Symphysodon, colloquially known as discus, is a genus of cichlids native to the Amazon river basin in South America. Due to their distinctive shape and bright colors, discus are popular as freshwater aquarium fish, their aquaculture in several countries in Asia is a major industry, they are sometimes referred to as pompadour fish. Following a review published in 2006, three species are recognized by FishBase: Symphysodon aequifasciatus Pellegrin, 1904 Symphysodon discus Heckel, 1840 Symphysodon tarzoo E. Lyons, 1959 Discus are fish from the genus Symphysodon, which includes the species S. aequifasciatus, S. discus and S. tarzoo, based on a taxonomic review published in 2006. A review published in 2007 came to the same result, but differed in nomenclature, as the species called S. tarzoo in the 2006 study was called S. aequifasciatus in the 2007 study, S. aequifasciatus in 2006 was S. haraldi in 2007. Further arguments have been made that S. tarzoo was not described in accordance with ICZN rules and thus should be considered invalid and replaced with S. haraldi considered a synonym of S. aequifasciatus by FishBase.
Other species have been proposed, but morphometric data varies as much between individuals from one location as across the whole range of all discus fish species. S. tarzoo applies to the red-spotted western population. S. aequifasciatus and S. discus, seem to hybridise in the wild or have diverged as they lack mitochondrial DNA lineage sorting but differ in color pattern and have dissimilar chromosomal translocation patterns. S. discus occurs in the Rio Negro. Whether S. haraldi is indeed distinct from S. aequifasciatus remains to be determined. A molecular study in 2011 found five main groups, which matched recognized phenotypes, they recognized them as evolutionarily significant species. Their assigning of scientific names to species differed to some extent from that used by earlier authors: Heckel, blue, Xingu group; the Xingu group lacks a scientific name, but it is possible that the correct name for the blue is S. haraldi. This taxonomy with four described valid species, S. discus, S. tarzoo, S. haraldi and S. aequifasciatus, has been adopted by the Catalog of Fishes.
Some hybridisation occurs between the brown discus and neighbouring forms, but overall they maintain their separate evolutionary trajectories. In addition to the wild discus, several captive variants achieved by selective breeding exist. Based on RAPD sequences, the captive variants popularly known as turquoise, ghost and solid red are derived from wild green and brown discus. Like cichlids from the genus Pterophyllum, all Symphysodon species have a laterally compressed body shape. In contrast to Pterophyllum, extended finnage is absent giving Symphysodon a more rounded shape, it is this body shape from which "discus", is derived. The sides of the fish are patterned in shades of green, red and blue; some of the more brightly marked variants are the result of selective breeding by aquarists and do not exist in the wild. Discus reach up to 12.3–15.2 cm in length, but captives have been claimed to reach 23 cm. Adults weigh 150–250 g. There is no clear sexual dimorphism for this fish. In breeding form varieties, solid red discus females are redder than males.
Symphysodon are social occurring in groups that may number many dozens of individuals, unique among cichlids of the Americas. When breeding, the pair moves away from the group to reduce the risk of cannibalism of the young; as for most cichlids, brood care is developed with both the parents caring for the young. Additionally, adult discus produce a secretion through their skin, which the larvae live off during their first four weeks. During the first two weeks, the parents stay near their young allowing them to feed easily. In the last two they swim away, resulting in the young being "weaned off" and starting to fend for themselves. Although rare in fish, more than 30 species of cichlids are known to feed their young with skin secretion to various extent, including Pseudetroplus and Uaru species. Sexual maturity is reached in one year. Recent research have shown that, through this unique parental care behaviour, Discus fish parents transmit key microorganisms to their fry; this parent-to-offspring transmission of important microorganisms might explain the high survival rate of discus fry raised with their parents, compared to the low survival rate of progenies raised artificially by Discus fish breeders.
