Breeding and Egg Development of Hymenochirus
boettgeri I will detail my tank environment and chemistry for those
who wish to compare and/or duplicate my conditions. The
mating, egg laying and development observations that follow were
the first I had witnessed and may not be typical behavior of
all H. boettgeri. Two batches of eggs were laid.
The first on January 19, 1998 and the second on January
29, 1998.
I am using a 10-gallon (38 liter) rectangular aquarium containing
approximately 9 gallons of water. The tank is furnished with
a combination of igneous rock, aquarium gravel, plastic plants
and African "iron wood". The wood is extremely dense
and heavier than water. It is available at most aquarium supply
shops.
Environment
The tank was relatively immature when the frogs were
placed in it, i.e. a full nitrogen conversion cycle
had not been established. I decided on the artificial plants
because I wasn't certain the water conditions would be right
for supporting live plants.
Aeration is provided at one end of the tank by means of an
"air stone" partially buried under rocks and gravel.
Filtration is provided by a submersible filter (manufactured
by Aquarium Systems) near the source of aeration. The filter
contains a mixture of activated charcoal and ammonia locking
resin. The flow of the filter is set to maximum. The outflow
of the filter is directed to minimize turbulence.
A 50 Watt submersible heater is located at the opposite end
of the tank . The daytime temperature is typically
77° F. (25° C.). with nighttime temperatures dropping
to 75° F.
The water is typically clear with no offensive odors.
The lighting is a single fluorescent tube with a duration
of 12 hours daily. The light is controlled by an appliance timer.
Chemistry
Water Hardness: Soft
pH level:
6.8 average (variable from 6.4 to 7.0)
Buffering capacity: Moderate
Ammonia (NH4): 2-3 PPM
Nitrite (NO2): 2-4 PPM
Nitrate (NO3):
less than 35 PPM
I am using a variety of products to condition the water. A
phosphate-based powder called Neutral Regulator is used
as needed to correct pH and buffer the water toward neutral (7.0).
Nova Aqua StressCoat with Aloe Vera is used to remove chlorine,
chloramine and heavy metals from replacement water. StressZyme
is used weekly to aid in the development of bacterial biology.
If ammonia levels go above 4 PPM then AmmoLock2 is used to help convert
anhydrous ammonia (NH3-N) to a non-toxic form (NH4).
The development of a fully functional nitrogen-conversion
biology has been slowed by two factors:
1. I decided not to employ an under-gravel filter system since
it would tend to pull the frog's food supply out of reach. 2.
The filter I am using does not provide a very large area for
bacterial development.
I am hoping that the frog tank will continue to develop toward
a 0 PPM ammonia, 0 PPM nitrite state. I have achieved this condition
in my 10-gallon community tank easily with an under-gravel filter
system.
Feeding
1 to 2 grams of frozen blood worms every 48 hours. The worms
are produced in Japan by The Nuromi Company. They are fortified
with various vitamins.
Mating
I can only estimate the approximate age of the mating pair
at about 1 year. The egg laying of Batch 1 occurred on January
19, 1998 starting at around 07:00 PST.
The mating was preceded by several nights of "croaking"
that lasted from 1 to 3 hours. The croaking started after the
tank light had been out for several minutes. The croaking is
apparently done while the frog is submerged. I suspect that the
frog is able to push air back and forth between its lungs and
vocal chords.
The mating was achieved by the male grasping the female firmly
around the abdomen from behind at a point just in front of her
hind legs (amplexus). The female did all the swimming with the
male keeping his hind legs relaxed. I observed the female swim
from the bottom of the tank to the surface where she rotated
so that her abdomen was facing upwards and parallel with the
surface. I observed a localized extension of her abdomen near
her tail. This extension broke the surface of the water whereupon
a single egg was deposited. The female returned to the bottom
of the tank and repeated the process after a few seconds. A total
of 25-30 eggs were laid during my observations.
The egg-laying procedure took only 1-2 seconds and was performed
in a near continuous motion. I did not observe any male genitalia
nor any sperm.
Amplexus lasted 10 hours, though I wasn't able to observe
them continuously during that time. Amplexus did not end
until the female became motionless and rigid for some minutes.
During that time any mobility was supplied by the male.
The Eggs
1-24 Hours
The eggs were spherical and buoyant when first laid. The newly
laid eggs were clear and 1-2 mm. in diameter with a dark gray
spherical yoke of approximately 1 mm. The eggs developed a sticky
coating soon after emerging from the female and would readily
stick to glass, wood, plastic and each other.
