Paddlefish are basal Chondrostean ray-finned fish. They have been referred to as "primitive fish" because they have evolved with few morphological changes since the earliest fossil records of the Late Cretaceous, seventy to seventy-five million years ago. Polyodontids are North American and Chinese. There are six known species: four extinct species known only from fossil remains, two extant species, including the American paddlefish, native to the Mississippi River basin in the U. S. and the critically endangered Chinese paddlefish, endemic to the Yangtze River Basin in China. Chinese paddlefish are commonly referred to as "Chinese swordfish", or "elephant fish". Paddlefish populations have declined throughout their historic range as a result of overfishing and the encroachment of human development, including the construction of dams that have blocked their seasonal upward migration to ancestral spawning grounds. Other detrimental effects include alterations of rivers which have changed natural flows resulting in the loss of spawning habitat and nursery areas.
Chinese paddlefish have not been seen since 2007, may now be extinct for many of the same reasons that have plagued the American species. During the initial stages of development from embryo to fry, paddlefish have no rostrum, it begins to form shortly after hatching. The rostrum of a Chinese paddlefish is narrow and sword-like while the rostrum of the American paddlefish is broad and paddle-like; some common morphological characteristics of paddlefish include a spindle-shaped, smooth skinned scaleless body, heterocercal tail, small poorly developed eyes. Unlike the filter-feeding American paddlefish, Chinese paddlefish are piscivores, predaceous, their jaws are more forward pointing which suggest they forage on small fishes in the water column, on shrimp, benthic fishes, crabs. The jaws of the American paddlefish are distinctly adapted for filter feeding only, they are ram suspension filter feeders with a diet that consists of zooplankton, small insects, insect larvae, small fish. The largest Chinese paddlefish on record measured 23 ft in length, was estimated to weigh a few thousand pounds.
They reach 9.8 ft and 1,100 lb. Although the American paddlefish is one of the largest freshwater fishes in North America, their recorded lengths and weights fall short in comparison to the larger Chinese paddlefish. American paddlefish reach 5 ft or more in length and can weigh more than 60 lb; the largest American paddlefish on record was caught in 1916 in Iowa. The fish was taken with a spear, measured 7 ft 1 in long and 45.5 in in the girth. A report published by J. R. Harlan and E. B. Speaker in Iowa Fish and Fishing said; the world record paddlefish caught on rod and reel was 54.25 in long. The fish was caught by Clinton Boldridge in a 5-acre pond in Kansas. Scientists once believed paddlefish used their rostrums to excavate bottom substrate, but have since determined with the aid of electron microscopy that paddlefish have electroreceptors on their rostrum's ampulla which are similar in structure to other Lorenzini; the electroreceptors can detect weak electrical fields which not only signal the presence of prey items in the water column, such as zooplankton, the primary diet of the American paddlefish, but they can detect the individual feeding and swimming movements of zooplankton's appendages.
Paddlefish have poorly developed eyes, rely on their electroreceptors for foraging. However, the rostrum is not the paddlefish's sole means of food detection; some reports incorrectly suggest that a damaged rostrum would render paddlefish less capable of foraging efficiently to maintain good health. Laboratory experiments, field research indicate otherwise. In addition to electroreceptors on the rostrum, paddlefish have sensory pores covering nearly half of the skin surface extending from the rostrum to the top of the head down to the tips of the operculum. Therefore, paddlefish with damaged or abbreviated rostrums are still able to forage and maintain good health. Over the past half century, paddlefish populations have been on the decline. Attributable causes are overfishing and the encroachment of human development, including the construction of dams which block their seasonal upward migration to ancestral spawning grounds. Other detrimental effects include alterations of rivers which have changed the natural flow, resulted in the loss of spawning habitat and nursery areas.
American paddlefish have been extirpated from much of their Northern peripheral range, including the Great Lakes and Canada, New York and Pennsylvania. There is growing concern about their populations in other states; the Chinese paddlefish is considered anadromous with upstream migration, however little is known about their migration habits and population structure. They are endemic to the Yangtze River Basin in China where they lived in the broad surfaced main stem rivers and shoal zones along the East China Sea. Research suggests they preferred to navigate the middle and lower layers of the water column, swam into large lakes. Chinese paddlefish are now believed to be extinct as there have been no sightings of specimens in the wild since 2003, past attempts of artificial propagation for restoration purposes have failed because of difficulties encountered in keeping captive fish alive. American
A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, a post-anal tail: these five anatomical features define this phylum. Chordates are bilaterally symmetric; the Chordata and Ambulacraria together form the superphylum Deuterostomia. Chordates are divided into three subphyla: Vertebrata. There are extinct taxa such as the Vetulicolia. Hemichordata has been presented as a fourth chordate subphylum, but now is treated as a separate phylum: hemichordates and Echinodermata form the Ambulacraria, the sister phylum of the Chordates. Of the more than 65,000 living species of chordates, about half are bony fish that are members of the superclass Osteichthyes. Chordate fossils have been found from as early as the Cambrian explosion, 541 million years ago. Cladistically, vertebrates - chordates with the notochord replaced by a vertebral column during development - are considered to be a subgroup of the clade Craniata, which consists of chordates with a skull.
