| Oikopleura dioica | |
|---|---|
 | |
| Oikopleura dioica | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Tunicata |
| Class: | Appendicularia |
| Order: | Copelata |
| Family: | Oikopleuridae |
| Genus: | Oikopleura |
| Species: | O. dioica |
| Binomial name | |
| Oikopleura dioica Fol, 1872 [1] | |
| Synonyms | |
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Oikopleura dioica is a species of small pelagic tunicate found in the surface waters of most of the world's oceans. It is used as a model organism in research into developmental biology.
Oikopleura dioica is a bioluminescent species. [2] Like other Oikopleuridans, O. dioica have a discrete body and tail as adults and retain their notochord throughout life. They resemble tadpoles in appearance with a body typically between 0.5 and 1 mm (0.02 and 0.04 in) long and a tail about four times that length.
Its body is ovoid and the tail slender. There are two sub-chordal cells outside the central core of muscle in the tail, which are easily observable some half to two thirds of the way down the length of the tail. The mouth has a small lower lip and the buccal glands are small and globular. The endostyle is large, extending nearly as far as the anus. The right lobe of the stomach forms a sac behind the entrance to the intestine. O. dioica sexes are separate, unlike in all other known appendicularians, and the ovary or testes are at the rear of the body. [3]
Oikopleura dioica is widely distributed over the continental shelf in tropical and temperate waters in all the world's oceans. [3] It is very abundant in surface waters but in colder seas is replaced by Oikopleura vanhoeffeni and Oikopleura labradoriensis . [4]
Every three or four hours, Oikopleura dioica creates a mucus net "house" which surrounds its body. Water is pumped through this house and minute food particles are filtered out of the water and then transferred into the mouth. Once the gelatinous net "houses" are too clogged to allow further filtration, they are then abandoned and drift down through the water to the seabed as "marine snow".
Oikopleura dioica is used as a model organism, a role for which it has several features to recommend it. It has the typical chordate body plan, it is simple to keep and breed in the laboratory, it produces large numbers of eggs and the generation time is only four days at 20 °C (68 °F). The body is also transparent, making it easier to study, and at hatching only consist of 550 cells. [5] The genome has been sequenced and contains about 15,000 genes, approximately half the number occurring in vertebrates. All central Hox genes have been lost. [6] Comparison of the genome with that of other chordates will help identify the genes which appeared early in the vertebrate lineage. Examination of intraspecific genomic variation has revealed extreme genome scrambling, despite the lack of morphological variation accompanying such vast genomic variation. [7]
In the Sars International Centre for Marine Molecular Biology, inbred lines have been developed using repeated matings of closely related individuals. The molecular base of a number of aspects of vertebrate development is identical in these simple chordates and in higher vertebrates. As an example, the brachyury gene and the homolog of the PAX2 gene both play a similar role in the development of tunicates as they do in vertebrates. Complex aspects of vertebral development such as the differentiation of the central nervous system can thus be studied in the laboratory.
A chordate is a deuterostomic bilaterial animal belonging to the phylum Chordata. All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa. These five synapomorphies are a notochord, a hollow dorsal nerve cord, an endostyle or thyroid, pharyngeal slits, and a post-anal tail.
Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction, metamorphosis, and the growth and differentiation of stem cells in the adult organism.
Hemichordata is a phylum which consists of triploblastic, eucoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and include two main classes: Enteropneusta, and Pterobranchia. A third class, Planctosphaeroidea, is known only from the larva of a single species, Planctosphaera pelagica. The class Graptolithina, formerly considered extinct, is now placed within the pterobranchs, represented by a single living genus Rhabdopleura.
Evolutionary developmental biology is a field of biological research that compares the developmental processes of different organisms to infer how developmental processes evolved.
A tunicate is an exclusively marine invertebrate animal, a member of the subphylum Tunicata. This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords. 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. However, doliolids still display segmentation of the muscle bands.
Larvaceans 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 2 mm (0.079 in) to 8 mm (0.31 in) in body length including the tail, although giant larvaceans can reach up to 10 cm (3.9 in) in length.
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 "tunic" made of a polysaccharide.
The lancelets, also known as amphioxi, consist of 32 described species of "fish-like" benthic filter feeding chordates in the subphylum Cephalochordata, class Leptocardii, and family Branchiostomatidae.
