Cyprinodon

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Cyprinodon is a genus of 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][4] Cyprinodon are small; the largest reaches Script error: No such module "convert". in length and most other species only reach about half that size.[1]

Evolution

Based on phylogenetic evidence, Cyprinodon diverged from its closest relative, the recently extinct Megupsilon, during the Late Miocene, and saw a rapid evolutionary radiation afterwards. The only known fossil species from the genus is C. breviradius from the late Miocene or early Pliocene-aged sediments of Death Valley National Park (originally considered part of the Late Eocene-aged Titus Canyon Formation).[5][6]

Distribution and habitat

File:Cyprinodon variegatus (S0103) (12598764423).jpg
Cyprinodon variegatus is the most widespread member of the genus.
File:Cyprinodon diabolis Wales, 1930.jpg
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 U.S. 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 Template:Cvt and the latter to an Template:Cvt shelf in a spring pool, but C. longidorsalis is now only found in captivity as its habitat has disappeared.[3][7] 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,[8][9] 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 remarkable 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 Template:Cvt, and C. pachycephalus up to Template:Cvt),[10][11] and those of hypersaline habitats where the salinity far exceeds that of sea water.[12][13] 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 Template:Cvt in less than 24 hours (in the coldest temperatures they bury into the substrate).[14] Some populations of C. nevadensis tolerate water temperatures between Template:Cvt, and C. salinus live in waters where the temperature may change by as much as Template:Cvt in a day and Template:Cvt in a season.[14][15] 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.[12]

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.[15][16][17][18][19] C. arcuatus was restricted to springs in the US state of Arizona and probably also in the Mexican state of Sonora,[16] while all the others were restricted to spring systems in Mexico.[20][21]

Three species from southwestern Nuevo León, C. alvarezi, C. longidorsalis and C. veronicae, have become extinct in the wild, only surviving in captivity.[20][22][23] 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.[24][25] Several others have very small remaining populations in the wild.[21] 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.[26] Primary threats to pupfish are habitat loss due to water extraction, drought and pollution, and introduced species.[3][21]

Behavior

Feeding

File:Cyprinodon Desquamator.jpg
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.[15][24] Some species mainly feed on small animals like aquatic insects.[13] C. variegatus, a species that otherwise has a diet typical of pupfish, will clean other fish by feeding on parasites on their body.[27]

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][24]

Breeding

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Cyprinodon pupfish are short-lived, typically reaching an age of no more than a year in the wild,[15] although some may reach as much as three years.[27] 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.[15] 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 Template:Cvt, they only breed from Template:Cvt.[15] However, there are exceptions like C. rubrofluviatilis that will breed at a relative wide range from Template:Cvt.[13] 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.[15] When breeding, males assume a relatively bright nuptial coloration.[15]

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.[15][28] In at least some species, small males will attempt to fertilize eggs by sneaking into a territory of a larger male.[28] 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.[15] 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.[15] The eggs of Cyprinodon pupfish are adhesive and stick to the substrate,[15] or they are covered in sand.[27]

Species

File:Cyprinodon brontotheroides.jpg
Cyprinodon brontotheroides (shown) and C. desquamator are both restricted to hypersaline lakes in the Bahamas
File:Sonoyta pupfish.jpg
Cyprinodon eremus in shallow water, which is preferred by most species in this genus
File:Julimes pupfish (Cyprinodon julimes) male.jpg
Cyprinodon julimes was only scientifically described in 2009
File:Cyprinodon rubrofluviatilis.jpg
Cyprinodon rubrofluviatilis, a relatively common species from Texas
scale-eating pupfish in the wild
Cyprinodon desquamator (shown), the scale-eating pupfish, in its natural habitat on San Salvador Island, Bahamas
File:Cyprinodon macrolepis.tif
Cyprinodon macrolepis male in an aquarium.

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

References

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  1. ↑ a b c Script error: No such module "Cite taxon".
  2. ↑ a b c d e f g h 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.
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  8. ↑ Contreras Balderas, S., and W. Bussing |(2013). Yucatan. Freshwater Ecoregions of the World. Retrieved 1 March 2013.
  9. ↑ Script error: No such module "Citation/CS1".
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  22. ↑ Template:Cite iucn
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  24. ↑ a b c Script error: No such module "Citation/CS1".
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  27. ↑ a b c Script error: No such module "citation/CS1".
  28. ↑ a b Script error: No such module "Citation/CS1".
  29. ↑ Script error: No such module "Citation/CS1".
  30. ↑ Template:Cite iucn
  31. ↑ Template:Cite iucn

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