|
Tunicate
Tunicates are marine invertebrates belonging to the subphylum Tunicata ( ). This grouping 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. Despite their simple appearance and very different adult form, their close relationship to the vertebrates is certain. Both groups are chordates, as evidenced by the fact that during their mobile larval stage, tunicates possess a notochord, a hollow dorsal nerve cord, pharyngeal slits, post-anal tail, and an endostyle. They resemble a tadpole. Tunicates are the only chordates that have lost their Myomere, myomeric segmentation, with the possible exception of the seriation of the gill slits. However, Doliolida, doliolids still display segmentation of the muscle bands. Some tunicates live as solitary individuals, but others replicate by budding and be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chordata
A chordate ( ) is a bilaterian animal belonging to the phylum Chordata ( ). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (Apomorphy and synapomorphy, synapomorphies) that distinguish them from other Taxon, taxa. These five synapomorphies are a notochord, a neural tube, hollow dorsal nerve cord, an endostyle or thyroid, pharyngeal slits, and a post-anus, anal tail. 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 inner mitochondrial membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cephalochordates. These CSIs provide molecular means to reliably distinguish chordates from all other animals. Chordates are divided into three phylum, subphyla: Vertebrata (fish, amphibians, reptiles, birds and mammals), whose notochor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ascidiacea
Ascidiacea, commonly known as the ascidians or sea squirts, is a paraphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer test or "tunic" made of the polysaccharide cellulose. Ascidians are found all over the world, usually in shallow water with salinities over 2.5%. While members of the Thaliacea (salps, doliolids and pyrosomes) and Appendicularia (larvaceans) swim freely like plankton, sea squirts are sessile animals after their larval phase: they then remain firmly attached to their substratum, such as rocks and shells. There are 2,300 species of ascidians and three main types: solitary ascidians, social ascidians that form clumped communities by attaching at their bases, and compound ascidians that consist of many small individuals (each individual is called a zooid) forming large colonies. Sea squirts feed by taking in water through a tube, the oral siphon. The water enters the mouth and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filter Feeder
Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a specialized filtering organ that sieves out and/or traps solids. Filter feeders can play an important role in condensing biomass and removing excess nutrients (such as nitrogen and phosphate) from the local waterbody, and are therefore considered water-cleaning ecosystem engineers. They are also important in bioaccumulation and, as a result, as indicator organisms. Filter feeders can be sessile, planktonic, nektonic or even neustonic (in the case of the buoy barnacle) depending on the species and the niches they have evolved to occupy. Extant species that rely on such method of feeding encompass numerous phyla, including poriferans ( sponges), cnidarians (jellyfish, sea pens and corals), arthropods ( krill, mysids and barna ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thaliacea
Thaliacea is a class of marine chordates within the subphylum Tunicate, Tunicata, comprising the salps, pyrosomes and doliolids. Unlike their benthic relatives the Ascidiacea, ascidians, from which they are believed to have emerged, thaliaceans are free-floating (pelagic) for their entire lifespan. The group includes species with complex life cycles, with both solitary and Colony (biology), colonial forms. Anatomy The three orders of thaliaceans are filter feeders. Pyrosoma, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Larvacean
Larvaceans, copelates or appendicularians, class Appendicularia, are solitary, free-swimming tunicates found throughout the world's oceans. While larvaceans are filter feeders like most other tunicates, they keep their tadpole-like shape as adults, with the notochord running through the tail. They can be found in the pelagic zone, specifically in the photic zone, or sometimes deeper. They are transparent planktonic animals, usually ranging from to in body length including the tail, although giant larvaceans can reach up to in length. Larvaceans are known for the large houses they build around their bodies to assist in filter-feeding. Secreted from mucus and cellulose, these structures often comprise several layers of filters and can reach up to ten times their body length. In some genera like '' Oikopleura'', houses are built and discarded every few hours, with sinking houses playing a key role in the oceanic carbon cycle. History The study of larvaceans began with the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebrates
Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest ranked grouping in the phylum Chordata. The vertebrates include mammals, birds, amphibians, and various classes of fish and reptiles. The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the Chondrichthyes, cartilaginous fish and the Osteichthyes, bony fish. Bony fish include the Sarcopterygii, lobe-finned fish, which gave rise to the tetrapods, the animals with four limbs. Despite their success, vertebrates still only make up less than five percent of all described animal species. The first vertebrates appeared in the Cambrian explosion some 518 million years ago. Jawed vertebrates evolved in the Ordovician, followed by bony fishes in the Devonian. T ... [...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. Hydroids and algae may grow on the outside of the tunicate and nudibranch Nudibranchs () ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shankouclava
''Shankouclava'' is an extinct genus of tunicates. It is one of two candidates for the oldest member of this group, dating to . It has been found in the Lower Cambrian Maotianshan Shale at Shankou village, Anning, near Kunming (South China). Each of the eight specimens found and used for description were isolated, suggesting that the genus was solitary and not colonial. Morphology ''Shankouclava'' had a soft, sac-like body that was elongated and pointed proximally. The body lengths of individuals vary from 2 cm (0.8 in) to 4 cm (1.6 in). Etymology The generic name is composed of the fossil locality, Shankou, and the Latin word ''clava'' (club-shaped). Classification A stem group tunicate affinity for ''Shankouclava'' has been broadly accepted, though some authors have expressed reservations that the evidence in favour of this affinity is not conclusive. Doubts regarding ''Shankouclavas tunicate affinities arose in the context of a long-running debate tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doliolida
The Doliolida are an order of small marine chordates of the subphylum Tunicata. They are in the class Thaliacea, which also includes the salps and pyrosomes. The doliolid body is small, typically 1–2 mm long, and barrel-shaped; it features two wide siphons, one at the front and the other at the back end, and eight or nine circular muscle strands reminiscent of barrel bands. Like all tunicates, except for the predatory tunicate, they are filter feeders. Unlike the related class Ascidiacea, which are sessile, but like the class Appendicularia, they are free-swimming plankton; cilia pump water through the body which drives them forward. As the water passes through, small particles and plankton on which the animal feeds are strained from the water by the gill slits. Doliolids can also move by contracting the muscular bands around the body creating a temporary water jet that thrusts them forward or backward quite quickly. The Doliolida have a complicated life cycle tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Invertebrates
Marine invertebrates are invertebrate animals that live in marine habitats, and make up most of the macroscopic life in the oceans. It is a polyphyletic blanket term that contains all marine animals except the marine vertebrates, including the non-vertebrate members of the phylum Chordata such as lancelets, sea squirts and salps. As the name suggests, marine invertebrates lack any mineralized tissue, mineralized axial skeleton, axial endoskeleton, i.e. the vertebral column, and some have evolved a rigid seashell, shell, test (biology), test or exoskeleton for protection and/or aquatic locomotion, locomotion, while others rely on hydroskeleton, internal fluid pressure to support their bodies. Marine invertebrates have a large variety of body plans, and have been categorized into over 30 phyla. Evolution The earliest animals were marine invertebrates, that is, vertebrates came later. Animals are multicellular eukaryotes, and are distinguished from plants, algae, and fungi by l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yarnemia
''Yarnemia ascidiformis'' is a fossil tentatively classified as a tunicate. While ''Y. ascidiformis'' looks similar to tunicates, the oldest unequivocal tunicate, ''Shankouclava'' dates to the Cambrian period, while ''Y. ascidiformis'' is Ediacaran in age. Discovery and name The holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ... fossil of ''Yarnemia'' was found from the Ustʹ Pinega Formation between 1976 and 1978, and described in 1984. The generic name ''Yarnemia'' comes from the village of Yarnema near which the first specimens were found. The specific epithet, ''ascidiformis'', refers to the likeness to ascidians. Description ''Yarnemia ascidiformis'' is a possible tunicate, growing up to in length, with the standard oblong body and two openings, or siphons, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subphylum
In zoological nomenclature, a subphylum is a taxonomic rank below the rank of phylum. The taxonomic rank of " subdivision" in fungi and plant taxonomy is equivalent to "subphylum" in zoological taxonomy. Some plant taxonomists have also used the rank of subphylum, for instance monocotyledons as a subphylum of phylum Angiospermae and vertebrates as a subphylum of phylum Chordata. Taxonomic rank Subphylum is: #subordinate to the phylum #superordinate to the infraphylum, which is in turn superordinate to parvphylum. Where convenient, subphyla in turn can be divided into infraphyla; in turn such an infraphylum also would be superordinate to any classes or superclasses in the hierarchy. Examples Not all fauna phyla are divided into subphyla. Those that are include: *Arthropoda: divided into subphyla Trilobitomorpha, Chelicerata, Myriapoda, and Pancrustacea * Brachiopoda: divided into subphyla Linguliformea, Craniformea and Rhynchonelliformea * Chordata: divided into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
