Salmon is the common name for several species of ray-finned fish in the family Salmonidae. Other fish in the same family include trout, char and whitefish. Salmon are native to tributaries of the North Pacific Ocean. Many species of salmon have been introduced into non-native environments such as the Great Lakes of North America and Patagonia in South America. Salmon are intensively farmed in many parts of the world. Salmon are anadromous: they hatch in fresh water, migrate to the ocean return to fresh water to reproduce. However, populations of several species are restricted to fresh water through their lives. Folklore has it. Tracking studies have shown this to be true. A portion of a returning salmon run may spawn in different freshwater systems. Homing behavior has been shown to depend on olfactory memory. Salmon date back to the Neogene; the term "salmon" comes from the Latin salmo, which in turn might have originated from salire, meaning "to leap". The nine commercially important species of salmon occur in two genera.
The genus Salmo contains the Atlantic salmon, found in the north Atlantic, as well as many species named trout. The genus Oncorhynchus contains eight species which occur only in the North Pacific; as a group, these are known as Pacific salmon. Chinook salmon have been introduced in New Patagonia. Coho, freshwater sockeye, Atlantic salmon have been established in Patagonia, as well. † Both the Salmo and Oncorhynchus genera contain a number of species referred to as trout. Within Salmo, additional minor taxa have been called salmon in English, i.e. the Adriatic salmon and Black Sea salmon. The steelhead anadromous form of the rainbow trout migrates to sea, but it is not termed "salmon". A number of other species have common names which refer to them as being salmon. Of those listed below, the Danube salmon or huchen is a large freshwater salmonid related to the salmon above, but others are marine fishes of the unrelated Perciformes order: Eosalmo driftwoodensis, the oldest known salmon in the fossil record, helps scientists figure how the different species of salmon diverged from a common ancestor.
The British Columbia salmon fossil provides evidence that the divergence between Pacific and Atlantic salmon had not yet occurred 40 million years ago. Both the fossil record and analysis of mitochondrial DNA suggest the divergence occurred by 10 to 20 million years ago; this independent evidence from DNA analysis and the fossil record rejects the glacial theory of salmon divergence. Atlantic salmon reproduce in northern rivers on both coasts of the Atlantic Ocean. Landlocked salmon live in a number of lakes in eastern North America and in Northern Europe, for instance in lakes Sebago, Ladoga, Saimaa, Vänern, Winnipesaukee, they are not a different species from the Atlantic salmon, but have independently evolved a non-migratory life cycle, which they maintain when they could access the ocean. Chinook salmon are known in the United States as king salmon or blackmouth salmon, as spring salmon in British Columbia. Chinook are the largest of all Pacific salmon exceeding 14 kg; the name tyee is used in British Columbia to refer to Chinook over 30 pounds, in the Columbia River watershed large Chinook were once referred to as June hogs.
Chinook salmon are known to range as far north as the Mackenzie River and Kugluktuk in the central Canadian arctic, as far south as the Central California coast. Chum salmon are known as dog, keta, or calico salmon in some parts of the US; this species has the widest geographic range of the Pacific species: south to the Sacramento River in California in the eastern Pacific and the island of Kyūshū in the Sea of Japan in the western Pacific. Coho salmon are known in the US as silver salmon; this species is found throughout the coastal waters of Alaska and British Columbia and as far south as Central California. It is now known to occur, albeit infrequently, in the Mackenzie River. Masu salmon or cherry salmon are found only in the western Pacific Ocean in Japan and Russia. A land-locked subspecies known as the Taiwanese salmon or Formosan salmon is found in central Taiwan's Chi Chia Wan Stream. Pink salmon, known as humpies in southeast and southwest Alaska, are found from northern California and Korea, throughout the northern Pacific, from the Mackenzie River in Canada to the Lena River in Siberia in shorter coastal streams.
