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78-400: Artemia is a genus of aquatic crustaceans also known as brine shrimp , Aqua Dragons or sea monkeys . It is the only genus in the family Artemiidae . The first historical record of the existence of Artemia dates back to the first half of the 10th century AD from Lake Urmia , Iran , with an example called by an Iranian geographer an "aquatic dog", although the first unambiguous record

156-453: A model organism for use in toxicological assays, despite the recognition that it is too robust an organism to be a sensitive indicator species . In pollution research Artemia , the brine shrimp, has had extensive use as a test organism and in some circumstances is an acceptable alternative to the toxicity testing of mammals in the laboratory. The fact that millions of brine shrimp are so easily reared has been an important help in assessing

234-608: A model organism used to test the toxicity of chemicals. Breeds of Artemia are sold as novelty gifts under the marketing name Sea-Monkeys . The brine shrimp Artemia comprises a group of seven to nine species very likely to have diverged from an ancestral form living in the Mediterranean area about 5.5  million years ago , around the time of the Messinian salinity crisis . The Laboratory of Aquaculture & Artemia Reference Center at Ghent University possesses

312-490: A nauplius , which is characterized by its use of antennae for swimming. Barnacles , a highly modified crustacean, use their antennae to attach to rocks and other surfaces. The second antennae in the burrowing Hippoidea and Corystidae have setae that interlock to form a tube or "snorkel" which funnels filtered water over the gills. Some claim insects evolved from prehistoric crustaceans, and they have secondary antennae like crustaceans, but not primary antennae. Antennae are

390-524: A brown colour. These eggs, also known as cysts, are metabolically inactive and can remain in total stasis for two years while in dry oxygen-free conditions, even at temperatures below freezing. This characteristic is called cryptobiosis , meaning "hidden life". While in cryptobiosis, brine shrimp eggs can survive temperatures of liquid air (−190 °C or −310 °F) and a small percentage can survive above boiling temperature (105 °C or 221 °F) for up to two hours. Once placed in briny (salt) water,

468-562: A convenient form of live feed for larval fish and crustaceans . Nauplii of the brine shrimp Artemia constitute the most widely used food item, and over 2,000 metric tons (2,200 short tons) of dry Artemia cysts are marketed worldwide annually with most of the cysts being harvested from the Great Salt Lake in Utah. In addition, the resilience of Artemia makes them ideal animals for running biological toxicity assays and it has become

546-419: A host plant's taste and odor. After the desired taste and odor has been identified, the female moth will deposit her eggs onto the plant. Giant swallowtail butterflies also rely on antenna sensitivity to volatile compounds to identify host plants. It was found that females are actually more responsive with their antenna sensing, most likely because they are responsible for oviposition on the correct plant. In

624-468: A larger Pancrustacea clade . The traditional classification of Crustacea based on morphology recognised four to six classes. Bowman and Abele (1982) recognised 652 extant families and 38 orders, organised into six classes: Branchiopoda , Remipedia , Cephalocarida , Maxillopoda, Ostracoda , and Malacostraca . Martin and Davis (2001) updated this classification, retaining the six classes but including 849 extant families in 42 orders. Despite outlining

702-468: A limbless abdomen, except from a telson and caudal rami which is present in many groups. The abdomen in malacostracans bears pleopods , and ends in a telson, which bears the anus , and is often flanked by uropods to form a tail fan . The number and variety of appendages in different crustaceans may be partly responsible for the group's success. Crustacean appendages are typically biramous , meaning they are divided into two parts; this includes

780-440: A raised portion of the insect's head capsule. The socket is closed off by the membrane into which the base of the scape is set. However, the antenna does not hang free on the membrane, but pivots on a rigidly sprung projection from the rim of the torulus. That projection on which the antenna pivots is called the antennifer . The whole structure enables the insect to move the antenna as a whole by applying internal muscles connected to

858-495: A spiral format. 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. In many decapods , 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

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936-583: A subphylum under the clade Mandibulata . It is now well accepted that the hexapods ( insects and entognathans ) emerged deep in the Crustacean group, with the completed pan-group referred to as Pancrustacea . The three classes Cephalocarida , Branchiopoda and Remipedia are more closely related to the hexapods than they are to any of the other crustaceans ( oligostracans and multicrustaceans ). The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm (0.004 in), to

