Biology:Thunnus

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Thunnus is a genus of ocean-dwelling, ray-finned bony fish from the mackerel family, Scombridae. More specifically, Thunnus is one of five genera which make up the tribe Thunnini – a tribe that is collectively known as the tunas. Also called the true tunas or real tunas, Thunnus consists of eight species of tuna (more than half of the overall tribe), divided into two subgenera.

Their coloring, metallic blue on top and shimmering silver-white on the bottom, helps camouflage them from above and below. Atlantic bluefin tuna, the largest member of this genus, can grow to 15 feet (4.6 m) long and weigh up to 1,500 pounds (680 kg). All tunas are extremely strong, muscular swimmers, and the yellowfin tuna is known to reach speeds of up to 50 miles per hour (80 km/h) when pursuing prey. As with all tunas, members of this genus are warm-blooded, which is a rare trait among fish; this enables them to tolerate cold waters and to dive to deeper depths.[1] Bluefin tunas, for example, are found in Newfoundland and Iceland, and also in the tropical waters of the Gulf of Mexico and the Mediterranean Sea, where some individuals go each year to spawn.

Due to overfishing, the range of this genus has declined significantly, having been effectively extirpated from the Black Sea, for example.[2]

Taxonomy

The word Thunnus is the Middle Latin form of the Greek thýnnos (θύννος, "tuna, tunny") – which is in turn derived from thynō (θύνω, "to rush; to dart").[3][4] The first known written use of the word was by Homer. Based on morphology and short-length mitochondrial DNA sequence data,[5] the genus Thunnus is currently classified into two subgenera: Thunnus (Thunnus) (the bluefin group), and Thunnus (Neothunnus) (the yellowfin group). However this classification has been questioned by a recent phylogenetic analysis of nuclear DNA sequence data, which resolved different relationships among species and did not support the traditional definition of the bluefin and yellowfin groups.[6][7] Specifically, these analyses substantiated the division of Pacific and Atlantic Tuna in two separate species and suggested that Bigeye Tuna were actually a member of subgenus Neothunnus, not subgenus Thunnus.[6] Earlier nuclear ribosomal DNA phylogenetic reconstructions also showed similar results.[8]

Fossil specimen

This genus has eight species in two subgenera:

Relative sizes of various tunas, with the Atlantic bluefin tuna (top) at about 8 ft (2.4 m) in this sample
The true tunas of the genus Thunnus, within the family Scombridae
Scombridae
Gasterochismatinae

Butterfly kingfishes (1 genus)

 
Scombrinae
 
 
Scombrini

Mackerels (2 genera) 50 px

 
 
 
 
Scomberomorini

Spanish Mackerels (3 genera) 50 px

 
 
 
 
Sardini

Bonitos (4 genera) 50 px

 
Thunnini
 

Allothunnus, slender tunas

 
 
 

Auxis, frigate tunas 50 px

 
 
 

Euthynnus, little tunas 50 px

 
 
 

Katsuwonus, skipjack tunas 50 px

 
 
Thunnus
subgenus Thunnus

bluefin group 50 px

 
subgenus Neothunnus

yellowfin group 50 px

 
(true tunas)
 
 
 
 
(Tunas)
 
 
 
 
 
 
Cladogram: Thunnus (bottom-right in image above) is one of five genera that make up the Thunnini tribe. Known as the true tunas, it comprises 8 of the 15 extant tuna species.[9]
Alternative evolutionary tree for Thunnus
 
 
 
 
 
 

T. albacares 50 px

 
 

T. obesus 50 px

 
 
 
 

T. tonggol

 
 

T. atlanticus 50 px

 
 
 
 

T. maccoyii

 
 
 
 

T. thynnus 50 px

 
 

T. orientalis

 
 
 
 

T. alalunga 50 px

 
 
An alternative phylogenetic reconstruction for the genus Thunnus, based on nuclear DNA sequence data, which modifies the traditionally recognized bluefin and yellowfin clades by placing Thunnus obesus within the yellowfin clade instead of in the bluefin clade.[6]

Species

Until recently, seven Thunnus species were thought to exist, and Atlantic bluefin tuna and Pacific bluefin tuna were subspecies of a single species. In 1999, Collette established that based on both molecular and morphological considerations, they are, in fact, distinct species.[10][11]

Template:Tuna table/header Template:Tuna table/Thunnus (Thunnus) Template:Tuna table/Thunnus (Neothunnus) |} The following fossil species are also known:[12][13]

In addition, two potential early species are known in "Thunnus" abchasicus Daniltshenko, 1951 from the Middle Eocene of Abkhazia[15], and "Thunnus" secretus Bannikov, 1979 from the Late Oligocene of Ukraine.[12] Both these species are only provisionally placed in Thunnus, as they share close anatomical similarities, but display fin spines in the second dorsal and anal fins, which are not present in modern Thunnus. This may indicate that these species likely fall outside the modern Thunnus crown group.[16] This is further supported by phylogenetic studies that have found that modern Thunnus species represent a rapid radiation that occurred within the last 10 million years.[17] Other early scombrids previously classified in Thunnus, such as those from the Early Eocene deposits of Monte Bolca in Italy, are now thought to represent different extinct genera.[18]

Maximum reported sizes of Thunnus species.

