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Fry Development/Rearing
Fry Development
The following images all come
from dropped eggs or stillborn embryos.
Four eggs dropped from female.
Eggs are cone shaped, approx. 3/32" in length.
Birth
Defects
Siamese twin taken
after specimen died.
Stage 1
The egg is deposited in the male's pouch and fertilized.
Stage 2
Stage 3
Stage 4
Stage 5
At stage 5 the seahorse has
eyes that are readily distinguished and very large, and you can clearly
see that the snout is beginning to fully "cleave" or split to form the
upper and lower half. They are significantly bigger in size, and
you can see their body, tail, and even their dorsal fin when you look closely
at them. Upon observation under a microscope or a magnifying glass,
you can also see other distinguishing features such as their heart, gills,
and air bladder.
Stage 6
At stage 6, their snouts are
fully cleaved, but still blunt and short. As you can see, their "triggers"
are developing, and their eyes are clear and more in proportion.
Under a microscope or magnifying glass, you can see their fins, internal
organs, and spinal column. Their tail is long. As you can see,
they are still very pink, and "yolky" looking in their bodies.
Stage 7
This is a picture of a fully developed baby Hippocampus Reidi as seen under the macro lens of our camera. As you can see, it is fully developed and has a snout that is to length and cleaved, eyes that are more in proportion to its head, etc. Under a magnifying glass, you can see the internal organs such as the heart, gills, and spinal column. The red line that runs the length of the body vertically may be one of its main arteries. These babies even have the beginnings of a small crown developing when they are born, and are also born with spines (ouch!) on their body. Structurally, they are a perfect replica of their adult parents in a much smaller form.
The simplest rearing tank is simply
a plain square with a heater, foam filter, and something for the fry to
hold onto. The above tank is actually a ten gallon with dividers
siliconed in to make three tanks. The orange square seen inside on
the left is "plastic canvas" available at most craft stores and is a favorite
to grab onto at night. This type of system works well for most species.
As a rule of thumb if the seahorse can hitch (grab onto something) right
after birth they most likely can be reared in this system.
Option 2: The advanced system.
This system is more involved both
in construction and function. Focusing on Hippocampus reidi as a
reference species, this tank works very well. This system consists
of a 3.5 gallon rectangular tank equipped with drip bars along the
edges to create surface turbulence. This prevents small fry from
getting stuck on the sides of the tank. This system also features
a flow through design, where as the water is pumped into the tank from
a wet/dry filter below and returned through a drain in the bottom of the
rearing tank. In addition to the wet/dry filter it also utilizes
an 8 watt uv sterilizer as well as a 5 micron mechanical filter.
Although I have not experimented much with this
method, I have raised a few fry with just a tank of green water.
This type of system is simply a tank set up in a well lit area and seeded
with copepods once the micro algae has taken off. The micro algae
acts as the filtration. I've had a few H kuda fry at one point that
were lying on the bottom of the rearing tank not doing well so we decided
to try just putting them into a tank of green water with some copepods.
We just kind of forgot about it until one day I saw three pairs of eyes
peeking out at us. The algae culture started crashing eventually
so I took them out and raised them as usual.
The first
factor is water quality. H reidi fry is very picky when it comes to this,
but not as picky as you may think. The most important aspect other than
your basics is pathogens. You can have the best water quality possible
but if there are parasites eating holes through your fry or bacteria infecting
them it doesn't matter. So how do you know if you have parasites? Things
to watch for are excessive twitching, grabbing themselves with their tail
like they're scratching at something (they usually are) The most effective
treatment for the parasites that have attacked the fry is formalin at a
quarter or half the recommended dose. The fry tolerate it very well, and
it won't hurt them any more than the parasites. Beware however that any
invertebrates such as snails, etc. won't like it either and it can actually
kill them. Copepods tolerate it well however. Temperature is
best around 80F. They do fine at a specific gravity of 1.024. As
a point of note you can lower the specific gravity to as low as 1.011.
This lower level inhibits some of the bacteria and parasites and lessens
the stress on the babies. I lower it over 2 days usually. Lower
it gradually so they don't go into shock. And I also raise it gradually
for the same reason. My reidis typically grow to 4-5 times
the size they were when they were born by week one, with survival rates
in the 90% range. Of course there are other factors, but this is an important
one. By the way I also use synthetic sea water and we live at the
base of the
mountains, so it is possible to raise these guys without
natural sea water. Bacteria can usually be controlled with a slight
dose of methylene blue. A recent batch of H fuscus were drooping
like flies until one drop of methylene blue and 1/4 tsp. formalin were
added. A week later I have not lost any.
The second factor is food quality.
This is where it can get really tough. Brazilian fry is famous for not
eating, eating then dying, etc. Unless you have no other options
they shouldn't eat baby brine until week 2. There is something about
it that clogs them up or gives them some severe problems. The biggest
problem is that it just plain isn't nutritious enough for them to develop
on. If you must feed them brine your best bet is with very
newly hatched, such as under 2 hours old. Decapsulating the cysts will
also help as the brine won't use up all their energy reserves breaking
out of the cysts. For details on
decapsulating I have the procedure outlined here.
Of course other species can do well on newly hatched artemia, just be sure to enrich it with a HUFA booster prior to feeding. For more on enrichment click here.
Rotifers are the next most common food offered. In order to have a good chance with them you'll need to enrich them first also. It's also a good idea to rinse them before feeding, which is an art in itself.
The absolute best food for reidi
fry in our opinion is copepods. Larval or not doesn't matter. I've
seen a reidi only a few hours old scarf down a full grown copepod larger
than a newly hatched brine shrimp, which only adds to the mystery of brine
killing them. Copepods don't need to be enriched, they are naturally high
in fats, lipids, and waxy
esters. For more information on culturing copepods
click here.
I feed our broods twice a day,
once in the morning and once at night. They seem to do just fine
on this schedule and I believe it's actually beneficial as it gives them
time to digest their food.
The third factor is tank and environment.
In the wild H. Reidi fry most likely float amongst the plankton layers.
I assume this because they don't hitch until two weeks old when they are
developing in our tanks. This presents all sorts of problems. In the ocean
there are no glass walls to crash into. I've tried several tank designs,
some just plain
crazy. My current system is the one out lined above
as the advanced system. Most other species will do fine in the simple
type system and this is all that is necessary.
4 week old H. reidi