The red spines are typical to these urchins in Hawaii
When I went underwater for my first snorkel in Hawaii, I was almost immediately met by the oddest-looking urchin that I had ever seen. After some research I found out that I was seeing my first Indo-Pacific endemic urchin, the Red Pencil Urchin; a.k.a. slate pencil urchin or red slate pencil urchin.
With its fat radiolas, or spines, it stood out in stark contrast to any of the urchins I had seen in the Caribbean. The red spines that are found on these urchins is actually most typical to Hawaii. In other parts of the globe, they are yellowish or brown. A fun fact about the spines is that they are porous allowing for fluids to pass through them.
The scientific name for the red pencil urchin is Heterocentrotus mamillatus. The urchin primarily feeds on algae. Many urchins live a sedentary lifestyle, but the red pencil urchin will travel up to 96 cm per day. Red pencil urchins face few predators, but Triggerfish, Wrasses, and Breams will eat this urchin.
This urchin feeds primarily on algae
Did You Know?
- They can survive in places with strong currents because their spines allow urchins to wedge themselves between rocks.
- The slate pencil urchin is a herbivore that only eats at night.
- They are also opportunistic feeders.
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[…] At the north end of Keawakapu Beach, there is a nice outcropping of reef that extends from the shore. We were able to partake in a number of snorkel adventures here and at the south end of the beach. We saw everything from sea turtles to eels and from humuhumunukunukuapua'a to sea urchins. […]