408
JAMES E. DEACON AND W. L. MINCKLEY
veloped in certain estuarine and marine fishes (Stebbins and Kalk, 1961;
Todd, 1968). Similar capabilities are present in marine-derived or obligate fresh water fishes of many mesic zones (Graham, 1911; Laird, 1956).
We know of no such adaptations in desert fishes.
In places with extremely porous bottom materials, such as coarse gravels
of creek beds, fishes may escape desiccation by moving into water flowing
through interstices (Stegman and Minckley, 1959). Neel (1951) suggested
that they might survive drought by moving into burrows of crayfish, much
as some coastal, marine fishes use mud burrows of invertebrates (Barlow,
1961a), or construct burrows of their own (Stebbins and Kalk, 1961 ). The
notorious burrowing and aestivating capabilities of some lungfishes are so
well publicized that reiteration here seems unnecessary.
In Australian deserts, gobiomorids and the native "minnows" (family
Galaxiidae, Galaxias spp.) may survive drought by burrowing in muds or
moist soils, much in the manner of lungfishes (Whitley, 1959). A great
number of species of diverse groups utilize this same type of avoidance
behavior in drying pools of tropical zones, especially those fishes having accessory respiratory devices. American pupfishes may live as long as
10 days in moist muds or organic debris. The mosquitofish has been
known to survive 4 days in the bottoms of almost dry reservoirs, if temperatures did not exceed 18°C, humidity remained higher than 85%, and the
fish were not exposed to direct sunlight (Afanasev, 1944). Many cyprinodont fishes bury in the substrate under severe conditions, especially in
colder weather, or as a means of escape (Cowles, 1934; Minckley and
Itzkowitz, 1967; Deacon, 1968a; Minckley and Klaassen, 1969a). The
longfin dace may also bury, but this has been infrequently and unsatisfactorily observed (Minckley and Barber, 1971 ).
It must be reemphasized that only a few of the fish species discussed
above live under desert conditions, and morphological and behavioral
adaptations of these types are found primarily in forms living in tropical
areas that enjoy high, but seasonal, rainfall. Overriding forces of desiccation under low humidities, high incident light, and usually high temperatures (plus, perhaps, accumulation of salts), appear too extreme for fish
life to persist in most instances of drought in deserts.
4. Direct Effects of Light
The broad importance of light and light-related factors in activity of
fishes, reproductive cycles, and so on, will be discussed in Section IV.
However, some direct effects of incident radiation may best be discussed
here. Intense solar radiation coupled with clear, shallow water may damage
fishes, although the results of desiccation of epidermis exposed to air may
confuse the issue somewhat. We have found longfin dace and pupfishes
JAMES E. DEACON AND W. L. MINCKLEY
veloped in certain estuarine and marine fishes (Stebbins and Kalk, 1961;
Todd, 1968). Similar capabilities are present in marine-derived or obligate fresh water fishes of many mesic zones (Graham, 1911; Laird, 1956).
We know of no such adaptations in desert fishes.
In places with extremely porous bottom materials, such as coarse gravels
of creek beds, fishes may escape desiccation by moving into water flowing
through interstices (Stegman and Minckley, 1959). Neel (1951) suggested
that they might survive drought by moving into burrows of crayfish, much
as some coastal, marine fishes use mud burrows of invertebrates (Barlow,
1961a), or construct burrows of their own (Stebbins and Kalk, 1961 ). The
notorious burrowing and aestivating capabilities of some lungfishes are so
well publicized that reiteration here seems unnecessary.
In Australian deserts, gobiomorids and the native "minnows" (family
Galaxiidae, Galaxias spp.) may survive drought by burrowing in muds or
moist soils, much in the manner of lungfishes (Whitley, 1959). A great
number of species of diverse groups utilize this same type of avoidance
behavior in drying pools of tropical zones, especially those fishes having accessory respiratory devices. American pupfishes may live as long as
10 days in moist muds or organic debris. The mosquitofish has been
known to survive 4 days in the bottoms of almost dry reservoirs, if temperatures did not exceed 18°C, humidity remained higher than 85%, and the
fish were not exposed to direct sunlight (Afanasev, 1944). Many cyprinodont fishes bury in the substrate under severe conditions, especially in
colder weather, or as a means of escape (Cowles, 1934; Minckley and
Itzkowitz, 1967; Deacon, 1968a; Minckley and Klaassen, 1969a). The
longfin dace may also bury, but this has been infrequently and unsatisfactorily observed (Minckley and Barber, 1971 ).
It must be reemphasized that only a few of the fish species discussed
above live under desert conditions, and morphological and behavioral
adaptations of these types are found primarily in forms living in tropical
areas that enjoy high, but seasonal, rainfall. Overriding forces of desiccation under low humidities, high incident light, and usually high temperatures (plus, perhaps, accumulation of salts), appear too extreme for fish
life to persist in most instances of drought in deserts.
4. Direct Effects of Light
The broad importance of light and light-related factors in activity of
fishes, reproductive cycles, and so on, will be discussed in Section IV.
However, some direct effects of incident radiation may best be discussed
here. Intense solar radiation coupled with clear, shallow water may damage
fishes, although the results of desiccation of epidermis exposed to air may
confuse the issue somewhat. We have found longfin dace and pupfishes