VII. DESERT FISHES
465
indicated that termination of latency of embryos occurred at the onset of
opercular movements, and that this could be stimulated by change in any
number of variables—oxygen, carbon dioxide, various ions, pH, or even
physical disturbance.
Of the fishes discussed, only Oryzias melastigma might be found under
desert conditions in India. One record of spawning in temporary waters
by Aphanius iberus, a cyprinodont in Spain, is intriguing but is not accompanied by other salient facts (Schreitmuller, 1921). That genus is ecologically quite similar to the American pupfishes, many of which live in
deserts (as do some Aphanius). Pupfish eggs have been known to hatch
within a few hours from muds of dried experimental ponds in Arizona
after resting there for about 1 week.
Kinne and Kinne (1962a) studied the effects of temperature, salinity,
and dissolved oxygen content on development of embryos of desert pupfish
and found that arrested development could be induced by various combinations of these variables; temperature-influenced developmental rates
alone created a variation in hatching time from 3.8 to 53 days (Kinne
and Kinne, 1962a). In Arizona ponds, all these factors might have come
into play. In another incident, eggs of Cyprinodon atrorus hatched from
mats of filamentous algae that had laid on the ground surface in full summer sun for 2 days. Again, the only result was contamination of a stock
of another pupfish, when the slightly moist (on the lower surface only)
mats were placed in a pool to provide cover for adults of Cyprinodon
elegans.
Eggs of longfin dace stranded in moist sand by fluctuating water levels
in Arizona creeks hatched normally when flooded (Minckley and Barber,
1971), but this did not obviously involve delayed hatching of the type
discussed above. Such must be a common occurrence in smaller streams
of arid areas, such as those inhabited by Fundulus kansae and F. zebrinus.
Eggs of longfin dace also can survive application of Derris (rotenone),
however, as attested to by a massive hatch closely following a fish eradication operation in Cave Creek, Arizona, in the spring of 1970. Percolation
of water through the sands most likely maintained the eggs on surficially
desiccated bars. Such percolation may also filter noxious substances.
C. FOODS AND FEEDING
Desert fishes are opportunistic in their feeding, as are most fish species.
Sources of food in desert springs, marshes, and intermittent streams typically consist of algae, aquatic invertebrates, and detrital material, the first
two of which, at least, may undergo marked diel and seasonal changes in
465
indicated that termination of latency of embryos occurred at the onset of
opercular movements, and that this could be stimulated by change in any
number of variables—oxygen, carbon dioxide, various ions, pH, or even
physical disturbance.
Of the fishes discussed, only Oryzias melastigma might be found under
desert conditions in India. One record of spawning in temporary waters
by Aphanius iberus, a cyprinodont in Spain, is intriguing but is not accompanied by other salient facts (Schreitmuller, 1921). That genus is ecologically quite similar to the American pupfishes, many of which live in
deserts (as do some Aphanius). Pupfish eggs have been known to hatch
within a few hours from muds of dried experimental ponds in Arizona
after resting there for about 1 week.
Kinne and Kinne (1962a) studied the effects of temperature, salinity,
and dissolved oxygen content on development of embryos of desert pupfish
and found that arrested development could be induced by various combinations of these variables; temperature-influenced developmental rates
alone created a variation in hatching time from 3.8 to 53 days (Kinne
and Kinne, 1962a). In Arizona ponds, all these factors might have come
into play. In another incident, eggs of Cyprinodon atrorus hatched from
mats of filamentous algae that had laid on the ground surface in full summer sun for 2 days. Again, the only result was contamination of a stock
of another pupfish, when the slightly moist (on the lower surface only)
mats were placed in a pool to provide cover for adults of Cyprinodon
elegans.
Eggs of longfin dace stranded in moist sand by fluctuating water levels
in Arizona creeks hatched normally when flooded (Minckley and Barber,
1971), but this did not obviously involve delayed hatching of the type
discussed above. Such must be a common occurrence in smaller streams
of arid areas, such as those inhabited by Fundulus kansae and F. zebrinus.
Eggs of longfin dace also can survive application of Derris (rotenone),
however, as attested to by a massive hatch closely following a fish eradication operation in Cave Creek, Arizona, in the spring of 1970. Percolation
of water through the sands most likely maintained the eggs on surficially
desiccated bars. Such percolation may also filter noxious substances.
C. FOODS AND FEEDING
Desert fishes are opportunistic in their feeding, as are most fish species.
Sources of food in desert springs, marshes, and intermittent streams typically consist of algae, aquatic invertebrates, and detrital material, the first
two of which, at least, may undergo marked diel and seasonal changes in