Fish are gill-bearing aquatic craniate animals that lack limbs with digits. They form a sister group to the tunicates. Included in this definition are the living hagfish and cartilaginous and bony fish as well as various extinct related groups. Tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered paraphyletic by excluding the tetrapods; because in this manner the term "fish" is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology, unless it is used in the cladistic sense, including tetrapods. The traditional term pisces is considered a typological, but not a phylogenetic classification; the earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era.
Many fish of the Paleozoic developed external armor. The first fish with jaws appeared in the Silurian period, after which many became formidable marine predators rather than just the prey of arthropods. Most fish are ectothermic, allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish can communicate in their underwater environments through the use of acoustic communication. Acoustic communication in fish involves the transmission of acoustic signals from one individual of a species to another; the production of sounds as a means of communication among fish is most used in the context of feeding, aggression or courtship behaviour. The sounds emitted by fish can vary depending on the stimulus involved, they can produce either stridulatory sounds by moving components of the skeletal system, or can produce non-stridulatory sounds by manipulating specialized organs such as the swimbladder.
Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams to the abyssal and hadal depths of the deepest oceans, although no species has yet been documented in the deepest 25% of the ocean. With 33,600 described species, fish exhibit greater species diversity than any other group of vertebrates. Fish are an important resource for humans worldwide as food. Commercial and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean, they are caught by recreational fishers, kept as pets, raised by fishkeepers, exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, as the subjects of art and movies. Fish do not represent a monophyletic group, therefore the "evolution of fish" is not studied as a single event. Early fish from the fossil record are represented by a group of small, armored fish known as ostracoderms. Jawless fish lineages are extinct.
An extant clade, the lampreys may approximate ancient pre-jawed fish. The first jaws are found in Placodermi fossils; the diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, or a combination of factors. Fish may have evolved from a creature similar to a coral-like sea squirt, whose larvae resemble primitive fish in important ways; the first ancestors of fish may have kept the larval form into adulthood, although the reverse is the case. Fish are a paraphyletic group: that is, any clade containing all fish contains the tetrapods, which are not fish. For this reason, groups such as the "Class Pisces" seen in older reference works are no longer used in formal classifications. Traditional classification divides fish into three extant classes, with extinct forms sometimes classified within the tree, sometimes as their own classes: Class Agnatha Subclass Cyclostomata Subclass Ostracodermi † Class Chondrichthyes Subclass Elasmobranchii Subclass Holocephali Class Placodermi † Class Acanthodii † Class Osteichthyes Subclass Actinopterygii Subclass Sarcopterygii The above scheme is the one most encountered in non-specialist and general works.
Many of the above groups are paraphyletic, in that they have given rise to successive groups: Agnathans are ancestral to Chondrichthyes, who again have given rise to Acanthodiians, the ancestors of Osteichthyes. With the arrival of phylogenetic nomenclature, the fishes has been split up into a more detailed scheme, with the following major groups: Class Myxini Class Pteraspidomorphi † Class Thelodonti † Class Anaspida † Class Petromyzontida or Hyperoartia Petromyzontidae Class Conodonta † Class Cephalaspidomorphi † Galeaspida † Pituriaspida † Osteostraci † Infraphylum Gnathostomata Class Placodermi † Class Chondrichthyes Class Acanthodii † Superclass Osteichthy
The bat ray is an eagle ray found in muddy or sandy sloughs and bays, kelp beds and rocky-bottomed shoreline in the eastern Pacific Ocean, between the Oregon coast and the Gulf of California. It is found in the area around the Galápagos Islands; the largest specimens can grow to a mass of 91 kg. They more range from 9.07–13.61 kg. Bat rays are euryhaline. Bat rays feed on mollusks and small fish on the seabed, using their winglike pectoral fins to move sand and expose prey animals, they may dig trenches up to 20 cm deep to expose buried prey, such as clams. Bat ray teeth are flat and pavementlike, forming tightly-packed rows that are used for crushing and grinding prey—the crushed shells are ejected and the flesh consumed; as with all elasmobranchs, these teeth are replaced continuously. While the bat ray, like other stingrays, has a venomous spine in its tail, it is not considered dangerous and uses the spine only when attacked or frightened; the bat ray is fished commercially in Mexico but not the United States.
