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64-466: Moina is a genus of crustaceans within the family Moinidae . The genus was first described by W. Baird in 1850. They are referred to as water fleas , but are related to the much larger Daphnia magna and the larger Daphnia pulex . This genus demonstrates the ability to survive in waters containing low oxygen levels , high salinity , and other impurities , including salt pans , and commonly eutrophication . An example of such an extreme habitat

128-456: A manca stage, which is similar in appearance to the adult. The lack of a free-swimming larval form has led to high rates of endemism in isopods, but has also allowed them to colonise the land, in the form of the woodlice . The larvae of many groups of mantis shrimp are poorly known. In the superfamily Lysiosquilloidea , the larvae hatch as antizoea larvae, with five pairs of thoracic appendages, and develop into erichthus larvae, where

192-635: 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 / ), 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

256-504: A few exceptions, such as the vestige of the fourth pereiopod in the larvae of Lucifer , and some pleopods in certain Anomura and crabs . In a more extreme example, the Sacculina and other Rhizocephala have a distinctive nauplius larva with its complex body structure, but the adult form lacks many organs due to extreme adaptation to its parasitic life style. Antonie van Leeuwenhoek

320-468: 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

384-468: 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

448-401: A megalopa or post-larva. This is followed by metamorphosis into an immature form, which broadly resembles the adult, and after further moults, the adult form is finally reached. Some crustaceans continue to moult as adults, while for others, the development of gonads signals the final moult. Any organs which are absent from the adults do not generally appear in the larvae, although there are

512-566: A metamorphosis, and some of which did not. In 1828 John Vaughan Thompson published a paper "On the Metamorphoses of the Crustacea, and on Zoea, exposing their singular structure and demonstrating they are not, as has been supposed, a peculiar Genus but the Larva of Crustacea!!" However his work was not believed due to crayfish not undergoing metamorphosis. This controversy persisted until the 1840s, and

576-591: A single copepodid stage. Once the gonads develop, there are no further moults. Chalimus (plural chalimi) is a stage of development of a copepod parasite of fish, such as the salmon louse ( Lepeophtheirus salmonis ). Chalimus Burmeister, 1834 is also a synonym for Lepeophtheirus Nordmann, 1832. The single genus in the Facetotecta , Hansenocaris , is only known from its larvae. They were first described by Christian Andreas Victor Hensen in 1887, and named "y-nauplia" by Hans Jacob Hansen , assuming them to be

640-487: 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

704-577: 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

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768-611: A transitional zone at the Yenisey River basin (Eastern Siberia). There is an increase of new phylogroups found in Northern Eurasia, an increase of 4 new Moina species in Japan and an increase of five new lineages in China. In the water bodies of the world, at least 4 species of Moina are non-native species. Moina contains these species: This Branchiopoda -related article is

832-557: Is also the stage at which a simple, unpaired eye is present. The eye is known for that reason as the "naupliar eye", and is often absent in later developmental stages, although it is retained into the adult form in some groups, such as the Notostraca . Some crustacean groups lack this larval type, isopods being one example. The genus Zoea was initially described by Louis Augustin Guillaume Bosc in 1802 for an animal now known to be

896-438: 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

960-517: Is called a puerulus and a slipper lobster post-larva is called a nisto . In the Branchiopoda , the offspring hatch as a nauplius or metanauplius larva. In the Mediterranean horseshoe shrimp Lightiella magdalenina , the young experience 15 stages following the nauplius, termed metanaupliar stages, and two juvenile stages, with each of the first six stages adding two trunk segments, and

1024-407: Is characterised by consisting of only three head segments, which are covered by a single carapace . The posterior body, when present, is unsegmented. Each head segment has a pair of appendages ; the antennules, antennae , and mandibles . This larval stage has various lifestyles; some are benthic while others are swimmers, some are feeding while others are non-feeders ( lecithotrophic ). The nauplius