Symphysodon feed on algae, other plant material and detritus, but eat small invertebrates. Invertebrates can make up 38% of the stomach content in wild S. aequifasciatus during the high-water season, but this decreases during the low-water season and year-round it is lower in the other species. Unlike more predatory cichlids, Symphysodon have long intestine
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians have a larval phase of their life cycle; the larva's appearance is very different from the adult form including different unique structures and organs that do not occur in the adult form. Their diet may be different. Larvae are adapted to environments separate from adults. For example, some larvae such as tadpoles live exclusively in aquatic environments, but can live outside water as adult frogs. By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population. Animals in the larval stage will consume food to fuel their transition into the adult form. In some species like barnacles, adults are immobile but their larvae are mobile, use their mobile larval form to distribute themselves; some larvae are dependent on adults to feed them. In many eusocial Hymenoptera species, the larvae are fed by female workers.
In Ropalidia marginata the males are capable of feeding larvae but they are much less efficient, spending more time and getting less food to the larvae. The larvae of some species do not develop further into the adult form; this is a type of neoteny. It is a misunderstanding; this could be the case, but the larval stage has evolved secondarily, as in insects. In these cases the larval form may differ more than the adult form from the group's common origin. Within Insects, only Endopterygotes show different types of larvae. Several classifications have been suggested by many entomologists, following classification is based on Antonio Berlese classification in 1913. There are four main types of endopterygote larvae types: Apodous larvae – no legs at all and are poorly sclerotized. Based on sclerotization, three apodous forms are recognized. Eucephalous – with well sclerotized head capsule. Found in Nematocera and Cerambycidae families. Hemicephalus – with a reduced head capsule, retractable in to the thorax.
Found in Tipulidae and Brachycera families. Acephalus – without head capsule. Found in Cyclorrhapha Protopod larvae – larva have many different forms and unlike a normal insect form, they hatch from eggs which contains little yolk. Ex. first instar larvae of parasitic hymenoptera. Polypod larvae – known as eruciform larvae, these larva have abdominal prolegs, in addition to usual thoracic legs, they poorly sclerotized and inactive. They live in close contact with the food. Best example is caterpillars of lepidopterans. Oligopod larvae – have well developed head capsule and mouthparts are similar to the adult, but without compound eyes, they have six legs. No abdominal prolegs. Two types can be seen: Campodeiform – well sclerotized, dorso-ventrally flattened body. Long legged predators with prognathous mouthparts.. Scarabeiform – poorly sclerotized, flat thorax and abdomen. Short legged and inactive burrowing forms.. Crustacean larvae Ichthyoplankton Spawn Non-larval animal juvenile stages and other life cycle stages: In Porifera: olynthus, gemmule In Cnidaria: ephyra, strobila, hydranth, medusa In Mollusca: paralarva, young cephalopods In Platyhelminthes: hydatid cyst In Bryozoa: avicularium In Acanthocephala: cystacanth In Insecta: Nymphs and naiads, immature forms in hemimetabolous insects Subimago, a juvenile that resembles the adult in Ephemeroptera Instar, intermediate between each ecdysis Pupa and chrysalis, intermediate stages between larva and imago Protozoan life cycle stages Apicomplexan life cycle Algal life cycle stages: Codiolum-phase Conchocelis-phase Marine larval ecology Media related to Larvae at Wikimedia Commons The dictionary definition of larva at Wiktionary Arenas-Mena, C.
