Crustacea Fossil range: Cambrian to recent Abludomelita obtusata, an amphipod Scientific classification Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Brünnich, 1772 Classes & Subclasses Branchiopoda Phyllopoda Sarsostraca Remipedia Cephalocarida Maxillopoda Thecostraca Tantulocarida Branchiura Pentastomida Mystacocarida Copepoda Ostracoda Myodocopa Podocopa Malacostraca Phyllocarida Hoplocarida Eumalacostraca

The nauplius larva of a dendrobranchiate

Porcellio scaber, the common rough woodlouse, a terrestrial crustacean

Pollicipes polymerus, the gooseneck barnacle

Glyphea pseudastacus, a fossil glypheoid

The crustaceans (Crustacea) are a large group of arthropods, comprising almost 52,000 described species ,^[1] and are usually treated as a subphylum . The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with Amphipoda (amphipods are an order of animals that includes over 7000 described Species of Shrimp -like Crustaceans ranging from 1 mm to 140 mm Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " Morten Thrane Brünnich ( September 30, 1737 - September 19, 1827) was a Danish Zoologist and Mineralogist. A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. Branchiopoda is a group of primitive and primarily Fresh water Crustaceans mostly resembling Shrimp. Triops longicaudatus (commonly called longtail tadpole shrimp, American tadpole shrimp or rice tadpole shrimp) is a freshwater Crustacean Fairy shrimp (Anostraca are branchiopods that include Brine shrimp. Remipedia is a class of blind Crustaceans found in deep caves connected to salt water in Australia and the Caribbean Sea. Cephalocarida is a class inside the Subphylum Crustacea that comprises only about nine Shrimp -like benthic Species. Maxillopoda is a class under the Phylum Arthropoda. It is also a class of Crustaceans (subphylum Crustacea) and the class is Thecostraca are a group of marine Invertebrates containing about 1320 described species Tantulocarida is a small subclass of the class Maxillopoda ( copepods and Barnacles) that consists of about 1200 Species. Branchiura, commonly called carp lice or fish lice are a group of parasitic Crustaceans of uncertain position within the Maxillopoda The Pentastomida are a group of parasitic Invertebrates commonly known as tongue worms due to the resemblance of some species to a vertebrate Tongue Mystacocarida are interstitial Crustaceans part of the Meiobenthos. Copepods are a group of small Crustaceans found in the sea and nearly every freshwater habitat and they constitute the biggest source of protein in the oceans Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance Traditionally the Myodocopa and Podocopa have been classified as subclasses within the class Ostracoda although there is some question about how closely related The Podocopa are a subclass of Ostracods. This subclass can be differentiated from the other subclass ( Myodocopa) by the morphology of the second antenna the The Malacostraca (Greek "soft shell" are the largest class of Crustaceans and include most of the animals that non-experts recognize as crustaceans including Leptostraca (from the Greek words for thin and shell   is an order of small marine Crustaceans Its members including the Mantis shrimp or stomatopods are marine Crustaceans the members of the order Stomatopoda. The Eumalacostraca (Greek "true soft shell" are a subclass of Crustaceans containing almost all living Malacostracans about 22000 described species Prawns are Crustaceans belonging to the sub-order Dendrobranchiata   Porcellio scaber (otherwise known as the common rough woodlouse or simply rough woodlouse) is a species of Woodlouse. Goose barnacles (suborder Lepadomorpha) sometimes Gooseneck barnacles, are filter-feeding Crustaceans that live attached to hard surfaces of The Glypheoidea (containing the glypheoid lobsters is a group of Lobster -like decapod Crustaceans which forms an important part of fossil faunas Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. In life a subphylum is a Taxonomic rank intermediate between phylum and superclass. ^[2] They include various familiar animals, such as crabs, lobsters, crayfish, shrimp and barnacles. Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy Clawed lobsters compose a family ( Nephropidae, sometimes also Homaridae) of large marine Crustaceans Lobsters are economically important as Crayfish, crawfish, crawdads, or crodgers are freshwater Crustaceans resembling small Lobsters to which they are closely True shrimp are swimming decapod Crustaceans classified in the Infraorder Caridea, found widely around the world in both fresh A barnacle is a type of Arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence distantly related to The majority of them are aquatic, living in either marine or fresh water environments, but a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs and woodlice. Marine is an Umbrella term. As an adjective it is usually applicable to things relating to the Sea or Ocean, such as Marine biology, Marine Freshwater is a word that refers to bodies of water such as Ponds lakes rivers and streams containing low concentrations of dissolved Salts and other Total dissolved An adaptation is a characteristic of an Organism that has been favored by Natural selection and Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy The Genus Coenobita contains about thirteen Species of terrestrial Hermit crabs They are able to live on land because of their Woodlice (known by many Common names see below) are Crustaceans with a rigid segmented long Exoskeleton and fourteen jointed limbs Crustaceans are among the most successful animals, and are as abundant in the oceans as much as insects are on land. Over half of animals in the world are marine copepod crustaceans. Copepods are a group of small Crustaceans found in the sea and nearly every freshwater habitat and they constitute the biggest source of protein in the oceans The majority of crustaceans are also motile, moving about independently, although a few taxonomic units are parasitic and live attached to their hosts (including sea lice, fish lice, whale lice, tongue worms, and Cymothoa exigua, all of which may be referred to as "crustacean lice"), and adult barnacles live a sessile life — they are attached headfirst to the substrate and cannot move independently. Motility is a biological term which refers to the ability to move spontaneously and actively consuming energy in the process Parasitism is a type of symbiotic relationship between Organisms of different Species. A sea louse (plural sea lice) is a name given to any oceanic stinging Larvae, which includes many juvenile Cnidarians (notably Linuche unguiculata Branchiura, commonly called carp lice or fish lice are a group of parasitic Crustaceans of uncertain position within the Maxillopoda The Whale louse is a parasitic Crustacean of the family Cyamidae, the only family in the infraorder Cyamida. The Pentastomida are a group of parasitic Invertebrates commonly known as tongue worms due to the resemblance of some species to a vertebrate Tongue Cymothoa exigua is a parasitic Crustacean of the family Cymothoidae. Sessile is a term in Biology with two distinct meanings In botany and medicine In Botany, sessile means "without a stalk Although most crustaceans are small, their morphology varies greatly and they include such large animals as lobsters 70 cm long and spider crabs with a leg span of nearly 4 m. A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International ^[3]

