60-667: Tetraconata Dohle, 2001 Pancrustacea is the clade that comprises all crustaceans , and all hexapods ( insects and relatives). This grouping is contrary to the Atelocerata hypothesis, in which Hexapoda and Myriapoda are sister taxa , and Crustacea are only more distantly related. As of 2010, the Pancrustacea taxon was considered well accepted, with most studies recovering Hexapoda within Crustacea. The clade has also been called Tetraconata , referring to having four cone cells in
120-525: A clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group , is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree . In the taxonomical literature, sometimes the Latin form cladus (plural cladi ) is used rather than the English form. Clades are
180-537: A larval form. For copepods, the egg hatches into a nauplius form, with a head and a tail but no true thorax or abdomen. The larva molts several times until it resembles the adult and then, after more molts, achieves adult development. The nauplius form is so different from the adult form that it was once thought to be a separate species. The metamorphosis had, until 1832, led to copepods being misidentified as zoophytes or insects (albeit aquatic ones), or, for parasitic copepods, 'fish lice '. Copepods are assigned to
240-479: A "ladder", with supposedly more "advanced" organisms at the top. Taxonomists have increasingly worked to make the taxonomic system reflect evolution. When it comes to naming , this principle is not always compatible with the traditional rank-based nomenclature (in which only taxa associated with a rank can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, phylogenetic nomenclature has been developed; it
300-402: A 2005 study of nuclear genomes Regier et al. suggest that Hexapoda is most closely related to Branchiopoda and Cephalocarida + Remipedia , thereby hexapods are "terrestrial crustaceans", thus supporting the Pancrustacea hypothesis that maxillopods are not monophyletic (in the following cladograms Maxillopoda subclasses are highlighted ). In addition, there appeared some evidence against
360-514: A 24-hour period. This is compared to uninfected females which, on average, ate 2.93 × 10 cells per day. Blastodinium -infected females of C. finmarchicus exhibited characteristic signs of starvation, including decreased respiration , fecundity, and fecal pellet production. Though photosynthetic , Blastodinium spp. procure most of their energy from organic material in the copepod gut, thus contributing to host starvation. Underdeveloped or disintegrated ovaries and decreased fecal pellet size are
420-623: A clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. Ages of clades cannot be directly observed. They are inferred, either from stratigraphy of fossils , or from molecular clock estimates. Viruses , and particularly RNA viruses form clades. These are useful in tracking
480-452: A direct result of starvation in female copepods. Parasitic infection by Blastodinium spp. could have serious ramifications on the success of copepod species and the function of entire marine ecosystems . Blastodinium parasitism is not lethal, but has negative impacts on copepod physiology, which in turn may alter marine biogeochemical cycles . Freshwater copepods of the Cyclops genus are
540-430: A low Reynolds number and therefore a high relative viscosity. One foraging strategy involves chemical detection of sinking marine snow aggregates and taking advantage of nearby low-pressure gradients to swim quickly towards food sources. Most free-living copepods feed directly on phytoplankton , catching cells individually. A single copepod can consume up to 373,000 phytoplankton per day. They generally have to clear
600-607: A predator is sensed, and can jump with high speed over a few millimetres. Many species have neurons surrounded by myelin (for increased conduction speed), which is very rare among invertebrates (other examples are some annelids and malacostracan crustaceans like palaemonid shrimp and penaeids ). Even rarer, the myelin is highly organized, resembling the well-organized wrapping found in vertebrates ( Gnathostomata ). Despite their fast escape response, copepods are successfully hunted by slow-swimming seahorses , which approach their prey so gradually, it senses no turbulence, then suck
660-636: A result of well-defined chloroplasts . At maturity, the trophont ruptures and Blastodinium spp. are released from the copepod anus as free dinospore cells. Not much is known about the dinospore stage of Blastodinium and its ability to persist outside of the copepod host in relatively high abundances. The copepod Calanus finmarchicus , which dominates the northeastern Atlantic coast , has been shown to be greatly infected by this parasite. A 2014 study in this region found up to 58% of collected C. finmarchicus females to be infected. In this study, Blastodinium -infected females had no measurable feeding rate over
SECTION 10
#1732849118181720-422: A revised taxonomy based on a concept strongly resembling clades, although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley . German biologist Emil Hans Willi Hennig (1913–1976) is considered to be the founder of cladistics . He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on