Indirect development, transdifferentiation and the macroregulatory evolution of metazoans. Philosophical Transactions of the Royal Society B: Biological Sciences. Feb 27, 2010 Vol.365 no.1540 653-669 Brusca, R. C. & Brusca, G. J.. Invertebrates. Sunderland, Mass.: Sinauer Associates. Hall, B. K. & Wake, M. H. eds.. The Origin and Evolution of Larval Forms. San Diego: Academic Press. Leis, J. M. & Carson-Ewart, B. M. eds.. The Larvae of Indo-Pacific Coastal Fishes. An Identification Guide to Marine Fish Larvae. Fauna Malesiana handbooks, vol. 2. Brill, Leiden. Minelli, A.. The larva. In: Perspectives in Animal Phylogeny and Evolution. Oxford University Press. P. 160-170. Link. Shanks, A. L.. An Identification Guide to the Larval Marine Invertebrates of the Pacific Northwest. Oregon State University Press, Corvallis. 256 pp. Smith, D. & Johnson, K. B.. A Guide to Marine Coastal Plankton and Marine Invertebrate Larvae. Kendall/Hunt Plublishing Company. Stanwell-Smith, D. Hood, A. & Peck, L. S.. A field guide to the pelagic invertebrates larvae of the maritime Antarctic.
British Antarctic Survey, Cambridge. Thyssen, P. J.. Keys for Identification of Immature Insects. In: Amendt, J. et al.. Current Concepts in Forensic Entomology, chapter 2, pp. 25–42. Springer: Dordrecht
Spirulina is a genus of cyanobacteria. Spirulina spp Arthrospira
The free-living nematode Panagrellus redivivus, is known to many aquarium enthusiasts and fish keepers as the micro-worm. It is a tiny roundworm used as the first food for larger kinds of newly-hatched fish, such as larval common carp; the microworm is used in aquaculture as food for a variety of fish and crustacean species. One of thirteen recognized species of Panagrellus, P. redivivus is about 50 μm in diameter and just over 1 mm in length visible to the naked eye. Subsisting on yeast, it is cultured at home on a substrate of flour paste or porridge inoculated with dry yeast. Females reach maturity in about three days and deliver live young rather than eggs, as most nematodes produce; the microworm has been used in genetic analysis studies, but not nearly as universally as its relative, Caenorhabditis elegans. In Vietnamese cuisine, cơm mẻ is a ingredient appears in many dishes such as buffalo meat and fish soup thanks to its sourness. Cơm mẻ is the cooked rice being lactic fermented by yeast and maintained with the existence of P. redivivus.
Kovaleva, E. S.. "Panagrellus redivivus as a molecular model for cyst nematodes". Journal of Nematology. 35: 348. Sautter J. Kaiser H. Focken U. Becker K.. "Panagrellus redivivus as a live food organism in the early rearing of the catfish Synodontis petricola". Aquaculture Research. 38: 653–659. Doi:10.1111/j.1365-2109.2007.01714.x. CS1 maint: Uses authors parameter Batchelder, E. "Panagrellus redivivus" at Unity College Nematodes Photos
Protozoa is an informal term for single-celled eukaryotes, either free-living or parasitic, which feed on organic matter such as other microorganisms or organic tissues and debris. The protozoa were regarded as "one-celled animals", because they possess animal-like behaviors, such as motility and predation, lack a cell wall, as found in plants and many algae. Although the traditional practice of grouping protozoa with animals is no longer considered valid, the term continues to be used in a loose way to identify single-celled organisms that can move independently and feed by heterotrophy. In some systems of biological classification, Protozoa is a high-level taxonomic group; when first introduced in 1818, Protozoa was erected as a taxonomic class, but in classification schemes it was elevated to a variety of higher ranks, including phylum and kingdom. In a series of classifications proposed by Thomas Cavalier-Smith and his collaborators since 1981, Protozoa has been ranked as a kingdom; the seven-kingdom scheme presented by Ruggiero et al. in 2015, places eight phyla under Kingdom Protozoa: Euglenozoa, Metamonada, Choanozoa sensu Cavalier-Smith, Percolozoa and Sulcozoa.