The Craniata and Tunicata compose the clade Olfactores. Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features: A notochord, a stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, in wholly aquatic species this helps the animal to swim by flexing its tail. A dorsal neural tube. In fish and other vertebrates, this develops into the spinal cord, the main communications trunk of the nervous system. Pharyngeal slits; the pharynx is the part of the throat behind the mouth. In fish, the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live. Post-anal tail. A muscular tail that extends backwards behind the anus. An endostyle; this is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.
It stores iodine, may be a precursor of the vertebrate thyroid gland. There are soft constraints that separate chordates from certain other biological lineages, but are not part of the formal definition: All chordates are deuterostomes; this means. All chordates are based on a bilateral body plan. All chordates are coelomates, have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm; the following schema is from the third edition of Vertebrate Palaeontology. The invertebrate chordate classes are from Fishes of the World. While it is structured so as to reflect evolutionary relationships, it retains the traditional ranks used in Linnaean taxonomy. Phylum Chordata †Vetulicolia? Subphylum Cephalochordata – Class Leptocardii Clade Olfactores Subphylum Tunicata – Class Ascidiacea Class Thaliacea Class Appendicularia Class Sorberacea Subphylum Vertebrata Infraphylum incertae sedis Cyclostomata Superclass'Agnatha' paraphyletic Class Myxini Class Petromyzontida or Hyperoartia Class †Conodonta Class †Myllokunmingiida Class †Pteraspidomorphi Class †Thelodonti Class †Anaspida Class †Cephalaspidomorphi Infraphylum Gnathostomata Class †Placodermi Class Chondrichthyes Class †Acanthodii Superclass Osteichthyes Class Actinopterygii Class Sarcopterygii Superclass Tetrapoda Class Amphibia Class Sauropsida Class Synapsida Craniates, one of the three subdivisions of chordates, all have distinct skulls.
They include the hagfish. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or all deuterostomes, are by their tails". Most craniates are vertebrates; these consist of a series of bony or cartilaginous cylindrical vertebrae with neural arches that protect the spinal cord, with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, are therefore not regarded as vertebrates, but as members of the craniates, the group from which vertebrates are thought to have evolved; however the cladistic exclusion of hagfish from the vertebrates is controversial, as they ma
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
The Alabama sturgeon, Scaphirhynchus suttkusi, is a critically endangered species of sturgeon native to the United States of America and now only believed to exist in 130 miles of the lower Alabama River. The fish has a distinctive yellowish-orange color, grows to a size of about 30 in long and 2 to 3 lb, is believed to have a lifespan of 12 to 20 years. Biologists have known of the fish since the 1950s or 1960s, but the large diversity of aquatic species in Alabama prevented formal identification until 1991; the Alabama sturgeon was first proposed for protected status in the early 1990s, although by the fish was so rare its survival was uncertain. The sturgeon's protection was opposed by a variety of industries located along Alabama's rivers for the feared economic impact; the opponents' main arguments were that it was extinct or that it was not a distinct species. In response to this opposition, the U. S. Fish and Wildlife Service ceased efforts to place the fish on the Endangered Species List.
Ray Vaughan, an environmental lawyer in Montgomery, sued the Service and, in 2000, requiring Fish and Wildlife to list the fish for protection. In 1993, state and federal biologists began a program to help save the Alabama sturgeon through a captive breeding program. Only six fish have been captured since all male; the last fish held in captivity died in 2002. The most recent specimen was captured in April 2007. After determining the fish was a male, sperm were collected, a small tracking device implanted, it was released once it had healed, it was hoped that the tagged fish would lead to others of its species, but in a year of tracking to date, this has not happened. In May 2008, the Fish and Wildlife Service proposed designating 245 miles of the Alabama River and 81 miles of the lower portion of its tributary, the Cahaba River, as critical habitat for the fish. Although the rivers are dammed at multiple locations, management of the river flows is expected to continue unchanged. In July 2009, fish researchers lost contact with the only known live Alabama Sturgeon.