Prehistorically, native tribes on the California coast in the San Francisco Bay area, fished bat rays in large numbers for food. Commercial growers have long trapped them in large numbers. In fact, crabs are principally responsible for oyster loss. Bat rays are not considered endangered or threatened. Bat Rays are popular in marine parks, visitors are allowed to touch or stroke the ray on the wing. Bat ray reproduction is ovoviviparous, they mate annually, in the spring or summer, have a gestation period of nine to twelve months. Litter sizes range from two to ten — pups emerge with their pectoral fins wrapped around the body, the venomous spine is flexible and covered in a sheath which sloughs off within hours of birth. Bat rays live up to 23 years. Bat rays copulate; the male inserts a clasper into the female's cloaca, channeling semen into the orifice to fertilize her eggs
Midges are a group of insects that include many kinds of small flies. They are found on every land area outside permanently arid deserts and the frigid zones; the term "midge" does not define any particular taxonomic group, but includes species in several families of Nematoceran Diptera. Some midges, such as many Phlebotominae and Simuliidae, are vectors of various diseases. Many others play useful roles as prey items such as various frogs and swallows. Others are important as detritivores, participating in various nutrient cycles; the habits of midges vary from species to species, though within any particular family, midges have similar ecological roles. One type of midge ceratopogonid midges is a major pollinator of Theobroma cacao because of its unique morphological and behavioral characteristics. Having natural pollinators has beneficial effects in both agricultural and biological production because it increases Theobroma cacao crop yield and density of predators of the midges. Examples of families that include species of midges include: Blephariceridae, net-winged midges Cecidomyiidae, gall midges Ceratopogonidae, biting midges Chaoboridae, phantom midges Chironomidae, non-biting midges Deuterophlebiidae, mountain midges Dixidae, meniscus midges Scatopsidae, dung midges Theumaleidae, solitary midges The Ceratopogonidae include serious blood-sucking pests, feeding both on humans and other mammals.
Some of them spread the livestock diseases blue tongue and African horse sickness – other species though, are at least nectar feeders and some suck insect bodily fluids. Most other midge families are not bloodsuckers, but it is not possible to generalise rigidly because of the vagueness of the term "midge". There is for example no objective basis for excluding the Psychodidae from the list, some of them are blood-sucking pests and disease vectors. Most midges, apart from the gall midges, are aquatic during the larval stage; some Cecidomyiidae are significant plant pests. The larvae of some Chironomidae are sometimes referred to as bloodworms. Non-biting midge flies are a common minor nuisance around man-made bodies of water. Mosquito Highland midge
In ecology, a habitat is the type of natural environment in which a particular species of organism lives. It is characterized by both biological features. A species' habitat is those places where it can find food, shelter and mates for reproduction; the physical factors are for example soil, range of temperature, light intensity as well as biotic factors such as the availability of food and the presence or absence of predators. Every organism has certain habitat needs for the conditions in which it will thrive, but some are tolerant of wide variations while others are specific in their requirements. A habitat is not a geographical area, it can be the interior of a stem, a rotten log, a rock or a clump of moss, for a parasitic organism it is the body of its host, part of the host's body such as the digestive tract, or a single cell within the host's body. Habitat types include polar, temperate and tropical; the terrestrial vegetation type may be forest, grassland, semi-arid or desert. Fresh water habitats include marshes, rivers and ponds, marine habitats include salt marshes, the coast, the intertidal zone, reefs, the open sea, the sea bed, deep water and submarine vents.