Notably, this kingdom excludes several major groups of organisms traditionally placed among the protozoa, including the ciliates, dinoflagellates and the parasitic apicomplexans, all of which are classified under Kingdom Chromista. Kingdom Protozoa, as defined in this scheme, does not form a natural group or clade, but a paraphyletic group or evolutionary grade, within which the members of Fungi and Chromista are thought to have evolved; the word "protozoa" was coined in 1818 by zoologist Georg August Goldfuss, as the Greek equivalent of the German Urthiere, meaning "primitive, or original animals". Goldfuss created Protozoa as a class containing; the group included not only single-celled microorganisms but some "lower" multicellular animals, such as rotifers, sponges, jellyfish and polychaete worms. The term Protozoa is formed from the Greek words πρῶτος, meaning "first", ζῶα, plural of ζῶον, meaning "animal"; the use of Protozoa as a formal taxon has been discouraged by some researchers because the term implies kinship with animals and promotes an arbitrary separation of "animal-like" from "plant-like" organisms.
In 1848, as a result of advancements in cell theory pioneered by Theodor Schwann and Matthias Schleiden, the anatomist and zoologist C. T. von Siebold proposed that the bodies of protozoans such as ciliates and amoebae consisted of single cells, similar to those from which the multicellular tissues of plants and animals were constructed. Von Siebold redefined Protozoa to include only such unicellular forms, to the exclusion of all metazoa. At the same time, he raised the group to the level of a phylum containing two broad classes of microorganisms: Infusoria, Rhizopoda; the definition of Protozoa as a phylum or sub-kingdom composed of "unicellular animals" was adopted by the zoologist Otto Bütschli—celebrated at his centenary as the "architect of protozoology"—and the term came into wide use. As a phylum under Animalia, the Protozoa were rooted in the old "two-kingdom" classification of life, according to which all living beings were classified as either animals or plants; as long as this scheme remained dominant, the protozoa were understood to be animals and studied in departments of Zoology, while photosynthetic microorganisms and microscopic fungi—the so-called Protophyta—were assigned to the Plants, studied in departments of Botany.
Criticism of this system began in the latter half of the 19th century, with the realization that many organisms met the criteria for inclusion among both plants and animals. For example, the algae Euglena and Dinobryon have chloroplasts for photosynthesis, but can feed on organic matter and are motile. In 1860, John Hogg argued against the use of "protozoa", on the grounds that "naturalists are divided in opinion—and some will continue so—whether many of these organisms, or living beings, are animals or plants." As an alternative, he proposed a new kingdom called Primigenum, consisting of both the protozoa and unicellular algae, which he combined together under the name "Protoctista". In Hoggs's conception, the animal and plant kingdoms were likened to two great "pyramids" blending at their bases in the Kingdom Primigenum. Six years Ernst Haeckel proposed a third kingdom of life, which he named Protista. At first, Haeckel included a few multicellular organisms in this kingdom, but in work he restricted the Protista to single-celled organisms, or simple colonies whose individual cells are not differentiated into different kinds of tissues.
Despite these proposals, Protozoa emerged as the preferred taxonomic placement for heterotrophic microorganisms such as amoebae and ciliates, remained so for more than a century. In the course of the 20th century, the old "two kingdom" system began to weaken, with the growing awareness that fungi did not belong among the plants, that most of the unicellular protozoa were no more related to the animals than they were to the plants. By mid-century, some biologists, such as Herbert Copeland, Robert H. Whittaker and Lynn Margulis, advocated the revival of Haeckel's Protista or Hogg's Protoctista as a kingdom-level eukaryotic group, alongside Plants and Fungi. A variety of multi-kingdom systems were proposed, Kingdoms Protista and Protoctista became well est
The Chironomidae comprise a family of nematoceran flies with a global distribution. They are related to the Ceratopogonidae and Thaumaleidae. Many species superficially resemble mosquitoes, but they lack the wing scales and elongated mouthparts of the Culicidae; the name Chironomidae stems from the Ancient Greek word kheironómos, "a pantomimist". This is a large taxon of insects. Males are recognized by their plumose antennae. Adults are known by a variety of vague and inconsistent common names by confusion with other insects. For example, chironomids are known as "lake flies" in parts of Canada and Lake Winnebago, but "bay flies" in the areas near the bay of Green Bay, Wisconsin, they are called "sand flies", "muckleheads", "muffleheads", "Canadian soldiers", or "American soldiers" in various regions of the Great Lakes area. They have been called "chizzywinks" in Florida. However, they are not mosquitoes of any sort, the term "sandflies" refers to various species of biting flies unrelated to the Chironomidae.
