The Strongylocentrotus franciscanus
commonly called Red Sea Urchin
is a Sea Urchin
found in the Pacific ocean, from Alaska
to Baja California
. It lives in shallow waters from the low-tide line to 90 m deep, and is typically found on rocky shores that are sheltered from extreme wave action.
A Sea Urchin’s spherical body is completely covered by sharp spines that can grow up to 8 cm. These spines grow on a hard shell called the “test”, which encloses the animal. The oldest ones have been measured to be around 19 cm in diameter. It can vary in color from red to dark burgundy. Rarely, albino specimens are found. A sea urchin has no visible eyes or legs. It has a mouth located on its underside, which is surrounded by 5 teeth. During larval development, the body of a sea urchin transitions from radial to bilateral symmetry.This bilaterally symmetrical larva, called an echinopluteus, subsequently develops a type of pentaradiate symmetry that characterises echinoderms. It crawls very slowly over the sea bottom using its spines as stilts, with the help of its tube feet
. Scattered among its spines are rows of tiny tube feet with suckers that help it to move and stick to the sea floor.
The animals have a mouth with special jaws (Aristotle's Lantern) located on the bottom (oral) surface. Their preferred diet is seaweeds, kelp and algae, which they scrape off and tear up from the sea floor. During larval development,... Read More