458
JAMES E. DEACON AND W. L. MINCKLEY
by species of that group seemed unlikely above 11° or 12° N latitude.
Variability in interpretation of scattered studies is again the rule, and no
broad pattern seems to exist.
Production of young throughout the year is, however, known from fishes
in some thermal springs at higher latitudes. Arnold (1970) found patterns
of gonadal development in Cyprinodon bijasciatus that included no pronounced differences, at the population level, between winter and summer
in thermal waters of the Cuatro Ciénegas basin. Individual fish appeared
to have cyclical development of gonads throughout the year. Young of
that species are present, in variable numbers, at all times, and studies of
length frequency distributions of various populations indicate relatively
constant recruitment. More reproductive activity is, however, evident in
summer than in winter, as based on relative numbers of territorial males
on breeding grounds. Espinosa (1968) found a similar asynchrony in development among females of the White River springfish {Crenichthys
baileyi) from warm springs in southern Nevada. Despite some seasonality
in reproduction by the population as a whole, some females spawned
in each month of the year. Espinosa summarized the spawning habits of
this springfish as follows :
. . . asynchronous, individual spawning periodicity, two spawning periods per
individual [per year], long spawning periods, and a protracted spawning season . . ."
A most complex pattern(s) certainly not under control of a single feature
such as day length.
Poeciliids living in constant temperature springs of Arizona (Gila topminnow; Schoenherr, 1970), Texas (Pecos gambusia, Gambusia nobilis),
and northern Mexico (Gambusia marshi, G. longispinis, and northern
platyfish, Xiphophorus gordoni), seem to reproduce year-round in constant
springs, but they demonstrate spring-summer surges in reproductive success
in a pattern similar to those of cyprinodontids. In the Cuatro Ciénegas basin,
fishes of tropical derivation (Mexican tetra and cichlids) rarely reproduce
in autumn, but seem to do so in all other seasons, and fishes of northern
affinities (sunfishes, catfishes, and minnows) appear to have more typical
spring-summer spawning periods.
Some fishes living in constant springs exhibit marked seasonality in reproduction that closely resembles that of species of streams and lakes of temperate zones, but the direct relationship of such cycles to physical factors in
the environment remains somewhat in doubt. Cyprinodon diabolis, for
example, lives at an almost constant 33°C, but has marked seasonality of
recruitment (James, 1969). Populations increase radically in March, and
JAMES E. DEACON AND W. L. MINCKLEY
by species of that group seemed unlikely above 11° or 12° N latitude.
Variability in interpretation of scattered studies is again the rule, and no
broad pattern seems to exist.
Production of young throughout the year is, however, known from fishes
in some thermal springs at higher latitudes. Arnold (1970) found patterns
of gonadal development in Cyprinodon bijasciatus that included no pronounced differences, at the population level, between winter and summer
in thermal waters of the Cuatro Ciénegas basin. Individual fish appeared
to have cyclical development of gonads throughout the year. Young of
that species are present, in variable numbers, at all times, and studies of
length frequency distributions of various populations indicate relatively
constant recruitment. More reproductive activity is, however, evident in
summer than in winter, as based on relative numbers of territorial males
on breeding grounds. Espinosa (1968) found a similar asynchrony in development among females of the White River springfish {Crenichthys
baileyi) from warm springs in southern Nevada. Despite some seasonality
in reproduction by the population as a whole, some females spawned
in each month of the year. Espinosa summarized the spawning habits of
this springfish as follows :
. . . asynchronous, individual spawning periodicity, two spawning periods per
individual [per year], long spawning periods, and a protracted spawning season . . ."
A most complex pattern(s) certainly not under control of a single feature
such as day length.
Poeciliids living in constant temperature springs of Arizona (Gila topminnow; Schoenherr, 1970), Texas (Pecos gambusia, Gambusia nobilis),
and northern Mexico (Gambusia marshi, G. longispinis, and northern
platyfish, Xiphophorus gordoni), seem to reproduce year-round in constant
springs, but they demonstrate spring-summer surges in reproductive success
in a pattern similar to those of cyprinodontids. In the Cuatro Ciénegas basin,
fishes of tropical derivation (Mexican tetra and cichlids) rarely reproduce
in autumn, but seem to do so in all other seasons, and fishes of northern
affinities (sunfishes, catfishes, and minnows) appear to have more typical
spring-summer spawning periods.
Some fishes living in constant springs exhibit marked seasonality in reproduction that closely resembles that of species of streams and lakes of temperate zones, but the direct relationship of such cycles to physical factors in
the environment remains somewhat in doubt. Cyprinodon diabolis, for
example, lives at an almost constant 33°C, but has marked seasonality of
recruitment (James, 1969). Populations increase radically in March, and