The scientific study of crustaceans is known as carcinology. Other names for carcinology are malacostracology, crustaceology and crustalogy, and a scientist who works in carcinology is a carcinologist, crustaceologist or crustalogist. A scientist, in the broadest sense refers to any person that engages in a systematic activity to acquire Knowledge or an individual that engages in such practices A carcinologist is a Scientist who studies Crustaceans or is otherwise involved in carcinology (the science of crustaceans

Structure of crustaceans

Crustaceans have three distinct body parts: head, thorax, and abdomen (or pleon), although the head and thorax may fuse to form a cephalothorax, an excellent example of tagmatization. Cephalon Inc ( is a US biopharmaceutical company co-founded in 1987 by Dr The thorax is a division of an Animal 's body that lies between the head and the Abdomen. In Vertebrates such as Mammals the abdomen (belly constitutes the part of the body between the Thorax (chest and Pelvis. The cephalothorax (call prosoma in some groups is an anatomical term used in Arachnids and Malacostracan Crustaceans for the In Invertebrate Biology, a tagma (plural tagmata) is a specialized grouping of Arthropodan segments such as the The head bears two pairs of antennae, three pairs of mouthparts, and usually eyes (two compound eyes, an unpaired eye, or both). Antennae (singular antenna) are paired Appendages connected to the front-most segments of Arthropods In Crustaceans they are The mouthparts of Arthropods have evolved into a number of forms each adapted to a different style or mode of feeding The thorax and pleon bear a number of lateral appendages, including the gills, and the tail ends with a telson. An appendage in the broadest sense is an additional or subsidiary part existing on or added to something which can generally still function if the appendage has never existed or A gill is an anatomical structure found in many aquatic organisms The telson is the last division of the body of a Crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas Crustacean appendages are used for swimming, crawling, and feeding. They may be highly modified as jaws and other structures, or may be lost. Smaller crustaceans respire through their body surface by diffusion ,^[4] and larger crustaceans respire with gills or, as shown by Birgus latro, with abdominal lungs . In Animal physiology, respiration is the transport of Oxygen from the outside air to the cells within tissues and the transport of Carbon dioxide Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement A gill is an anatomical structure found in many aquatic organisms The coconut crab ( Birgus latro) is the largest land-living Arthropod in the world ^[5] Both systems (diffusion and gills) were being used by various crustaceans as early as the Middle Cambrian . The Middle Cambrian (also known as Albertan, Acadian, St David's, or Saint David's) is the second of three geological epochs of the ^[6]

