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1 Non-mammalian; 2 See also; 3 References; 4 External links ... Hence accumulation of waste is much slower and there are no special organs ofexcretion. ...
Fishare very diverse and are categorized in many ways. This article is an overview of some of the more common types of fish. Although most fishspecies have probably been discovered and described, about 250 new ones are still discovered every year. According to FishBase, 31,500 species of fish had been described by January 2010. That is more than the combined total of all other vertebrates: mammals, amphibians, reptiles and birds.
Fish systematics is the formal description and organisation of fish taxa into systems. It is complex and still evolving. Controversies over "arcane, but important, details of classification are still quietly raging."
The term "fish" describes any non-tetrapodchordate, (i.e., an animal with a backbone), that has gills throughout life and has limbs, if any, in the shape of fins. Unlike groupings such as birds or mammals, fish are not a single clade but a paraphyletic collection of taxa, including jawless, cartilaginous and skeletal types.
Jawless fish are the most primitive fish. There is current debate over whether these are really fish at all. They have no jaw, no scales, no paired fins, and no bony skeleton. Their skin is smooth and soft to the touch, and they are very flexible. Instead of a jaw, they possess an oral sucker. They use this to fasten on to other fish, and then use their rasp-like teeth to grind through their host's skin into the viscera. Jawless fish inhabit both fresh and salt water environments. Some are anadromous, moving between both fresh and salt water habitats.
Extant jawless fish are either lamprey or hagfish. Juvenile lamprey feed by sucking up mud containing micro-organisms and organic debris. The lamprey has well developed eyes, while the hagfish has only primitive eyespots. The hagfish coats itself and carcasses it finds with noxious slime to deter predators, and periodically ties itself into a knot to scrape the slime off. It is the only invertebrate fish and the only animal which has a skull but no vertebral column. It has four hearts, two brains, and a paddle-like tail.
Cartilaginous fish have a cartilaginous skeleton. However, their ancestors were bony animals, and were the first fish to develop paired fins. Cartilaginous fish don't have swim bladders. Their skin is covered in denticles, that are as rough as sandpaper. Because cartilaginous fish do not have bone marrow, the spleen and special tissue around the gonads produces red blood cells. Some cartilaginous fishes possess an organ called Leydig's Organ which also produces red blood cells.
Bony fish include the lobe finned fish and the ray finned fish. The lobe finned fish is the class of fleshy finned fishes, consisting of lungfish, and coelacanths. They are bony fish with fleshy, lobed paired fins, which are joined to the body by a single bone. These fins evolved into the legs of the first tetrapod land vertebrates, amphibians. Ray finned fishes are so-called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays").
There are three types of ray finned fishes: the chondrosteans, holosteans, and teleosts. The chondrosteans and holosteans are primitive fishes sharing a mixture of characteristics of teleosts and sharks. In comparison with the other chondrosteans, the holosteans are closer to the teleosts and further from sharks.
Teleosts are the most advanced or "modern" fishes. They are overwhelmingly the dominant class of fishes (or for that matter, vertebrates) with nearly 30,000 species, covering about 96 percent of all extant fish species. They are ubiquitous throughout fresh water and marine environments from the deep sea to the highest mountain streams. Included are ne
Deep sea fish is a term for fish that live below the photic zone of the ocean. The lanternfish is, by far, the most common deep sea fish. Other deep sea fish include the flashlight fish, cookiecutter shark, bristlemouths, anglerfish, and viperfish.
Because the photic zone typically extends only a few hundred meters below the water, about 90% of the ocean volume is invisible to humans. The deep sea is also an extremely hostile environment, with pressures between 20 and 1,000 atmospheres (between 2 and 100 megapascals), temperatures between 3 and 10 degrees Celsius, and a lack of oxygen. Most fish that have evolved in this harsh environment are not capable of surviving in laboratory conditions, and attempts to keep them in captivity have led to their deaths. For this reason little is known about them, as there are limitations to the amount of fruitful research that can be carried out on a dead specimen and deep sea exploratory equipment is very expensive. As such, many species are known only to scientists and have therefore retained their scientific name.
The fish of the deep sea are among the strangest and most elusive creatures on Earth. In this deep unknown lie many unusual creatures we still have yet to study. Since many of these fish live in regions where there is no natural illumination, they cannot rely solely on their eyesight for locating prey and mates and avoiding predators; deep sea fish have evolved appropriately to the extreme sub-photic region in which they live. Many deep sea fish are bioluminescent, with extremely large eyes adapted to the dark. Some have long feelers to help them locate prey or attract mates in the pitch black of the deep ocean. The deep sea angler fish in particular has a long fishing-rod-like adaptation protruding from its face, on the end of which is a bioluminescent piece of skin that wriggles like a worm to lure its prey. The lifecycle of deep sea fish can be exclusively deep water although some species are born in shallower water and sink on becoming born.
Due to the poor level of photosynthetic light reaching deep sea environments, most fish need to rely on organic matter sinking from higher levels, or, in rare cases, hydrothermal vents for nutrients. This makes the deep sea much poorer in productivity than shallower regions. Consequently many species of deep sea fish are noticeably smaller and have larger mouths and guts than those living at shallower depths. It has also been found that the deeper a fish lives, the more jelly-like its flesh and the more minimal its bone structure. This makes them slower and less agile than surface fish.
