species found in the estuaries and mangroves of Africa, Australia and Asia. In their most common form, the shell colour varies from a deep, mottled green to very dark brown. Generally cooked with their shells on, when they moult their shells, they can be served as a seafood delicacy, one of many types of soft shell crab. Some consider them to be among the tastiest of crab species and they have a huge demand in South Asian countries where they are often bought alive in the markets. In the northern states of Australia and especially Queensland, mud crabs are relatively common and generally prized above other seafood within the general public.

These crabs are highly canniballistic in nature and when another crab undergoes moulting the hard shelled ones attack the moulting crabs and devour them. The females can give birth to 1 million offspring which can grow up to 3.5 kg in size and have a shell width of up to 24 cm wide. Some of the larger crabs can bite through a wooden broom handle^{citation needed}.

Mud crab can be killed by placing them in a freezer for up to two hours.[1]

Aquaculture

There has been a huge interest in the aquaculutre of this species due to their high demand/price, high flesh content and rapid growth rates in captivity. In addition they have a high tolerance to both nitrate  ¹ and ammonia (particularly NH₃) tolerance (twice that of the similar sized Portunus pelagicus), which is beneficial because ammonia-N is often the most limiting factor on closed aquaculture systems ². Their high ammonia-N tolerance may be attributed to various unique physiological responses which may have arisen due to their habitat preferences ². However their aquaculture has been limited due to the often low and unpredictable larvae survival. This may be due to inadequate nutrition, disease, "moult death syndrome" (due to their highly cannibalistic behaviour during the megalopa stage), inadequate protocols (e.g. sub-optimal environmental conditions) or a combination of all.

References

1. ^ N. Romano & C. Zeng (2007). Effects of potassium on nitrate mediated changes to osmoregulation in marine crabs. Aquatic Toxicology 85 202-208
2. ^ ^{a b} N. Romano & C. Zeng (2007). "Acute toxicity of ammonia and its effects on the haemolymph osmolality, ammonia-N, pH and ionic composition of early juvenile mud crabs, Scylla serrata (Forskål)". Comparative Biochemistry and Physiology a 148 (2): 278–285. doi:10.1016/j.cbpa.2007.04.018. 

External links

• Australia: Queensland government page on mangrove crab
• Catching, killing, cleaning and cooking mud crab
• Cycle of the mud crab