The Caridea, commonly known as caridean shrimp or true shrimp, from Ancient Greek , ( karís, karídos, “shrimp”), are an infraorder of shrimp within the order Decapoda. This infraorder contains all species of true shrimp. They are found widely around the world in both fresh water and seawater. Many other animals with similar names – such as the mud shrimp of Axiidea and the boxer shrimp of Stenopodidea – are not true shrimp, but many have evolved features similar to true shrimp.
Biology
Carideans are found in every kind of aquatic habitat, with the majority of species being marine. Around a quarter of the described species are found in
fresh water, however, including almost all the members of the species-rich family
Atyidae and the
Palaemonidae subfamily
Palaemoninae.
They include several commercially important species, such as
Macrobrachium rosenbergii, and are found on every continent except
Antarctica.
The marine species are found at depths to ,
and from the tropics to the polar regions.
In addition to the great variety in habitat, carideans vary greatly in form, from species a few millimetres long when fully grown,
Most carideans are omnivore, but some are specialised for particular modes of feeding. Some are filter feeding, using their seta (bristly) legs as a sieve; some scrape algae from rocks. The snapping shrimp of the genus Alpheus snap their claws to create a shock wave that stuns prey. Many cleaner shrimp, which groom reef fish and feed on their parasites and necrosis, are carideans.
Lifecycle
Unlike
Dendrobranchiata, Carideans brood their eggs rather than releasing them into the water. Caridean larvae undergo all naupliar development within the egg, and eclose as a
zoea. The zoea stage feeds on
phytoplankton. There can be as few as two zoea stages, (e.g. some freshwater
Palaemonidae), or as many as 13, (e.g. some
Pandalidae). The post-zoeal larva, often called a decapodid, resembles a miniature adult, but retains some larval characteristics. The decapodid larva will metamorphose a final time into a post-larval juvenile: a young shrimp having all the characteristics of adults.
Most adult carideans are
benthic animals living primarily on the sea floor.
Common species include Pandalus borealis (the "pink shrimp"), Crangon crangon (the "brown shrimp") and the snapping shrimp of the genus Alpheus. Depending on the species and location, they grow from about long, and live between 1.0 and 6.5 years.
Commercial fishing
The most significant commercial species among the carideans is
Pandalus borealis,
[ Pandalus borealis (Krøyer, 1838) FAO, Species Fact Sheet. Retrieved September 2012.] followed by
Crangon crangon.
[ Crangon crangon (Linnaeus, 1758) FAO, Species Fact Sheet. Retrieved September 2012.] The wild-capture production of
P. borealis is about ten times that of
C. crangon. In 1950, the position was reversed, with the capture of
C. crangon about ten times that of
P. borealis.
In 2010, the global aquaculture of all shrimp and prawn species (3.5 million tonnes) slightly exceeded the global wild capture (3.2 million tonnes).
Systematics and related taxa
Shrimp of the infraorder Caridea are more closely related to
and
than they are to the members of the sub-order
Dendrobranchiata (prawns).
Biologists distinguish these two groups based on differences in their
gill structures. The gill structure is lamellar in carideans but branching in dendrobranchiates. The easiest practical way to separate true shrimp from dendrobranchiates is to examine the second
Somite. The second segment of a carideans overlaps both the first and the third segment, while the second segment of a dendrobranchiate overlaps only the third segment.
They also differ in that carideans typically have two pairs of chelae (claws), while dendrobranchiates have three.
A third group, the
Stenopodidea, contains around 70 species and differs from the other groups in that the third pairs of legs is greatly enlarged.
Procarididea are the sister group to the Caridea, comprising only eleven species.
The cladogram below shows Caridea's relationships to other relatives within Decapoda, from analysis by Wolfe et al., 2019.
The below cladogram shows the internal relationships of eight selected families within Caridea, with the Atyidae (freshwater shrimp) being the most basal:
Taxonomy
The infraorder Caridea is divided into 15 superfamilies:
Fossil record
The
fossil record of the Caridean is sparse, with only 57 exclusively fossil species known.
The earliest of these cannot be assigned to any family, but date from the
Lower Jurassic and
Cretaceous.
A number of extinct genera cannot be placed in any superfamily:
-
Acanthinopus Pinna, 1974
-
Alcmonacaris Polz, 2009
-
Bannikovia Garassino & Teruzzi, 1996
-
Blaculla Münster, 1839
-
Buergerocaris Schweigert & Garassino, 2004
-
Gampsurus von der Marck, 1863
-
Hefriga Münster, 1839
-
Leiothorax Pinna, 1974
-
Parvocaris Bravi & Garassino, 1998
-
Pinnacaris Garassino & Teruzzi, 1993
See also
External links
