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Tunicates
A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time called Urochordata, and the term urochordates is still sometimes used for these animals. They are the only chordates that have lost their myomeric segmentation, with the possible exception of the 'seriation of the gill slits'. Some tunicates live as solitary individuals, but others replicate by budding and become colonies, each unit being known as a zooid. They are marine filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. During their respiration and feeding, they take in water through the incurrent (or inhalant) siphon and expel the filtered water through the excurrent (or exhalant) siphon. Most adult tunicates are sessile, immobile and perman ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. Vertebrates comprise such groups as the following: * jawless fish, which include hagfish and lampreys * jawed vertebrates, which include: ** cartilaginous fish (sharks, rays, and ratfish) ** bony vertebrates, which include: *** ray-fins (the majority of living bony fish) *** lobe-fins, which include: **** coelacanths and lungfish **** tetrapods (limbed vertebrates) Extant vertebrates range in size from the frog species ''Paedophryne amauensis'', at as little as , to the blue whale, at up to . Vertebrates make up less than five percent of all described animal species; the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thaliacea
The Thaliacea comprise a class of marine animals within the subphylum Tunicata. Unlike their benthic relatives the ascidians, thaliaceans are free-floating (pelagic) for their entire lifespan. The group includes species with complex life cycles, with both solitary and colonial forms. Anatomy The three orders of thaliaceans are filter feeders. Pyrosomes are colonial animals, with multiple tiny ascidian-like zooids arranged in a cylinder closed at one end. All of the atrial siphons point inwards, emptying into a single, common cloaca in the centre of the cylinder. As the water exhaled by the zooids exits through a common opening, the water movement slowly propels the pyrosome through the sea. Salps and doliolids have a transparent barrel-shaped body through which they pump water, propelling them through the sea, and from which they extract food. The bulk of the body consists of the large pharynx. Water enters the pharynx through the large buccal siphon at the front end of the a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filter Feeder
Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish (including some sharks). Some birds, such as flamingos and certain species of duck, are also filter feeders. Filter feeders can play an important role in clarifying water, and are therefore considered ecosystem engineers. They are also important in bioaccumulation and, as a result, as indicator organisms. Fish Most forage fish are filter feeders. For example, the Atlantic menhaden, a type of herring, lives on plankton caught in midwater. Adult menhaden can filter up to four gallons of water a minute and play an important role in clarifying ocean water. They are also a natural check to the deadly red tide. Extensive article on the role of menhaden in the ecosystem and possible resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chordata
A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These five synapomorphies include a notochord, dorsal hollow nerve cord, endostyle or thyroid, pharyngeal slits, and a post-anal tail. The name “chordate” comes from the first of these synapomorphies, the notochord, which plays a significant role in chordate structure and movement. Chordates are also Bilateral symmetry, bilaterally symmetric, have a coelom, possess a circulatory system, and exhibit Metameric, metameric segmentation. In addition to the morphological characteristics used to define chordates, analysis of genome sequences has identified two conserved signature indels (CSIs) in their proteins: cyclophilin-like protein and mitochondrial inner membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Larvaceans
Larvaceans, class Appendicularia, are solitary, free-swimming tunicates found throughout the world's oceans. Like most tunicates, larvaceans are filter feeders. Unlike most other tunicates, they live in the pelagic zone, specifically in the photic zone, or sometimes deeper. They are transparent planktonic animals, generally less than in body length, excluding the tail. Anatomy The adult larvaceans resemble the tadpole-like larvae of most tunicates. Like a common tunicate larva, the adult Appendicularia have a discrete trunk and tail. Larvaceans produce a "house" made of mucopolysaccharides and cellulose. In most species, the house surrounds the animal like a bubble. Even for species in which the house does not completely surround the body, such as ''Fritillaria (tunicate), Fritillaria'', the house is always present and attached to at least one surface. These houses are discarded and replaced regularly as the animal grows in size and its filters become clogged; in ''Oikopleura'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelids, echinoderms and cnidarians. The majority of animal species are invertebrates; one estimate puts the figure at 97%. Many invertebrate taxa have a greater number and variety of species than the entire subphylum of Vertebrata. Invertebrates vary widely in size, from 50 μm (0.002 in) rotifers to the 9–10 m (30–33 ft) colossal squid. Some so-called invertebrates, such as the Tunicata and Cephalochordata, are more closely related to vertebrates than to other invertebrates. This makes the invertebrates paraphyletic, so the term has little meaning in taxonomy. Etymology The word "invertebrate" comes from the Latin word ''vertebra'', whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycarpa Aurata