The fish had been given an electronic tracking device in hopes that the fish would lead them to other members of the species, but the device stopped working. In August 2013, the Fish and Wildlife Service released the "Recovery Plan for the Alabama Sturgeon", it includes a plan to establish a captive stock that can produce fingerlings to be released back into the wild and to improve the habitat in the Alabama River through operational changes at Claiborne and Millers Ferry Lock and Dams. Studies from 2014 and 2015 indicated that despite the few sightings over the last decade, the species is still extant; this is due to numerous traces of recent Alabama sturgeon DNA found in water samples gathered from the river. Alabama sturgeon page of the U. S. Fish and Wildlife Service's Endangered Species Program site Alabama Sturgeon of the Mobile basin at the Alabama Department of Conservation and Natural Resources WKRG News 5 - Scientists lose contact with lone Alabama sturgeon via the Internet Archive Wayback machine "Scaphirhynchus suttkusi".
Integrated Taxonomic Information System. Retrieved 6 April 2007. Froese and Pauly, eds.. "Scaphirhynchus suttkusi" in FishBase. April 2007 version
White sturgeon is a species of sturgeon in the family Acipenseridae of the order Acipenseriformes. They are an anadromous fish species ranging in the Eastern Pacific. However, some are landlocked in the Columbia River Drainage and Lake Shasta in California, with reported sightings in northern Baja California, Mexico. A. transmontanus is distinguished by the two rows of four to eight ganoid bony plates between the anus and anal fin, with about 45 rays present in the dorsal fin. Coloring can range from gray to brownish on the dorsal side, paler on the ventral side, gray fins. Barbels are situated anterior to the mouth, closer to the snout than the mouth. At sexual maturity, A. transmontanus can reach 160 cm in length, while the maximum length recorded of any age class is 610 cm, with common lengths around 210 cm. While age at maturity is uncertain, possible age ranges of known A. transmontanus specimens range from 11–34 years old. The maximum published weight known was 816 kg with a reported age of 104 years.
Alternate common names include: Pacific Sturgeon, Oregon Sturgeon, Columbia Sturgeon, Snake River Sturgeon and Sacramento Sturgeon. With the etymology referring to, Acipsenser: Latin, acipsener = sturgeon, transmontanus; the specific name is derived from the Latin acipenser and montanus. The White Sturgeon is part of a Pacific clade of species including Kaluga, Green and Amur Sturgeon. Recent genetic analysis supports a close relationship between and, only found in Asia, showing a common ancestor between the two around 45.8 million years ago. Using microsatellites, genetic differentiation between different river systems in the Pacific Northwest and California is high enough to be able to distinguish between White Sturgeon populations and validate a structure in which watershed resides in. Extant sturgeon species are polyploid, containing more than two paired sets of chromosomes, derived from an extinct ancestor containing 60 chromosomes. Genome duplication during sturgeon evolution has led to three different groups of species with 120, 240, 360 chromosomes.
Recent study of microsatellite inheritance in White sturgeon supports that it is an ancestral octoploid, with 240 chromosomes. White Sturgeon are native to several large North American rivers, they live in estuaries of large rivers, but migrate to spawn in freshwater, travel long distances between river systems. Reproducing populations have been documented along the West Coast, from northern Mexico up to the Aleutian Islands in Alaska. White Sturgeon are found in deep, soft bottomed areas of estuaries, where movements in the water column is dependent on salinity. Historical ranges have been modified by overharvesting, habitat changes due to dams, river regulations. In the lower Fraser River, British Columbia and abundance are assessed by acoustic tags and mark recapture methods. While the model developed by Robichaud and Nelson assumes a closed homogenous population, acoustic tags and mark-recapture data shows that they are sedentary during the winter months and mobile in the spring and fall, with data indicating that they leave the Fraser River and enter the Strait of Georgia during their mobile periods.
Construction of dams for hydroelectric power production affects seasonal movement of White Sturgeon in many river systems, with the Columbia River Basin being a large contributor to shifts in the distribution and movement. The dams present in the basin have blocked the upstream movement of sturgeon, due to designs of fish ladders being more specified for salmon and steelhead. While downstream passage of sturgeon through the dams has been reported, the route of passage was never identified. Downstream movement through the dams are only possible through operating turbines, open spill gates and the ice and trash sluiceway. Larval White Sturgeon 10–11 mm in TL experience the highest mortality when they transition from endogenous to exogenous feeding, around 8–14 days post-hatch depending on conditions. Once larval metamorphose into young of the year and juveniles, they feed on the substrate, dominantly spp. relying on water currents to carry them downriver to areas of suitable food. The availability of spp. could play a key role in the survival of larval and YOY White Sturgeon in the Columbia River and could explain the apparent poor survival of larvae and YOY in some Snake and Columbia River reservoirs that have successful spawning but poor recruitment.