As arthropods, crustaceans have a stiff exoskeleton, which must be shed to allow the animal to grow (ecdysis or molting). Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " An exoskeleton is an external Skeleton that supports and protects an animal's body in contrast to the internal Endoskeleton of for example a Human. Ecdysis is the Molting of the Cuticula in Arthropods and related groups ( Ecdysozoa) Various parts of the exoskeleton may be fused together; this is particularly noticeable in the carapace, the thick dorsal shield seen on many crustaceans that often forms a protective chamber for the gills. A carapace is a dorsal section of an Exoskeleton or shell in a number of animal groups Crustacean appendages are typically biramous, meaning they are divided into two parts; this includes the second pair of antennae, but not the first, which is uniramous. An appendage in the broadest sense is an additional or subsidiary part existing on or added to something which can generally still function if the appendage has never existed or The arthropod leg is a form of jointed Appendage of Arthropods usually used for Walking. The arthropod leg is a form of jointed Appendage of Arthropods usually used for Walking. There is some doubt whether this is a derived state, as had been traditionally assumed, or whether it may be a primitive state, with the branching of the limbs being lost in all extant arthropod groups except the crustaceans. One piece of evidence supporting the latter view is the biramous nature of trilobite limbs . Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita. ^[7]

The main body cavity is an expanded circulatory system, through which blood is pumped by a heart located near the dorsum. The alimentary canal consists of a straight tube that often has a gizzard-like gastric mill for grinding food and a pair of digestive glands that absorb food. Structures that function as kidneys are located near the antennae. A brain exists in the form of ganglia close to the antennae, and a collection of major ganglia is found below the gut. ^[3]

Despite their diversity of form, crustaceans are united by the special larval form known as the nauplius. A larva ( Latin; plural larvae) is a juvenile form of Animal with indirect development, undergoing Metamorphosis (for example A nauplius (plural nauplii) is the first Larva of animals classified as Crustaceans (subphylum of Arthropoda)

Although a few are hermaphroditic, most crustaceans have separate sexes, which are distinguished by appendages on the abdomen called swimmerets or, more technically, pleopods (penis). A hermaphrodite is an organism having both male and female reproductive organs The decapod Crustacean such as a crab lobster shrimp or prawn is made up of nineteen Body segments grouped into two main body parts the Cephalothorax The first (and sometimes the second) pair of pleopods are specialised in the male for sperm transfer. Many terrestrial crustaceans (such as the Christmas Island red crab) mate seasonally and return to the sea to release the eggs. The Christmas Island red crab ( Gecarcoidea natalis) is a Species of terrestrial Crab endemic to Christmas Island and the Others, such as woodlice lay their eggs on land, albeit in damp conditions. Woodlice (known by many Common names see below) are Crustaceans with a rigid segmented long Exoskeleton and fourteen jointed limbs In many decapods, the females retain the eggs until they hatch into free-swimming larvae. The decapods or Decapoda ( literally means "ten footed") are an order of Crustaceans within the class Malacostraca, including many

Taxonomy

Although the classification of crustaceans has been quite variable, the system used by Martin and Davis ^[1] is the most authoritative, and largely supersedes earlier works.

