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Crayfish, sometimes called crawfish, or crawdads are freshwater crustaceans resembling small lobsters, to which they are closely related. They are found in bodies of fresh water that do not freeze to the bottom, and which have shelter against predators. Some crayfish have been found living as much as 3 m (10 feet) underground.


Moulting: Crayfish need to moult as they grow because their hard exoskeletons do not allow much room for expansion. Baby crayfish can moult on a daily basis but as they grow older, the regularity of moults decreases to a period of weeks or even months. The first few days after a moult, a crayfish's skin is very soft and it is very vulnerable to attacks from other animals and crayfish.

Early Signs: The early signs of moulting include lack of appetite and a slowdown in activity. During this period the crayfish ingests calcium into an internal organ, not into the exoskeleton.

Hiding: When the crayfish is ready to moult, it will try to find a hiding spot. Then it will move onto its back and begin fanning its pincers, legs and swimmerets (under the tail) in order to get as much oxygen as possible. The carapace will begin to crack behind the head; the new appendages then pierce the old shell; and then after about five minutes, a sudden, violent movement will detach the old shell from the crayfish.

Vulnerable: The freshly moulted crayfish will invariably be larger as part of the growing process, but is vulnerable on several fronts. Firstly, the shell is very soft and vulnerable to predators, including other crayfish and fish. The crayfish needs to eat the old shell to replace the lost calcium and stengthen the weakened carapace.


Pets: Crayfish are sometimes kept as pets in freshwater aquariums. They prefer foods like shrimp pellets or various vegetables but will eat most leftover fish food. They also have a big appetite for plants and will eat most aquarium plants. They can be aggressive and may attempt to eat fish. However, crayfish are actually fairly shy and may often attempt to hide under leaves or rocks. If you are going to keep a crayfish as a pet, remember to give it some hiding space. At night, some fish become less energetic and settle to the bottom. The crayfish might see it as a danger and hurt or kill it with its claws. Crayfish are great escape artists and may try to climb out of the tank so any holes in the hood should be covered. In nations where imported alien crayfish are a danger to rivers, such as England, catching and keeping crayfish as pets is one of the main means of the spread of destructive species - since they are often flung back into a different river.

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 Kingdom: Animalia

 Phylum: Arthropoda

 Subphylum: Crustacea

 Class: Malacostraca

 Order: Decapoda

 Suborder: Pleocyemata

 Infraorder: Astacidea