The group includes the largest terrestrial animal of Antarctica. The biodiversity of the Chironomidae goes unnoticed because they are notoriously difficult to identify and ecologists record them by species groups; each morphologically distinct group comprises a number of morphologically identical species that can only be identified by rearing adult males or by cytogenetic analysis of the polytene chromosomes. Polytene chromosomes were observed in the larval salivary glands of Chironomus midges by Balbiani in 1881, they form through repeated rounds of DNA replication without cell division, resulting in characteristic light and dark banding patterns which can be used to identify inversions and deletions which allow species identification. Larval stages of the Chironomidae can be found in any aquatic or semiaquatic habitat, including treeholes, rotting vegetation, in sewage and artificial containers, they form an important fraction of the macrozoobenthos of most freshwater ecosystems. They are associated with degraded or low-biodiversity ecosystems because some species have adapted to anoxic conditions and are dominant in polluted waters.
Larvae of some species are bright red in color due to a hemoglobin analog. Their ability to capture oxygen is further increased by their making undulating movements. Many reference sources in the past century or so have repeated the assertion that the Chironomidae do not feed as adults, but an increasing body of evidence contradicts this view. Adults of many species do, in fact; the natural foods reported include fresh fly droppings, pollen and various sugar-rich materials. The question whether feeding is of practical importance has by now been settled for some Chironomus species, at least; some authors suggest the males apply the resources obtained in feeding differently. Males expend the extra energy on flight, while females use their food resources to achieve longer lifespans; the respective strategies should be compatible with maximal probability of successful mating and reproduction in those species that do not mate after eclosion, in particular in species that have more than one egg mass maturing, the less developed masses being oviposited after a delay.
Such variables would be relevant to species that exploit wind for dispersal, laying eggs at intervals. Chironomids that feed on nectar or pollen may well be of importance as pollinators, but current evidence on such points is anecdotal. However, the content of protein and other nutrients in pollen, in comparison to nectar, might well contribute to the females' reproductive capacities. Adults can be pests, they can damage paint and other surfaces with their droppings. When large numbers of adults die, they can build up into malodorous piles, they can provoke allergic reactions in sensitive individuals. Larvae and pupae are important food items for fish, such as trout, banded killifish, sticklebacks, for many other aquatic organisms as well such as newts. Many aquatic insects, such as various predatory hemipterans in the families Nepidae and Corixidae eat Chironomidae in their aquatic phases. So do predatory water beetles in families such as the Dytiscidae and Hydrophilidae; the flying midges are eaten by insectivorous birds, such as swallows and martins.
They are preyed on by bats and flying predatory insects, such as Odonata and dance flies. The Chironomidae are important as indicator organisms, i.e. the presence, absence, or quantities of various species in a body of water can indicate whether pollutants are present. Their fossils are used by palaeolimnologists as indicators of past environmental changes, including past climatic variability. Contemporary specimens are used by forensic entomologists as medico-legal markers for the postmortem interval assessment. A number of chironomid species inhabit marine habitats. Midges of the genus Clunio are found in the intertidal zone, where they have adjusted their entire life cycle to the rhythm of the tides; this made the species Clunio marinus an important model species for research in the field of chronobiology. Anhydrobiosis is the ability of an organism to survive in the dry state. Anhydrobiotic larvae of the African chironomid P
The goldfish is a freshwater fish in the family Cyprinidae of order Cypriniformes. It is one of the most kept aquarium fish. A small member of the carp family, the goldfish is native to East Asia, it was first selectively bred in Ancient China more than a thousand years ago, several distinct breeds have since been developed. Goldfish breeds vary in size, body shape, fin configuration and colouration. Starting in ancient China, various species of carp have been bred and reared as food fish for thousands of years; some of these gray or silver species have a tendency to produce red, orange or yellow colour mutations. During the Tang dynasty, it was popular to raise carp in ornamental watergardens. A natural genetic mutation produced gold rather than silver colouration. People began to breed the gold variety instead of the silver variety, keeping them in ponds or other bodies of water. On special occasions at which guests were expected, they would be moved to a much smaller container for display. By the Song dynasty, the selective domestic breeding of goldfish was established.