Six classes of crustaceans are generally recognised:

• Branchiopoda — including brine shrimp (Artemia) and Triops (Notostraca)
• Remipedia — a small class restricted to deep caves connected to salt water, called anchialine caves
• Cephalocarida — horseshoe shrimp
• Maxillopoda — various groups, including barnacles and copepods. Branchiopoda is a group of primitive and primarily Fresh water Crustaceans mostly resembling Shrimp. Brine shrimp are a species of aquatic Crustaceans of the Genus Artemia. Members of the order Notostraca (colloquially referred to as notostracans, called Triops, tadpole shrimp or shield shrimp Remipedia is a class of blind Crustaceans found in deep caves connected to salt water in Australia and the Caribbean Sea. Cephalocarida is a class inside the Subphylum Crustacea that comprises only about nine Shrimp -like benthic Species. Maxillopoda is a class under the Phylum Arthropoda. It is also a class of Crustaceans (subphylum Crustacea) and the class is A barnacle is a type of Arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence distantly related to Copepods are a group of small Crustaceans found in the sea and nearly every freshwater habitat and they constitute the biggest source of protein in the oceans It contains Mystacocarida and Branchiura, which are sometimes treated as their own classes. Mystacocarida are interstitial Crustaceans part of the Meiobenthos. Branchiura, commonly called carp lice or fish lice are a group of parasitic Crustaceans of uncertain position within the Maxillopoda
• Ostracoda — small animals with bivalve shells
• Malacostraca — the largest class, with the largest and most familiar animals, such as crabs, lobsters, shrimp, krill and woodlice. Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance The Malacostraca (Greek "soft shell" are the largest class of Crustaceans and include most of the animals that non-experts recognize as crustaceans including Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy Clawed lobsters compose a family ( Nephropidae, sometimes also Homaridae) of large marine Crustaceans Lobsters are economically important as True shrimp are swimming decapod Crustaceans classified in the Infraorder Caridea, found widely around the world in both fresh Krill are a type of Shrimp -like marine Invertebrate animal These small Crustaceans are important organisms of the Zooplankton, particularly Woodlice (known by many Common names see below) are Crustaceans with a rigid segmented long Exoskeleton and fourteen jointed limbs

The exact relationships of the Crustacea to other taxa are not yet entirely clear. Under the Pancrustacea hypothesis ,^[8] Crustacea and Hexapoda (insects and allies) are sister groups. Pancrustacea is a proposed Taxon, comprising all Crustaceans and hexapods   The subphylum Hexapoda (from the Greek for six legs) constitutes the largest (in terms of number of species grouping of Arthropods and includes the Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described Cladistics is the hierarchical classification of Species based on evolutionary ancestry Studies using DNA sequences tend to show a paraphyletic Crustacea, with the insects (but not necessarily other hexapods) nested within that clade. A DNA sequence or genetic sequence is a succession of letters representing the Primary structure of a real or hypothetical DNA Molecule In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor

Fossil record

Those crustaceans that have soft exoskeletons reinforced with calcium carbonate, such as crabs and lobsters, tend to preserve well as fossils, but many crustaceans have only thin exoskeletons. An exoskeleton is an external Skeleton that supports and protects an animal's body in contrast to the internal Endoskeleton of for example a Human. Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3 Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy Clawed lobsters compose a family ( Nephropidae, sometimes also Homaridae) of large marine Crustaceans Lobsters are economically important as Most of the fossils known are from coral reef or shallow sea floor environments, but many crustaceans live in open seas, on deep sea floors or in burrows. Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water A burrow is a hole or tunnel dug into the ground by an Animal to create a space suitable for habitation temporary refuge or as a byproduct of locomotion Crustaceans tend, therefore, to be more rare in the fossil record than trilobites. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita. Some crustaceans are reasonably common in Cretaceous and Caenozoic rocks, but barnacles have a particularly poor fossil record, with very few specimens from before the Mesozoic era. The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of The Cenozoic (also Caenozoic or Cainozoic) Era (ˌsiːnəˈzoʊɪk/ /ˌsɛn- (meaning "new life" ( Greek ( kainos) "new" The Mesozoic Era is one of three geologic eras of the Phanerozoic eon.