1014-468: A unit, in spite of being articulated. However, some funicles are complex and very mobile. For example, the Scarabaeidae have lamellate antennae that can be folded tightly for safety or spread openly for detecting odours or pheromones . The insect manages such actions by changes in blood pressure, by which it exploits elasticity in walls and membranes in the funicles, which are in effect erectile. In

1092-438: Is an open circulatory system , where blood is pumped into the haemocoel by a heart located near the dorsum. Malacostraca have haemocyanin as the oxygen-carrying pigment, while copepods, ostracods, barnacles and branchiopods have haemoglobins . 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; this structure goes in

1170-423: Is considered segmented if each of the annuli is separate from those around it and has individual muscle attachments. Flagellate antennae, on the other hand, have muscle attachments only around the base, acting as a hinge for the flagellum —a flexible string of annuli with no muscle attachment. There are several notable non-sensory uses of antennae in crustaceans. Many crustaceans have a mobile larval stage called

1248-505: Is one in which two haploid products from the same meiosis combine to form a diploid zygote . Diploid Artemia parthenogenetica reproduce by automictic parthenogenesis with central fusion (see diagram) and low but nonzero recombination. Central fusion of two of the haploid products of meiosis (see diagram) tends to maintain heterozygosity in transmission of the genome from mother to offspring, and to minimise inbreeding depression . Low crossover recombination during meiosis likely restrains

1326-537: Is produced in Asia, with China alone producing nearly half the world's total. Non-decapod crustaceans are not widely consumed, with only 118,000 tons of krill being caught, despite krill having one of the greatest biomasses on the planet. Antenna (biology) Antennae are connected to the first one or two segments of the arthropod head. They vary widely in form but are always made of one or more jointed segments. While they are typically sensory organs ,

1404-420: Is shed periodically. In female Artemia, a moult precedes every ovulation . For brine shrimp, many functions, including swimming, digestion and reproduction are not controlled through the brain; instead, local nervous system ganglia may control some regulation or synchronisation of these functions. Autotomy, the voluntary shedding or dropping of parts of the body for defence, is also controlled locally along

1482-694: Is some debate as to whether or not Cambrian animals assigned to Ostracoda are truly ostracods , which would otherwise start in the Ordovician . The only classes to appear later are the Cephalocarida , which have no fossil record, and the Remipedia , which were first described from the fossil Tesnusocaris goldichi , but do not appear until the Carboniferous . Most of the early crustaceans are rare, but fossil crustaceans become abundant from

1560-607: Is the report and drawings made by Schlösser in 1757 of animals from Lymington , England . Artemia populations are found worldwide, typically in inland saltwater lakes, but occasionally in oceans. Artemia are able to avoid cohabiting with most types of predators, such as fish, by their ability to live in waters of very high salinity (up to 25%). The ability of the Artemia to produce dormant eggs, known as cysts , has led to extensive use of Artemia in aquaculture . The cysts may be stored indefinitely and hatched on demand to provide

1638-526: Is thought to be just 1 ⁄ 10 to 1 ⁄ 100 of the total number as most species remain as yet undiscovered . Although most crustaceans are small, their morphology varies greatly and includes both the largest arthropod in the world – the Japanese spider crab with a leg span of 3.7 metres (12 ft) – and the smallest, the 100- micrometre -long (0.004 in) Stygotantulus stocki . Despite their diversity of form, crustaceans are united by

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1716-617: The Marmorkrebs crayfish. In many crustaceans, the fertilised eggs are released into the water column , while others have developed a number of mechanisms for holding on to the eggs until they are ready to hatch. Most decapods carry the eggs attached to the pleopods , while peracarids , notostracans , anostracans , and many isopods form a brood pouch from the carapace and thoracic limbs. Female Branchiura do not carry eggs in external ovisacs but attach them in rows to rocks and other objects. Most leptostracans and krill carry

1794-492: The Artemia genome was assembled and annotated , revealing a genome containing an unequaled 58% of repeats , genes with unusually long introns and adaptations unique to the extremophilic nature of Artemia in high salt and low oxygen environments. These adaptations include a unique energy-intensive endocytosis -based salt excretion strategy resembling salt excretion strategies of plants, as well as several survival strategies for extreme environments it has in common with

