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58-611: Lipke Bijdeley Holthuis (21 April 1921 – 7 March 2008) was a Dutch carcinologist , considered one of the "undisputed greats" of carcinology, and "the greatest carcinologist of our time". Holthuis was born in Probolinggo , East Java and obtained his doctorate from Leiden University on 23 January 1946. He was appointed the assistant curator of the Rijksmuseum van Natuurlijke Historie (now Naturalis ) in Leiden in 1941. He

116-417: A Dutch scientist is a stub . You can help Misplaced Pages by expanding it . This article about a zoologist is a stub . You can help Misplaced Pages by expanding it . 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 / ),

174-486: A calcified exoskeleton, but mineralized skeletons did not become common until the beginning of the Cambrian period, with the rise of the " small shelly fauna ". Just after the base of the Cambrian, these miniature fossils become diverse and abundant – this abruptness may be an illusion since the chemical conditions which preserved the small shells appeared at the same time. Most other shell-forming organisms appeared during

232-432: A calcified exoskeleton. Some Cloudina shells even show evidence of predation, in the form of borings. The fossil record primarily contains mineralized exoskeletons, since these are by far the most durable. Since most lineages with exoskeletons are thought to have started with a non-mineralized exoskeleton which they later mineralized, it is difficult to comment on the very early evolution of each lineage's exoskeleton. It

290-406: A common misconception, echinoderms do not possess an exoskeleton and their test is always contained within a layer of living tissue. Exoskeletons have evolved independently many times; 18 lineages evolved calcified exoskeletons alone. Further, other lineages have produced tough outer coatings, such as some mammals, that are analogous to an exoskeleton. This coating is constructed from bone in

348-403: 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 a subphylum under the clade Mandibulata . It is now well accepted that

406-468: 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

464-468: 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

522-495: 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

580-438: 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

638-488: Is eventually hardened. In contrast, moulting reptiles shed only the outer layer of skin and often exhibit indeterminate growth. These animals produce new skin and integuments throughout their life, replacing them according to growth. Arthropod growth, however, is limited by the space within its current exoskeleton. Failure to shed the exoskeleton once outgrown can result in the animal's death or prevent subadults from reaching maturity, thus preventing them from reproducing. This

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696-544: Is in creating the proteins and polysaccharides required for the shell's composite structure , not in the precipitation of the mineral components. Skeletonization also appeared at almost the same time that animals started burrowing to avoid predation, and one of the earliest exoskeletons was made of glued-together mineral flakes, suggesting that skeletonization was likewise a response to increased pressure from predators. Ocean chemistry may also control which mineral shells are constructed of. Calcium carbonate has two forms,

754-602: Is known, however, that in a very short course of time, just before the Cambrian period, exoskeletons made of various materials – silica, calcium phosphate , calcite , aragonite , and even glued-together mineral flakes – sprang up in a range of different environments. Most lineages adopted the form of calcium carbonate which was stable in the ocean at the time they first mineralized, and did not change from this mineral morph - even when it became less favourable. Some Precambrian (Ediacaran) organisms produced tough but non-mineralized outer shells, while others, such as Cloudina , had

812-509: 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. Exoskeleton Examples of exoskeletons in animals include the cuticle skeletons shared by arthropods ( insects , chelicerates , myriapods and crustaceans ) and tardigrades , as well as

870-694: 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

928-402: Is the mechanism behind some insect pesticides, such as Azadirachtin . Exoskeletons, as hard parts of organisms, are greatly useful in assisting the preservation of organisms, whose soft parts usually rot before they can be fossilized. Mineralized exoskeletons can be preserved as shell fragments. The possession of an exoskeleton permits a couple of other routes to fossilization . For instance,

986-526: 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

1044-617: 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

1102-713: 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,

1160-471: 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

1218-401: 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

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1276-515: The armadillo , and hair in the pangolin . The armour of reptiles like turtles and dinosaurs like Ankylosaurs is constructed of bone; crocodiles have bony scutes and horny scales. Since exoskeletons are rigid, they present some limits to growth. Organisms with open shells can grow by adding new material to the aperture of their shell, as is the case in gastropods , bivalves , and other molluscans . A true exoskeleton, like that found in panarthropods, must be shed via moulting ( ecdysis ) when

1334-509: 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

1392-634: 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

1450-413: 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

1508-804: The skeletal cups formed by hardened secretion of stony corals , the test /tunic of sea squirts and sea urchins , and the prominent mollusc shell shared by snails , clams , tusk shells , chitons and nautilus . Some vertebrate animals, such as the turtle , have both an endoskeleton and a protective exoskeleton . Exoskeletons contain rigid and resistant components that fulfil a set of functional roles in addition to structural support in many animals, including protection, respiration, excretion, sensation, feeding and courtship display , and as an osmotic barrier against desiccation in terrestrial organisms. Exoskeletons have roles in defence from parasites and predators and in providing attachment points for musculature . Arthropod exoskeletons contain chitin ;