Sampling via deep trawling indicates that lanternfish account for as much as 65% of all deep sea fish biomass. Indeed, lanternfish are among the most widely distributed, populous, and diverse of all vertebrates, playing an important ecological role as prey for larger organisms. With an estimated global biomass of 550 - 660 million metric tonnes, several times the entire world fisheries catch, lanternfish also account for much of the biomass responsible for the deep scattering layer of the world's oceans. In the Southern Ocean, Myctophids provide an alternative food resource to krill for predators such as squid and the King Penguin. Although plentiful and prolific, currently only a few commercial lanternfish fisheries exist: These include limited operations off South Africa, in the sub-Antarctic, and in the Gulf of Oman.
A 2006 study by Canadianscientists has found five species of deep sea fish â€“ roundnose grenadier, onion-eye grenadier, blue hake, spiny eel and spinytail skateâ€“ to be on the verge of extinction due to the shift of commercial fishing from continental shelves to the slopes of the continental shelves, down to depths of 1600 meters. The slow reproduction of these fishâ€“ they reach sexual maturity at about the same age as human beings â€“ is one of the main reasons that they cannot recover from the excessive fishing.
The Siamese fighting fish (Betta splendens), also known as the betta (particularly in the US) and simply as the fighter, is a popular species of freshwateraquariumfish. The name of the genus is derived from ikan bettah, taken from a local dialect of Thailand (Siam). Betta is (). The wild ancestors of this fish are native to the rice paddies of Thailand, peninsular Malaysia and Cambodia and are called pla-kad or trey krem ("Fighting Fish") in Thai.
B. splendens usually grow to an overall length of about 5 cm , though some varieties reach 5-8 inches in length. Although known for their brilliant colors and large, flowing fins, the natural coloration of B. splendens is a dull green and brown, and the fins of wild specimens are relatively short. However, brilliantly colored and longer finned varieties (i.e. Veiltail; Delta; Superdelta; and Halfmoon) have been developed through selective breeding.
This species lives approximately 2â€“5 years in captivity, generally between 3-4, rarely 5â€“6 years, fed with anabolics 7â€“9 years.
The fish is a member of the gouramifamily (family Osphronemidae) of orderPerciformes, but was formerly classified among the Anabantidae. Although there are nearly 50 other members of the Bettagenus, B. splendens is the most popular species amongaquarium hobbyists, particularly in the United States.
Siamese fighting fish have upturned mouths and are primarily carnivorous surface feeders, although some vegetable matter may be eaten. In the wild, they feed on zooplankton including crustaceans and the larvae of mosquitoes and other insects, such as flies, crickets, or grasshoppers. Fish who feed on a wide range of foods live longer, have richer colors, and heal fin damage more quickly. Typically, commercial betta pellets are a combination of mashed shrimp meal, wheat flour, fish meal, brine shrimp, bloodworms, and vitamins. These fish will also eat live or frozen bloodworms, mosquitolarvae, brine shrimp or daphnia.
Reproduction and early development
The male betta will flare his gills, twist his body, and spread his fins, if interested in the female. The female will darken in color, then curve her body back and forth. Males build bubble nests of various sizes and thicknesses at the surface of the water. The act of spawning itself is called a "nuptial embrace", for the male wraps his body around the female; around 10-41 eggs are released during each embrace, until the female is exhausted of eggs. The male, in his turn, releases milt into the water, and fertilization takes place externally. During and after spawning, the male uses his mouth to retrieve sinking eggs and deposit them in the bubble nest (during mating the female sometimes assists her partner, but more often she will simply devour all the eggs that she manages to catch). Once the female has released all of her eggs, she is chased away from the male's territory, as it is likely that she'll eat the eggs due to hunger. Henceforth, the eggs remain in the male's care. He carefully keeps them in his bubble nest, making sure none fall to the bottom, and repairing the bubble nest as needed. Incubation lasts for 24â€“36 hours, and the newly-hatched larvae remain in the nest for the next 2â€“3 days, until their yolk sacs are fully absorbed. Afterwards the fry leave the nest and the free-swimming stage begins. It is common practice in the aquarium hobby to remove the male at this point, so that he would not eat his young (although it has been suggested that this danger is overrated). In this first period of their lives, B. splendens fry are totally dependent on their gills; the labyrinth organ which allows the species to breathe atmospheric oxygen typically develops at 3 to 6 weeks of age, depending on the general growth rate, which can be highly variable. The juveniles can reach sexual maturity at an age as early as 3 months.
B. splendens can be hybridized with B. imbellis, Betta sp. Mahachai and B. smaragdina, though with the latter the fry tend to have low survival rates. As well as these hybrids within the Betta genus, there have been reports of the inter generic hybridizing of Betta splendens and Macropodus opercularis, the Paradise Fish.
B. splendens have been affectionately nicknamed "The Jewel of the Orient" due to their beauty and wide range of colors which are produced through selective breeding.
Wild fish only exhibit strong colors when agitated. However, breeders have been able to make this coloration permanent, and a wide variety of hues breed true. A wide variety of colors are available to the aquarist such as red, blue, turquoise, orange, yellow, green,bright blue with pink highlights, cream and even true white (the "Opaque" white, not to be confused with albino). The shades of blue, turquoise and green are slightly iridescent, and can appear to change color with different lighting conditions or viewing angles; this is because these colors (unlike black or red) are not due to pigments, but created through refraction within a layer of translucent guanine crystals. Breeders have also developed different color patterns such as marble and butterfly, as well as metallic shades like copper, gold, or platinum (these were obtained by crossing B. splendens to other Betta species).
Breeders around the world continue to develop new varieties. Often, the male of the species are sold
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