Sea Urchin Tide Pool Colouring

Sea urchins are round, spiny relatives of sea stars and sand dollars. Roughly 1,000 species live in oceans worldwide, from shallow tropical reefs and rocky tide pools to cold deep seafloors. Many common shore urchins have a hard inner shell, called a test, about 3 to 10 centimetres across, not counting the spines. Some species grow larger. Lifespan varies enormously: small kinds may live only a few years, many survive for decades, and the red sea urchin of the North Pacific can live for more than a century. The drawing shows a general tide-pool urchin resting safely among rocks, shells, and seaweed. Every spine attaches to the test with a tiny ball-and-socket joint, so the animal can point its spines in different directions for protection and movement. Between the spines are tube feet that help the urchin crawl, breathe, hold objects, and pass food toward its mouth. Five toothlike parts form a remarkable chewing device called Aristotle's lantern. Many urchins graze on algae, scraping it from rocks, although diets differ among species. Their grazing can keep reef surfaces open for new growth, but when predators disappear, too many urchins may create an “urchin barren” by eating most of a kelp forest. Sea otters, lobsters, crabs, triggerfish, and wolf eels are among their predators. Choose purple, deep red, forest green, black, pink, or brown for a realistic urchin. You can colour the central test a medium shade and make alternating rings of spines darker and lighter. Keep narrow white highlights along a few spines so the round body feels shiny. Because every spine has a clear outline, colour from its wide base toward its pointed tip with careful straight strokes. Use warm grey, tan, and reddish brown on the rocks, cream and peach on the shells, and olive or emerald green on the seaweed. The shallow water can be pale turquoise with white ripples. For a cheerful fantasy version, arrange the spines like a colour wheel—red, orange, yellow, green, blue, and violet circling the centre—while leaving the small central five-part pattern clearly visible.

◫ A4 size✎ Bold outlines♡ Ages 3–8

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