lthough similar in looks, habits
and often confused by the aquarist, Corydoras hastatus
and C. pygmaeus, Knaack,1966 have differing reproductive
modes. Previous efforts to induce C. hastatus
to spawn have met with no success, although spawning
of their own volition had been observed in my Corydoras
community tank, where two young C. hastatus have
been produced over a six-month period.
may not have spawned in the prepared tank because only
ten fish were available - 5 males, 3 females and 2 juvenile
fish. This I felt was a little low in numbers as
C. hastatus are a naturally shoaling fish.
My total stock of 10 C. hastatus were introduced
into a 61cm x 25cm x 25cm tank filled to 10cm with stock
tank water (pH 6.87 Temp. 72°F). Substrate was Dorset
pea and sandy outcrops. The tank was planted with different
Cryptocoryne's and pieces of bogwood. After the fish
were introduced the tank was topped up with fresh tap
water - Temp. 72°F. the tank was lit by room lighting.
A week and several water changes later, the C. hastatus
were very inactive. All of them were hiding at the rear
of the tank and were seldom seen shoaling in the normal
manner. This action was expected. I decided to introduce
10 C. pygmaeus. This should lift the C. hastatus
off the gravel and make them feel more at ease.
It had paid off. Both C. hastatus and C.pygmaeus
were shoaling together and feeding well. Water conditions
were pH 6.8, temp. 72°F.
The fish have been observed for the past few days and
the extra fish have made a great difference. C.pygmaeus
spawned, laying 40 - 50 eggs on the front glass and
on the plants. The spawning was typical of C. aeneus
(Gill,1858) and C. paleatus (Jenyns, 1842).,
i.e. plenty of activity. The C. pygmaeus were
not removed as the C. hastatus have become very
active and the eggs were not being eaten. Checking the
tank that evening, 5 male C. hastatus were seen
chasing one female. There was a very interesting point
the female's eyes were completely black. The iris was
not visible - only the pupils could be seen and they
were jet black. The males chased the female for 2 hours
and no eggs were laid. I was ready to give up when I
noticed the female with one very small egg held firmly
in her ventral fins. Actual delivery of the egg was
not seen, but the males were all quivering round her
at this time. (The other females were shoaling with
the C. pygmaeus and their eyes were normal. With
the egg cradled in her ventral fins, she then began
to swim over and under the plant leaves with the males
in close pursuit. They seemed to be cleaning the leaves.
She swam around with the one egg for half an hour, before
depositing it under a plant leaf. I am quite sure only
one egg was laid at this time.
This spawning activity has continued in the evening
for 2 weeks. Only one female spawning at a time, and
laying only one egg. Whether or nor it is the same female
each time is hard to tell as they are all similar in
size. During the period when the C. hastatus
spawned, fry were seen in the tank. They were silver
in colour with 2 - 4 dark patches along the back. Some
had a distinct black patch through the caudal peduncle.
As the fry grew, 4 C.hastatus fry of varying
sizes were seen swimming with the 30 C. pygmaeus
1) To date (mid-
March). The C. pygmaaeus have not spawned again,
but still the odd C. hastatus appears. Could
the C. hastatus be a periodic spawner, as are
some of the Julidochromis species from Lake Tanganyika?
2) The eyes
of the spawning female turned completely black. The
gold iris vanished and the full eye appeared black.
3) The growth
rate of the C. hastatus is quicker than that
of C. pygmaeus. The older C.hastatus are
1cm whereas the 30 C.pygmaeus are under 6mm.
Powder food was fed as soon as the first fry were seen
and thereafter every day in small quantities for any
newly hatched fry. Brine shrimp and micro worm were
fed along with normal daily food for adult fish.
the high mortality rate reported by some aquarists,
which can occur at 4/ 6 weeks period, i.e. the fry will
try to lift to the water surface and spin to the bottom
(water depth does not matter). The fry were very weak
and wasting away and would die in a week. The size of
the fry seems to be the important factor - not the age.
I have a few theories:
a) At first I thought that a nutritional
deficiency was the trouble. If the fry were left with
the parents the high mortality rate did not occur. Perhaps
the parents helped feed the fry, or they received nutrition
from mulm caused by the parents. Of course you will
lose some due to the parents eating fry or eggs. No
deaths occurred. Could the fry be developing their secondary
breathing system and getting chilled (as do anabantids
when the labyrinth organ is developing). Lately, a very
high success rate with C. barbatus (Quoy &
Gaimard,1824) and C. aeneus, with the parents
removed, perhaps the tanks were higher than normally
used and so water and air temperature were not equal
Or can it be put down to bad management.
This article first appeared in
the Catfish Association of Great Britain Newsletter