1872-713: The Carboniferous , as are the first true mantis shrimp. In the Decapoda , prawns and polychelids appear in the Triassic, and shrimp and crabs appear in the Jurassic . The fossil burrow Ophiomorpha is attributed to ghost shrimps, whereas the fossil burrow Camborygma is attributed to crayfishes. The Permian–Triassic deposits of Nurra preserve the oldest (Permian: Roadian) fluvial burrows ascribed to ghost shrimps (Decapoda: Axiidea, Gebiidea) and crayfishes (Decapoda: Astacidea, Parastacidea), respectively. However,

1950-471: The Carboniferous period onwards. Within the Malacostraca, no fossils are known for krill , while both Hoplocarida and Phyllopoda contain important groups that are now extinct as well as extant members (Hoplocarida: mantis shrimp are extant, while Aeschronectida are extinct; Phyllopoda: Canadaspidida are extinct, while Leptostraca are extant ). Cumacea and Isopoda are both known from

2028-479: The Coleoptera and Hymenoptera. They are important for insects like ants that follow scent trails, for bees and wasps that need to "sniff" the flowers that they visit, and for beetles such as Scarabaeidae and Curculionidae that need to fold their antennae away when they self-protectively fold up all their limbs in defensive attitudes. Because the funicle is without intrinsic muscles, it generally must move as

2106-585: The Hexapoda , both Collembola and Diplura have antenna, but Protura do not. Antennal fibrillae play an important role in Culex pipiens mating practices. The erection of these fibrillae is considered to be the first stage in reproduction. These fibrillae serve different functions across the sexes. As antennal fibrillae are used by female C. pipiens to locate hosts to feed on, male C. pipiens utilize them to locate female mates. The three basic segments of

2184-401: The Japanese spider crab with a leg span of up to 3.8 m (12.5 ft) and a mass of 20 kg (44 lb). Like other arthropods , crustaceans have an exoskeleton , which they moult to grow. They are distinguished from other groups of arthropods, such as insects , myriapods and chelicerates , by the possession of biramous (two-parted) limbs, and by their larval forms , such as

2262-716: The United States Fish and Wildlife Service to add A. monica to the endangered species list under the Endangered Species Act (1973). The diversion of water by the Los Angeles Department of Water and Power resulted in rising salinity and concentration of sodium hydroxide in Mono Lake. Despite the presence of trillions of brine shrimp in the lake, the petition contended that the increase in pH would endanger them. The threat to

2340-442: The antennal lobe in the brain . From there, neurons in the antennal lobes connect to mushroom bodies that identify the odour. The sum of the electrical potentials of the antennae to a given odour can be measured using an electroantennogram . In the monarch butterfly , antennae are necessary for proper time-compensated solar compass orientation during migration. Antennal clocks exist in monarchs, and they are likely to provide

2418-907: The chelicerates and proturans , which have none, all non-crustacean arthropods have a single pair of antennae. Crustaceans bear two pairs of antennae. The pair attached to the first segment of the head are called primary antennae or antennules . This pair is generally uniramous, but is biramous in crabs and lobsters and remipedes . The pair attached to the second segment are called secondary antennae or simply antennae . The second antennae are plesiomorphically biramous, but many species later evolved uniramous pairs. The second antennae may be significantly reduced (e.g. remipedes) or apparently absent (e.g. barnacles ). The subdivisions of crustacean antennae have many names, including flagellomeres (a shared term with insects), annuli, articles, and segments. The terminal ends of crustacean antennae have two major categorizations: segmented and flagellate. An antenna

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2496-472: The ecological niche that can protect them from predators. Physiologically, optimal levels of salinity are about 30–35‰, but due to predators at these salt levels, brine shrimp seldom occur in natural habitats at salinities of less than 60–80‰. Locomotion is achieved by the rhythmic beating of the appendages acting in pairs. Respiration occurs on the surface of the legs through fibrous, feather-like plates (lamellar epipodites). Males differ from females by having

2574-671: The embryos induced to develop from hit eggs died at different developmental stages. Crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are a part of the subphylum Crustacea ( / k r ə ˈ s t eɪ ʃ ə / ), a large, diverse group of mainly aquatic arthropods including decapods ( shrimps , prawns , crabs , lobsters and crayfish ), seed shrimp , branchiopods , fish lice , krill , remipedes , isopods , barnacles , copepods , opossum shrimps , amphipods and mantis shrimp . The crustacean group can be treated as