780-463: A rounded or beaked head, although considerable variation exists in this pattern. The head is fused with the first one or two thoracic segments, while the remainder of the thorax has three to five segments, each with limbs. The first pair of thoracic appendages is modified to form maxillipeds , which assist in feeding. The abdomen is typically narrower than the thorax, and contains five segments without any appendages, except for some tail-like "rami" at
840-472: A saltwater aquarium, copepods are typically stocked in the refugium . Copepods are sometimes found in public main water supplies, especially systems where the water is not mechanically filtered, such as New York City , Boston , and San Francisco . This is not usually a problem in treated water supplies. In some tropical countries, such as Peru and Bangladesh , a correlation has been found between copepods' presence and cholera in untreated water, because
900-429: A suffix added should be e.g. "dracohortian". A clade is by definition monophyletic , meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics ,
960-447: A teardrop-shaped body and large antennae . Like other crustaceans, they have an armoured exoskeleton , but they are so small that in most species, this thin armour and the entire body is almost totally transparent. Some polar copepods reach 1 cm ( 1 ⁄ 2 in). Most copepods have a single median compound eye , usually bright red and in the centre of the transparent head. Subterranean species may be eyeless, and members of
1020-399: Is a sister group to Hexapoda , and Branchiopoda is a sister group to (Remipedia + Hexapoda). Thus, their data strongly suggest that Branchiopoda is more closely related to Hexapoda and Remipedia than to Multicrustacea. Based on these data, they propose the following scenario of evolution of Branchiopoda, Remipedia and Hexapoda: under the impact of predatory fishes their common ancestors go to
1080-499: Is also used with a similar meaning in other fields besides biology, such as historical linguistics ; see Cladistics § In disciplines other than biology . The term "clade" was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis , the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch . Many commonly named groups – rodents and insects , for example – are clades because, in each case,
1140-464: Is divided into four lineages: Oligostraca ( Ostracoda , Mystacocarida , Branchiura , Pentastomida ), Vericrustacea ( Malacostraca , Thecostraca , Copepoda , Branchiopoda ), Xenocarida ( Cephalocarida , Remipedia ) and Hexapoda , with Xenocarida as a sister group to the Hexapoda (comprising "Miracrustacea"). New clades proposed by Regier et al. are: Of these proposed clades, only Multicrustacea
1200-471: Is in turn included in the mammal, vertebrate and animal clades. The idea of a clade did not exist in pre- Darwinian Linnaean taxonomy , which was based by necessity only on internal or external morphological similarities between organisms. Many of the better known animal groups in Linnaeus's original Systema Naturae (mostly vertebrate groups) do represent clades. The phenomenon of convergent evolution
1260-515: Is responsible for many cases of misleading similarities in the morphology of groups that evolved from different lineages. With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary tree of life . The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed
SECTION 20
#17328491181811320-489: Is still controversial. As an example, see the full current classification of Anas platyrhynchos (the mallard duck) with 40 clades from Eukaryota down by following this Wikispecies link and clicking on "Expand". The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade Dracohors , which was made by haplology from Latin "draco" and "cohors", i.e. "the dragon cohort "; its form with
1380-476: Is usually the main time-averaged source of propulsion, beating like oars to pull the animal through the water. However, different groups have different modes of feeding and locomotion, ranging from almost immotile for several minutes (e.g. some harpacticoid copepods ) to intermittent motion (e.g., some cyclopoid copepods ) and continuous displacements with some escape reactions (e.g. most calanoid copepods ). Some copepods have extremely fast escape responses when
1440-559: The Ostracoda monophyly: that Ostracoda subclass Podocopa may form a clade with Branchiura . Chelicerata Ostracoda Branchiura Copepod Thecostraca and Tantulocarida Malacostraca Remipedia Cephalocarida Branchiopoda Hexapoda A 2010 study of nuclear genomes (Regier et al. ) strongly supports Pancrustacea and strongly favour Mandibulata ( Myriapoda + Pancrustacea) over Paradoxopoda (Myriapoda + Chelicerata ). According to this study, Pancrustacea
1500-430: The carbon cycle . They are usually the dominant members of the zooplankton , and are major food organisms for small fish such as the dragonet , banded killifish , Alaska pollock , and other crustaceans such as krill in the ocean and in fresh water. Some scientists say they form the largest animal biomass on earth. Copepods compete for this title with Antarctic krill ( Euphausia superba ). C. glacialis inhabits
