Cyprinodon

Cyprinodon is a genus of small pupfishes found in waters that range from fresh to hypersaline. The genus is primarily found in Mexico, the Caribbean Islands and southern United States (Arizona, California, Florida, Nevada, New Mexico, Oklahoma and Texas), but C. variegatus occurs as far north as Massachusetts and along the entire Gulf of Mexico coastline, and C. dearborni and C. variegatus are found in northern South America.[1][2] Many species have tiny ranges and are highly threatened, in some cases already extinct.[2][3] Cyprinodon are small; the largest reaches 10 cm (3.9 in) in length and most other species only reach about half that size.[1]

Cyprinodon
Cyprinodon radiosus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Cyprinodontidae
Subfamily: Cyprinodontinae
Genus: Cyprinodon
Lacépède, 1803
Type species
Cyprinodon variegatus
Lacépède, 1803
Synonyms
  • Encrates Gistel, 1848
  • Lebia Oken, 1817
  • Prinodon Rafinesque, 1815
  • Trifarcius Poey, 1860

Distribution and habitat
Cyprinodon variegatus is the most widespread member of the genus.
Cyprinodon diabolis is very rare; its entire native range is the Devils Hole in Nevada

A few Cyprinodon species have quite large ranges, notably C. variegatus, but the vast majority have small ranges, typically restricted to one or two Mexican states or US states, Hispaniola, or a Bahaman island. C. longidorsalis and C. diabolis have both been said to have the smallest native range of any vertebrate species, with the former being restricted to a spring pool that covers about 10 m2 (110 sq ft) and the latter to an 18 m2 (190 sq ft) shelf in a spring pool, but C. longidorsalis is now only found in captivity as its habitat has disappeared.[3][4] While most Cyprinodon species have separate distributions, seven (C. beltrani, C. esconditus, C. labiosus, C. maya, C. simus, C. suavium and C. verecundus) are endemic in Lake Chichancanab in Quintana Roo, Mexico,[5][6] and three (the endemic C. brontotheroides and C. desquamator, and the widespread C. variegatus) live in the hypersaline lakes on San Salvador Island in the Bahamas.[2] In a few other cases separate species do come into contact towards the edges of their distributions where they often hybridize, notably C. eximius X C. pachycephalus and C. atrorus X C. bifasciatus, but also C. variegatus in places where it has been introduced by humans into the ranges of other Cyprinodon species.[2]

Although the individual Cyprinodon species often have a highly specific habitat, overall the genus occurs in a remarkably range of places, such as springs (including those isolated in deserts), pools, lakes, coastal lagoons, creeks, streams and rivers. Their salinity and temperature range is very broad, like those living in hot springs (taken to the extreme in C. julimes in water up to 46 °C or 115 °F, and C. pachycephalus up to 49 °C or 120 °F),[7][8] and those of hypersaline habitats where the salinity far exceeds that of sea water.[9][10] Certain species may even experience very large variations in the temperature and salinity over a relatively short period. For example, some populations of C. variegatus live in water where the temperature has been known to change from 15 to −1.8 °C (59 to 29 °F) in less than 24 hours (in the coldest temperatures they bury into the substrate).[11] Some populations of C. nevadensis tolerate water temperatures between 2 and 44 °C (36–111 °F), and C. salinus live in waters where the temperature may change by as much as 19 °C (34 °F) in a day and 40 °C (72 °F) in a season.[11][12] Furthermore, the salinity of C. salinus' habitat may vary from less than one-third of that of sea water to almost five times as much as sea water in a season.[9]

Conservation status

Most species in the genus are seriously threatened. C. arcuatus, C. ceciliae, C. inmemoriam, C. nevadensis calidae and an undescribed species popularly known as the "Perrito de Sandia" are already extinct.[12][13][14][15][16] C. arcuatus was restricted to springs in the US state of Arizona and probably also in the Mexican state of Sonora,[13] while all the others were restricted to spring systems in Mexico.[17][18]

Three species from southwestern Nuevo León, C. alvarezi, C. longidorsalis and C. veronicae, have become extinct in the wild, only surviving in captivity.[17][19][20] A few other Mexican species still considered endangered or vulnerable by the IUCN, including at least C. maya, C. simus and C. verecundus of Lake Chichancanab, also appear to only survive in captivity.[21][22] Several others have very small remaining populations in the wild.[18] Among the species that survive in the wild, the rarest is perhaps C. diabolis from the tiny Devils Hole in Nevada; in recent decades its population has fluctuated between a few tens and a few hundred individuals.[23] Primary threats to pupfish are habitat loss due to water extraction, drought and pollution, and introduced species.[3][18]

