The mud crab or mangrove crab is a species of crab dwelling principally in estuaries and mangroves throughout Africa, Australia and Asia. Their colour varies from green to dark brown. Adults can reach a maximum of 25 to 28 centimeters and weigh 2 to 3 kilograms, and typical adult sizes are between 15 to 18 centimeters for males. The animal has a carapace (protective shell) with four blunt frontal teeth. Its robust claws are strong and have several spines. The rear legs are flattened to allow swimming. The mud crab is an extremely popular animal in aquaculture production.
 Sealife Base. n.d. Scylla serrata. Accessed April 2018. http://www.sealifebase.org/summary/Scylla-serrata.html
As its name suggests, S. serrata is found mainly in mangrove ecosystems and estuaries. S. serrata is principally a carnivore: the animal preys on small invertebrates such as molluscs, crustaceans, as well as on small quantities of detritus and plant material. When they reach 9 centimeters width, the species become sexually mature. Males grab females with their chelipeds (claws) and first pair of legs and can carry them for several days until they molt. At this point, the females are turned over so that the males can deliver their spermatozoa. These may be retained by the females for several weeks before being used for fertilization. This copulation can lead to multiple clutches of up to 2 million eggs each. Egg-bearing females tend to migrate offshore (in the nearby sea) for up to 50 kilometers where they will spawn.
S. serrata is not currently evaluated by the IUNC Red List of Threatened Species. The mud crab being common throughout the Indo-Pacific, its survival is not presently threatened. However, in some areas, it is heavily overfished, and this practice has warranted the establishment of marine protected areas in some locations. The crab may also suffer from habitat destruction.
 FAO. 2018. Scylla serrata. Accessed April 2018. http://www.fao.org/fishery/culturedspecies/Scylla_serrata/en