1088-476: Is considerable variation in the number of larval stages. In the South American freshwater genus Aegla , the young hatch from the eggs in the adult form. Squat lobsters pass through four, or occasionally five, larval states, which have a long rostrum , and a spine on either side of the carapace ; the first post-larva closely resembles the adult. Porcelain crabs have two or three larval stages, in which

1152-696: 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. Crustacean larvae Many crustacean larvae were not immediately recognised as larvae when they were discovered, and were described as new genera and species. The names of these genera have become generalised to cover specific larval stages across wide groups of crustaceans, such as zoea and nauplius . Other terms described forms which are only found in particular groups, such as

1216-669: 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

1280-534: Is the highly saline Makgadikgadi Pans of Botswana , which supports prolific numbers of Moina belli . The Moina are known to be found in various types of bodies of water in Eurasia where new found research indicates that there is an increased presence of biodiversity in regions of Northern Eurasia, Japan and China. According to genetic data, whole the genus Moina is divided into two big faunistic groups: European-Western Siberian and Eastern Siberian-Far Eastern, with

1344-521: 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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1408-611: 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

1472-698: 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,

1536-465: 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

1600-401: 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

1664-434: The egg yolk (lecithotrophy). In species with normal development, eggs are roughly 1% of the size of the adult; in species with abbreviated development, and therefore more yolk in the eggs, the eggs may reach 1/9 of the adult's size. The post-larva of shrimp is called parva , after the species Acanthephyra parva described by Henri Coutière , but which was later recognised as the larva of Acanthephyra purpurea . In

1728-612: The furcilia stages, segments with pairs of swimmerets are added, beginning at the frontmost segments, with each new pair only becoming functional at the next moult. After the final furcilia stage, the krill resembles the adult. Apart from the prawns of the suborder Dendrobranchiata , all decapod crustaceans brood their eggs on the female's pleopods. This has resulted in development in decapod crustaceans being generally abbreviated. There are at most nine larval stages in decapods, as in krill , and both decapod nauplii and krill nauplii often lack mouthparts and survive on nutrients supplied in

1792-399: The glaucothoe of hermit crabs , or the phyllosoma of slipper lobsters and spiny lobsters . At its most complete, a crustacean's life cycle begins with an egg , which is usually fertilised , but may instead be produced by parthenogenesis . This egg hatches into a pre-larva or pre-zoea. Through a series of moults, the young animal then passes through various zoea stages, followed by

1856-629: 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

1920-413: 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

1984-514: The stomach contents of the Early Cretaceous bony fish Tharrhias . Copepods have six naupliar stages, followed by a stage called the copepodid , which has the same number of body segments and appendages in all copepods. The copepodid larva has two pairs of unsegmented swimming appendages, and an unsegmented "hind-body" comprising the thorax and the abdomen. There are typically five copepodid stages, but parasitic copepods may stop after

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2048-515: 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,

2112-536: The Anomura, rather than with the other crabs. Apart from the Dromiacea, all crabs share a similar and distinctive larval form. The crab zoea has a slender, curved abdomen and a forked telson , but its most striking features are the long rostral and dorsal spines, sometimes augmented by further, lateral spines. These spines can be many times longer than the body of the larva. Crab prezoea larvae have been found fossilised in

2176-702: 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

2240-629: 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

2304-407: The adult form, and many names have been erected for this stage in different groups. William Elford Leach erected the genus Megalopa in 1813 for a post-larval crab; a copepod post-larva is called a copepodite ; a barnacle post-larva is called a cypris ; a shrimp post-larva is called a parva ; a hermit crab post-larva is called a glaucothoe ; a spiny lobster / furry lobsters post-larva

2368-406: 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 ,

2432-448: 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

2496-627: 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

2560-444: 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

2624-456: 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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2688-560: The first descriptions of a complete series of larval forms were not published until the 1870s ( Sidney Irving Smith on the American lobster in 1873; Georg Ossian Sars on the European lobster in 1875, and Walter Faxon on the shrimp Palaemonetes vulgaris in 1879). The genus name Nauplius was published posthumously by Otto Friedrich Müller in 1785 for animals now known to be the larvae of copepods . The nauplius stage (plural: nauplii )