Behavior

Feeding
Cyprinodon desquamator, the only known scale-eating species of pupfish

Most Cyprinodon species feed on algae, cyanobacteria and detritus, but may also supplement their diet with small crustaceans and aquatic insect larvae.[12][21] Some species mainly feed on small animals like aquatic insects.[10] C. variegatus, a species that otherwise has a diet typical of pupfish, will clean other fish by feeding on parasites on their body.[24]

In the two places where several species live together they have diverged into different niches, including the fish-eating C. maya (Lake Chichancanab), zooplankton-eating C. simus (Lake Chichancanab), amphipod- and bivalve-eating C. labiosus and C. verecundus (Lake Chichancanab), scale-eating C. desquamator (San Salvador Island lakes), and ostracod- and gastropod-eating C. brontotheroides (San Salvador Island lakes).[2][21]

Breeding
On left: Cyprinodon macularius pair during courtship (male above).
On right: Cyprinodon salinus pair during spawning (male with yellowish back).

Cyprinodon pupfish are short-lived, typically reaching an age of no more than a year in the wild,[12] although some may reach as much as three years.[24] Especially those from habitats that experience major environmental fluctuations (for example, large variations in temperature) rapidly reach maturity and are already able to breed when 1–1.5 month old.[12] Despite some species' ability to survive in a wide temperature range, their requirements for breeding often are much more specific. For example, although some populations of C. nevadensis can live in water that ranges between 2 and 44 °C (36–111 °F), they only breed from 24 to 30 °C (75–86 °F).[12] However, there are exceptions like C. rubrofluviatilis that will breed at a relative wide range from 13 to 34 °C (55–93 °F).[10] Consequently, pupfish living in stable habitats breed year-round, but those in more seasonal habitats generally only at certain times of the year where the conditions are optimal.[12] When breeding, males assume a relatively bright nuptial coloration.[12]

There are two primary breeding strategies: In species of small isolated habitats like springs, each large male (or medium-sized male, if large males are absent) defends a territory and displays to visiting females that will lay their eggs inside the territory.[12][25] In at least some species, small males will attempt to fertilize eggs by sneaking into a territory of a larger male.[25] Once deposited, neither sex cares for the eggs, although they do get a level of protection by being inside the territory of a male. A male will attempt to attract several females to lay their eggs in his territory and a female may lay eggs in the territories of several males.[12] Another breeding strategy is used by species that inhabit rivers. Here the males do not maintain a territory and groups of pupfish gather to breed. A male typically will lead a female to the edge of the group to spawn, although on occasion it may occur in the middle of the group.[12] The eggs of Cyprinodon pupfish are adhesive and stick to the substrate,[12] or they are covered in sand.[24]

Species
Cyprinodon brontotheroides (shown) and C. desquamator are both restricted to hypersaline lakes in the Bahamas
Cyprinodon eremus in shallow water, which is preferred by most species in this genus
Cyprinodon julimes was only scientifically described in 2009
Cyprinodon rubrofluviatilis, a relatively common species from Texas

There are currently 49 recognized species in this genus:[1][2]