Habitats change over time. This may be due to a violent event such as the eruption of a volcano, an earthquake, a tsunami, a wildfire or a change in oceanic currents. Other changes come as a direct result of human activities; the introduction of alien species can have a devastating effect on native wildlife, through increased predation, through competition for resources or through the introduction of pests and diseases to which the native species have no immunity. The word "habitat" has been in use since about 1755 and derives from the Latin habitāre, to inhabit, from habēre, to have or to hold. Habitat can be defined as the natural environment of an organism, the type of place in which it is natural for it to live and grow, it is similar in meaning to a biotope. The chief environmental factors affecting the distribution of living organisms are temperature, climate, soil type and light intensity, the presence or absence of all the requirements that the organism needs to sustain it. Speaking, animal communities are reliant on specific types of plant communities.
Some plants and animals are generalists, their habitat requirements are met in a wide range of locations. The small white butterfly for example is found on all the continents of the world apart from Antarctica, its larvae feed on a wide range of Brassicas and various other plant species, it thrives in any open location with diverse plant associations. The large blue butterfly is much more specific in its requirements. Disturbance is important in the creation of biodiverse habitats. In the absence of disturbance, a climax vegetation cover develops that prevents the establishment of other species. Wildflower meadows are sometimes created by conservationists but most of the flowering plants used are either annuals or biennials and disappear after a few years in the absence of patches of bare ground on which their seedlings can grow. Lightning strikes and toppled trees in tropical forests allow species richness to be maintained as pioneering species move in to fill the gaps created. Coastal habitats can become dominated by kelp until the seabed is disturbed by a storm and the algae swept away, or shifting sediment exposes new areas for colonisation.
Another cause of disturbance is when an area may be overwhelmed by an invasive introduced species, not kept under control by natural enemies in its new habitat. Terrestrial habitat types include forests, grasslands and deserts. Within these broad biomes are more specific habitats with varying climate types, temperature regimes, soils and vegetation types. Many of these habitats grade into each other and each one has its own typical communities of plants and animals. A habitat may suit a particular species well, but its presence or absence at any particular location depends to some extent on chance, on its dispersal abilities and its efficiency as a coloniser. Freshwater habitats include rivers, lakes, ponds and bogs. Although some organisms are found across most of these habitats, the majority have more specific requirements; the water velocity, its temperature and oxygen saturation are important factors, but in river systems, there are fast and slow sections, pools and backwaters which provide a range of habitats.
Aquatic plants can be floating, semi-submerged, submerged or grow in permanently or temporarily saturated soils besides bodies of water. Marginal plants provide important habitat for both invertebrates and vertebrates, submerged plants provide oxygenation of the water, absorb nutrients and play a part in the reduction of pollution. Marine habitats include brackish water, bays, the open sea, the intertidal zone, the sea bed and deep / shallow water zones. Further variations include rock pools, sand banks, brackish lagoons and pebbly beaches, seagrass beds, all supporting their own flora and fauna; the benth
The mallard is a dabbling duck that breeds throughout the temperate and subtropical Americas and North Africa and has been introduced to New Zealand, Peru, Uruguay, Chile, the Falkland Islands, South Africa. This duck belongs to the subfamily Anatinae of the waterfowl family Anatidae; the male birds have a glossy green head and are grey on their wings and belly, while the females have brown-speckled plumage. Both sexes have an area of white-bordered black or iridescent blue feathers called a speculum on their wings; the mallard is 50 -- 65 cm long. The wingspan is 81–98 cm and the bill is 4.4 to 6.1 cm long. It is slightly heavier than most other dabbling ducks, weighing 0.72–1.58 kg. Mallards live in wetlands, eat water plants and small animals, are social animals preferring to congregate in groups or flocks of varying sizes; this species is the main ancestor of most breeds of domesticated ducks. The female lays eight to thirteen creamy white to greenish-buff spotless eggs, on alternate days. Incubation takes 27 to 28 days and fledging takes 50 to 60 days.