Hox genes, a subset of homeobox genes, are a group of related genes that specify regions of the body plan of an embryo along the head-tail axis of animals. Hox proteins encode and specify the characteristics of 'position', ensuring that the correct structures form in the correct places of the body. For example, Hox genes in insects specify which appendages form on a segment, and Hox genes in vertebrates specify the types and shape of vertebrae that will form. In segmented animals, Hox proteins thus confer segmental or positional identity, but do not form the actual segments themselves.
Ciona intestinalis is an ascidian, a tunicate with very soft tunic. Its Latin name literally means "pillar of intestines", referring to the fact that its body is a soft, translucent column-like structure, resembling a mass of intestines sprouting from a rock. It is a globally distributed cosmopolitan species. Since Linnaeus described the species, Ciona intestinalis has been used as a model invertebrate chordate in developmental biology and genomics. Studies conducted between 2005 and 2010 have shown that there are at least two, possibly four, sister species. More recently it has been shown that one of these species has already been described as Ciona robusta. By anthropogenic means, the species has invaded various parts of the world and is known as an invasive species.
The starlet sea anemone is a species of small sea anemone in the family Edwardsiidae native to the east coast of the United States, with introduced populations along the coast of southeast England and the west coast of the United States. Populations have also been located in Nova Scotia, Canada. This sea anemone is found in the shallow brackish water of coastal lagoons and salt marshes where its slender column is usually buried in the mud and its tentacles exposed. Its genome has been sequenced and it is cultivated in the laboratory as a model organism, but the IUCN has listed it as being a "Vulnerable species" in the wild.
Oikopleura is a genus of tunicates in the class Appendicularia (larvaceans). It forms a mucus house every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small particles, down to the nanoplankton that includes (pelagic) bacteria.
Strongylocentrotus purpuratus is a species of sea urchin in the family Strongylocentrotidae commonly known as the purple sea urchin. It lives along the eastern edge of the Pacific Ocean extending from Ensenada, Mexico, to British Columbia, Canada. This sea urchin species is deep purple in color, and lives in lower inter-tidal and nearshore sub-tidal communities. Its eggs are orange when secreted in water. January, February, and March function as the typical active reproductive months for the species. Sexual maturity is reached around two years. It normally grows to a diameter of about 10 cm (4 inches) and may live as long as 70 years.
The 2R hypothesis or Ohno's hypothesis, first proposed by Susumu Ohno in 1970, is a hypothesis that the genomes of the early vertebrate lineage underwent two whole genome duplications, and thus modern vertebrate genomes reflect paleopolyploidy. The name derives from the 2 rounds of duplication originally hypothesized by Ohno, but refined in a 1994 version, and the term 2R hypothesis was probably coined in 1999. Variations in the number and timings of genome duplications typically still are referred to as examples of the 2R hypothesis.
Botrylloides violaceus is a colonial ascidian. It is commonly known as the chain tunicate, but has also been called several other common names, including: lined colonial tunicate, orange sheath tunicate, orange tunicate, and violet tunicate. Its native range is in the northwest Pacific from southern China to Japan and Siberia. Colonies grow on solid substrates and consist of individuals arranged in twisting rows. Outside its native range, it is considered an invasive species and is becoming more common in coastal waters of North America and other waters around the world, likely being spread by shipping industries.
Chordate genomics is the study of the evolution of the chordate clade based on a comparison of the genomes of several species within the clade. The field depends on whole genome data of organisms. It uses comparisons of synteny blocks, chromosome translocation, and other genomic rearrangements to determine the evolutionary history of the clade, and to reconstruct the genome of the founding species.
Branchiostoma lanceolatum, the European lancelet or Mediterranean amphioxus is a lancelet in the subphylum Cephalochordata. It is a marine invertebrate with a notochord but no backbone and is used as a model organism to study the evolutionary development of vertebrates.
Oikopleura cophocerca is a species of small pelagic tunicate found in the surface waters of most of the world's oceans. It superficially resembles a tadpole and is surrounded by a transparent mucus net known as a "house".
The Michael Sars Centre is a research institute at the University of Bergen located in Bergen, Norway. It consists of an international community of scientists that use advanced technologies to study the unique molecular and cellular biology of marine organisms.
