Pumpkins are a classic symbol of Hallowe’en. We love carving our own jack-o-lanterns and making them glow with candles inside.
Today’s Hallowe’en sea creature is… the sea pumpkin! The sea pumpkin is a cute name given to the shells (or tests) left behind when sea urchins die. Their rounded shapes with radiating lines certainly remind us of little pumpkins.
There are about 950 species of sea urchins (class Echinoidea) and they are found in all oceans from the intertidal to 5000 meters deep. They have pentameric symmetry (as opposed to our bilateral symmetry), meaning that everything they have on the outside can be split into fives. They are covered in spines to protect them from predators.
Fun fact: sea urchins have sharp, self-sharpening teeth they use to graze for food and even bite through rock. Check out this electron microscope image that scientists at the University of Wisconsin captured. It earned them a prize thanks to the International Science & Engineering Visualization Challenge sponsored by the National Science Foundation and the journal Science. Who knew that scary could be so beautiful?