Juveniles less than 600 mm TL are known to feed on tube-dwelling amphipods, isopods and other benthic invertebrates, as well as on the eggs and fry of other fish species. Adults greater than 600 mm consume a variety prey species, adjusting to a piscivorous diet of herring, starry flounder, goby, as well as benthic items such as invasive overbite clam. With feeding movements influenced due to tidal cycles, studies show more active movement at night, hinting that White Sturgeon may be nocturnal foragers. Studies have shown that dietary lipid requirements on larval White Sturgeon effect overall body composition, plasma biochemical parameters and liver fatty acids. With increasing dietary lipid levels, whole body and muscle lipid conten
The bastard sturgeon, fringebarbel sturgeon, ship sturgeon, spiny sturgeon, or thorn sturgeon is a species of fish in the Acipenseridae family. Abundant in the Black and Caspian seas, its range is now limited to the Ural River, with a possible relict populations in the Rioni River in Georgia and the Safid Rud in Iran; the healthiest population is one in Lake Balkhash in Kazakhstan, well outside its natural range, where they were introduced in the 1960s for commercial purposes. It has been reported. Gesner, J. Freyhof, J. & Kottelat, M. 2010. Acipenser nudiventris. 2013 IUCN Red List of Threatened Species. Downloaded on 30 March 2014. Specific
Russia the Russian Federation, is a transcontinental country in Eastern Europe and North Asia. At 17,125,200 square kilometres, Russia is by far or by a considerable margin the largest country in the world by area, covering more than one-eighth of the Earth's inhabited land area, the ninth most populous, with about 146.77 million people as of 2019, including Crimea. About 77 % of the population live in the European part of the country. Russia's capital, Moscow, is one of the largest cities in the world and the second largest city in Europe. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a wide range of environments and landforms. From northwest to southeast, Russia shares land borders with Norway, Estonia, Latvia and Poland, Ukraine, Azerbaijan, China and North Korea, it shares maritime borders with Japan by the Sea of Okhotsk and the U. S. state of Alaska across the Bering Strait. However, Russia recognises two more countries that border it, Abkhazia and South Ossetia, both of which are internationally recognized as parts of Georgia.
The East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, the medieval state of Rus arose in the 9th century. In 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus' disintegrated into a number of smaller states; the Grand Duchy of Moscow reunified the surrounding Russian principalities and achieved independence from the Golden Horde. By the 18th century, the nation had expanded through conquest and exploration to become the Russian Empire, the third largest empire in history, stretching from Poland on the west to Alaska on the east. Following the Russian Revolution, the Russian Soviet Federative Socialist Republic became the largest and leading constituent of the Union of Soviet Socialist Republics, the world's first constitutionally socialist state; the Soviet Union played a decisive role in the Allied victory in World War II, emerged as a recognized superpower and rival to the United States during the Cold War.
The Soviet era saw some of the most significant technological achievements of the 20th century, including the world's first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the world's second largest economy, largest standing military in the world and the largest stockpile of weapons of mass destruction. Following the dissolution of the Soviet Union in 1991, twelve independent republics emerged from the USSR: Russia, Belarus, Uzbekistan, Azerbaijan, Kyrgyzstan, Tajikistan and the Baltic states regained independence: Estonia, Lithuania, it is governed as a federal semi-presidential republic. Russia's economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2018. Russia's extensive mineral and energy resources are the largest such reserves in the world, making it one of the leading producers of oil and natural gas globally; the country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction.
Russia is a great power as well as a regional power and has been characterised as a potential superpower. It is a permanent member of the United Nations Security Council and an active global partner of ASEAN, as well as a member of the Shanghai Cooperation Organisation, the G20, the Council of Europe, the Asia-Pacific Economic Cooperation, the Organization for Security and Co-operation in Europe, the World Trade Organization, as well as being the leading member of the Commonwealth of Independent States, the Collective Security Treaty Organization and one of the five members of the Eurasian Economic Union, along with Armenia, Belarus and Kyrgyzstan; the name Russia is derived from Rus', a medieval state populated by the East Slavs. However, this proper name became more prominent in the history, the country was called by its inhabitants "Русская Земля", which can be translated as "Russian Land" or "Land of Rus'". In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus' by modern historiography.
The name Rus itself comes from the early medieval Rus' people, Swedish merchants and warriors who relocated from across the Baltic Sea and founded a state centered on Novgorod that became Kievan Rus. An old Latin version of the name Rus' was Ruthenia applied to the western and southern regions of Rus' that were adjacent to Catholic Europe; the current name of the country, Россия, comes from the Byzantine Greek designation of the Rus', Ρωσσία Rossía—spelled Ρωσία in Modern Greek. The standard way to refer to citizens of Russia is rossiyane in Russian. There are two Russian words which are commonly