What is depicted in the picture?

Sea urchins are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone.

The spherical, hard shells of sea urchins are round and spiny, ranging in diameter from 3 to 10 cm (1 to 4 in). Sea urchins move slowly, crawling with tube feet, and also propel themselves with their spines. Although algae are the primary diet, sea urchins also eat slow-moving (sessile) animals. In the food chain, the predators who eat sea urchins are the sea otter and the starfish, the wolf eel, the triggerfish, and human beings.

The animals have been studied since the 19th century as model organisms in developmental biology, as their embryos were easy to observe; this has continued with studies of their genomes because of their unusual fivefold symmetry and relationship to chordates.