The Late Jurassic lithographic limestones of Solnhofen, Bavaria, which are famous as the home of Archaeopteryx, are relatively rich in decapod crustaceans, such as Eryon (an eryonoid), Aeger (a prawn) or Pseudastacus (a lobster). The Late Jurassic (or Malm) Epoch of the Jurassic Period is the unit of geologic time from 161 The Solnhofen limestone is a Jurassic Konservat-Lagerstätte that preserves a rare assemblage of Fossilized organisms some of which such as sea jellies Solnhofen is a municipality in the district of Weißenburg-Gunzenhausen in the region of Franconia in the Land of Bavaria in Bavaria ( German:, with an area of 70553 Km² (27241 square miles and almost 12 Archaeopteryx, sometimes referred to by its German name Urvogel ("original bird" or "first bird" is the earliest and most primitive Bird The decapods or Decapoda ( literally means "ten footed") are an order of Crustaceans within the class Malacostraca, including many The family Polychelidae contains thirty-four Species of blind, Benthic Lobster -like Crustaceans They are found throughout the Prawns are Crustaceans belonging to the sub-order Dendrobranchiata   Clawed lobsters compose a family ( Nephropidae, sometimes also Homaridae) of large marine Crustaceans Lobsters are economically important as The "lobster bed" of the Greensand formation from the Cretaceous period, which occurs at Atherfield on the Isle of Wight, contains many well preserved examples of the small glypheoid lobster Mecochirus magna. Greensand is an olive-green coloured Sandstone rock which is commonly found in narrow bands particularly associated with bands of Chalk and The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of Little Atherfield is a Village on the Isle of Wight. The Isle of Wight is situated off the south coast of England. The Isle of Wight is an English Island and county in the English Channel between three and five miles (8 km from the south coast of the The Glypheoidea (containing the glypheoid lobsters is a group of Lobster -like decapod Crustaceans which forms an important part of fossil faunas Crabs have been found at a number of sites, such as the Cretaceous Gault clay and the Eocene London clay. The Gault Clay is a formation of stiff blue Clay deposited in a calm fairly deep water marine environment during the Lower Cretaceous Period (Upper and Middle The Eocene epoch (558 ± 02 - 339 ± 01 Ma) is a major division of the Geologic timescale and the second epoch of the Palaeogene period in The London Clay is a Marine geological formation of Ypresian (Lower Eocene Epoch c

Consumption

Crustacean output in 2005

Many crustaceans are consumed by humans, and nearly 10,000,000 tons were produced in 2005 . Units of mass There are three similar units of Mass called the ton: Long ton (simply ton in countries such as the United ^[9] The vast majority of this output is of decapod crustaceans: crabs, lobsters, shrimp and prawns. The decapods or Decapoda ( literally means "ten footed") are an order of Crustaceans within the class Malacostraca, including many Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy Clawed lobsters compose a family ( Nephropidae, sometimes also Homaridae) of large marine Crustaceans Lobsters are economically important as True shrimp are swimming decapod Crustaceans classified in the Infraorder Caridea, found widely around the world in both fresh Prawns are Crustaceans belonging to the sub-order Dendrobranchiata   Over 70% by weight of all crustaceans caught for consumption are shrimp and prawns, and over 80% is produced in Asia, with China alone producing nearly half the world's total. Non-decapod crustaceans are not widely consumed, with only 130,000 tons of krill being caught, despite krill having one of the greatest biomasses on the planet. Krill are a type of Shrimp -like marine Invertebrate animal These small Crustaceans are important organisms of the Zooplankton, particularly Biomass refers to living and recently dead Biological material that can be used as fuel or for industrial production

References

General references

• Frederick Schram (1986). Frederick Robert Schram (born August 11, 1943 in Chicago, Illinois) is an American Palaeontologist and Carcinologist Crustacea. Oxford University Press, 620 pp. ISBN 0-19-503742-1.  

External links

• Crustacea.net, an online resource on the biology of crustaceans