It is the smallest of the Pacific species, with an average weight of 1.6 to 1.8 kg. Sockeye salmon are known in the US as red salmon; this lake-rearing species is found south as far as the Klamath River in California in the eastern Pacific and northern Hokkaidō island in Japan in the western Pacific and as far north as Bathurst Inlet in the Canadian Arctic in the east and the Anadyr River in Siberia in the west. Although most adult Pacific salmon feed on small fish and squid, sockeye feed on plankton they filter through gill rakers. Kokanee salmon are the land-locked form of sockeye salmon. Danube salmon, or huchen, are the largest permanent freshwater salmonid species. Salmon eggs are laid in freshwater streams at high latitudes; the eggs hatch into alevin or sac fry
Gold dust day gecko
The gold dust day gecko is a diurnal species of gecko. It lives in northern Madagascar, on the island of Comoros, it inhabits various kinds of trees and houses. The gold dust day gecko feeds on insects and nectar, it is known as the mascot of GEICO. One subspecies is recognized: Phelsuma laticauda angularis; this lizard belongs to the smaller day geckos, can reach a total length of about 15–22 cm. The body colour is a bright green or yellowish green or even blue. Typical for this day gecko are the yellow speckles on the upper back. There are three rust-coloured transverse bars on the head. On the lower back there are three tapering red bars; the tail is flattened. The under side is off-white; these day geckos feed on various insects and other invertebrates, are capable of eating other smaller lizards. They eat soft, sweet fruit and pollen and nectar from flowers congregating in groups of many individuals to feed off of one plant; the males of this species can be quite quarrelsome. They do not accept other males in their territory.
In captivity, where the females cannot escape, the males may seriously wound a female. The females lay up to 5 pairs of eggs. At a temperature of 28 °C, the young will hatch after 40–45 days; the juveniles measure 55–60 mm. They should be kept separately since the juveniles can be quite quarrelsome. Sexual maturity is reached after 10–12 months; these animals should need a large, well-planted terrarium. The temperature should drop to around 20 °C at night; the humidity should be maintained between 65 and 75%. In captivity, these animals can be fed with crickets, fruit flies, maggots and houseflies, they will eat fruits such as mango and so will accept commercially available fruit mixes like Repashy fruit mix or Pangea. Christenson and Greg. Day Geckos In Captivity. Ada, Oklahoma: Living Art Publishing. P. 194. ISBN 0-9638130-2-1. Henkel, F.-W.. Amphibien und Reptilien Madagaskars, der Maskarenen, Seychellen und Komoren. Stuttgart: Ulmer. ISBN 3-8001-7323-9. McKeown, Sean; the general care and maintenance of day geckos.
Lakeside, CA: Advanced Vivarium Systems
The coelacanths constitute a now-rare order of fish that includes two extant species in the genus Latimeria: the West Indian Ocean coelacanth found near the Comoro Islands off the east coast of Africa and the Indonesian coelacanth. They follow the oldest-known living lineage of Sarcopterygii, which means they are more related to lungfish and tetrapods than to ray-finned fishes, they are found along the coastlines of the Indonesia. The West Indian Ocean coelacanth is a critically endangered species. Coelacanths belong to the subclass Actinistia, a group of lobed-finned fish related to lungfish and certain extinct Devonian fish such as osteolepiforms, porolepiforms and Panderichthys. Coelacanths were thought to have become extinct in the Late Cretaceous, around 66 million years ago, but were rediscovered in 1938 off the coast of South Africa; the coelacanth was long considered a "living fossil" because scientists thought it was the sole remaining member of a taxon otherwise known only from fossils, with no close relations alive, that it evolved into its current form 400 million years ago.
However, several recent studies have shown that coelacanth body shapes are much more diverse than thought. The word Coelacanth is an adaptation of the Modern Latin Cœlacanthus, from the Greek κοῖλ-ος, it is a common name for the oldest living line of Sarcopterygii, referring to the hollow caudal fin rays of the first fossil specimen described and named by Louis Agassiz in 1839. The genus name Latimeria commemorates Marjorie Courtenay-Latimer who discovered the first specimen in a fish market; the coelacanth, related to lungfishes and tetrapods, was believed to have been extinct since the end of the Cretaceous period. More related to tetrapods than to the ray-finned fish, coelacanths were considered transitional species between fish and tetrapods. On 23 December 1938, the first Latimeria specimen was found off the east coast of South Africa, off the Chalumna River. Museum curator Marjorie Courtenay-Latimer discovered the fish among the catch of a local angler, Captain Hendrick Goosen. Latimer contacted a Rhodes University ichthyologist, J. L. B.
Smith, sending him drawings of the fish, he confirmed the fish's importance with a famous cable: "MOST IMPORTANT PRESERVE SKELETON AND GILLS = FISH DESCRIBED."Its discovery 66 million years after it was believed to have become extinct makes the coelacanth the best-known example of a Lazarus taxon, an evolutionary line that seems to have disappeared from the fossil record only to reappear much later. Since 1938, West Indian Ocean coelacanth have been found in the Comoros, Tanzania, Madagascar, in iSimangaliso Wetland Park, Kwazulu-Natal in South Africa; the Comoro Islands specimen was discovered in December 1952. Between 1938 and 1975, 84 specimens were recorded; the second extant species, Indonesian coelacanth, was described from Manado, North Sulawesi, Indonesia in 1999 by Pouyaud et al. based on a specimen discovered by Mark V. Erdmann in 1998 and deposited at the Indonesian Institute of Sciences. Erdmann and his wife Arnaz Mehta first encountered a specimen at a local market in September 1997, but took only a few photographs of the first specimen of this species before it was sold.
