The dwarf sturgeon, little shovelnose sturgeon, or small Amu-dar shovelnose sturgeon is a species of fish in the family Acipenseridae. It is found in Tajikistan and Uzbekistan; the Pseudoscaphirhynchus hermanni population is recorded to be a rare species. There are few recordings of this species being caught, but there are accusations that fishermen are unknowingly catching them; the population trend of this species is decreasing. The Pseudoscaphirhynchus hermanni is being negatively affected due to dams, water extraction and high levels of water pollution including mineral fertilizers, pesticides for cotton agriculture, drainage waste. More survey work on this species is needed to determine the status of their population. Overall this species is recorded to be a critically endangered species; the Pseudoscaphirhynchus hermanni has a diet of midge larvae. The Pseudoscaphirhynchus hermanni is known to be found in the areas of Asia, Turkmenistan, Amu Darya river, the Syr Darya river; the Pseudoscaphirhynchus hermanni has been recorded reaching a maximum length of 27.5 centimeters or 10.82 inches.
The maximum reported weight of this species is 0.11 pounds. The oldest reported age of this species is six years old; this species is considered to be potamodromous. This species is recorded to be sensitive to chemicals in the water; the Pseudoscaphirhynchus hermanni is recorded to live in freshwater or salty environments within a demersal depth range. This species lives in a temperate climate; the common names of the Pseudoscaphirhynchus hermanni in various languages include the following: Dwarf Sturgeon: English Little Shovelnose Sturgeon: English Little Amu-Darya Shovelnose: English Lopatonos hermannův: Czech Nibylopstons amu-daryjski: Polish Pikkulapiosampi: Finnish Амударьинский малый лопатонос: Russian Лжелопатонос амударьинский малый: Russian 短尾拟铲鲟: Mandarin Chinese 短尾擬鏟鱘: Mandarin Chinese 난쟁이철갑상어: Korean Sturgeon Specialist Group 1996. Pseudoscaphirhynchus hermanni. 2006 IUCN Red List of Threatened Species. Downloaded on 4 August 2007. Pseudoscaphirhynchus hermanni at FishBase
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
The Amu Darya called the Amu or Amo River, known by its Latin name Oxus, is a major river in Central Asia. It is formed by the junction of the Vakhsh and Panj rivers, in the Tigrovaya Balka Nature Reserve on the border between Tajikistan and Afghanistan, flows from there north-westwards into the southern remnants of the Aral Sea. In ancient times, the river was regarded as the boundary between Greater Turan. Persian: آمودریا, translit. Âmudaryâ. Ôxos). In classical antiquity, the river was known as the Ōxus in Latin and Ὦξος in Greek — a clear derivative of Vakhsh, the name of the largest tributary of the river. In Vedic Sanskrit, the river is referred to as Vakṣu; the Brahmanda Purana refers to the river as Chaksu. The Avestan texts too refer to the River as Yakhsha/Vakhsha. In Middle Persian sources of the Sassanid period the river is known as Wehrōd; the name Amu is said to have come from the medieval city of Āmul, in modern Turkmenistan, with Darya being the Persian word for "river". Medieval Arabic and Islamic sources call the river Jayhoun, derived from Gihon, the biblical name for one of the four rivers of the Garden of Eden.
Western travelers in the 19th century mentioned that one of the names by which the river was known in Afghanistan was Gozan, that this name was used by Greek, Chinese, Persian and Afghan historians. However, this name is no longer used. "Hara and to the river of Gozan...""the Gozan River is the River Balkh, i.e. the Oxus or the Amu Darya...""... and were brought into Halah, Habor, Hara, to the river Gozan..." The river's total length is 2,400 kilometres and its drainage basin totals 534,739 square kilometres in area, providing a mean discharge of around 97.4 cubic kilometres of water per year. The river is navigable for over 1,450 kilometres. All of the water comes from the high mountains in the south where annual precipitation can be over 1,000 mm. Before large-scale irrigation began, high summer evaporation meant that not all of this discharge reached the Aral Sea – though there is some evidence the large Pamir glaciers provided enough melt water for the Aral to overflow during the 13th and 14th centuries.
Since the end of the 19th century there have been four different claimants as the true source of the Oxus: The Pamir River, which emerges from Lake Zorkul in the Pamir Mountains, flows west to Qila-e Panja, where it joins the Wakhan River to form the Panj River. The Sarhad or Little Pamir River flowing down the Little Pamir in the High Wakhan Lake Chamaktin, which discharges to the east into the Aksu River, which in turn becomes the Murghab and Bartang rivers, which joins the Panj Oxus branch 350 kilometres downstream at Roshan Vomar in Tajikistan. An ice cave at the end of the Wakhjir valley, in the Wakhan Corridor, in the Pamir Mountains, near the border with Pakistan. A glacier joins the Pamir River about 50 kilometres downstream. Bill Colegrave's expedition to Wakhan in 2007 found that both claimants 2 and 3 had the same source, the Chelab stream, which bifurcates on the watershed of the Little Pamir, half flowing into Lake Chamaktin and half into the parent stream of the Little Pamir/Sarhad River.
