Eggs and Newly Hatched Larval Fish
In the images below I tried to capture the development of
the fish from fertilized egg through a larval stage called wigglers. The
highest magnification photographs of the eggs and wigglers were made with
the subject on microscope slides. The slides were put over a colored and
textured background for artistic effect. Photographs of eggs and wigglers
on the breeding slate were made while the slate was in the aquarium. The
high magnification required limited the depth of field of the image. Free
swimming fry were photographed in a "micro aquarium" made with microscope
slides and aquarium sealant.
The development and growth of tropical Angelfish
click on the pictures below to see the full-size image
|This egg is 60 hours old and almost ready to hatch. Inside the egg
the larval fish is curled around the yolk sack. The head of the fish is
at the top of this image. Under a low power microscope the beating heart
is clearly visible and one can easily observe blood flow through the unhatched
fish (the egg wall and fish body is quite transparent).
|Fungus is a threat to the eggs before hatching. The egg on the right has
been attacked by fungus. I add methalene blue to the water immediately
after the eggs are laid to control fungus.
|Typically the parents lay eggs on a breeding slate or on the leaf of
a plant. If the tank has no other occupants good parents will care for
the eggs and raise the fry. Occasionally I have had a mating pair watch
over the eggs even in a community tank but not many fry will survive in
such an environment. When I want to raise a batch of fry I move the slate
to an empty (well cycled) tank immediately after spawning. A bubbler will
keep oxygenated water flowing over the eggs.
|After hatching, the fish enter a larval stage and are called "wigglers".
The wigglers remain attached to the slate by a sticky filament which emerges
from their head. I don't know the technical name of this appendage. It
drops off when the wigglers become free swimming.
|This wiggler hatched 24 hours ago. In the larval stage the fish live
off of a yolk sack and do not eat food. The eyes and internal organs are
still developing at this point.
|This wiggler, 48 hours after hatching, has consumed most of the yolk
sack. It will be free swimming in about another day. The eyes are well
developed and respiration can be observed (with a magnifying glass).
|Click here to see close up photographs of free swimming
Once the fry are free swimming (three to five days after hatching, depending
on the water temperature) they will need to eat. For the first day or two
they can survive eating microscopic organisms (infusoria) in the tank.
Some breeders will add yolk from a hard boiled egg pressed through a fine
cloth into the tank. The best food source, however, is freshly hatched
I use a home made hatchery. For close up photographs of newly hatched
brine shrimp, information on how to build a hatchery and hatch them, please
click on the link below.
|Information on hatching Brine Shrimp