2652-634: The nauplius stage of branchiopods and copepods . Most crustaceans are free-living aquatic animals , but some are terrestrial (e.g. woodlice , sandhoppers ), some are parasitic (e.g. Rhizocephala , fish lice , tongue worms ) and some are sessile (e.g. barnacles ). The group has an extensive fossil record , reaching back to the Cambrian . More than 7.9 million tons of crustaceans per year are harvested by fishery or farming for human consumption, consisting mostly of shrimp and prawns . Krill and copepods are not as widely fished, but may be

2730-413: The pereon or thorax , and the pleon or abdomen . The head and thorax may be fused together to form a cephalothorax , which may be covered by a single large carapace . The crustacean body is protected by the hard exoskeleton , which must be moulted for the animal to grow. The shell around each somite can be divided into a dorsal tergum , ventral sternum and a lateral pleuron. Various parts of

2808-515: The zoea (pl. zoeæ or zoeas ). This name was given to it when naturalists believed it to be a separate species. It follows the nauplius stage and precedes the post-larva . Zoea larvae swim with their thoracic appendages , as opposed to nauplii, which use cephalic appendages, and megalopa, which use abdominal appendages for swimming. It often has spikes on its carapace , which may assist these small organisms in maintaining directional swimming. In many decapods , due to their accelerated development,

2886-723: The Asian shore crab, Hemigrapsus sanguineus . Since the opening of the Suez Canal , close to 100 species of crustaceans from the Red Sea and the Indo-Pacific realm have established themselves in the eastern Mediterranean sub-basin, with often significant impact on local ecosystems. Most crustaceans have separate sexes , and reproduce sexually . In fact, a recent study explains how the male T. californicus decide which females to mate with by dietary differences, preferring when

2964-706: The Hexapoda is distinctly closer to e.g. a Multicrustacean than an Oligostracan is. Crustaceans have a rich and extensive fossil record , which begins with animals such as Canadaspis and Perspicaris from the Middle Cambrian age Burgess Shale . Most of the major groups of crustaceans appear in the fossil record before the end of the Cambrian, namely the Branchiopoda , Maxillopoda (including barnacles and tongue worms ) and Malacostraca ; there

3042-771: The Mediterranean region. Among the highly localized species are A. urmiana from Lake Urmia in Iran. Once abundant, the species has drastically declined due to drought, leading to fears that it was almost extinct. However, a second population of this species has recently been discovered in the Koyashskoye Salt Lake , Ukraine . A. monica , the species commonly known as Mono Lake brine shrimp, can be found in Mono Lake , Mono County, California . In 1987, Dennis D. Murphy from Stanford University petitioned

3120-580: The Russian Bion-3 ( Cosmos 782 ), Bion-5 ( Cosmos 1129 ), Foton 10, and Foton 11 flights. Some of the Russian flights carried European Space Agency experiments. On Apollo 16 and Apollo 17, the cysts traveled to the Moon and back. Cosmic rays that passed through an egg would be detected on the photographic film in its container. Some eggs were kept on Earth as experimental controls as part of

3198-479: The adult. Many crustaceans, for example, have free-swimming larvae that use their antennae for swimming. Antennae can also locate other group members if the insect lives in a group, like the ant . The common ancestor of all arthropods likely had one pair of uniramous (unbranched) antenna-like structures, followed by one or more pairs of biramous (having two major branches) leg-like structures, as seen in some modern crustaceans and fossil trilobites . Except for

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3276-406: The animals with the greatest biomass on the planet, and form a vital part of the food chain. The scientific study of crustaceans is known as carcinology (alternatively, malacostracology , crustaceology or crustalogy ), and a scientist who works in carcinology is a carcinologist . The body of a crustacean is composed of segments, which are grouped into three regions: the cephalon or head ,

3354-607: The crepuscular hawk moth ( Manduca sexta ), antennae aid in flight stabilization. Similar to halteres in Dipteran insects, the antennae transmit coriolis forces through the Johnston's organ that can then be used for corrective behavior. A series of low-light, flight stability studies in which moths with flagellae amputated near the pedicel showed significantly decreased flight stability over those with intact antennae. To determine whether there may be other antennal sensory inputs,

3432-511: The effects of a large number of environmental pollutants on the shrimps under well controlled experimental conditions. Overall, brine shrimp are abundant, but some populations and localized species do face threats, especially from habitat loss to introduced species . For example, A. franciscana of the Americas has been widely introduced to places outside its native range and is often able to outcompete local species, such as A. salina in