Therefore, the Chelab stream may be properly considered the true source or parent stream of the Oxus. The Panj River forms the border of Tajikistan, it flows west to Ishkashim where it turns north and north-west through the Pamirs passing the Tajikistan–Afghanistan Friendship Bridge. It subsequently forms the border of Afghanistan and Uzbekistan for about 200 kilometres, passing Termez and the Afghanistan–Uzbekistan Friendship Bridge, it delineates the border of Afghanistan and Turkmenistan for another 100 kilometres before it flows into Turkmenistan at Atamurat. It flows across Turkmenistan south to north, passing Türkmenabat, forms the border of Turkmenistan and Uzbekistan from Halkabat, it is split by the Tuyamuyun Hydro Complex into many waterways that used to form the river delta joining the Aral Sea, passing Urgench, Daşoguz, other cities, but it does not reach what is left of the sea any more and is lost in the desert. Use of water from the Amu Darya for irrigation has been a major contributing factor to the shrinking of the Aral Sea since the late 1950s.
Historical records state that in different periods, the river flowed into the Aral Sea, into the Caspian Sea, or both, similar to the Syr Darya. The 534,769 square kilometres of the Amu Darya drainage basin include most of Tajikistan, the southwest corner of Kyrgyzstan, the northeast corner of Afghanistan, a narrow portion of eastern Turkmenistan and the western half of Uzbekistan. Part of the Amu Darya basin divide in Tajikistan forms that country's border with China and Pakistan. About 61% of the drainage lies within Tajikistan and Turkmenistan, while 39% is in Afghanistan; the abundant water flowing in the Amu Darya comes entirely from glaci
A karyotype is the number and appearance of chromosomes in the nucleus of a eukaryotic cell. The term is used for the complete set of chromosomes in a species or in an individual organism and for a test that detects this complement or measures the number. Karyotypes describe the chromosome count of an organism and what these chromosomes look like under a light microscope. Attention is paid to their length, the position of the centromeres, banding pattern, any differences between the sex chromosomes, any other physical characteristics; the preparation and study of karyotypes is part of cytogenetics. The study of whole sets of chromosomes is sometimes known as karyology; the chromosomes are depicted in a standard format known as a karyogram or idiogram: in pairs, ordered by size and position of centromere for chromosomes of the same size. The basic number of chromosomes in the somatic cells of an individual or a species is called the somatic number and is designated 2n. In the germ-line the chromosome number is n.p28 Thus, in humans 2n = 46.
So, in normal diploid organisms, autosomal chromosomes are present in two copies. There may, or may not, be sex chromosomes. Polyploid cells haploid cells have single copies; the study of karyotypes is important for cell biology and genetics, the results may be used in evolutionary biology and medicine. Karyotypes can be used for many purposes. Chromosomes were first observed in plant cells by Carl Wilhelm von Nägeli in 1842, their behavior in animal cells was described by Walther Flemming, the discoverer of mitosis, in 1882. The name was coined by another German anatomist, Heinrich von Waldeyer in 1888, it is New Latin from Ancient Greek κάρυον karyon, "kernel", "seed", or "nucleus", τύπος typos, "general form"). The next stage took place after the development of genetics in the early 20th century, when it was appreciated that chromosomes were the carrier of genes. Lev Delaunay in 1922 seems to have been the first person to define the karyotype as the phenotypic appearance of the somatic chromosomes, in contrast to their genic contents.
The subsequent history of the concept can be followed in the works of C. D. Darlington and Michael JD White. Investigation into the human karyotype took many years to settle the most basic question: how many chromosomes does a normal diploid human cell contain? In 1912, Hans von Winiwarter reported 47 chromosomes in spermatogonia and 48 in oogonia, concluding an XX/XO sex determination mechanism. Painter in 1922 was not certain whether the diploid of humans was 46 or 48, at first favoring 46, but revised his opinion from 46 to 48, he insisted on humans having an XX/XY system. Considering the techniques of the time, these results were remarkable. In textbooks, the number of human chromosomes remained at 48 for over thirty years. New techniques were needed to correct this error. Joe Hin Tjio working in Albert Levan's lab was responsible for finding the approach: Using cells in tissue culture Pretreating cells in a hypotonic solution, which swells them and spreads the chromosomes Arresting mitosis in metaphase by a solution of colchicine Squashing the preparation on the slide forcing the chromosomes into a single plane Cutting up a photomicrograph and arranging the result into an indisputable karyogram.
