Purple Sea Urchins- Hedgehogs of the Sea

Going to the tide pools at low tide is one of the coolest things to do. Stepping on a Sea Urchin... probably not one of the coolest things to do. These purple spiny creatures are a common site in most tide pools up and down the coast from Alaska and British Columbia all the way down to the Baja Peninsula, Cedros Island, Mexico. Its can  reach densities of up to several hundred animals per square yard. The purple sea urchin averages about 3 1/4 inches (8.5 cm) across; the spines are about 1/3 inch (1 cm) long. Its color ranges from a light purple to a deep reddish-purple color (juveniles are green).

Life Cycle

January- March is when Purple Sea Urchins reproduce. On occasion reproduction can occur even until July. Purple sea urchins reach sexual maturity at the age of 2-5 years. At this time they are about 25mm/less than an inch in diameter or greater. Once sexually mature, female Sea Urchins release several million tiny, jelly-coated eggs at a time called gametes into the ocean where fertilization occurs externally. Eggs and sperm are released through five gonopores.

 As they develop, the tiny larvae (called the pluteus, which have bi-lateral symmetry) swim in the sea and are a component of zoo-plankton. The fertilized egg then settles and begins to grow into an adult. After the egg is fertilized and settles onto a substrate, the urchin begins to develop. The test develops quickly to protect the young urchin. The plates of the test begin to form individually and grow tighter together to form the test. It takes several months for juvenile sea urchins to form completely.  The time from fertilization to a reproductive adult is from 2 to 5 years. As with most echinoderms, the sexes are usually separate. There is however an occasional hermaphrodite.

Purple Sea Urchins

Home

Purple Sea Urchins can be found in the tide pools off the West Coast of North America in the Pacific Ocean from Canada all the way down to the Baja Peninsula. They live in the low inter-tidal zone 0-10m/0-33 ft on coral and rocks

Purple Sea Urchin Habitat

Food

Sea Urchins, feed by scraping away at seaweeds and fixed animals and its favorite food is the giant kelp Macrocystis pyrifera. In the past, when sea otters were hunted, urchin numbers increased explosively in some areas. Which in turn hurt the giant kelp because they can chew through kelp hold fasts, setting the plants adrift. They also eat algae that grows on rocks as well as decomposing things such as fish, crabs sponges, mussels, and barnecles 

Sea Urchins are prey to many predators including but not limited to Sea Otters, Sunflower Stars, California Sheephead and Humans. Sea otters that regularly eat purple sea urchins are easily detected—their bones and teeth turn sea urchin purple!(known as echinochrome staining)

Sea Otter scull and teeth stained by Sea Urchins

Underside of the Purple Sea Urchin

Sea Urchin Body

Sea Urchin Roe, Eggs, Uni

Sea Urchins without Spines

Conservation Status

There is no immediate threats to this creatures status

Fast Facts

•  Scientific Name: Strongylocentrotus Purpuratus
• Sea Urchins are part of the Echinoderm family. Echinoderm  is a Greek word meaning “spiny-skinned.”
• Sometimes call the Sea Hedgehog
• Until 1994, the United States was the world largest supplier of uni or sea urchin roe, to Japan
• Male and female urchins are monomorphic; they are not physically distinguishable from one another.
• Sea Urchins do not have a brain but instead rely on their water-vascular system which is like a circulatory system and comprises of water-filled channels that run through the body of the sea urchin.
• If you step on a Sea Urchin urinating on it will not help.... 
• Soaking the area in hot water (110-130˚F) for up to an hour and a half can break down the venom and help to alleviate the pain. 
• Spines need to be removed carefully with tweezers.
• Urchin's pedicellarines (the poisonous clasping mechanisms hidden between some urchin’s spines) can be removed by shaving the area with shaving cream and a razor.
• Going to your primary care physician is all was a good course of action

Sources

Monterey Bay Aquarium-Purple Sea Urchins

Enchanted Learning-Sea Urchins

California Agriculture- Sea Urchin Roe

Animal Diversity-Purple Sea Urchin

Oceana-Purple Sea Urchin
Sea Otters and Purple Sea Urchins

“Live in the sunshine, swim the sea, drink the wild air.” Ralph Waldo Emerson