3510-448: The eggs between their thoracic limbs; some copepods carry their eggs in special thin-walled sacs, while others have them attached together in long, tangled strings. Crustaceans exhibit a number of larval forms, of which the earliest and most characteristic is the nauplius . This has three pairs of appendages , all emerging from the young animal's head, and a single naupliar eye. In most groups, there are further larval stages, including

3588-495: The eggs hatch within a few hours. The nauplius larvae are less than 0.4 mm in length when they first hatch. Parthenogenesis is a natural form of reproduction in which growth and development of embryos occur without fertilisation . Thelytoky is a particular form of parthenogenesis in which the development of a female individual occurs from an unfertilised egg. Automixis is a form of thelytoky, but there are different kinds of automixis. The kind of automixis relevant here

3666-684: The evidence that Maxillopoda was non-monophyletic, they retained it as one of the six classes, although did suggest that Maxillipoda could be replaced by elevating its subclasses to classes. Since then phylogenetic studies have confirmed the polyphyly of Maxillipoda and the paraphyletic nature of Crustacea with respect to Hexapoda. Recent classifications recognise ten to twelve classes in Crustacea or Pancrustacea, with several former maxillopod subclasses now recognised as classes (e.g. Thecostraca , Tantulocarida , Mystacocarida , Copepoda , Branchiura and Pentastomida ). The following cladogram shows

3744-409: The exact nature of what they sense and how they sense it is not the same in all groups. Functions may variously include sensing touch , air motion, heat, vibration (sound), and especially smell or taste . Antennae are sometimes modified for other purposes, such as mating, brooding, swimming, and even anchoring the arthropod to a substrate . Larval arthropods have antennae that differ from those of

3822-444: The exoskeleton may be fused together. Each somite , or body segment can bear a pair of appendages : on the segments of the head, these include two pairs of antennae , the mandibles and maxillae ; the thoracic segments bear legs , which may be specialised as pereiopods (walking legs) and maxillipeds (feeding legs). Malacostraca and Remipedia (and the hexapods) have abdominal appendages. All other classes of crustaceans have

3900-662: The extremophilic tardigrade . Fish farm owners search for a cost-effective, easy to use, and available food that is preferred by the fish. From cysts, brine shrimp nauplii can readily be used to feed fish and crustacean larvae just after a one-day incubation . Instar I (the nauplii that just hatched and with large yolk reserves in their body) and instar II nauplii (the nauplii after first moult and with functional digestive tracts) are more widely used in aquaculture, because they are easy for operation, rich in nutrients, and small, which makes them suitable for feeding fish and crustacean larvae live or after drying. Artemia found favor as

3978-456: The females are algae-fed instead of yeast-fed. A small number are hermaphrodites , including barnacles , remipedes , and Cephalocarida . Some may even change sex during the course of their life. Parthenogenesis is also widespread among crustaceans, where viable eggs are produced by a female without needing fertilisation by a male. This occurs in many branchiopods , some ostracods , some isopods , and certain "higher" crustaceans, such as

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4056-457: The flagellum. Such groups include the Symphyla , Collembola and Diplura . In many true insects, especially the more primitive groups such as Thysanura and Blattodea , the flagellum partly or entirely consists of a flexibly connected string of small ring-shaped annuli . The annuli are not true flagellomeres, and in a given insect species the number of annuli generally is not as consistent as

4134-519: The funicle is taken to comprise the segments between the club and the pedicel. Quite commonly the funicle beyond the pedicel is quite complex in Endopterygota such as beetles, moths and Hymenoptera , and one common adaptation is the ability to fold the antenna in the middle, at the joint between the pedicel and the flagellum. This gives an effect like a "knee bend", and such an antenna is said to be geniculate . Geniculate antennae are common in

4212-674: The great radiation of crustaceans occurred in the Cretaceous , particularly in crabs, and may have been driven by the adaptive radiation of their main predators, bony fish . The first true lobsters also appear in the Cretaceous. Many crustaceans are consumed by humans, and nearly 10,700,000  tons were harvested in 2007; the vast majority of this output is of decapod crustaceans : crabs , lobsters , shrimp , crawfish , and prawns . Over 60% by weight of all crustaceans caught for consumption are shrimp and prawns, and nearly 80%

