Cyprinodon
13 species
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. Many species have tiny ranges and are highly threatened, in some cases already extinct. Cyprinodon are small; the largest reaches 10 cm (3.9 in) in length and most other species only reach about half that size.
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. 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, 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. 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.
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 46 °C or 115 °F, and C. pachycephalus up to 49 °C or 120 °F), and those of hypersaline habitats where the salinity far exceeds that of sea water. 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). 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. 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.
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. Many species have tiny ranges and are highly threatened, in some cases already extinct. Cyprinodon are small; the largest reaches 10 cm (3.9 in) in length and most other species only reach about half that size.
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. 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, 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. 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.
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 46 °C or 115 °F, and C. pachycephalus up to 49 °C or 120 °F), and those of hypersaline habitats where the salinity far exceeds that of sea water. 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). 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. 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.