In 1162, the empress of the Song Dynasty ordered the construction of a pond to collect the red and gold variety. By this time, people outside the imperial family were forbidden to keep goldfish of the gold variety, yellow being the imperial colour; this is the reason why there are more orange goldfish than yellow goldfish though the latter are genetically easier to breed. The occurrence of other colours was first recorded in 1276. During the Ming dynasty, goldfish began to be raised indoors, which permitted selection for mutations that would not be able to survive in ponds; the first occurrence of fancy-tailed goldfish was recorded in the Ming Dynasty. In 1603, goldfish were introduced to Japan. In 1611, goldfish were introduced from there to other parts of Europe. During the 1620s, goldfish were regarded in southern Europe because of their metallic scales, symbolised good luck and fortune, it became tradition for married men to give their wives a goldfish on their first anniversary, as a symbol for the prosperous years to come.
This tradition died, as goldfish became more available, losing their status. Goldfish were first introduced to North America around 1850 and became popular in the United States; as of April 2008, the largest goldfish in the world was believed by the BBC to measure 19 inches, be living in the Netherlands. At the time, a goldfish named "Goldie", kept as a pet in a tank in Folkestone, was measured as 15 inches and over 2 pounds, named as the second largest in the world behind the Netherlands fish; the secretary of the Federation of British Aquatic Societies stated of Goldie's size that "I would think there are a few bigger goldfish that people don't think of as record holders in ornamental lakes". In July 2010, a goldfish measuring 16 inches and 5 pounds was caught in a pond in Poole, thought to have been abandoned there after outgrowing a tank. Goldfish have one of the most studied senses of vision in fish. Goldfish have four kinds of cone cells, which are sensitive to different colours: red, green and ultraviolet.
The ability to distinguish between four different primary colours classifies them as tetrachromats. Goldfish have one of the most studied senses of hearing in fish, they have two otoliths, permitting the detection of sound particle motion, Weberian ossicles connecting the swimbladder to the otoliths, facilitating the detection of sound pressure. Goldfish have strong associative learning abilities, as well as social learning skills. In addition, their visual acuity allows them to distinguish between individual humans. Owners may notice that fish react favorably to them while hiding when other people approach the tank. Over time, goldfish learn to associate their owners and other humans with food "begging" for food whenever their owners approach. Goldfish that have constant visual contact with humans stop considering them to be a threat. After being kept in a tank for several weeks, sometimes months, it becomes possible to feed a goldfish by hand without it shying away. Goldfish have a memory-span of at least three months and can distinguish between different shapes and sounds.
By using positive reinforcement, goldfish can be trained to recognize and to react to light signals of different colours or to perform tricks. Fish respond to certain colours most evidently in relation to feeding. Fish learn to anticipate feedings provided. Goldfish are gregarious, displaying schooling behaviour, as well as displaying the same types of feeding behaviours. Goldfish may display similar behaviours. Goldfish have learned behaviours, both as groups and as individuals, that stem from native carp behaviour, they are a generalist species with varied feeding and predator avoidance behaviours that contribute to their success. As fish they can be described as "friendly" towards each other. Does a goldfish harm another goldfish, nor do the males harm the females during breeding; the only real threat that goldfish present to each other is competing for food. Commons and other f