460
JAMES E. DEACON AND W. L MINCKLEY
tors may be more important in creating seasonal spawning cycles in desert
fishes we have studied (see also Liu, 1969) than are physical or chemical
features of the environment.
In addition to seasonal cycles, diel patterns of reproductive activity may
be complex and quite precise. Hermaphroditic rivulus {Rivulus marmoratus) self-fertilizes at dawn and oviposits at noon, and there is a seasonal change in the pattern that appears controlled by light. Sexuality
of the fish is also under some environmental control (Harrington, 1961,
1963, 1967). Ovulation in the rice fish (Oryzias latipes) is under light and
temperature control, and it occurs between 0100 and 0500 hours. Oviposition occurs between 0400 and 0700 hours, and only follows the stimulation of mating contacts between the sexes (Egami, 1959a,b; Egami and
Nambu, 1961). Visual stimuli, physical contact, and a diversity of environmental cues are used by other cyprinodontids in their diel pattern of
sexual activities (Breder and Rosen, 1966), but precise studies are again
needed prior to generalizing too far.
No such detailed work has been done on desert cyprinodontids of North
America. Such fish do display complex sequences of behavior relative to
diel changes in environment (Itzkowitz, 1968; Itzkowitz and Minckley,
1969; Liu, 1969; Arnold, 1970). Pupfishes move about only in the day,
resting at night within or upon the substrate. Breeding males are highly territorial, and conspicuous, generally defending areas along shallow shorelines.
Territorial males may remain in their areas at night, as in C. macularius
(Barlow, 1961b), or they may move elsewhere. At first light, schooling and
feeding behavior prevail for a time (Liu, 1969) under most circumstances.
Territories are established or reoccupied shortly before (in midsummer)
or within a seasonally variable period after sunlight strikes the water
surface. In some species a territory is occupied continuously by a given
male for a period of days or perhaps weeks. Males are highly active in
defense of territories at the peak of breeding, but there are marked seasonal and diurnal variations in fluctuating environments that appear to be
related principally to thermal changes. Figure 9 was constructed as a conceptual model of territorial activity in a pupfish. It is based on obervation
of numerous species, but principally upon qualitative observations of
Cyprinodon atrorus in nature and in outdoor experimental ponds.
2. Ovum and Larval Ecology
Parental care of ova and young in desert fishes is as diverse as the species present, ranging from none, where eggs are broadcast over the bottom
and young fend for themselves; through indirect, where ova are laid and
hatch within the territories of male pupfish, and therefore receive protection; to extreme in livebearers and in some cichlids. Specific information on
JAMES E. DEACON AND W. L MINCKLEY
tors may be more important in creating seasonal spawning cycles in desert
fishes we have studied (see also Liu, 1969) than are physical or chemical
features of the environment.
In addition to seasonal cycles, diel patterns of reproductive activity may
be complex and quite precise. Hermaphroditic rivulus {Rivulus marmoratus) self-fertilizes at dawn and oviposits at noon, and there is a seasonal change in the pattern that appears controlled by light. Sexuality
of the fish is also under some environmental control (Harrington, 1961,
1963, 1967). Ovulation in the rice fish (Oryzias latipes) is under light and
temperature control, and it occurs between 0100 and 0500 hours. Oviposition occurs between 0400 and 0700 hours, and only follows the stimulation of mating contacts between the sexes (Egami, 1959a,b; Egami and
Nambu, 1961). Visual stimuli, physical contact, and a diversity of environmental cues are used by other cyprinodontids in their diel pattern of
sexual activities (Breder and Rosen, 1966), but precise studies are again
needed prior to generalizing too far.
No such detailed work has been done on desert cyprinodontids of North
America. Such fish do display complex sequences of behavior relative to
diel changes in environment (Itzkowitz, 1968; Itzkowitz and Minckley,
1969; Liu, 1969; Arnold, 1970). Pupfishes move about only in the day,
resting at night within or upon the substrate. Breeding males are highly territorial, and conspicuous, generally defending areas along shallow shorelines.
Territorial males may remain in their areas at night, as in C. macularius
(Barlow, 1961b), or they may move elsewhere. At first light, schooling and
feeding behavior prevail for a time (Liu, 1969) under most circumstances.
Territories are established or reoccupied shortly before (in midsummer)
or within a seasonally variable period after sunlight strikes the water
surface. In some species a territory is occupied continuously by a given
male for a period of days or perhaps weeks. Males are highly active in
defense of territories at the peak of breeding, but there are marked seasonal and diurnal variations in fluctuating environments that appear to be
related principally to thermal changes. Figure 9 was constructed as a conceptual model of territorial activity in a pupfish. It is based on obervation
of numerous species, but principally upon qualitative observations of
Cyprinodon atrorus in nature and in outdoor experimental ponds.
2. Ovum and Larval Ecology
Parental care of ova and young in desert fishes is as diverse as the species present, ranging from none, where eggs are broadcast over the bottom
and young fend for themselves; through indirect, where ova are laid and
hatch within the territories of male pupfish, and therefore receive protection; to extreme in livebearers and in some cichlids. Specific information on