The zebrafish (Danio rerio)

24h of zebrafish embryonic development (Rolf Karlstrom and Don Kane; Development 123:461, 1966)

From zygote to free-swiming larva in 48 hours

Up there should be a couple of videos showing the embryonic development of zebrafish. If they don't work, follow the links. That's what I'm working with for my Ph.D. thesis. The development of this animal is astonishingly fast. That helps a lot the embryological studies and the fact that it's completely transparent during the first 24 hours (after that, it starts developing the pigment cells that will create the stripe pattern typicall of this fish) makes it perfect for visualization (as you can see in the videos). Another great advantage is the number of genetical tools available. You can microinject the eggs with DNA, RNA (antisense or sense), morpholinos, proteins, antibodies, chemicals, whatever you want in order to alter the genetic profile of the developing embryo and see the effects of the injected substance. The use of morpholinos (chemical analogs of nucleic acids, but more stable; they work by complementary hybridisation with the target mRNA in the embryo, thus blocking its expression into protein) is particularly helpful because it allows you to abolish the expression of the genes you want to in a very specific and stable way (more than antisense RNA) without having to generate transgenic knock-out fish. Could we say any more about this wonderful system? Sure! There are vast collections of mutants (albino lines are quite useful for visualization of processes happening during the second day of development) and the genome is being sequenced (there is a very advanced draft publicly available, coming from shotgun assemblies as well as some full BAC clones sequencing). If that wasn't enough, they breed like flies, so it's possible to perform "proper" statistical tests with the experiments. In conclusion, this fish is the Drosophila of the vertebrates. And they look great in your home aquarium (especially the mutants ;-)