Ah, the evils of strong drink. Or weak drink. You all know that you shouldn’t drink alcohol to excess during pregnancy, and the reason is that it can affect fetal development. We take zebrafish eggs and put them on a real bender: we soak them in various concentrations of alcohol (which are hard to compare with human blood alcohol levels, I’m afraid, but trust me: these are such gross levels of ethanol that mere humans would be dead and pickled. Fish are tough), and let them stew for hours. Since fish development is much, much faster than human development, it’s rather like having a woman start drinking straight Everclear a few weeks after discovering she’s pregnant, and staying snockered throughout the first trimester.
So don’t try this at home, kids.
The animal on the left is a teetotaler control. The one on the right is going to get washed in 3% alcohol at about 4 hours of development. It’ll be obvious; a label will pop up, and also the eggs are embedded in agar to immobilize them, and the agar will go cloudy and dark for a while as the alcohol soaks in.
Even if you aren’t intimately familiar with fish embryology, you should be able to see that the one on the right develops more slowly. Especially at the end, the one on the left will be twitching vigorously and spinning in the chorion, while the lush on the right is much slower. There are also some subtle deformities in tail shape, and you might notice odd schmutzy gunk on the animal’s epidermis…more about that later.
Also, you’ll notice that we started both recordings immediately after fertilization—I was hovering over the tank, and as soon as momma and daddy squirted out the gametes, I scooped them up and slapped ‘em down in a dish, to guarantee that everything was starting precisely in synchrony. These movies start a little earlier and go on a little longer than the previous example.