The rainbow-edge tallweed is a type of poisonous weed with a chromatophore-laden edge that changes color in rapidly propagating stripes.
Weeds are multicellular, photosynthetic organisms common in the reefs whose cells contain green and purple chloroplasts. This gives them a dark, grey-blue color. Some weeds are small, soft-skinned, and ruffled in order to better exchange dissolved nutrients. On the other hand, most are large and have thick, tough skins to deter herbivores. To exchange nutrients, they have a vascular system that includes blood, heart(s), and gills distinct from the light-gathering leaves (if any). Cells throughout the body freely detach and ride through the bloodstream, soak up the nutrients they need in the gills, storing them in vacuoles, again ride through the bloodstream, and finally take the place of another cell with depleted vacuoles. Often, the blood pathways will change position the same way rivers erode one bank and build up another. Gas in the vacuoles in each cell is what makes most weeds so buoyant.
Tallweeds are one family of tall, single fronds attached by holdfast to the seafloor with small, spiral gills placed periodically down the middle on only one side and that reproduces by spores (both sexual and asexual) produced anywhere on the skin – one species of which is toxic and has a multicolored edge.