Prawns
Prawns are decapod crustaceans, belonging to the sub-order Dendrobranchiata. The term "prawn" is also used in various contexts for other animals, especially caridean shrimp. They are found worldwide and include commercially significant species, such as the whiteleg shrimpLitopenaeus vannamei, white shrimp Litopenaeus setiferus, Indian prawn Fenneropenaeus indicusand tiger prawn Penaeus monodon.
Characteristics
Prawns are similar in appearance to other small, swimming decapods, such as shrimp (Caridea) and boxer shrimp (Stenopodidea), but can be distinguished by the gill structure which is branching in prawns (hence the name, dendro = "tree"; branchia = "gill"), but is lamellar in shrimp. One exception is the family Luciferidae, which lack gills as adults. Prawns usually have claws on three pairs of their legs, while shrimp have claws on only two. The sister taxon to Dendrobranchiata is Pleocyemata, which contains all the true shrimp, crabs, lobsters, etc. Unlike almost all other decapods, prawns do not brood their eggs on the pleopods, but release the eggs into the water after fertilisation.
Classification
Living prawns are divided among seven families, five in the superfamily Penaeoidea, and two in theSergestoidea, although molecular evidence disagrees with some aspects of the current classifications. Collectively, these include 540 extant species, and nearly 100 exclusively fossil species. A further two families are known only from fossils.
Prawns are decapod crustaceans, belonging to the sub-order Dendrobranchiata. The term "prawn" is also used in various contexts for other animals, especially caridean shrimp. They are found worldwide and include commercially significant species, such as the whiteleg shrimpLitopenaeus vannamei, white shrimp Litopenaeus setiferus, Indian prawn Fenneropenaeus indicusand tiger prawn Penaeus monodon.
Characteristics
Prawns are similar in appearance to other small, swimming decapods, such as shrimp (Caridea) and boxer shrimp (Stenopodidea), but can be distinguished by the gill structure which is branching in prawns (hence the name, dendro = "tree"; branchia = "gill"), but is lamellar in shrimp. One exception is the family Luciferidae, which lack gills as adults. Prawns usually have claws on three pairs of their legs, while shrimp have claws on only two. The sister taxon to Dendrobranchiata is Pleocyemata, which contains all the true shrimp, crabs, lobsters, etc. Unlike almost all other decapods, prawns do not brood their eggs on the pleopods, but release the eggs into the water after fertilisation.
Classification
Living prawns are divided among seven families, five in the superfamily Penaeoidea, and two in theSergestoidea, although molecular evidence disagrees with some aspects of the current classifications. Collectively, these include 540 extant species, and nearly 100 exclusively fossil species. A further two families are known only from fossils.
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