Guardian: Jens Vogt
Cactus algae have the ability to move their protoplasm around. During the day all of the living fluid that make up their cells (chloroplasts, nuclei etc.) are in their leaves so they can photosynthesise. At night this fluid will flow down into their roots to hide and they will turn white, like ghosts. A fish, crab or snail may eat a leaf but it will be an empty casing and the following day the leaves that survived will refill with life.