2752-458: The genus Phyllosoma erected by William Elford Leach in 1817. They are flattened and transparent, with long legs and eyes on long eyestalks. After passing through 8–10 phyllosoma stages, the larva undergoes "the most profound transformation at a single moult in the Decapoda", when it develops into the so-called puerulus stage, which is an immature form resembling the adult animal. The members of

2816-662: 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%

2880-401: The larva of a crab . The zoea stage (plural: zoeas or zoeae ), only found in members of Malacostraca , is characterised by the use of the thoracic appendages for swimming and a large dorsal spine. The post-larva or Megalopae , also found exclusively in the Malacostraca, is characterised by the use of abdominal appendages (pleopods) for propulsion. The post-larva is usually similar to

2944-420: The larvae go through several stages called nauplius , pseudometanauplius , metanauplius , calyptopsis and furcilia stages, each of which is sub-divided into several sub-stages. The pseudometanauplius stage is exclusive to the so-called "sac-spawners". Until the metanauplius stage, the larvae are reliant on the yolk reserves, but from the calyptopsis stage, they begin to feed on phytoplankton . During

3008-432: The last four segments being added singly. The larvae of remipedes are lecithotrophic , consuming egg yolk rather than using external food sources. This characteristic, which is shared with malacostracan groups such as the Decapoda and Euphausiacea (krill) has been used to suggest a link between Remipedia and Malacostraca. Amphipod hatchlings resemble the adults. Young isopod crustaceans hatch directly into

3072-422: 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

3136-608: The marine lobsters , there are three larval stages, all similar in appearance. Freshwater crayfish embryos differ from those of other crustaceans in having 40 ectoteloblast cells, rather than around 19. The larvae show abbreviated development, and hatch with a full complement of adult appendages with the exceptions of the uropods and the first pair of pleopods . The larvae of the Achelata ( slipper lobsters , spiny lobsters and furry lobsters ) are unlike any other crustacean larvae. The larvae are known as phyllosoma , after

3200-401: 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

3264-610: The pleopods appear. In the Squilloidea , a pseudozoea larva develops into an alima larva, while in Gonodactyloidea , a pseudozoea develops into an erichthus . A single fossil stomatopod larva has been discovered, in the Upper Jurassic Solnhofen lithographic limestone . The life cycle of krill is relatively well understood, although there are minor variations in detail from species to species. After hatching,

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3328-451: The preceding stages, the glaucothoe is symmetrical, and although the glaucothoe begins as a free-swimming form, it often acquires a gastropod shell to live in; the coconut crab , Birgus latro , always carries a shell when the immature animal comes ashore, but this is discarded later. Although they are classified as crabs , the larvae of Dromiacea are similar to those of the Anomura, which led many scientists to place dromiacean crabs in

3392-429: 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

3456-511: The rostrum and the posterior spine on the carapace are "enormously long". Hermit crabs pass through around four larval stages. The post-larva is known as the glaucothoe , after a genus named by Henri Milne-Edwards in 1830. The glaucothoe is 3 millimetres (0.12 in) long in Pagurus longicarpus , but glaucothoe larvae up to 20 mm (0.79 in) are known, and were once thought to represent animals which had failed to develop correctly. Like

3520-446: 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

3584-510: 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

3648-473: 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

3712-500: 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

3776-412: The traditional infraorder Thalassinidea can be divided into two groups on the basis of their larvae. According to Robert Gurney , the "homarine group" comprises the families Axiidae and Callianassidae , while the "anomuran group" comprises the families Laomediidae and Upogebiidae . This split corresponds with the division later confirmed with molecular phylogenetics . Among the Anomura , there

3840-412: 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

3904-426: 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

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3968-447: 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

4032-412: 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

4096-409: Was the first person to observe the difference between larval crustaceans and the adults when he watched the eggs of Cyclops hatching in 1699. Despite this, and other observations over the following decades, there was controversy among scientists about whether or not metamorphosis occurred in crustaceans, with conflicting observations presented, based on different species, some of which went through

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