''Polycarpa aurata'', also known as the ox heart ascidian, the gold-mouth sea squirt or the ink-spot sea squirt, is a species of tunicate in the family Styelidae. Description ''Polycarpa aurata'' grows to a height of . It has an urn-shaped, hollow body with two siphons, one at the top and the other on the side. The body colour of this tunicate is white with purple and orange patches and purple lines. The inside is yellow or orange and this is visible around the rim of the siphons. Distribution This species is found in the tropical eastern Indian Ocean and the western Pacific Ocean. Its range includes the Philippines, Indonesia and northern Australia. Its depth range is . Biology Tunicates feed by drawing water in through the branchial siphon at the top, filtering out phytoplankton, bacteria and other food particles, before expelling the water through the atrial siphon at the side. Sometimes hydroids and algae grow on the outside of the tunicate and nudibranchs such as ''Nem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Larvacea
Larvaceans, class Appendicularia, are solitary, free-swimming tunicates found throughout the world's oceans. Like most tunicates, larvaceans are filter feeders. Unlike most other tunicates, they live in the pelagic zone, specifically in the photic zone, or sometimes deeper. They are transparent planktonic animals, generally less than in body length, excluding the tail. Anatomy The adult larvaceans resemble the tadpole-like larvae of most tunicates. Like a common tunicate larva, the adult Appendicularia have a discrete trunk and tail. Larvaceans produce a "house" made of mucopolysaccharides and cellulose. In most species, the house surrounds the animal like a bubble. Even for species in which the house does not completely surround the body, such as ''Fritillaria'', the house is always present and attached to at least one surface. These houses are discarded and replaced regularly as the animal grows in size and its filters become clogged; in ''Oikopleura'', a house is kept for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Notochord
In anatomy, the notochord is a flexible rod which is similar in structure to the stiffer cartilage. If a species has a notochord at any stage of its life cycle (along with 4 other features), it is, by definition, a chordate. The notochord consists of inner, vacuolated cells covered by fibrous and elastic sheaths, lies along the anteroposterior axis (''front to back''), is usually closer to the dorsal than the ventral surface of the embryo, and is composed of cells derived from the mesoderm. The most commonly cited functions of the notochord are: as a midline tissue that provides directional signals to surrounding tissue during development, as a skeletal (structural) element, and as a vertebral precursor. In lancelets the notochord persists throughout life as the main structural support of the body. In tunicates the notochord is present only in the larval stage, being completely absent in the adult animal. In these invertebrate chordates, the notochord is not vacuolated. In all ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myomere
Myomeres are blocks of skeletal muscle tissue arranged in sequence, commonly found in aquatic chordates. Myomeres are separated from adjacent myomeres by connective fascia (myosepta) and most easily seen in larval fishes or in the olm. Myomere counts are sometimes used for identifying specimens, since their number corresponds to the number of vertebrae in the adults. Location varies, with some species containing these only near the tails, while some have them located near the scapular or pelvic girdles. Depending on the species, myomeres could be arranged in an epaxial or hypaxial manner. Hypaxial refers to ventral muscles and related structures while epaxial refers to more dorsal muscles. The horizontal septum divides these two regions in vertebrates from cyclostomes to gnathostomes. In terrestrial chordates, the myomeres become fused as well as indistinct, due to the disappearance of myosepta. Shape The shape of myomeres varies by species. Myomeres are commonly zig-zag, " ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Stage 3
Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approximately to the first appearance of trilobites, about million years ago, though the globally asynchronous appearance of trilobites warrants the use of a separate, globally synchronous marker to define the base. The upper boundary and beginning of Cambrian Stage 4 is informally defined as the first appearance of the trilobite genera ''Olenellus'' or '' Redlichia'' around million years ago. Naming The International Commission on Stratigraphy has not officially named the 3rd stage of the Cambrian. The stage approximately corresponds to the "Atdabanian", which is used by geologists working in Siberia. Biostratigraphy The oldest trilobite known is ''Lemdadella'' which appears at the beginning of the '' Fallotaspis'' zone. The Cambrian radiati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Budding
Budding or blastogenesis is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. For example, the small bulb-like projection coming out from the yeast cell is known as a bud. Since the reproduction is asexual, the newly created organism is a clone and excepting mutations is genetically identical to the parent organism. Organisms such as hydra use regenerative cells for reproduction in the process of budding. In hydra, a bud develops as an outgrowth due to repeated cell division at one specific site. These buds develop into tiny individuals and, when fully mature, detach from the parent body and become new independent individuals. Internal budding or endodyogeny is a process of asexual reproduction, favored by parasites such as ''Toxoplasma gondii''. It involves an unusual process in which two daughter cells are produced inside a mother cell, which is then consumed by the offspring prior to their s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
