Watching zebrafish make stripes

Our summer research program is winding down, and preparation for the fall semester teaching is winding up. My student, Katrine Sjovold, and I have been trying to figure out what early melanocytes are doing — it’s a very simple and accessible system to observe cell motility, because the cells label themselves with melanin and we don’t need to do any of that persnickety cell injection stuff, or buy expensive dyes, or buy expensive cameras capable of detecting fluorescence (although we’ve tried a little of that here at the end of the summer, and I’ve been appropriately impressed that my research camera actually can see DiI fluorescence, even if it’s not designed for it).

Anyway, one of the things we’ve been doing is making time-lapse videos of melanocytes after they start making pigment and as they’re linking up and consolidating to form stripes. Here’s one example, a time-lapse where we take one image every 3 minutes over a day and an evening of growth.

You can see that we’re looking down on the dorsal side of the animal, in the region of the hindbrain (see the fourth ventricle, and the ears, deep and out of focus?). You may also notice that one of the melanocytes spontaneously decides to die and quickly breaks down into a few darkly pigmented blobs.

I’ve also uploaded a few other videos, but keep in mind these aren’t polished, perfect videos — these are bits and piece of our working data collection.


  1. Michael says

    “Melanocytes expand and contract” Do they? Or is it the melanosomes being dispersed and centered?

  2. says

    That’s something we have to dig into — I mentioned that we’re trying DiI labeling to give us an independent measure of cell boundaries.

  3. blf says

    And here I’d always thought it was relatives of Maxwell’s Demon, equipped with very small paintbrushes and buckets of paint, who did all the stripe-making…

  4. John Harshman says

    Why is it that zebra fish are model organisms, and zebra finches are model organisms, but actual zebras are not?

  5. blf says

    It’s well known that zebras are total jerks.

    The trolls of the animal world ?

    (I am aware zebras are mean and nasty and dangerous.)

  6. kestrel says

    Um. Whoops, :-) I’m sorry, you have awakened my inner pedant, my apologies. Zebras are not actually mean, nasty and dangerous… in a way. They are not domesticated animals. Expecting them to be tame, quiet and safe is a sort of human thing that just does not always come true. Zebras are wild animals with a pretty huge startle response and an epic desire for continued existence. That may not be compatible with humans trying to get them to “behave” (which is such an odd thing to say, they *are* behaving, just not how a human would like them to). I guess zebras are not all that keen on being domesticated. However. If you observe them quietly in the wild you will find them peaceful and wary.

    These are amazing videos. I did not realize such things could be observed! Incredible!

  7. kesci says

    I’m not impressed. Let me offer some advice on how to put stripes on zebra fish. First gather some branches (that elm marked for death will do). Next, strip the bark off the branches. Lastly, place the branches vertically in each fish tank so that the fish can see them while they copulate. It worked for Jacob in Genesis.

  8. says

    Except…zebrafish stripes are horizontal. I think, though, that I can rescue your protocol by placing the branches, and then turning the tanks sideways.

  9. blf says

    If you observe [zebras] quietly in the wild you will find them peaceful and wary.

    Unless you are a lion (e.g.), especially, perhaps, at the end of your “observing”. Then you run a significant risk of being kicked so hard — by both rear legs — your jaw will go into orbit.

  10. Tethys says

    Huh, the first stages of stripes look an awful lot like bacterial colonies, or a mycelium.

  11. kesci says

    Hey, I’m referencing a biblical miracle here, so details (regarding stripe orientation) just don’t matter.

  12. kesci says

    Ok PZ. I turned the fish tank sideways. It didn’t work. You owe me a couple of Zebrafish. Now Excuse me while I clean up the mess.