After confirming that it was a unique discovery, Erdmann returned to Sulawesi in November 1997 to interview fishermen to look for further examples. A second specimen was caught by a fisherman in July 1998 and it was handed to Erdmann; the coelacanth has no real commercial value apart from being coveted by museums and private collectors. As a food fish it is worthless, as its tissues exude oils that give the flesh a foul flavor; the coelacanth's continued survival may be threatened by commercial deep-sea trawling, in which coelacanths are caught as bycatch. Coelacanths are the lobe-finned fishes. Externally, several characteristics distinguish the coelacanth from other lobe-finned fish, they possess a three-lobed caudal fin called a trilobate fin or a diphycercal tail. A secondary tail extending past the primary tail separates the upper and lower halves of the coelacanth. Cosmoid scales act as thick armor to protect the coelacanth's exterior. Several internal traits aid in differentiating coelacanths from other lobe-finned fish.
At the back of the skull, the coelacanth possesses a hinge, the intracranial joint, which allows it to open its mouth wide. Coelacanths retain an oil-filled notochord, a hollow, pressurized tube, replaced by the vertebral column early in embryonic development in most other vertebrates; the coelacanth heart is shaped differently from that of most modern fish, with its chambers arranged in a straight tube. The coelacanth braincase is 98.5% filled with fat. The cheeks of the coelacanth are unique because the opercular bone is small and holds a large soft-tissue opercular flap. A spiracular chamber is present. Coelacanth possess a unique rostral organ within the ethmoid region of the braincase. Unique to extant coelacanths is the presence of a "fatty lung" or a fat-filled single-lobed vestigial lung, homologous to other fishes' swim bladder; the parallel development of a fatty organ for buoyancy control suggest a unique specialization for deep-water habitats. There has been discovered small, hard but flexible plates around the vestigial lung in adult specimen, though not around the fatty organ.
The plates most had a regulation
A scute or scutum is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, the feet of birds. The term is used to describe the anterior portion of the mesonotum in insects as well as some arachnids. Scutes are similar to serve the same function. Unlike the scales of lizards and snakes, which are formed from the epidermis, scutes are formed in the lower vascular layer of the skin and the epidermal element is only the top surface. Forming in the living dermis, the scutes produce a horny outer layer, superficially similar to that of scales. Scutes will not overlap as snake scales; the outer keratin layer is shed piecemeal, not in one continuous layer of skin as seen in snakes or lizards. The dermal base may produce dermal armour. Scutes with a bony base are properly called osteoderms. Dermal scutes are found in the feet of birds and tails of some mammals, are believed to be the primitive form of dermal armour in reptiles; the term is used to describe the heavy armour of the armadillo and the extinct Glyptodon, is used as an alternative to scales in describing snakes or certain fishes, such as sturgeons, shad and menhaden.
The turtle's shell is covered by scutes formed of keratin. They are built to horn, beak, or nail in other species; the tarsometatarsus and toes of most birds are covered in two types of scales. Large scutes run along the dorsal side of the tarsometatarsus and toes, whereas smaller scutellae run along the sides. Both structures share histochemical homology with reptilian scales, however work on their evolutionary development has revealed that the scales in bird feet have secondarily evolved via suppression of the feather-building genetic program. Unblocking the feather suppression program results in feathers growing in place of scales along the tarsometatarsus and toes. Dinosaur species close to the origin of birds have been shown to have had "hind wings" made of feathers growing from these areas, suggesting that the acquisition of feathers in dinosaurs was a whole-body event; the bottoms of bird feet are covered in keeled scale-like structures known as reticulae. Evolutionary developmental studies on these scale-like structures have revealed that they are composed of alpha keratin.
