The pufferfish known as the Torafugu (Takifugu rubripes) has at least two claims to fame. First, the genome of this species was the first vertebrate genome to be sequenced and made publicly available after the human genome. Pufferfish genomes are the smallest known for vertebrates, only around 400 Mb (about an eighth the size of the human genome). Pufferfishes were suggested as appealing "model" vertebrates for genomic analysis in part because, although compact, theirgenomes have essentially the same genes and regulatory sequences as other vertebrates, so less effort is needed to obtain a comparable amount of information (Brenner et al. 1993). Analysis of the Torafugu genome together with the genomes of another pufferfish,Tetraodon nigroviridis, and other vertebrates have provided new insights into the evolution of vertebrates (e.g., Jaillon et al. 2004). For technical information about the Torafugu genome, visit the Fugu Genome Project webpage.
Torafugus's second claim to fame is as a dangerous delicacy in Japan. Fugu is a Japanese dish prepared in various ways from certain species of pufferfish (Takifugu, Lagocephalus, Sphoeroides) or porcupinefish (Diodon)--but especialy from Ta. rubripes. What makes fugu so exciting and sets it apart from other fish sold in restaurants is that it is potentially deadly. Fugu can contain lethal amounts of the poison tetrodotoxin (TTX) in its organs, especially the liver and ovaries, and also in the skin. The poison paralyzes the muscles while the victim remains fully conscious until eventually dying from asphyxiation. There is no known antidote. Even miniscule traces of the toxin are said to cause the diner’s lips to go numb and turn his mind to the possibility that this could be his last meal. With the stakes so high, chefs must be highly trained to prepare fugu and it is not widely available outside Japan—in fact, it is illegal to sell it in most or all of the European Union and its preparation and sale is tightly regulated in the United States.
Different pufferfish species and different body parts vary substantially in their TTX concentration (Noguchi and Arakawa 2008). Some recent research has indicated that the toxin may be derived from TTX-laden bacteria working their way up the food chain to the pufferfish, making safe-to-eat farmed fugu a possibility (e.g., see Noguchi and Arakawa 2008; Yuan et al. 2011). Some purists, predictably, insist that the taste of farmed fugu cannot compare with the sublime flavor of the wild fish—or could it just be the lack of adrenaline in the diner’s body that tames the flavor of poison-free farmed fugu? Food writer Adam Platt's 2008 account of dining on fugu in Tokyo can be read in New York Magazine.
The genus Takifugu includes around two dozen species, all of which are found in marine waters around China, Korea, and Japan, although additional morphological and genetic analyses are needed to resolve some taxonomic questions (e.g., see Song et al 2001; Reza et al 2008). Yamanoue et al. (2008) used whole mitochondrial genome sequences from 15 Takifugu species and eight other tetraodontid pufferfishes (plus two outgroups.) to investigate phylogenetics relationships within this Takifugu. Their analyses indicated that Takifugu species are very closely related to each other and speciated over a relatively short period in the limited area of the East Asian marine waters.
Takifugu rubripes, commonly known as the Japanese puffer, Tiger puffer, or torafugu (Japanese: 虎河豚), is a pufferfish in the genus Takifugu. It is distinguished by a very small genome that has been fully sequenced because of its use as a model species and is in widespread use as a reference in genomics.[3]
The species is often referred to in the genomics literature as Fugu rubripes. The genus Fugu is a synonym of the currently preferred Takifugu.[4] Takifugu is Japanese for puffer and rubripes comes from the Latin ruber and pēs meaning ruddy foot.
The species is known from the Sea of Japan, East China Sea and Yellow Sea north to southern Sakhalin, at depths of 10–135 m (33–443 ft). It is a demersal species. Spawning occurs in estuaries; young fish can tolerate a wide range of salinities and will remain in river mouths and lagoons, maturing for one year before migrating permanently to the open ocean.[1]
A feature of this species is that it has a very small genome, which is used as a ‘reference’ for identifying genes and other elements in human and other vertebrate genomes. The genome was published in 2002 by the International Fugu Genome Consortium via whole genome shotgun sequencing. After being initiated in 1989, it was the first vertebrate genome after the human genome to be made publicly available.[5] It remains among the smallest known vertebrate genomes; its number of base pairs is ~6% and the number of previously known protein-coding genes ~13% that of the human genome, although the number of chromosomes (22) is comparable to that of humans (23). This makes it particularly useful for comparative studies. Current estimates show a total of 392,376,244 base pairs, 1,138 known and 18,093 novel protein-coding genes, and 593 RNA genes.[6]
One type of torafugu, 22-seiki fugu (meaning "22nd-century fugu"), has been genetically modified by removing four leptin receptor genes that control appetite. The result has increased appetite and weight gain, growing on average 1.9 times faster than normal torafugu. It is sold commercially as food.[7][8]
As some other pufferfish, some organs of the Japanese puffer contain tetrodotoxin and are highly toxic. The toxin is highly concentrated in liver and ovaries, slightly present in the intestines and flesh, and absent from skin and testes.[1]
The Japanese puffer is classified as Near Threatened by the IUCN. It is one of the most valuable commercial fishes in Japan, and although current catches (101 tonnes / year in 2004, down from a peak of 2,000 tonnes in 1987) are small compared to those of many other commercial species such as sardines and anchovy, they appear to be unsustainable and prevent the recovery of the species from earlier over-exploitation. Gear restrictions (most catches occur by longline fishing) and adjustments of fishery seasons to protect juveniles have been recommended to aid recovery. The species is extensively raised in aquaculture.[1]
{{cite journal}}: Missing or empty |title= (help)CS1 maint: uses authors parameter (link) Takifugu rubripes, commonly known as the Japanese puffer, Tiger puffer, or torafugu (Japanese: 虎河豚), is a pufferfish in the genus Takifugu. It is distinguished by a very small genome that has been fully sequenced because of its use as a model species and is in widespread use as a reference in genomics.
