Cyprinodon is a genus ofpupfishes found in waters that range fromfresh tohypersaline. The genus is primarily found in Mexico, theCaribbean Islands and southern United States (Arizona,California,Florida,Nevada,New Mexico,Oklahoma andTexas), butC. variegatus occurs as far north asMassachusetts and along the entireGulf of Mexico coastline, andC. dearborni andC. 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 10 cm (3.9 in) in length and most other species only reach about half that size.[1]
A fewCyprinodon species have quite large ranges, notablyC. variegatus, but the vast majority have small ranges, typically restricted to one or twoMexican states orU.S. states,Hispaniola, or aBahaman island.C. longidorsalis andC. 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, butC. longidorsalis is now only found in captivity as its habitat has disappeared.[3][7] While mostCyprinodon species have separate distributions, seven (C. beltrani,C. esconditus,C. labiosus,C. maya,C. simus,C. suavium andC. verecundus) areendemic inLake Chichancanab inQuintana Roo, Mexico,[8][9] and three (the endemicC. brontotheroides andC. desquamator, and the widespreadC. variegatus) live in thehypersaline lakes onSan 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 oftenhybridize, notablyC. eximius XC. pachycephalus andC. atrorus XC. bifasciatus, but alsoC. variegatus in places where it has beenintroduced by humans into the ranges of otherCyprinodon species.[2]
Although the individualCyprinodon 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. Theirsalinity and temperature range is very broad, like those living inhot springs (taken to the extreme inC. julimes in water up to 46 °C or 115 °F, andC. pachycephalus up to 49 °C or 120 °F),[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 ofC. 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).[14] Some populations ofC. nevadensis tolerate water temperatures between 2 and 44 °C (36–111 °F), andC. 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.[14][15] Furthermore, the salinity ofC. 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]
Most species in the genus are seriously threatened.C. arcuatus,C. ceciliae,C. inmemoriam,C. nevadensis calidae and anundescribed 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 ofArizona and probably also in the Mexican state ofSonora,[16] while all the others were restricted to spring systems in Mexico.[20][21]
Three species from southwestern Nuevo León,C. alvarezi,C. longidorsalis andC. veronicae, have becomeextinct in the wild, only surviving in captivity.[20][22][23] A few other Mexican species still consideredendangered orvulnerable by theIUCN, including at leastC. maya,C. simus andC. 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 perhapsC. diabolis from the tinyDevils Hole inNevada; 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]
MostCyprinodon species feed onalgae,cyanobacteria anddetritus, 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, willclean other fish by feeding on parasites on their body.[27]
In the two places where several species live together they have diverged into differentniches, including thefish-eatingC. maya (Lake Chichancanab),zooplankton-eatingC. simus (Lake Chichancanab),amphipod- andbivalve-eatingC. labiosus andC. verecundus (Lake Chichancanab),scale-eatingC. desquamator (San Salvador Island lakes), andostracod- andgastropod-eatingC. brontotheroides (San Salvador Island lakes).[2][24]
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 ofC. 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).[15] However, there are exceptions likeC. rubrofluviatilis that will breed at a relative wide range from 13 to 34 °C (55–93 °F).[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 aterritory 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 bysneaking 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 ofCyprinodon pupfish are adhesive and stick to the substrate,[15] or they are covered in sand.[27]
Cyprinodon brontotheroides (shown) andC. desquamator are both restricted tohypersaline lakes in the BahamasCyprinodon eremus in shallow water, which is preferred by most species in this genusCyprinodon julimes was only scientifically described in 2009Cyprinodon rubrofluviatilis, a relatively common species from TexasCyprinodon desquamator (shown), the scale-eating pupfish, in its natural habitat on San Salvador Island, BahamasCyprinodon macrolepis male in an aquarium.
There are currently 49 recognized species in this genus:[1][2]
^abcdefghMartin, 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.
^abcContreras-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.
^abcHassan-Williams, C.; T.H. Bonner (2007)."Cyprinodon rubrofluviatilis". Texas Freshwater Fishes, Texas State University - San Marcos, Department of Biology. Retrieved26 August 2019.
^abBennett, W.A.; T.L. Beitinger (1997). "Temperature Tolerance of the Sheepshead Minnow, Cyprinodon variegatus".Copeia.1997 (1):77–87.doi:10.2307/1447842.JSTOR1447842.
^abcCeballos, G.; E.D. Pardo; L.M. Estévez; H.E. Pérez, eds. (2016).Los peces dulceacuícolas de México en peligro de extinción. Fondo de Cultura Económic.ISBN978-607-16-4087-1.
^"Devils Hole Pupfish". U.S. Fish and Wildlife Service. December 2, 2013. Retrieved7 October 2018.
^abcHassan-Williams, C.; T.H. Bonner (2007)."Cyprinodon variegatus". Texas Freshwater Fishes, Texas State University - San Marcos, Department of Biology. Retrieved26 August 2019.
^abLeiser, 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.S2CID42642403.
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