These data have led some researchers to suggest that reticulae are in fact truncated feathers The term "scutum" is used in insect anatomy, as an alternative name for the anterior portion of the mesonotum. In the hard ticks, the Ixodidae, the scutum is a rigid, sclerotised plate on the anterior dorsal surface, just posterior to the head. In species with eyes, the eyes are on the surface of the scutum; the flexible exoskeleton posterior to the rigid scutum of the female tick, is called the alloscutum, the region that stretches to accommodate the blood with which the mature female tick becomes engorged. Males do not engorge nearly as drastically as females, so they do not need a flexible alloscutum. In some species of Opiliones, fused abdominal segments are referred to as a scutum. Osteoderms Scale Snake scales Keratin Skin Skeleton
In biology, homology is the existence of shared ancestry between a pair of structures, or genes, in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats, the arms of primates, the front flippers of whales and the forelegs of dogs and horses are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor; the term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was explained by Charles Darwin's theory of evolution in 1859, but had been observed before this, from Aristotle onwards, it was explicitly analysed by Pierre Belon in 1555. In developmental biology, organs that developed in the embryo in the same manner and from similar origins, such as from matching primordia in successive segments of the same animal, are serially homologous.
Examples include the legs of a centipede, the maxillary palp and labial palp of an insect, the spinous processes of successive vertebrae in a vertebral column. Male and female reproductive organs are homologous if they develop from the same embryonic tissue, as do the ovaries and testicles of mammals including humans. Sequence homology between protein or DNA sequences is defined in terms of shared ancestry. Two segments of DNA can have shared ancestry because of either a speciation event or a duplication event. Homology among proteins or DNA is inferred from their sequence similarity. Significant similarity is strong evidence that two sequences are related by divergent evolution from a common ancestor. Alignments of multiple sequences are used to discover the homologous regions. Homology remains controversial in animal behaviour, but there is suggestive evidence that, for example, dominance hierarchies are homologous across the primates. Homology was noticed by Aristotle, was explicitly analysed by Pierre Belon in his 1555 Book of Birds, where he systematically compared the skeletons of birds and humans.
The pattern of similarity was interpreted as part of the static great chain of being through the mediaeval and early modern periods: it was not seen as implying evolutionary change. In the German Naturphilosophie tradition, homology was of special interest as demonstrating unity in nature. In 1790, Goethe stated his foliar theory in his essay "Metamorphosis of Plants", showing that flower part are derived from leaves; the serial homology of limbs was described late in the 18th century. The French zoologist Etienne Geoffroy Saint-Hilaire showed in 1818 in his theorie d'analogue that structures were shared between fishes, reptiles and mammals; when Geoffroy went further and sought homologies between Georges Cuvier's embranchements, such as vertebrates and molluscs, his claims triggered the 1830 Cuvier-Geoffroy debate. Geoffroy stated the principle of connections, namely that what is important is the relative position of different structures and their connections to each other; the Estonian embryologist Karl Ernst von Baer stated what are now called von Baer's laws in 1828, noting that related animals begin their development as similar embryos and diverge: thus, animals in the same family are more related and diverge than animals which are only in the same order and have fewer homologies.
Von Baer's theory recognises that each taxon has distinctive shared features, that embryonic development parallels the taxonomic hierarchy: not the same as recapitulation theory. The term "homology" was first used in biology by the anatomist Richard Owen in 1843 when studying the similarities of vertebrate fins and limbs, defining it as the "same organ in different animals under every variety of form and function", contrasting it with the matching term "analogy" which he used to describe different structures with the same function. Owen codified 3 main criteria for determining if features were homologous: position and composition. In 1859, Charles Darwin explained homologous structures as meaning that the organisms concerned shared a body plan from a common ancestor, that taxa were branches of a single tree of life; the word homology, coined in about 1656, is derived from the Greek ὁμόλογος homologos from ὁμός homos "same" and λόγος logos "relation". Biological structures or sequences in different taxa are homologous if they are derived from a common ancestor.
Homology thus implies divergent evolution. For example, many insects possess two pairs of flying wings. In beetles, the first pair of wings has evolved into a pair of hard wing covers, while in Dipteran flies the second pair of wings has evolved into small halteres used for balance; the forelimbs of ancestral vertebrates have evolved into the front flippers of whales, the wings of birds, the running forelegs of dogs and horses, the short forelegs of frogs and lizards, the grasping hands of primates including humans. The same major forearm bones are found in fossils of lobe-finned fish such as Eusthenopteron; the opposite of homologous organs are analogous organs which do similar jobs in two taxa that were not present in their most recent common ancestor but rather evolved separately. For example, the wings of insects and birds evolved independently in separated groups, converged functionally to support powered flight, so they are analogous; the wings of a sycamore maple seed and the wings of a bird are analogous but not homologous, as they develop from quite different structures.