The work took place in 1955, was published in 1956. The karyotype of humans includes only 46 chromosomes; the great apes have 48 chromosomes. Human chromosome 2 is now known to be a result of an end-to-end fusion of two ancestral ape chromosomes; the study of karyotypes is made possible by staining. A suitable dye, such as Giemsa, is applied after cells have been arrested during cell division by a solution of colchicine in metaphase or prometaphase when most condensed. In order for the Giemsa stain to adhere all chromosomal proteins must be digested and removed. For humans, white blood cells are used most because they are induced to divide and grow in tissue culture. Sometimes observations may be made on non-dividing cells; the sex of an unborn fetus can be determined by observation of interphase cells. Six different characteristics of karyotypes are observed and compared: Differences in absolute sizes of chromosomes. Chromosomes can vary in absolute size by as much as twenty-fold between genera of the same family.
For example, the legumes Lotus tenuis and Vicia faba each have six pairs of chromosomes, yet V. faba chromosomes are many times larger. These differences reflect different amounts of DNA duplication. Differences in the position of centromeres; these differences came about through translocations. Differences in relative size of chromosomes; these differences arose from segmental interchange of unequal lengths. Differences in basic number of chromosomes; these differences could have resulted from successive unequal translocations which removed all the essential genetic material from a chromosome, permitting its loss without penalty to the organism or through fusion. Humans have one pair fewer chromosomes than the great apes. Human chromosome 2 appears to have resulted from the fusion of two ancestral chromosomes, many of the genes of those two original chromosomes have been translocated to other chromosomes. Differences in number and position of satellites. Satellites are small bodies attached to a chromosome by a thin thread.
Differences in degree and distribution of heterochromatic regions. Het
Actinopterygii, or the ray-finned fishes, constitute a class or subclass of the bony fishes. The ray-finned fishes are so called because their fins are webs of skin supported by bony or horny spines, as opposed to the fleshy, lobed fins that characterize the class Sarcopterygii; these actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the link or connection between these fins and the internal skeleton. Numerically, actinopterygians are the dominant class of vertebrates, comprising nearly 99% of the over 30,000 species of fish, they are ubiquitous throughout freshwater and marine environments from the deep sea to the highest mountain streams. Extant species can range in size from Paedocypris, at 8 mm, to the massive ocean sunfish, at 2,300 kg, the long-bodied oarfish, at 11 m. Ray-finned fishes occur in many variant forms; the main features of a typical ray-finned fish are shown in the adjacent diagram. In nearly all ray-finned fish, the sexes are separate, in most species the females spawn eggs that are fertilized externally with the male inseminating the eggs after they are laid.
Development proceeds with a free-swimming larval stage. However other patterns of ontogeny exist, with one of the commonest being sequential hermaphroditism. In most cases this involves protogyny, fish starting life as females and converting to males at some stage, triggered by some internal or external factor. Protandry, where a fish converts from male to female, is much less common than protogyny. Most families use external rather than internal fertilization. Of the oviparous teleosts, most do not provide parental care. Viviparity, ovoviviparity, or some form of parental care for eggs, whether by the male, the female, or both parents is seen in a significant fraction of the 422 teleost families. Viviparity is rare and is found in about 6% of teleost species. Male territoriality "preadapts" a species for evolving male parental care. There are a few examples of fish; the mangrove rivulus is an amphibious, simultaneous hermaphrodite, producing both eggs and spawn and having internal fertilisation.
This mode of reproduction may be related to the fish's habit of spending long periods out of water in the mangrove forests it inhabits. Males are produced at temperatures below 19 °C and can fertilise eggs that are spawned by the female; this maintains genetic variability in a species, otherwise inbred. The earliest known fossil actinopterygiian is Andreolepis hedei. Remains have been found in Russia and Estonia. Actinopterygians are divided into the subclasses Neopterygii; the Neopterygii, in turn, are divided into the infraclasses Teleostei. During the Mesozoic and Cenozoic the teleosts in particular diversified and as a result, 96% of all known fish species are teleosts; the cladogram shows the major groups of actinopterygians and their relationship to the terrestrial vertebrates that evolved from a related group of fish. Approximate dates are from al.. 2012. The polypterids are the sister lineage of all other actinopterygians, the Acipenseriformes are the sister lineage of Neopterygii, Holostei are the sister lineage of teleosts.