4290-516: The groups with more uniform antennae (for example: millipedes ), all segments are called antennomeres . Some groups have a simple or variously modified apical or subapical bristle called an arista (this may be especially well-developed in various Diptera ). Olfactory receptors on the antennae bind to free-floating molecules, such as water vapour , and odours including pheromones . The neurons that possess these receptors signal this binding by sending action potentials down their axons to

4368-503: The lake's water levels was addressed by a revision to California State Water Resources Control Board 's policy, and the US Fish and Wildlife Service found on 7 September 1995 that the Mono Lake brine shrimp did not warrant listing. Scientists have taken the eggs of brine shrimp to outer space to test the impact of radiation on life. Brine shrimp cysts were flown on the U.S. Biosatellite 2 , Apollo 16 , and Apollo 17 missions, and on

4446-420: The largest known Artemia cyst collection, a cyst bank containing over 1,700 Artemia population samples collected from different locations around the world. Artemia is a typical primitive arthropod with a segmented body to which is attached broad leaf-like appendages . The body usually consists of 19 segments, the first 11 of which have pairs of appendages, the next two which are often fused together carry

4524-422: The layer allow light to reach the retina. As the larvae mature into adults, the layer migrates to a new position behind the retina where it works as a backscattering mirror that increases the intensity of light passing through the eyes, as seen in many nocturnal animals. In an effort to understand whether DNA repair processes can protect crustaceans against DNA damage , basic research was conducted to elucidate

4602-536: The nervous system. Artemia have two types of eyes. They have two widely separated compound eyes mounted on flexible stalks. These compound eyes are the main optical sense organ in adult brine shrimps. The median eye, or the naupliar eye , is situated anteriorly in the centre of the head and is the only functional optical sense organ in the nauplii, which is functional until the adult stage. Brine shrimp can tolerate any levels of salinity from 25 ‰ to 250‰ (25–250 g/L), with an optimal range of 60‰–100‰, and occupy

4680-421: The number of flagellomeres in most species. In many beetles and in the chalcidoid wasps , the apical flagellomeres form a club shape, called the clava . The collective term for the segments between the club and the antennal base is the funicle ; traditionally in describing beetle anatomy, the term "funicle" refers to the segments between the club and the scape . However, traditionally in working on wasps

4758-401: The oceans as insects are on land. Most 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

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4836-414: The primary olfactory sensors of insects and are accordingly well-equipped with a wide variety of sensilla (singular: sensillum ). Paired, mobile, and segmented, they are located between the eyes on the forehead. Embryologically, they represent the appendages of the second head segment. All insects have antennae, however they may be greatly reduced in the larval forms. Amongst the non-insect classes of

4914-482: The primary timing mechanism for sun compass orientation. In the African cotton leafworm , antennae have an important function in signaling courtship. Specifically, antennae are required for males to answer the female mating call. Although females do not require antennae for mating, a mating that resulted from a female without antennae was abnormal. In the diamondback moth , antennae serve to gather information about

4992-429: The repair mechanisms used by Penaeus monodon (black tiger shrimp). Repair of DNA double-strand breaks was found to be predominantly carried out by accurate homologous recombinational repair. Another, less accurate process, microhomology-mediated end joining , is also used to repair such breaks. The expression pattern of DNA repair related and DNA damage response genes in the intertidal copepod Tigriopus japonicus

5070-485: The reproductive organs, and the last segments lead to the tail. The total length is usually about 8–10 millimetres (0.31–0.39 in) for the adult male and 10–12 mm (0.39–0.47 in) for the female, but the width of both sexes, including the legs, is about 4 mm (0.16 in). The body of Artemia is divided into head, thorax , and abdomen. The entire body is covered with a thin, flexible exoskeleton of chitin to which muscles are attached internally and which

5148-514: The scape. The pedicel is flexibly connected to the distal end of the scape and its movements in turn can be controlled by muscular connections between the scape and pedicel. The number of flagellomeres can vary greatly between insect species, and often is of diagnostic importance. True flagellomeres are connected by membranous linkage that permits movement, though the flagellum of "true" insects does not have any intrinsic muscles. Some other Arthropoda do however have intrinsic muscles throughout

5226-446: The sea to release the eggs. Others, such as woodlice , lay their eggs on land, albeit in damp conditions. In most decapods, the females retain the eggs until they hatch into free-swimming larvae. Most crustaceans are aquatic, living in either marine or freshwater environments, but a few groups have adapted to life on land, such as terrestrial crabs , terrestrial hermit crabs , and woodlice . Marine crustaceans are as ubiquitous in

