8
MAINTAINING FISHES
Stance that represses reproduction (Swingle, 1956).
We may thus consider this material as a water pollutant. This phenomenon is well enough recognized
that in hatcheries it is utilized as a means of preventing goldfish from spawning too early in the spring.
The fish are crowded during the early spring and
moved to a less crowded condition when the operator
desires them to commence spawning.
It has been shown (Rose, 1959) that tadpoles release into the water a material which inhibits the
growth of other tadpoles, and there is some evidence
that such a material may be produced by fishes. If
such is the case, the matter should prove to be of
great interest to aquarists. In order to illustrate the
possible nature of such substances we might review
some of the characteristics of the material that Rose
worked with in tadpoles.
When tadpoles are crowded, one or two of a group
will greatly exceed the others in growth.
The larger tadpoles produced something that inhibited the growth of the smaller ones.
If small tadpoles in a separate tank were exposed
to water from a tank containing large tadpoles the
growth of the smaller ones was inhibited.
Inhibiting is prevented by heating the water to
60° to 70° C, by filtering through fine filter paper or
by aging the water for a month.
The presence of plants and other animals reduces
the inhibiting effect.
The inhibitive agent is apparently produced only by
rapidly growing tadpoles. It is thus said to be a
feed-back phenomenon.
The inhibiting agents are specific although inhibi-
MAINTAINING FISHES
Stance that represses reproduction (Swingle, 1956).
We may thus consider this material as a water pollutant. This phenomenon is well enough recognized
that in hatcheries it is utilized as a means of preventing goldfish from spawning too early in the spring.
The fish are crowded during the early spring and
moved to a less crowded condition when the operator
desires them to commence spawning.
It has been shown (Rose, 1959) that tadpoles release into the water a material which inhibits the
growth of other tadpoles, and there is some evidence
that such a material may be produced by fishes. If
such is the case, the matter should prove to be of
great interest to aquarists. In order to illustrate the
possible nature of such substances we might review
some of the characteristics of the material that Rose
worked with in tadpoles.
When tadpoles are crowded, one or two of a group
will greatly exceed the others in growth.
The larger tadpoles produced something that inhibited the growth of the smaller ones.
If small tadpoles in a separate tank were exposed
to water from a tank containing large tadpoles the
growth of the smaller ones was inhibited.
Inhibiting is prevented by heating the water to
60° to 70° C, by filtering through fine filter paper or
by aging the water for a month.
The presence of plants and other animals reduces
the inhibiting effect.
The inhibitive agent is apparently produced only by
rapidly growing tadpoles. It is thus said to be a
feed-back phenomenon.
The inhibiting agents are specific although inhibi-