The Elopomorpha appears to be the most basic teleosts. The listing below follows Phylogenetic Classification of Bony Fishes with notes when this differs from Nelson, ITIS and FishBase and extinct groups from Van der Laan 2016. Order †? Asarotiformes Schaeffer 1968 Order †? Discordichthyiformes Minikh 1998 Order †? Paphosisciformes Grogan & Lund 2015 Order †? Scanilepiformes Selezneya 1985 Order †Cheirolepidiformes Kazantseva-Selezneva 1977 Order †Paramblypteriformes Heyler 1969 Order †Rhadinichthyiformes Order †Palaeonisciformes Hay 1902 Order †Tarrasiiformes sensu Lund & Poplin 2002 Order †Ptycholepiformes Andrews et al. 1967 Order †Redfieldiiformes Berg 1940 Order †Haplolepidiformes Westoll 1944 Order †Aeduelliformes Heyler 1969 Order †Platysomiformes Aldinger 1937 Order †Dorypteriformes Cope 1871 Order †Eurynotiformes Sallan & Coates 2013 Subclass Cladistii Pander 1860 Order †Guildayichthyiformes Lund 2000 Order Polypteriformes Bleeker 1859 Clade Actinopteri Cope 1972 s.s. Order †Elonichthyiformes Kazantseva-Selezneva 1977 Order †Phanerorhynchiformes Order †Saurichthyiformes Berg 1937 Subclass Chondrostei Order †Birgeriiformes Jin 2001 Order †Chondrosteiformes Order Acipenseriformes Berg 1940 Subclass Neopterygii Regan 1923 sensu Xu & Wu 2012 Order †Pholidopleuriformes Berg 1937 Order †Peltopleuriformes Lehman 1966 Order †Perleidiformes Berg 1937 Order †Luganoiiformes Lehman 1958 Order †Pycnodontiformes Berg 1937 Infraclass Holostei Muller 1844 Division Halecomorpha Cope 1872 sensu Grande & Bemis 1998 Order †Parasemionotiformes Lehman 1966 Order †Ionoscopiformes Grande & Bemis 1998 Order Amiiformes Huxley 1861 sensu Grande & Bemis 1998 Division Ginglymodi Cope 1871 Order †Dapediiformes Thies & Waschkewitz 2015 Order †Semionotiformes Arambourg & Bertin 1958 Order Lepisosteiformes Hay 1929 Clade Teleosteomorpha Arratia 2000 sensu Arratia 2013 Order †Prohaleciteiformes Arratia 2017 Division Aspidorhynchei Nelson, Grand & Wilson 2016 Order †Aspidorhynchiformes Bleeker 1859 Order †Pachycormiformes Berg 1937 Infraclass Teleostei Müller 1844 sensu Arratia 2013 Order †?
Araripichthyiformes Order †? Ligulelliiformes Taverne 2011 Order †? Tselfatiiformes Nelson 1994 Order †Pholidophori
Dabry's sturgeon is a species of fish in the sturgeon family, Acipenseridae. Other common names include Yangtze sturgeon, Chiangjiang sturgeon, river sturgeon, it is endemic to the Yangtze River Basin in China. It was a food fish of commercial importance, its populations declined drastically, in the early 1980s, it was designated an endangered species and commercial harvest was banned. It has been listed as a critically endangered species by the IUCN since 1996; this sturgeon has been known to reach 2.5 m in length, but it is much smaller. Its body is blue-gray above and yellowish white with five rows of scutes; the head is triangular and the snout is long with the mouth located on the underside. There are two pairs of barbels; the fish lives in slow-moving river waters over substrates of mud. It feeds on aquatic plants and small fish; this species is potamodromous, never leaving fresh water. It spawns in the upper Yangtze during March and April, sometimes around November and December. Males spawn each year.
The female produces 57,000 to 102,000 eggs. This was once a common fish in the Yangtze system, it was known from the main river and some of its larger tributaries, as well as some lakes attached to the system. By the late 20th century, it was extirpated from the lower river and limited to the upper reaches in Sichuan; the main causes of its drastic decline include overfishing, including the overharvesting of juveniles. The construction of dams, such as the Three Gorges Dam, blocked the movement of the fish along the river, restricting it to the upper reaches, it caused habitat fragmentation and degradation. Increased development and deforestation on land near the river has increased pollution from wastewater and runoff; the fish has been bred in captivity since the 1970s. Thousands of individuals have been released into the river, but are not breeding; this restocking may be the only effort preventing the extinction of the species. List of endangered and protected species of China
Scaphirhynchinae is a subfamily of sturgeon which includes two genera comprising a total of six species. Genus Scaphirhynchus Heckel, 1835 Scaphirhynchus albus Scaphirhynchus platorynchus Scaphirhynchus suttkusi J. D. Williams & Clemmer, 1991 Genus Pseudoscaphirhynchus Nikolskii, 1900 Pseudoscaphirhynchus fedtschenkoi Pseudoscaphirhynchus hermanni Pseudoscaphirhynchus kaufmanni Animal Diversity Web