A structure can be only analogous at another. Pterosaur and bat wings are analogous as wings
Bird anatomy, or the physiological structure of birds' bodies, shows many unique adaptations aiding flight. Birds have a light skeletal system and light but powerful musculature which, along with circulatory and respiratory systems capable of high metabolic rates and oxygen supply, permit the bird to fly; the development of a beak has led to evolution of a specially adapted digestive system. These anatomical specializations have earned birds their own class in the vertebrate phylum. Birds have many bones that are hollow with criss-crossing trusses for structural strength; the number of hollow bones varies among species, though large gliding and soaring birds tend to have the most. Respiratory air sacs form air pockets within the semi-hollow bones of the bird's skeleton; the bones of diving birds are less hollow than those of non-diving species. Penguins and puffins are without pneumatized bones entirely. Flightless birds, such as ostriches and emus, have pneumatized femurs and, in the case of the emu, pneumatized cervical vertebrae.
The bird skeleton is adapted for flight. It is lightweight but strong enough to withstand the stresses of taking off and landing. One key adaptation is the fusing of bones such as the pygostyle; because of this, birds have a smaller number of bones than other terrestrial vertebrates. Birds lack teeth or a true jaw, instead have a beak, far more lightweight; the beaks of many baby birds have a projection called an egg tooth, which facilitates their exit from the amniotic egg, which falls off once it has done its job. The vertebral column is divided into five sections of vertebrae: Cervical Trunk vertebrae fused in the notarium. Synsacrum; this region is similar to the sacrum in mammals and is unique in the pigeon because it is a fusion of the sacral and caudal vertebra. It supports terrestrial locomotion of the pigeon's legs. Caudal: This region is similar to the coccyx in mammals and helps control the movement of feathers during flight. Pygostyle: This region is made up of 4 to 7 fused vertebrae and is the point of feather attachment.
The neck of a bird is composed of 13–25 cervical vertebrae enabling birds to have increased flexibility. A flexible neck allows many birds with immobile eyes to move their head more productively and center their sight on objects that are close or far in distance. Most birds have about three times as many neck vertebrae than humans, which allows for increased stability during fast movements such as flying and taking-off; the neck plays a role in head-bobbing, present in at least 8 out of 27 orders of birds, including Columbiformes and Gruiformes. Head-bobbing is an optokinetic response which stabilizes a birds surroundings as they alternate between a thrust phase and a hold phase. Head-bobbing is synchronous with the feet. Data from various studies suggest that the main reason for head-bobbing in some birds is for the stabilization of their surroundings, although it is uncertain why some but not all bird orders show head-bob. Birds are the only vertebrates to have fused a keeled breastbone; the keeled sternum serves as an attachment site for the muscles used in swimming.
Flightless birds, such as ostriches, lack a keeled sternum and have denser and heavier bones compared to birds that fly. Swimming birds have a wide sternum, walking birds have a long sternum, flying birds have a sternum, nearly equal in width and height; the chest consists of the furcula and coracoid, together with the scapula, form the pectoral girdle. The side of the chest is formed by the ribs. Birds have uncinate processes on the ribs; these are hooked extensions of bone which help to strengthen the rib cage by overlapping with the rib behind them. This feature is found in the tuatara; the skull consists of five major bones: the frontal, parietal and nasal, the mandible. The skull of a normal bird weighs about 1% of the bird's total body weight; the eye occupies a considerable amount of the skull and is surrounded by a sclerotic eye-ring, a ring of tiny bones. This characteristic is seen in reptiles. Broadly speaking, avian skulls consist of many non-overlapping bones. Paedomorphosis, maintenance of the ancestral state in adults, is thought to have facilitated the evolution of the avian skull.
In essence, adult bird skulls will resemble the juvenile form of their theropod dinosaur ancestors. As the avian lineage has progressed and has paedomorphosis has occurred, they have lost the postorbital bone behind the eye, the ectopterygoid at the back of the palate, teeth; the palate structures have become altered with changes reductions, seen in the ptyergoid and jugal bones. A reduction in the adductor chambers has occurred These are all conditions seen in the juvenile form of their ancestors; the premaxillary bone has hypertrophied to form the beak while the maxilla has become diminished, as suggested by both developmental and paleontological studies. This expansion into the beak has occurred in tandem with the loss of a functional hand and the developmental of a point at the front of the beak that resembles a "finger"; the premaxilla is known to play a large role in feeding behaviours in fish. The structure of the avian skull has important implications for their feeding behaviours. Birds show independen