Lophogastrida
Encyclopedia
Lophogastrida is an order
of malacostraca
n crustacean
s in the superorder Peracarida
. They are shrimp
-like animals that mostly inhabit the relatively deep pelagic waters of the oceans throughout the world.
Most lophogastridan species are 1–8 cm (0.393700787401575–3.1 ) long, but Gnathophausia ingens can be up to 35 cm (13.8 in), probably the largest pelagic crustacean in the world. Some 56 extant species in total are currently known. They are classified into three families and nine genera.
The external features of the Lophogastrida include stalked compound eyes, a carapace
that covers the head and thoracic
segments, and a muscular cylindrical abdomen
. The carapace often extends beyond the head to form an elongated rostrum
. As with other Peracarida, the Lophogastrida are separated from true shrimp in that they carry their developing embryos and young in a brood pouch
, or marsupium, and they thus lack a separate planktonic larval stage.
Previously, the Lophogastrida were classified as a suborder of a broader peracaridan order Mysidacea
, together with the Mysida (and Stygiomysida), but that taxon is currently generally abandoned. Features distinguishing the Lophogastrida from the Mysida include the absence of statocyst
s in their uropods, and the presence of well-developed biramous pleopods on the abdomen, as well as molecular characters.
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of malacostraca
Malacostraca
Malacostraca is the largest of the six classes of crustaceans, containing over 25,000 extant species, divided among 16 orders. Its members display a greater diversity of body forms than any other class of animals, and include crabs, lobsters, shrimp, krill, woodlice, scuds , mantis shrimp and many...
n crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s in the superorder Peracarida
Peracarida
The superorder Peracarida is a large group of malacostracan crustaceans, having members in marine, freshwater, and terrestrial habitats. They are chiefly defined by the presence of a brood pouch, or marsupium, formed from thin flattened plates borne on the basalmost segments of the legs Other...
. They are shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
-like animals that mostly inhabit the relatively deep pelagic waters of the oceans throughout the world.
Most lophogastridan species are 1–8 cm (0.393700787401575–3.1 ) long, but Gnathophausia ingens can be up to 35 cm (13.8 in), probably the largest pelagic crustacean in the world. Some 56 extant species in total are currently known. They are classified into three families and nine genera.
The external features of the Lophogastrida include stalked compound eyes, a carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
that covers the head and thoracic
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
segments, and a muscular cylindrical abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
. The carapace often extends beyond the head to form an elongated rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
. As with other Peracarida, the Lophogastrida are separated from true shrimp in that they carry their developing embryos and young in a brood pouch
Brood pouch (Peracarida)
The marsupium or brood pouch, is a characteristic feature of Peracarida, including the orders Amphipoda, Isopoda and Cumacea. It is an egg chamber formed by oostegites, which are appendices which are attached to the coxae of the first pereiopods...
, or marsupium, and they thus lack a separate planktonic larval stage.
Previously, the Lophogastrida were classified as a suborder of a broader peracaridan order Mysidacea
Mysidacea
Mysida is a group of small, shrimp-like crustaceans, an order in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch, or marsupium, in females. Mysids are mostly found in marine waters throughout the world, but are also important in...
, together with the Mysida (and Stygiomysida), but that taxon is currently generally abandoned. Features distinguishing the Lophogastrida from the Mysida include the absence of statocyst
Statocyst
The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, echinoderms, cephalopods, and crustaceans. A similar structure is also found in Xenoturbella. The statocyst consists of a sac-like structure containing a mineralised mass and numerous...
s in their uropods, and the presence of well-developed biramous pleopods on the abdomen, as well as molecular characters.