The ducklings are precocial and capable of swimming as soon as they hatch. The mallard is considered to be a species of least concern by the International Union for Conservation of Nature. Unlike many waterfowl, mallards are considered an invasive species in some regions, it is a adaptable species, being able to live and thrive in urban areas which may have supported more localised, sensitive species of waterfowl before development. The non-migratory mallard interbreeds with indigenous wild ducks of related species through genetic pollution by producing fertile offspring. Complete hybridisation of various species of wild duck gene pools could result in the extinction of many indigenous waterfowl; the wild mallard is the ancestor of most domestic ducks, its evolved wild gene pool gets genetically polluted by the domesticated and feral mallard populations. The mallard was one of the many bird species described in the 1758 10th edition of Systema Naturae by Carl Linnaeus, he gave it two binomial names: Anas platyrhynchos and Anas boschas.
The latter was preferred until 1906 when Einar Lönnberg established that A. platyrhynchos had priority as it appeared on an earlier page in the text. The scientific name comes from Latin Anas, "duck" and Ancient Greek πλατυρυγχος, platyrhynchus, "broad-billed"; the genome of Anas platyrhynchos was sequenced in 2013. The name Mallard referred to any wild drake, it is sometimes still used this way, it was derived from the Old French malart or mallart for "wild drake" although its true derivation is unclear. It may be related to, or at least influenced by, an Old High German masculine proper name Madelhart, clues lying in the alternate English forms "maudelard" or "mawdelard". Masle has been proposed as an influence. Mallards interbreed with their closest relatives in the genus Anas, such as the American black duck, with species more distantly related, such as the northern pintail, leading to various hybrids that may be fertile; this is quite unusual among such different species, is because the mallard evolved rapidly and during the Late Pleistocene.
The distinct lineages of this radiation are kept separate due to non-overlapping ranges and behavioural cues, but have not yet reached the point where they are genetically incompatible. Mallards and their domesticated conspecifics are fully interfertile. Genetic analysis has shown that certain mallards appear to be closer to their Indo-Pacific relatives while others are related to their American relatives. Mitochondrial DNA data for the D-loop sequence suggests that mallards may have evolved in the general area of Siberia. Mallard bones rather abruptly appear in food remains of ancient humans and other deposits of fossil bones in Europe, without a good candidate for a local predecessor species; the large ice age palaeosubspecies that made up at least the European and west Asian populations during the Pleistocene has been named Anas platyrhynchos palaeoboschas. Mallards are differentiated in their mitochondrial DNA between North American and Eurasian populations, but the nuclear genome displays a notable lack of genetic structure.
Haplotypes typical of American mallard relatives and spotbills can be found in mallards around the Bering Sea. The Aleutian Islands hold a population of mallards that appear to be evolving towards a subspecies, as gene flow with other populations is limited; the paucity of morphological differences between the Old World mallards and the New World mallard demonstrates the extent to which the genome is shared among them such that birds like the Chinese spot-billed duck are similar to the Old World mallard, birds such as the Hawaiian duck are similar to the New World mallard. The size of the mallard varies clinally; the mallard is a medium-sized waterfowl species, slightly heavier than most other dabbling ducks. It is 50–65 cm long – of which the body makes up around two-thirds – has a wingspan of 81–98 cm,:505 and weighs 0.72–1.58 kg. Among standard measurements, the wing chord is 25.7 to 30.6 cm, the bill is 4.4 to 6.1 cm (
An anchovy is a small, common forage fish of the family Engraulidae. Most species are found in marine waters, but several will enter brackish water and some in South America are restricted to fresh water; the more than 140 species are placed in 17 genera. Anchovies are classified as oily fish. Anchovies are small, green fish with blue reflections due to a silver-colored longitudinal stripe that runs from the base of the caudal fin, they range from 2 to 40 cm in adult length, their body shapes are variable with more slender fish in northern populations. The snout is blunt with sharp teeth in both jaws; the snout contains a unique rostral organ, believed to be sensory in nature, although its exact function is unknown. The mouth is larger than that of herrings and silversides, two fish which anchovies resemble in other respects; the anchovy eats plankton and hatched fish. Anchovies are found in scattered areas throughout the world's oceans, but are concentrated in temperate waters, are rare or absent in cold or warm seas.