1560-406: The class Copepoda within the superclass Multicrustacea in the subphylum Crustacea . An alternative treatment is as a subclass belonging to class Hexanauplia . They are divided into 10 orders . Some 13,000 species of copepods are known, and 2,800 of them live in fresh water. Copepods vary considerably, but are typically 1 to 2 mm ( 1 ⁄ 32 to 3 ⁄ 32 in) long, with
1620-562: The littoral zone , then ancestors of Branchiopoda go to the ephemeral freshwater habitat , whereas ancestors of Remipedia go to the anchialine cave , and ancestors of Hexapoda go to the land . Chelicerata Ostracoda Copepod Thecostraca and Tantulocarida Malacostraca Branchiopoda Remipedia Hexapoda Chelicerata Ostracoda Copepod Thecostraca and Tantulocarida Malacostraca Branchiopoda Remipedia Hexapoda Chelicerata Ostracoda Clade In biological phylogenetics ,
1680-559: The ommatidia . The term "Tetraconata" is preferred by some scientists in order to avoid confusion with the use of "pan-" to indicate a clade that includes a crown group and all of its stem group representatives. A monophyletic Pancrustacea has been supported by several molecular studies, in most of which the subphylum Crustacea is paraphyletic with regard to hexapods (that is, that hexapods, including insects, are derived from crustacean ancestors). This means that within pancrustacea, only some members are actually crustaceans, hexapods being
1740-572: The Middle Jurassic of France , around 168 million years old. Live copepods are used in the saltwater aquarium hobby as a food source and are generally considered beneficial in most reef tanks. They are scavengers and also may feed on algae, including coralline algae . Live copepods are popular among hobbyists who are attempting to keep particularly difficult species such as the mandarin dragonet or scooter blenny . They are also popular to hobbyists who want to breed marine species in captivity. In
1800-537: The Norwegian Sea into the Barents Sea. Because of their smaller size and relatively faster growth rates, and because they are more evenly distributed throughout more of the world's oceans, copepods almost certainly contribute far more to the secondary productivity of the world's oceans, and to the global ocean carbon sink than krill, and perhaps more than all other groups of organisms together. The surface layers of
1860-623: The cholera bacteria attach to the surfaces of planktonic animals. The larvae of the guinea worm must develop within a copepod's digestive tract before being transmitted to humans. The risk of infection with these diseases can be reduced by filtering out the copepods (and other matter), for example with a cloth filter . Copepods have been used successfully in Vietnam to control disease-bearing mosquitoes such as Aedes aegypti that transmit dengue fever and other human parasitic diseases . The copepods can be added to water-storage containers where
Pancrustacea - Misplaced Pages Continue
1920-419: The copepod host ingests the unicellular dinospore of the parasite. The dinospore is not digested and continues to grow inside the intestinal lumen of the copepod. Eventually, the parasite divides into a multicellular arrangement called a trophont. This trophont is considered parasitic, contains thousands of cells, and can be several hundred micrometers in length. The trophont is greenish to brownish in color as
1980-419: The copepod into their snout too suddenly for the copepod to escape. Several species are bioluminescent and able to produce light. It is assumed this is an antipredatory defense mechanism. Finding a mate in the three-dimensional space of open water is challenging. Some copepod females solve the problem by emitting pheromones , which leave a trail in the water that the male can follow. Copepods experience
2040-550: The copepod takes on the adult form. The entire process from hatching to adulthood can take a week to a year, depending on the species and environmental conditions such as temperature and nutrition (e.g., egg-to-adult time in the calanoid Parvocalanus crassirostris is ~7 days at 25 °C (77 °F) but 19 days at 15 °C (59 °F). Copepods jump out of the water - porpoising. The biophysics of this motion has been described by Waggett and Buskey 2007 and Kim et al 2015. Planktonic copepods are important to global ecology and
2100-546: The deep sea. About half of the estimated 14,000 described species of copepods are parasitic and many have adapted extremely modified bodies for their parasitic lifestyles. They attach themselves to bony fish, sharks, marine mammals, and many kinds of invertebrates such as corals, other crustaceans, molluscs, sponges, and tunicates. They also live as ectoparasites on some freshwater fish. In addition to being parasites themselves, copepods are subject to parasitic infection. The most common parasites are marine dinoflagellates of
2160-502: The edge of the Arctic icepack, especially in polynyas where light (and photosynthesis) is present, in which they alone comprise up to 80% of zooplankton biomass. They bloom as the ice recedes each spring. The ongoing large reduction in the annual ice pack minimum may force them to compete in the open ocean with the much less nourishing C. finmarchicus , which is spreading from the North Sea and
