Courtship and Spawning
J. ornatus does not exhibit a conspicuous courtship before
spawning. Signs of a new spawning are an increase in activity inside
the shelter with new excavations and both specimens exhibiting a
prolapse of their genital ducts.
The spawning area chosen by the couple can vary from one
spawning to another, without any obvious preference for smooth or
rough surfaces. The only clear condition seems to be that spawning
occurs on a hidden surface of a given structure, such as under the
roof of a cave.
It is not easy to watch them lay eggs, because they spawn at night
or at dawn in most cases. Occasionally, the process begins at sunset
and we can catch some aspects of it. It is generally observed that
once the female is introduced to the shelter, she turns her body
and begins to deposit a row of eggs on the chosen area. After a
few seconds, she turns again and leaves the shelter swimming in a
normal position. Then the male enters the shelter and performs a
sequence similar to that described, presumably fertilizing the eggs
that were just deposited. After a brief pause, the female enters again,
and this cycle is repeated several times.
A plaque of eggs from an adult J. ornatus couple usually occupies
approximately 2 square inches ( 12 square cm) and contains between
30 and 50 eggs. Each egg is attached to the spawning substrate by
only a small portion of its surface. The eggs are gray-green in color,
have an elliptical outline, and measure 2 mm.
As soon as the spawning is done, both specimens periodically
inspect the eggs. During visits, their operations consist of fanning
eggs and performing cleanup actions by way of a precise pecking
between the eggs.
In my tanks, J. ornatus reproduces monthly for the standard
period of about nine months, followed by a rest period of about
Egg and Larvae Development
Embryonic development occurs rapidly. The larvae hatch in a
wide temperature range of 72° to 82°F ( 22° to 28°C) between 60
and 72 hours after spawning. After breaking the chorion (encasing
membrane), the larvae move and attach to the first surface they
find. Each larva is fixed by the head via secretions of the glands
it has there at this development stage and makes vibratory
movements with the back half of its body.
Larvae at birth measure 4 mm. Having not yet completed their
development, feeding depends on their substantial yolk sac. After
two days, the jaws are still bound, but by the end of the third day,
the larvae show open mouths, gill cappings detached and moving,
and fully formed eyes.
At four days old, larvae leave their
attachments frequently, a change that
coincides with the appearance of
pectoral and caudal fins. Between the
fifth and sixth day of life, the larvae
can be observed swimming on the
hidden structure surface where they
were born. The yolk sac is already
reabsorbed at this point, and the
larvae catch their first exogenous
food, mainly protozoa and rotifers
present in the aquarium.
Parental Behavior in
The parents pay close attention to
their progeny during the first three
to four days. As soon as the larvae
hatch, they collect and release them
into a nearby hollow. As soon as
the larvae are free-swimming, this
parental behavior ends. The fry still
enjoy the protection provided by
staying within the boundaries of the territory defended by
the couple, but no communication between parents and fry is
observed—except when the couple quickly retreat into the shelter,
which prompts a “body to ground” response in the shoal of fry.
With one week of age, the fry have grown to 5 mm, swimming
with their bellies oriented to structure surface; they aren’t seen
in midwater at this stage. During the second week of life, the fry
are scattered throughout the territory, by then measuring 7 mm
and easily catching enriched Artemia nauplii and Cyclops, which I
supplement with a thin mixture of fish flesh, crustaceans, mollusks,
and various vegetables.
The larval development stages of J. ornatus.