1566-515: 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,

1624-723: 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

1682-457: The Cambrian period, with the Bryozoans being the only calcifying phylum to appear later, in the Ordovician . The sudden appearance of shells has been linked to a change in ocean chemistry which made the calcium compounds of which the shells are constructed stable enough to be precipitated into a shell. However, this is unlikely to be a sufficient cause, as the main construction cost of shells

1740-650: 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

1798-465: The addition of calcium carbonate makes them harder and stronger, at the price of increased weight. Ingrowths of the arthropod exoskeleton known as apodemes serve as attachment sites for muscles. These structures are composed of chitin and are approximately six times stronger and twice the stiffness of vertebrate tendons . Similar to tendons, apodemes can stretch to store elastic energy for jumping, notably in locusts . Calcium carbonates constitute

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1856-449: The animal starts to outgrow it. A new exoskeleton is produced beneath the old one, and the new skeleton is soft and pliable before shedding the old one. The animal will typically stay in a den or burrow during moulting, as it is quite vulnerable to trauma during this period. Once at least partially set, the organism will plump itself up to try to expand the exoskeleton. The new exoskeleton is still capable of growing to some degree before it

1914-406: 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 ,

1972-594: The description of 428 new taxa: 2 new families, 5 subfamilies, 83 genera and 338 species. 67 taxa were named after him between 1953 ( Hippolyte holthuisi ) and 2009 ( Caridina holthuisi , Lysmata holthuisi ). However, in Fransen, C.H.J.M., De Grave, S., Ng, P.K.L. 2010, an additional 50 taxa were named after him. In 1972 Holthuis received an honorary doctorate from the Norwegian University of Science and Technology (NTNU) . This article about

2030-448: 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

2088-684: 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

2146-444: 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

2204-456: 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

2262-413: The fossil record shortly before the base of the Cambrian period , 550  million years ago . The evolution of a mineralised exoskeleton is considered a possible driving force of the Cambrian explosion of animal life, resulting in a diversification of predatory and defensive tactics. However, some Precambrian ( Ediacaran ) organisms produced tough outer shells while others, such as Cloudina , had

2320-674: 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%

2378-422: 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

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2436-421: The magnesium/calcium ratio of the oceans appears to have a negligible impact on organisms' success, which is instead controlled mainly by how well they recover from mass extinctions. A recently discovered modern gastropod Chrysomallon squamiferum that lives near deep-sea hydrothermal vents illustrates the influence of both ancient and modern local chemical environments: its shell is made of aragonite, which

2494-426: The molluscs, whose shells often comprise both forms, most lineages use just one form of the mineral. The form used appears to reflect the seawater chemistry – thus which form was more easily precipitated – at the time that the lineage first evolved a calcified skeleton, and does not change thereafter. However, the relative abundance of calcite- and aragonite-using lineages does not reflect subsequent seawater chemistry –

2552-401: 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

2610-614: The parts of organisms that were already mineralised are usually preserved, such as the shells of molluscs. It helps that exoskeletons often contain "muscle scars", marks where muscles have been attached to the exoskeleton, which may allow the reconstruction of much of an organism's internal parts from its exoskeleton alone. The most significant limitation is that, although there are 30-plus phyla of living animals, two-thirds of these phyla have never been found as fossils, because most animal species are soft-bodied and decay before they can become fossilised. Mineralized skeletons first appear in

2668-429: 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

2726-446: 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

2784-518: 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

2842-404: The shells of molluscs, brachiopods , and some tube-building polychaete worms. Silica forms the exoskeleton in the microscopic diatoms and radiolaria . One mollusc species, the scaly-foot gastropod , even uses the iron sulfides greigite and pyrite . Some organisms, such as some foraminifera , agglutinate exoskeletons by sticking grains of sand and shell to their exterior. Contrary to

2900-479: 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

2958-437: The stable calcite and the metastable aragonite, which is stable within a reasonable range of chemical environments but rapidly becomes unstable outside this range. When the oceans contain a relatively high proportion of magnesium compared to calcium, aragonite is more stable, but as the magnesium concentration drops, it becomes less stable, hence harder to incorporate into an exoskeleton, as it will tend to dissolve. Except for

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3016-511: The strong layer can resist compaction, allowing a mould of the organism to be formed underneath the skeleton, which may later decay. Alternatively, exceptional preservation may result in chitin being mineralised, as in the Burgess Shale , or transformed to the resistant polymer keratin , which can resist decay and be recovered. However, our dependence on fossilised skeletons also significantly limits our understanding of evolution. Only

3074-510: 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

3132-412: 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

3190-426: 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

3248-450: 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

3306-412: 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

3364-496: Was the most prolific carcinologist of the 20th century, publishing 620 papers (108 of which were in the Leiden Museum Journals ) totalling 12,795 pages which is an average of 185 pages per year and an average of approximately 21 pages per paper. These were published on many groups of crustaceans , their natural history and nomenclature, and the history of carcinology. This steady stream of publications resulted in

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