Overfishing

The worldwide demand for sushi and sashimi, coupled with increasing population growth, has resulted in global stocks of the species being overfished[19] and bluefin is the most endangered and considered "a serious conservation concern".[20] Complicating the efforts for sustainable management of bluefin fish stocks within national exclusive economic zones (EEZ) is bluefin migrate long distances and hunt in the midocean that is not part of any country's EEZ, so have been vulnerable to overfishing by multiple countries' fishing fleets. International agreements and conventions are good-faith agreements and are difficult to monitor or enforce.[21] Though this fish has been farmed in captivity by the Japanese and by the Australians with the help of the Japanese,[22] yields are lower than other farmed fish due to the slow growth rate of bluefin tuna, therefore keeping prices high.[21] On December 30, 2012, a 222-kilogram (489 lb) bluefin tuna caught off northeastern Japan, was sold at the Tsukiji fish market in Tokyo for a record 155.4 million yen ($1.76 million) – a unit price of JP¥ 1.274 million/kg (US$3,600/lb).[23]

References

  1. ↑ Bernal, Diego; Brill, Richard W.; Dickson, Kathryn A.; Shiels, Holly A. (2017-12-01). "Sharing the water column: physiological mechanisms underlying species-specific habitat use in tunas" (in en). Reviews in Fish Biology and Fisheries 27 (4): 843–880. doi:10.1007/s11160-017-9497-7. ISSN 1573-5184. Bibcode: 2017RFBF...27..843B. https://www.research.manchester.ac.uk/portal/en/publications/sharing-the-water-column-physiological-mechanisms-underlying-speciesspecific-habitat-use-in-tunas(ad10e79b-2fb8-4bb2-bc86-96eb245d23b9).html. Retrieved 2019-12-01. 
  2. ↑ Hogan, C. Michael, Overfishing. Encyclopedia of Earth. eds. Sidney Draggan and Cutler Cleveland. National council for Science and the Environment, Washington DC
  3. ↑ θύννος in Liddell, Henry George; Scott, Robert (1940) A Greek–English Lexicon, revised and augmented throughout by Jones, Sir Henry Stuart, with the assistance of McKenzie, Roderick. Oxford: Clarendon Press. In the Perseus Digital Library, Tufts University.
  4. ↑ θύνω in Liddell and Scott.
  5. ↑ Alvarado Bremer, J.R.; Naseri, I.; Ely, B. (2016). "ROrthodox and unorthodox phylogenetic relationships among tunas revealed by the nucleotide sequence analysis of the mitochondrial DNA control region". Journal of Fish Biology 50 (3): 540–554. doi:10.1111/j.1095-8649.1997.tb01948.x. 
  6. ↑ 6.0 6.1 6.2 Díaz-Arce, Natalia; Arrizabalaga, Haritz; Murua, Hilario; Irigoien, Xabier; Rodríguez-Ezpelata, Naiara (2016). "RAD-seq derived genome-wide nuclear markers resolve the phylogeny of tunas". Molecular Phylogenetics and Evolution 102: 202–207. doi:10.1016/j.ympev.2016.06.002. PMID 27286653. Bibcode: 2016MolPE.102..202D. 
  7. ↑ Ciezarek, Adam G.; Osborne, Owen G.; Shipley, Oliver N.; Brooks, Edward J.; Tracey, Sean R.; McAllister, Jaime D.; Gardner, Luke D.; Sternberg, Michael J. E. et al. (2019-01-01). "Phylotranscriptomic Insights into the Diversification of Endothermic Thunnus Tunas" (in en). Molecular Biology and Evolution 36 (1): 84–96. doi:10.1093/molbev/msy198. ISSN 0737-4038. PMID 30364966. 
  8. ↑ Chow, S.; Nakagawa, T.; Suzuki, N.; Takeyama, H.; Matsunaga, T. (2006). "Phylogenetic relationships among Thunnus species inferred from rDNA ITS1 sequence". Journal of Fish Biology 68 (A): 24–35. doi:10.1111/j.0022-1112.2006.00945.x. Bibcode: 2006JFBio..68...24C. 
  9. ↑ Graham, Jeffrey B.; Dickson, Kathryn A. (2004). "Tuna Comparative Physiology". The Journal of Experimental Biology 207 (23): 4015–4024. doi:10.1242/jeb.01267. PMID 15498947. Bibcode: 2004JExpB.207.4015G. 
  10. ↑ Collette, B.B. (1999). "Mackerels, molecules, and morphology". in Séret, B.. 5th Indo-Pacific Fish Conference: Nouméa, New Caledonia, 3–8 November 1997. Paris: Société Française d'Ichtyologie [u.a.]. pp. 149–164. ISBN 978-2-9507330-5-4. https://books.google.com/books?id=-0cWAQAAIAAJ. Retrieved 2017-09-16. 
