This painting is of a nudibranch, also called a sea slug. They come in a myriad variety of colors and shapes, and I love how otherworldly yet very real they are. Fun Facts about Chromodoris nudibranchs: Chromodoris nudibranchs feed on sponges and sequester toxins from them to make their own bodies poisonous to predators. This toxicity is often signaled by their bright colors.