They are very accepting of a wide range of temperatures and salinity. Large schools can be found in brackish areas with muddy bottoms, as in estuaries and bays; the European anchovy is abundant in the Mediterranean in the Alboran Sea, Aegean Sea and the Black Sea. This species is caught along the coasts of Crete, Sicily, France, Turkey and Spain, they are found on the coast of northern Africa. The range of the species extends along the Atlantic coast of Europe to the south of Norway. Spawning occurs between October and March, but not in water colder than 12 °C; the anchovy appears to spawn at least 100 km near the surface of the water. The anchovy is a significant food source for every predatory fish in its environment, including the California halibut, rock fish, shark and coho salmon, it is extremely important to marine mammals and birds. Anchovies, like most clupeoids, are filter-feeders; as water passes through the mouth and out the gills, food particles are sieved by gill rakers and transferred into the esophagus.
* Type species On average, the Turkish commercial fishing fleet catches around 300,000 tons per year in winter. The largest catch is in December; the Peruvian anchovy fishery is one of the largest in the world, far exceeding catches of the other anchovy species. In 1973 it collapsed catastrophically due to the combined effects of overfishing and El Niño and did not recover for two decades. A traditional method of processing and preserving anchovies is to gut and salt them in brine, allow them to cure, pack them in oil or salt; this results in a characteristic strong flavor and the flesh turns deep grey. Pickled in vinegar, as with Spanish boquerones, anchovies are milder and the flesh retains a white color. In Roman times, anchovies were the base for the fermented fish sauce garum. Garum had a sufficiently long shelf life for long-distance commerce, was produced in industrial quantities. Anchovies were eaten raw as an aphrodisiac. Today, they are used in small quantities to flavor many dishes; because of the strong flavor, they are an ingredient in several sauces and condiments, including Worcestershire sauce, Caesar salad dressing, Gentleman's Relish, many fish sauces, in some versions of Café de Paris butter.
For domestic use, anchovy fillets are packed in oil or salt in small tins or jars, sometimes rolled around capers. Anchovy paste is available. Fishermen use anchovies as bait for larger fish, such as tuna and sea bass; the strong taste people associate with anchovies is due to the curing process. Fresh anchovies, known in Italy as alici, have a much milder flavor. In Sweden and Finland, the name anchovies is related to a traditional seasoning, hence the product "anchovies" is made of sprats and herring can be sold as "anchovy-spiced". Fish from the family Engraulidae are instead known as sardell in Sweden and sardelli in Finland, leading to confusion when translating recipes. Anchovies portal Sardine Chavez FP, Ryan J, Lluch-Cota SE and Ñiquen CM From Anchovies to Sardines and Back: Multidecadal Change in the Pacific Ocean Science 229217–221. Froese and Daniel Pauly, eds.. "Engraulidae" in FishBase. January 2006 version. Miller DJ "Anchovy" CalCOFI Reports, 5: 20–26. Nizinski MS and Munroe TA FAO species catalogue, volume 2: Clupeoid Fishes of the World, Anchovies Pages 764–780, FAO Fisheries Synopsis 125, Rome.
ISBN 92-5-102340-9. Pacific States Marine Fisheries Commission Northern Anchovy The dictionary definition of anchovy at Wiktionary Fisheries Ebb and Flow in 50-Year Cycle National Geographic News. Chisholm, Hugh, ed.. "Anchovy". Encyclopædia Britannica. Cambridge University Press