A chordate is a deuterostomic 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. The name "chordate" comes from the first of these synapomorphies, the notochord, which plays a significant role in chordate body plan structuring and movements. Chordates are also bilaterally symmetric, have a coelom, possess a closed circulatory system, and exhibit metameric segmentation.
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.
Pharyngeal slits are filter-feeding organs found among deuterostomes. Pharyngeal slits are repeated openings that appear along the pharynx caudal to the mouth. With this position, they allow for the movement of water in the mouth and out the pharyngeal slits. It is postulated that this is how pharyngeal slits first assisted in filter-feeding, and later, with the addition of gills along their walls, aided in respiration of aquatic chordates. These repeated segments are controlled by similar developmental mechanisms. Some hemichordate species can have as many as 200 gill slits. Pharyngeal clefts resembling gill slits are transiently present during the embryonic stages of tetrapod development. The presence of pharyngeal arches and clefts in the neck of the developing human embryo famously led Ernst Haeckel to postulate that "ontogeny recapitulates phylogeny"; this hypothesis, while false, contains elements of truth, as explored by Stephen Jay Gould in Ontogeny and Phylogeny. However, it is now accepted that it is the vertebrate pharyngeal pouches and not the neck slits that are homologous to the pharyngeal slits of invertebrate chordates. Pharyngeal arches, pouches, and clefts are, at some stage of life, found in all chordates. One theory of their origin is the fusion of nephridia which opened both on the outside and the gut, creating openings between the gut and the environment.
The ParaHox gene cluster is an array of homeobox genes from the Gsx, Xlox (Pdx) and Cdx gene families.
Ciona is a genus of sea squirts in the family Cionidae.
Botryllus schlosseri is a colonial ascidian tunicate. It is commonly known as the star tunicate, but it also has several other common names, including star ascidian and golden star tunicate. Colonies grow on slow-moving, submerged objects, plants, and animals in nearshore saltwater environments.
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.
Albert Erives is a developmental geneticist who studies transcriptional enhancers underlying animal development and diseases of development (cancers). Erives also proposed the pacRNA model for the dual origin of the genetic code and universal homochirality. He is known for work at the intersection of genetics, evolution, developmental biology, and gene regulation. He has worked at the California Institute of Technology, University of California, Berkeley, and Dartmouth College, and is an associate professor at the University of Iowa.
Michael Levine is an American developmental and cell biologist at Princeton University, where he is the Director of the Lewis-Sigler Institute for Integrative Genomics and a Professor of Molecular Biology.
Didemnum vexillum is a species of colonial tunicate in the family Didemnidae. It is commonly called sea vomit, marine vomit, pancake batter tunicate, or carpet sea squirt. It is thought to be native to Japan, but it has been reported as an invasive species in a number of places in Europe, North America and New Zealand. It is sometimes given the nickname "D. vex" because of the vexing way in which it dominates marine ecosystems when introduced into new locations; however, the species epithet vexillum actually derives from the Latin word for flag, and the species was so named because of the way colonies' long tendrils appear to wave in the water like a flag.
Relaxin family peptide hormones in humans are represented by seven members: three relaxin-like (RLN) and four insulin-like (INSL) peptides: RLN1, RLN2, RNL3, INSL3, INSL4, INSL5, INSL6. This subdivision into two classes is based primarily on early findings, and does not reflect the evolutionary origins or physiological differences between peptides. For example, it is known that the genes coding for RLN3 and INSL5 arose from one ancestral gene, and INSL3 shares origin with RLN2 and its multiple duplicates: RLN1, INSL4, INSL6.
Voltage sensitive phosphatases or voltage sensor-containing phosphatases, commonly abbreviated VSPs, are a protein family found in many species, including humans, mice, zebrafish, frogs, and sea squirt.
Ciona savignyi is a marine animal sometimes known as the Pacific transparent sea squirt or solitary sea squirt. It is a species of tunicates in the family Cionidae. It is found in shallow waters around Japan and has spread to the west coast of North America where it is regarded as an invasive species.
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.
Sugar transporter SWEET1, also known as RAG1-activating protein 1 and stromal cell protein (SCP), is a membrane protein that in humans is encoded by the SLC50A1 gene. SWEET1 is the sole transporter from the SLC50 (SWEET) gene family present in the genomes of most animal species, with the exception of the nematode Caenorhabditis elegans, which has seven.
Ciona robusta is a species of marine invertebrate in the genus Ciona of the family Cionidae. The holotype was collected on the northeastern coast of Honshu Island, Japan. Populations of Ciona intestinalis known as Ciona intestinalis type A found in the Mediterranean Sea, the Pacific Ocean, east coast of North America, and the Atlantic coasts of South Africa have been shown to be Ciona robusta.