References
  1. Froese, Rainer and Pauly, Daniel, eds. (2018). Species of Cyprinodon in FishBase. October 2018 version.
  2. Martin, C. H., and P. C. Wainwright (2013). Multiple Fitness Peaks on the Adaptive Landscape Drive Adaptive Radiation in the Wild. Science 339(6116): 208-211.
  3. Contreras-Balderas, S.; L. Lozano-Vilano (1996). "Extinction of most Sandia and Potosí valleys (Nuevo León, Mexico) endemic pupfishes, crayfishes and snails". Ichthyol. Explor. Freshwaters. 7 (1): 33–40.
  4. Helfman, G.; B.B. Collette; D.E. Facey; B.W. Bowen (2009). The Diversity of Fishes: Biology, Evolution, and Ecology. Wiley-Blackwell. p. 413. ISBN 978-1-4051-2494-2.
  5. Contreras Balderas, S., and W. Bussing |(2013). Yucatan. Freshwater Ecoregions of the World. Retrieved 1 March 2013.
  6. Strecker, U. (2006). "The impact of invasive fish on an endemic Cyprinodon species flock (Teleostei) from Laguna Chichancanab, Yucatan, Mexico". Ecology of Freshwater Fish. 15 (4): 408–418. doi:10.1111/j.1600-0633.2006.00159.x.
  7. Clarke, A. (2017). Principles of Thermal Ecology: Temperature, Energy and Life. Oxford University Press. p. 323. ISBN 978-0-19-955166-8.
  8. Maiz-Tome, L. (2019). "Cyprinodon pachycephalus". IUCN Red List of Threatened Species. 2019: e.T6162A12524752. doi:10.2305/IUCN.UK.2019-2.RLTS.T6162A3106242.en. Retrieved 26 August 2019.{{cite iucn}}: error: |doi= / |page= mismatch (help)
  9. Otto, R.G.; S.D. Gerking (1973). "Heat Tolerance of a Death Valley Pupfish (Genus Cyprinodon)". Physiological Zoology. 46 (1): 43–49. doi:10.1086/physzool.46.1.30152515.
  10. Hassan-Williams, C.; T.H. Bonner (2007). "Cyprinodon rubrofluviatilis". Texas Freshwater Fishes, Texas State University - San Marcos, Department of Biology. Retrieved 26 August 2019.
  11. Bennett, W.A.; T.L. Beitinger (1997). "Temperature Tolerance of the Sheepshead Minnow, Cyprinodon variegatus". Copeia. 1997 (1): 77–87. doi:10.2307/1447842. JSTOR 1447842.
  12. Moyle, P.B.; R.M. Yoshiyame; J.E. Williams; E.D. Wirkamanayake (1995). "Fish Species of Special Concern in California" (PDF). California Department of Fish and Game. Archived from the original (PDF) on 23 March 2012.
  13. Smith, K.; Darwall, W.R.T. (2013). "Cyprinodon arcuatus". IUCN Red List of Threatened Species. 2013. Retrieved 8 October 2018.CS1 maint: ref=harv (link)
  14. Contreras-Balderas, S.; Almada-Villela, P. (1996). "Cyprinodon ceciliae". IUCN Red List of Threatened Species. 1996. Retrieved 1 March 2013.CS1 maint: ref=harv (link)
  15. Contreras-Balderas, S.; Almada-Villela, P. (1996). "Cyprinodon inmemoriam". IUCN Red List of Threatened Species. 1996. Retrieved 1 March 2013.CS1 maint: ref=harv (link)
  16. Contreras-Balderas, S.; Almada-Villela, P. (1996). "Cyprinodon spp.". IUCN Red List of Threatened Species. 1996. Retrieved 1 March 2013.CS1 maint: ref=harv (link)
  17. Contreras-MacBeath, T.; M.B. Rodríguez; V. Sorani; C. Goldspink; G.M. Reid (2014). "Richness and endemism of the freshwater fishes of Mexico". Journal of Threatened Taxa. 6 (2): 5421–5433. doi:10.11609/JoTT.o3633.5421-33.
  18. Ceballos, G.; E.D. Pardo; L.M. Estévez; H.E. Pérez, eds. (2016). Los peces dulceacuícolas de México en peligro de extinción. ISBN 978-607-16-4087-1.
  19. Contreras-Balderas, S.; Almada-Villela, P. (1996). "Cyprinodon alvarezi". IUCN Red List of Threatened Species. 1996. Retrieved 1 March 2013.CS1 maint: ref=harv (link)
  20. Contreras-Balderas, S.; Almada-Villela, P. (1996). "Cyprinodon longidorsalis". IUCN Red List of Threatened Species. 1996. Retrieved 1 March 2013.CS1 maint: ref=harv (link)
  21. Martin, C.; P.C. Wainwright (2011). "Trophic novelty is linked to exceptional rates of morphological diversification in two adaptive radiations of Cyprinodon pupfish". Evolution. 65 (8): 2197–2212. doi:10.1111/j.1558-5646.2011.01294.x. PMID 21790569.
  22. Martin, C.H.; Crawford, J.E.; Turner, B.J.; Simons, L.H. (2016). "Diabolical survival in Death Valley: recent pupfish colonization, gene flow and genetic assimilation in the smallest species range on earth". Proc Biol Sci. 283 (1823): 20152334. doi:10.1098/rspb.2015.2334. PMC 4795021. PMID 26817777.
  23. "Devils Hole Pupfish". U.S. Fish and Wildlife Service. December 2, 2013. Retrieved 7 October 2018.
  24. Hassan-Williams, C.; T.H. Bonner (2007). "Cyprinodon variegatus". Texas Freshwater Fishes, Texas State University - San Marcos, Department of Biology. Retrieved 26 August 2019.
  25. Leiser, J.K.; M. Itzkowitz (2002). "The relative costs and benefits of territorial defense and the two conditional male mating tactics in the Comanche Springs pupfish (Cyprinodon elegans)". Acta Ethol. 5 (1): 65–72. doi:10.1007/s10211-002-0066-1.
  26. Gonzales, V. (2019). "Cyprinodon latifasciatus". IUCN Red List of Threatened Species. 2019. Retrieved 1 April 2020.CS1 maint: ref=harv (link)
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