After 12 hours the yoke had enlarged by about 50% and had
a slightly mottled appearance. The eggs that proved to be non-viable
had a yoke that was milky white.
24-48 Hours
The nucleus had developed into a rudimentary tadpole shape after
36 hours. The color of the embryo had become uniformly gray with
a darker region extending along the back from head to tail. An
eye spot could be observed using a 10X loop. After 48 hours the
eye spot could be seen without magnification. The embryo had
enlarged by about 50%.
48-96 Hours
The embryo continued to develop rapidly. By 72 hours more structures
could be seen developing: eyes, tail, mouth, etc. What appeared
to be a yoke sack could be observed at the base of the tail.
The size of the embryo did not increase significantly.
By 96 hours all the tadpoles had emerged from the clear casing
and were free swimming. The yoke sack structure was still visible.
At the 24-hour mark I moved approximately 15 eggs into a device
normally used to feed live tubiflex worms to fish. This clear-plastic
device is cone shaped and extends into the water with small holes
to allow the worms to emerge. I had hoped to keep the tadpoles
isolated in this device to watch them develop and to ensure that
they had a food supply when they were ready to feed. I lost 5
embryos within 72 hours: they stopped developing and turned white.
I believe that some of this loss can be blamed on damage that
occurred during the move. Additional loss occurred to the embryos
developing in the tank. A number of other eggs continued their
development where they came to rest within the tank.
The free-swimming tadpoles gradually migrated out of the worm
feeder as they were small enough to fit through the holes. My
best estimate puts the tadpoles at 3-4 mm. in length and less
than 1 mm. wide at 1-2 days of age. I estimate that a total of
15-20 tadpoles hatched.
Three days after the tadpoles left the worm feeder I briefly
observed one tadpole swimming in the tank. It was still very
small and I soon lost sight of it among the rocks and plants.
It is possible that the tadpoles are continuing to develop in
hiding. My guess is that they do not need to breathe from the
surface after hatching but can respire through their tail membrane.
I am hoping that they have been able to feed on the remnants
of the adult's food.
January 30, 1998
Batch 2 numbered approximately 100 eggs. They
were laid by the same female during amplexus by the same male.
Mating appeared to be complete by 07:00 and the bulk of
the eggs appeared to be 8-10 hours old. Amplexus ended by
07:30.
I was better prepared this time to transfer
and isolate the eggs. I used a modified Monoject 412 syringe
to gently remove clumps of eggs from their resting place
and put them into a 4" X 3" fine-mesh net that was
secured to the side of the tank. I positioned the net so
that its rim is about 1/2" above the surface of the water.
I transferred approximately 30 eggs that appeared viable. Approximately 20 eggs hatched within
72 hours with the remainder proving non-viable.
Feeding
I am feeding the tadpoles a product called LiquiFry No. 1
For Egglayers, manufactured by Interpet Ltd.. The product
contains infusoria culture and small clumps of white matter
made from whole egg. The tadpoles appear to be skimming
the milky portion from the surface.
February 1st
Water Hardness: Soft
pH level:
6.4 average (variable from 6.4 to 6.8)
Buffering capacity: Moderate
Ammonia (NH4): 1-2 PPM
Nitrite (NO2): 1 PPM
Nitrate (NO3): less than
35 PPM
The tank chemistry was changing during the time that the
eggs were developing. It is my experience that the pH
tends to drop as the tank matures. The delta between
the levels of January 19 and February 1 suggest that a full
nitrogen conversion cycle is becoming operational. I have taken
extra care not to change the pH too suddenly to avoid putting
the tadpoles into shock.
I made a surprising discovery. I spotted a relatively
large tadpole swimming in the tank. I was able to
transfer him to the net and examine him with a 10X loop. He appears
to be the sole surviving tadpole from Batch 1 and I have
named him Lucky. He is approximately twice the size of
those from Batch 2. I have observed Lucky eating
small bits of the white matter from the LiquiFry.
Behavior
Under 10X magnification it is obvious that the newly
hatched tadpoles swim inverted. They swim slowly in this
position less than a millimeter below the surface. They
apparently feed in this manner but I've had difficulty observing
their mouths clearly. When they are resting they will
typically right themselves. They will swim away very quickly
from a small disturbance of the water in their vicinity.
After 72 hours many of the tadpoles from Batch 2 are
swimming in a righted orientation.
Other Observations
At 72 hours the tadpoles have developed dark pigmentation
along their body and tail. Their bodies have taken on
a more square shape when viewed from above. Lucky
(at 10 days of age) has developed gold flecks that
run laterally from between his eyes to the tip of his tail.
 
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