418
JAMES E. DEACON AND W. L MINCKLEY
Most eurythermal fishes of deserts can survive water temperatures below
2°C (Table I ) , and a number of kinds successfully live beneath ice cover
for brief periods, which occur even in Death Valley on occasion (Wauer,
1962). More stenothermal species, such as those of tropical derivation living at the limits of their ranges, or occupants of large, permanent springs,
may die at much higher temperatures. Herichthys ( = Cichlosoma)
cyanogutattus, the only cichlid native to the United States, suffers severe
mortality when temperatures drop to 14°C (Hubbs, 1951). All three undescribed cichlid species from the Cuatro Ciénegas basin die at temperatures ranging from 10° to 15°C, with young living longer than adults.
Marine fishes are, in general, far more stenothermous than freshwater
species, and catastrophic mortalities have been recorded in shallow, coastal
waters when rapid cooling occurs (Gunter, 1952). The freshwater Cyprinodon bijasciatus has a similarly high lower temperature tolerance in warmspring populations, but some stocks in tiny creeks are considerably broader
in their low-temperature capabilities (Arnold, 1970). Moapa coriacea,
Crenichthys baileyi, C. nevadae, and Eremichthys acros occur only in temperatures above 18°C or so, even though considerable habitats having lower
temperatures is available to them (Hubbs and Miller, 1948b; Wilson et
al, 1966; unpublished data).
Some desert species now essentially restricted to constant temperature
springs are far more eurythermal than might be expected. The desert dace
has not been taken at temperatures lower than 18°C in nature (Hubbs
and Miller, 1948b; Nyquist, 1963), but it can withstand short-term cooling
to 2°C under laboratory conditions. Many forms of Cyprinodon from constant-temperature habitats have over-wintered, even under short periods
of ice cover, in experimental ponds in Arizona (C. elegans from Phantom
Spring, Texas, C. n. nevadensis from Saratoga Springs, California and
other subspecies of nevadensis from the Death Valley system, and C. macularius from the source of Quitobaquito Spring, Arizona). All these have
adjacent populations that live in marshes, pools, or canals subject to seasonal variations. Even the Devil's Hole pupfish {Cyprinodon diabolis),
which has lived in Devil's Hole, Nevada, for millenia at a presumably constant temperature near 33°C, can tolerate a range of 8° to 38°C (James,
1969), at least for short periods. This eurythermality coupled with depositional evidence for variations in water level suggests, however, that habitat
temperatures may well have been considerably more variable than previously assumed.
Seasonal changes in temperature to which desert fishes are subjected
are preceded by gradual, natural acclimation, and probably are less critical
than diurnal ranges which occur. A major feature of warm deserts is the
vast fluctuation in air temperatures during a day. Below 1000 meters in
JAMES E. DEACON AND W. L MINCKLEY
Most eurythermal fishes of deserts can survive water temperatures below
2°C (Table I ) , and a number of kinds successfully live beneath ice cover
for brief periods, which occur even in Death Valley on occasion (Wauer,
1962). More stenothermal species, such as those of tropical derivation living at the limits of their ranges, or occupants of large, permanent springs,
may die at much higher temperatures. Herichthys ( = Cichlosoma)
cyanogutattus, the only cichlid native to the United States, suffers severe
mortality when temperatures drop to 14°C (Hubbs, 1951). All three undescribed cichlid species from the Cuatro Ciénegas basin die at temperatures ranging from 10° to 15°C, with young living longer than adults.
Marine fishes are, in general, far more stenothermous than freshwater
species, and catastrophic mortalities have been recorded in shallow, coastal
waters when rapid cooling occurs (Gunter, 1952). The freshwater Cyprinodon bijasciatus has a similarly high lower temperature tolerance in warmspring populations, but some stocks in tiny creeks are considerably broader
in their low-temperature capabilities (Arnold, 1970). Moapa coriacea,
Crenichthys baileyi, C. nevadae, and Eremichthys acros occur only in temperatures above 18°C or so, even though considerable habitats having lower
temperatures is available to them (Hubbs and Miller, 1948b; Wilson et
al, 1966; unpublished data).
Some desert species now essentially restricted to constant temperature
springs are far more eurythermal than might be expected. The desert dace
has not been taken at temperatures lower than 18°C in nature (Hubbs
and Miller, 1948b; Nyquist, 1963), but it can withstand short-term cooling
to 2°C under laboratory conditions. Many forms of Cyprinodon from constant-temperature habitats have over-wintered, even under short periods
of ice cover, in experimental ponds in Arizona (C. elegans from Phantom
Spring, Texas, C. n. nevadensis from Saratoga Springs, California and
other subspecies of nevadensis from the Death Valley system, and C. macularius from the source of Quitobaquito Spring, Arizona). All these have
adjacent populations that live in marshes, pools, or canals subject to seasonal variations. Even the Devil's Hole pupfish {Cyprinodon diabolis),
which has lived in Devil's Hole, Nevada, for millenia at a presumably constant temperature near 33°C, can tolerate a range of 8° to 38°C (James,
1969), at least for short periods. This eurythermality coupled with depositional evidence for variations in water level suggests, however, that habitat
temperatures may well have been considerably more variable than previously assumed.
Seasonal changes in temperature to which desert fishes are subjected
are preceded by gradual, natural acclimation, and probably are less critical
than diurnal ranges which occur. A major feature of warm deserts is the
vast fluctuation in air temperatures during a day. Below 1000 meters in