5304-399: The second antennae markedly enlarged, and modified into clasping organs used in mating. Adult female brine shrimp ovulate approximately every 140 hours. In favourable conditions, the female brine shrimp can produce eggs that almost immediately hatch. While in extreme conditions, such as low oxygen level or salinity above 150‰, female brine shrimp produce eggs with a chorion coating which has

5382-518: The second pair of antennae, but not the first, which is usually uniramous , the exception being in the Class Malacostraca where the antennules may be generally biramous or even triramous. It is unclear whether the biramous condition is a derived state which evolved in crustaceans, or whether the second branch of the limb has been lost in all other groups. Trilobites , for instance, also possessed biramous appendages. The main body cavity

5460-479: The special larval form known as the nauplius . The exact relationships of the Crustacea to other taxa are not completely settled as of April 2012 . Studies based on morphology led to the Pancrustacea hypothesis, in which Crustacea and Hexapoda ( insects and allies) are sister groups . More recent studies using DNA sequences suggest that Crustacea is paraphyletic , with the hexapods nested within

5538-510: The substrate and cannot move independently. Some branchiurans are able to withstand rapid changes of salinity and will also switch hosts from marine to non-marine species. Krill are the bottom layer and most important part of the food chain in Antarctic animal communities. Some crustaceans are significant invasive species , such as the Chinese mitten crab, Eriocheir sinensis , and

5616-552: The tests. Also, as the take-off in a spacecraft involves a lot of shaking and acceleration , one control group of egg cysts was accelerated to seven times the force of gravity and vibrated mechanically from side to side for several minutes so that they could experience the same violence of a rocket take-off. About 400 eggs were in each experimental group. All the egg cysts from the experiment were then placed in salt water to hatch under optimum conditions. The results showed A. salina eggs are highly sensitive to cosmic radiation; 90% of

5694-913: The transition from heterozygosity to homozygosity over successive generations. In their first stage of development, Artemia do not feed but consume their own energy reserves stored in the cyst. Wild brine shrimp eat microscopic planktonic algae . Cultured brine shrimp can also be fed particulate foods including yeast , wheat flour , soybean powder or egg yolk . Artemia comprises sexually reproducing, diploid species and several obligate parthenogenetic Artemia populations consisting of different clones and ploidies (2n->5n). Several genetic maps have been published for Artemia . The past years, different transcriptomic studies have been performed to elucidate biological responses in Artemia , such as its response to salt stress, toxins, infection and diapause termination. These studies also led to various fully assembled Artemia transcriptomes . Recently,

5772-464: The typical insect antenna are the scape or scapus (base), the pedicel or pedicellus (stem), and finally the flagellum , which often comprises many units known as flagellomeres . The pedicel (the second segment) contains the Johnston's organ which is a collection of sensory cells. The scape is mounted in a socket in a more or less ring-shaped sclerotised region called the torulus , often

5850-412: The updated relationships between the different extant groups of the paraphyletic Crustacea in relation to the class Hexapoda . Ostracoda Mystacocarida Branchiura Pentastomida Malacostraca Copepoda Tantulocarida Thecostraca Cephalocarida Branchiopoda   Remipedia Hexapoda According to this diagram, the Hexapoda are deep in the Crustacea tree, and any of

5928-426: The zoea is the first larval stage. In some cases, the zoea stage is followed by the mysis stage, and in others, by the megalopa stage, depending on the crustacean group involved. Providing camouflage against predators, the otherwise black eyes in several forms of swimming larvae are covered by a thin layer of crystalline isoxanthopterin that gives their eyes the same color as the surrounding water, while tiny holes in

6006-450: Was analyzed after ultraviolet irradiation. This study revealed increased expression of proteins associated with the DNA repair processes of non-homologous end joining , homologous recombination , base excision repair and DNA mismatch repair . The name "crustacean" dates from the earliest works to describe the animals, including those of Pierre Belon and Guillaume Rondelet , but the name

6084-412: Was not used by some later authors, including Carl Linnaeus , who included crustaceans among the " Aptera " in his Systema Naturae . The earliest nomenclatural valid work to use the name "Crustacea" was Morten Thrane Brünnich 's Zoologiæ Fundamenta in 1772, although he also included chelicerates in the group. The subphylum Crustacea comprises almost 67,000 described species , which

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