  11. ↑ Tanaka, Y.; Satoh, K.; Iwahashi, M.; Yamada, H. (2006). "Growth-dependent recruitment of Pacific bluefin tuna Thunnus orientalis in the northwestern Pacific Ocean". Marine Ecology Progress Series 319: 225–235. doi:10.3354/meps319225. Bibcode: 2006MEPS..319..225T. 
  12. ↑ 12.0 12.1 Bannikov, A. F. (1979). "The Thunninae and their phylogenetic relationships". Paleontological Journal 13 (3): 355-363. https://www.researchgate.net/publication/291945464_The_Thunninae_and_their_phylogenetic_relationships. 
  13. ↑ "PBDB Taxon". https://paleobiodb.org/classic/basicTaxonInfo?rdr=1&taxon_no=36215. 
  14. ↑ California Academy of Sciences (1890). Occasional papers of the California Academy of Sciences. California Academy of Sciences. San Francisco : California Academy of Sciences. https://archive.org/details/occasionalpaper00calif/occasionalpaper00calif/. 
  15. ↑ Danil'chenko, P. G. (1951-04-11). "[Tunny of the Eocene epoch in deposits of the Caucasus"]. Doklady Akademii nauk SSSR 77 (5): 881–883. ISSN 0002-3264. PMID 14822869. https://pubmed.ncbi.nlm.nih.gov/14822869. 
  16. ↑ Monsch, Kenneth A.; Bannikov, Alexandre F. (2011). "New taxonomic synopses and revision of the scombroid fishes (Scombroidei, Perciformes), including billfishes, from the Cenozoic of territories of the former USSR" (in en). Earth and Environmental Science Transactions of The Royal Society of Edinburgh 102 (4): 253–300. doi:10.1017/S1755691011010085. ISSN 1755-6910. https://www.cambridge.org/core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh/article/abs/new-taxonomic-synopses-and-revision-of-the-scombroid-fishes-scombroidei-perciformes-including-billfishes-from-the-cenozoic-of-territories-of-the-former-USSR/37C191646AD6ECED0B473DE94B6971EC. 
  17. ↑ Santini, F.; Carnevale, G.; Sorenson, L. (2013-06-01). "First molecular scombrid timetree (Percomorpha: Scombridae) shows recent radiation of tunas following invasion of pelagic habitat". Italian Journal of Zoology 80 (2): 210–221. doi:10.1080/11250003.2013.775366. ISSN 1125-0003. https://doi.org/10.1080/11250003.2013.775366. 
  18. ↑ Monsch, Kenneth A. (2006). "A revision of scombrid fishes (Scombroidei, Perciformes) from the Middle Eocene of Monte Bolca, Italy" (in en). Palaeontology 49 (4): 873–888. doi:10.1111/j.1475-4983.2006.00566.x. ISSN 0031-0239. https://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2006.00566.x. 
  19. ↑ George Karleskint; Richard Turner; James Small (2009). Introduction to Marine Biology. Cengage Learning. p. 522. ISBN 978-0-495-56197-2. https://books.google.com/books?id=0JkKOFIj5pgC&pg=PA522. 
  20. ↑ "Tuna, Bluefin". http://www.montereybayaquarium.org/cr/SeafoodWatch/web/sfw_factsheet.aspx?gid=69. 
  21. ↑ 21.0 21.1 "Managed to death". The Economist. 2008-10-30. https://www.economist.com/science-and-technology/2008/10/30/managed-to-death. 
  22. ↑ Thunnus orientalis#Farming
  23. ↑ "A bluefin tuna sells for record $1.76M in Tokyo". USA Today. 4 January 2013. https://www.usatoday.com/story/news/world/2013/01/04/bluefin-tuna-tokyo-sushi/1810557/?dlvrit=206567. Retrieved 5 January 2013. 

Further reading

  • Charles Clover. 2004. The End of the Line: How Overfishing Is Changing the World and What We Eat. Ebury Press, London. ISBN 0-09-189780-7
  • Newlands, Nathaniel K.; Molly E. Lutcavage; Tony J. Pitcher (2006). "Atlantic Bluefin Tuna in the Gulf of Maine, I: Estimation of Seasonal Abundance Accounting for Movement, School and School-Aggregation Behaviour". Environmental Biology of Fishes 77 (2): 177–195. doi:10.1007/s10641-006-9069-5. ISSN 0378-1909. Bibcode: 2006EnvBF..77..177N. 

Template:Tuna

Wikidata ☰ Q2346039 entry



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