Answer to the Friday Whatsit for July 16, 2010
One fish, two fish, red fish, that’s a fish???
Yes, this thing that looks like something from a Dr. Seuss book is a zebrafish (Danio rerio) embryo. The eyes are to the right, and the big green ball on the left is the yolk sac. As the fish grows to adulthood the eyes become more proportional and the yolk sac disappears, used up to fuel the growing fish.
Piriya guessed Drosophila melanogaster, an excellent guess considering its importance as a model organism, but alas we have no fruit flies today. Plus I think she really just wanted to name drop FlyNap (mmmmm . . . FlyNap) to give me a laugh. Which it did.
Zebrafish are tropical members of the minnow family, native to East India and Burma/Myanmar. Dr. George Streisinger’s work at the University of Oregon in the 1970’s is considered by many to be the founding work using zebrafish as a model organism. Zebrafish are now one of the most important model organisms in developmental biology and genetics — so important they have their own scientific journal and a cookie on the Not So Humble Pie blog (I know, I know, a cookie at Humble Pie doesn’t mean anything, it’s just fun).
Scientists use them because they don’t take a lot of space or time to care for, they develop rapidly, and they have relatively large eggs and embryos that are transparent, making it easy to see what’s going on inside as the fish develops. This one is only rainbow-colored because I false colored the stacks of pictures used to make the image. I did a quick z (depth)-stack using three different filters, collecting whatever glowed/reflected back, then a maximum intensity projection to flatten the image into one plane. No fish were harmed in the making of this picture (zebrafish have their own version of FlyNap, this little guy was just sleeping).