Here’s another of Casey Dunn’s Creature Casts, this time on shifting color spots in marine snails.
Pigment cells are always very, very cool. I’ve been intrigued by them for a long time — they show up in my time-lapse recordings of developing zebrafish and are always active. Here’s a quick one, a few hours of time in a roughly 24 hour old zebrafish embryo, compressed to about 30 seconds. You can see one corner of the dark eye at the bottom left of the image, and that oval structure near the middle with two spots in it is the ear and its otoliths. The melanocytes are writhing over the side of the head and down onto the yolk sac; they’re not quite as colorful as the snail, but then, the zebrafish is a mostly black and white animal.