2220-420: The eggs have a tough shell and can lie dormant for extended periods if the pond dries up. Eggs hatch into nauplius larvae, which consist of a head with a small tail , but no thorax or true abdomen. The nauplius moults five or six times, before emerging as a "copepodid larva". This stage resembles the adult, but has a simple, unsegmented abdomen and only three pairs of thoracic limbs. After a further five moults,
2280-447: The equivalent to about a million times their own body volume of water every day to cover their nutritional needs. Some of the larger species are predators of their smaller relatives. Many benthic copepods eat organic detritus or the bacteria that grow in it, and their mouth parts are adapted for scraping and biting. Herbivorous copepods, particularly those in rich, cold seas, store up energy from their food as oil droplets while they feed in
2340-455: The extant harpacticoid family Canthocamptidae , suggesting that copepods had already substantially diversified by this time. Possible microfossils of copepods are known from the Cambrian of North America. Transitions to parasitism have occurred within copepods independently at least 14 different times, with the oldest record of this being from damage to fossil echinoids done by cyclopoids from
2400-451: The fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual, a population , or a species ( extinct or extant ). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over
2460-403: The genera Copilia and Corycaeus possess two eyes, each of which has a large anterior cuticular lens paired with a posterior internal lens to form a telescope. Like other crustaceans, copepods possess two pairs of antennae; the first pair is often long and conspicuous. Free-living copepods of the orders Calanoida, Cyclopoida, and Harpacticoida typically have a short, cylindrical body, with
Pancrustacea - Misplaced Pages Continue
2520-459: The genus Blastodinium , which are gut parasites of many copepod species. Twelve species of Blastodinium are described, the majority of which were discovered in the Mediterranean Sea . Most Blastodinium species infect several different hosts, but species-specific infection of copepods does occur. Generally, adult copepod females and juveniles are infected. During the naupliar stage,
2580-546: The group consists of a common ancestor with all its descendant branches. Rodents, for example, are a branch of mammals that split off after the end of the period when the clade Dinosauria stopped being the dominant terrestrial vertebrates 66 million years ago. The original population and all its descendants are a clade. The rodent clade corresponds to the order Rodentia, and insects to the class Insecta. These clades include smaller clades, such as chipmunk or ant , each of which consists of even smaller clades. The clade "rodent"
2640-485: The guinea worm is endemic. The presence of copepods in the New York City water supply system has caused problems for some Jewish people who observe kashrut . Copepods, being crustaceans, are not kosher, nor are they quite small enough to be ignored as nonfood microscopic organisms, since some specimens can be seen with the naked eye. Hence, large specimens are certainly non-Kosher. However, some species are visible to
2700-576: The intermediate host of the Guinea worm ( Dracunculus medinensis ), the nematode that causes dracunculiasis disease in humans. This disease may be close to being eradicated through efforts by the U.S. Centers for Disease Control and Prevention and the World Health Organization . Despite their modern abundance, due to their small size and fragility, copepods are extremely rare in the fossil record. The oldest known fossils of copepods are from
2760-590: The last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic . Some of the relationships between organisms that the molecular biology arm of cladistics has revealed include that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria , and multicellular organisms may have evolved from archaea. The term "clade"
2820-456: The late Carboniferous ( Pennsylvanian ) of Oman , around 303 million years old, which were found in a clast of bitumen from a glacial diamictite . The copepods present in the bitumen clast were likely residents of a subglacial lake which the bitumen had seeped upwards through while still liquid, before the clast subsequently solidified and was deposited by glaciers. Though most of the remains were undiagnostic, at least some likely belonged to
2880-518: The latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses. Three methods of defining clades are featured in phylogenetic nomenclature : node-, stem-, and apomorphy-based (see Phylogenetic nomenclature§Phylogenetic definitions of clade names for detailed definitions). The relationship between clades can be described in several ways: The age of
2940-442: The main exception. The evidence for this clade derives from molecular data and morphological characteristics. The molecular data consists of comparisons of nuclear ribosomal RNA genes , mitochondrial ribosomal RNA genes, and protein coding genes. The morphological data consists of ommatidial structures (see arthropod eye ), the presence of neuroblasts , and the form and style of axonogenesis by pioneer neurons . In
