Pupfish

Pupfish are small killifishes, especially species in the genus Cyprinodon. Many inhabit isolated desert springs, saline lakes, or other sharply constrained waters.

Cyprinodontidae: A family of small ray-finned fishes that includes pupfish and other killifishes. Pupfish belong to this family, whose members often occupy shallow coastal or inland waters.
Osmoregulation: The regulation of water and dissolved-ion balance in an organism. Pupfish in saline habitats must regulate internal salt and water despite external conditions.
Devils Hole pupfish: A critically endangered pupfish population confined to Devils Hole, a geothermal pool in Nevada. Its tiny habitat makes the risks facing isolated pupfish populations unusually stark.
Adaptive radiation: The diversification of a lineage into species adapted to different ecological niches. Closely related pupfish have diversified across distinct desert springs and water conditions.
Cyprinodon: A genus of killifishes containing many pupfish species, including desert-spring endemics. This is the principal genus associated with pupfish and their isolated habitats.
Euryhalinity: The ability of an aquatic organism to tolerate a wide range of salinities. Some pupfish survive salinity changes that exclude less tolerant freshwater fishes.
Amargosa pupfish: A pupfish native to the Amargosa River system and nearby waters in the Mojave Desert. Its populations illustrate how desert drainage systems can contain distinct, localized forms.
Speciation: The evolutionary process by which populations become distinct species. Geographic isolation among spring systems can restrict gene flow and promote pupfish divergence.
Killifish: A common name for small fishes in several families, many living in shallow or temporary waters. Pupfish are a distinctive group within the wider assemblage called killifishes.
Thermal tolerance: The range of temperatures an organism can withstand while maintaining function and survival. Desert springs can become hot, testing pupfish limits on body temperature and performance.

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CyprinodontiformesBroader topic: Pupfishes are a distinctive lineage within the order.