Being a Killifish enthusiast for many a long year, I'd bred quite a lot of species in days gone by but never really given a thought towards the embryonic stage and the processes involved in fry development from the day the egg is laid until the fry eventually emerges.
Armed with a little USB microscope I will, by means of pictures try to set that record straight. I will use the same egg each day. I cannot however predict if the egg will go full term until hatch but I will persevere with this project until I get this topic to completion. Please bare with me as this is as new to me as it is to you.

The following egg comes from an initial batch of 12 eggs of Aphyosemion elberti Mali Mombal JVC 07 laid on Mon 17th Aug 2009
and comes from a tank containing a sexed trio (1 Male:2 Females)
I hope to show you the embryonic development within the egg from spawning to hatch.
The egg development time should be anywhere between 12 to 21 days and is temperature dependant.

I hope you enjoy this, as I delve into something a little different.
The image below is of the egg in a globule of water on a glass slide. The egg is in the centre of the picture. The debris around the egg are fragments of Peat

Day 1) Mon 17th Aug 2009.
The egg has just been harvested from the mop and stored upon wet Peat Moss.
Cell division has already started. The colouration of the egg is whitish opaque/semi transparent.
The egg diameter is around 1.5mm, Incubated at a temperature of 76'F.

Day 2) Tue 18th August 2009
As you can see from the image above a substantial change has taken place in regards to development within the membrane. There is now a much more solid mass.

Day 3) Wed 19th Aug 2009.
Again a marked increase in development. At the bottom left of the egg, there appears to be some semblance of the backbone starting to form.
I do not know what the dark speckling inside the egg is at the present moment. I'm no scientist, but I would be curious to find out what, if anything, they actually represent. You can also see that the developing fish embryo has grown somewhat and now fills the egg cavity more fully than in the previous days.

Day 4) Thurs 20th Aug 2009.
Another 24 hours have passed and you can now see that there are two large darkened spheres on the embryo body itself Possibly the eyes starting to form.

Day 5) Fri 21st Aug 2009.
Annimation....Today I can report that the first visible signs of a heartbeat within the egg has been noticed, it is located between and just slightly above the two dark spheres (possible eyes). It is reddish/brown in colouration and is pumping away. I will try to get a small video clip uploaded at some point in the days ahead to show this new truly amazing development

Day 6) Sat 22nd Aug 2009.
The formation of the fry has really took on another great transformation today with the tail section being clearly visible wrapped around the inside of the egg wall. The heart is still pumping hard.

I have managed to take a short video of this phenomenon today....If you look closely you can see the heart pumping directly behind the two eyes.

Day 7) Sun 23rd Aug 2009.
The tail is clearly visible from this overhead shot.
The abdomen area is still ball shaped, I will expect this to trim off and elongate in the comming days prior to hatching.

Day 8) Mon 24th Aug 2009.
One full week has passed in the day in a life of a fish embryo, things are still moving at pace, the internal organs have darkend and the tail section seems to have thickened and lengthened somewhat.

Day 9) Tue 25th Aug 2009.
The tail section really looks a lot more broader today, and as expected, the ball shaped abdomen area has become more streamline and elongated as the internal organs develop and grow. Interestingly the eyes have yet to form properly.

Day 10) Wed 26th Aug 2009.
Today we can see some resemblance of the Iris's forming in the eye areas. There is a sac under the throat which may be the stomach or initial yolk sac. There appears to be a lot of activity in this small area. A lot of fluids being pumped around within.

Day 11) Thurs 27th Aug 2009.
The most noticeable things about today's development are the iris's of the eyes, they now peer out at you as the embryo takes on a more fish like appearance.

Day 12) Fri 28th Aug 2009.
The fry broke free from it's egg casing around 2pm today. It's a fully viable fish (swim bladder inflated) it is deporting correctly and taking initial feeds of Microworm and Brineshrimp. I hope this will be the first of many........
Thank you for following this thread, I hope that you have enjoyed this mini journey as much as I have.

N.B. All images in this thread are my own work. If you wish to use any of the above images, please ask.