3000-411: The male copepod grips the female with his first pair of antennae, which is sometimes modified for this purpose. The male then produces an adhesive package of sperm and transfers it to the female's genital opening with his thoracic limbs. Eggs are sometimes laid directly into the water, but many species enclose them within a sac attached to the female's body until they hatch. In some pond-dwelling species,
3060-484: The mosquitoes breed. Copepods, primarily of the genera Mesocyclops and Macrocyclops (such as Macrocyclops albidus ), can survive for periods of months in the containers, if the containers are not completely drained by their users. They attack, kill, and eat the younger first- and second- instar larvae of the mosquitoes. This biological control method is complemented by community trash removal and recycling to eliminate other possible mosquito-breeding sites. Because
SECTION 50
#17328491181813120-484: The naked eye, but are small enough that they only appear as little white specks. These are problematic, as it is a question as to whether they are considered visible enough to be non-Kosher. When a group of rabbis in Brooklyn, New York , discovered these copepods in the summer of 2004, they triggered such debate in rabbinic circles that some observant Jews felt compelled to buy and install filters for their water. The water
3180-470: The oceans are believed to be the world's largest carbon sink, absorbing about 2 billion tons of carbon a year, the equivalent to perhaps a third of human carbon emissions , thus reducing their impact. Many planktonic copepods feed near the surface at night, then sink (by changing oils into more dense fats) into deeper water during the day to avoid visual predators. Their moulted exoskeletons , faecal pellets, and respiration at depth all bring carbon to
3240-579: The spread of viral infections . HIV , for example, has clades called subtypes, which vary in geographical prevalence. HIV subtype (clade) B, for example is predominant in Europe, the Americas and Japan, whereas subtype A is more common in east Africa. Copepod Copepods ( / ˈ k oʊ p ə p ɒ d / ; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat . Some species are planktonic (living in
3300-656: The spring and summer on plankton blooms . These droplets may take up over half of the volume of their bodies in polar species. Many copepods (e.g., fish lice like the Siphonostomatoida ) are parasites, and feed on their host organisms. In fact, three of the 10 known orders of copepods are wholly or largely parasitic, with another three comprising most of the free-living species. Most nonparasitic copepods are holoplanktonic, meaning they stay planktonic for all of their lifecycles, although harpacticoids, although free-living, tend to be benthic rather than planktonic. During mating,
3360-483: The tip. Parasitic copepods (the other seven orders) vary widely in morphology and no generalizations are possible. Because of their small size, copepods have no need of any heart or circulatory system (the members of the order Calanoida have a heart, but no blood vessels ), and most also lack gills . Instead, they absorb oxygen directly into their bodies. Their excretory system consists of maxillary glands. The second pair of cephalic appendages in free-living copepods
3420-585: The water column), some are benthic (living on the sediments), several species have parasitic phases , and some continental species may live in limnoterrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds, puddles, damp moss, or water-filled recesses of plants ( phytotelmata ) such as bromeliads and pitcher plants . Many live underground in marine and freshwater caves, sinkholes , or stream beds. Copepods are sometimes used as biodiversity indicators . As with other crustaceans, copepods have
3480-463: The water in these containers is drawn from uncontaminated sources such as rainfall, the risk of contamination by cholera bacteria is small, and in fact no cases of cholera have been linked to copepods introduced into water-storage containers. Trials using copepods to control container-breeding mosquitoes are underway in several other countries, including Thailand and the southern United States . The method, though, would be very ill-advised in areas where
3540-431: Was confirmed in later molecular studies. Myriapoda Ostracoda Branchiura Pentastomida Mystacocarida Branchiopoda Copepod Thecostraca Malacostraca Remipedia Cephalocarida Hexapoda In a 2012 molecular study, von Reumont et al. challenge the monophyly of Vericrustacea: they present four versions of Pancrustacea cladogram (figures 1–4), and in all four figures Remipedia
3600-556: Was ruled kosher by posek Yisrael Belsky , chief posek of the OU and one of the most scientifically literate poskim of his time. Meanwhile, Rabbi Dovid Feinstein , based on the ruling of Rabbi Yosef Shalom Elyashiv - the two widely considered to be the greatest poskim of their time - ruled it was not kosher until filtered. Several major kashrus organizations (e.g OU Kashrus and Star-K ) require tap water to have filters. The Nickelodeon television series SpongeBob SquarePants features
#180819