Marine Life‎ > ‎Hawaii‎ > ‎Invertebrates‎ > ‎

Sea Urchins

Echinothrix calamaris

       
(1: Lighthouse, Lanai / 2: Shark Fin, Lanai / 3-4: Pawai, Kona / 5: Kua Bay, Kona / 6: Harbor Ledges, Kauai / 7 : Kahalu'u Beach Park, Kona / 8: Sea Tiger, Oahu)


Blue-Black Urchin

Echinothrix diadema

 
(1-2: Kamaole Beach Park III, Maui)


Collector Urchin

Tripneustes gratilla

       
(1: First Cathedral, Lanai / 2: Mala Pier, Maui / 3: Kahalu'u Beach Park, Kona / 4: Hammerhead Point, Kona / 5: Garden Eel Cove, Kona / 6: Turtle Canyons, Oahu / 7: Olowalu, Maui)

In the 2nd picture, the urchin is inhabiting an old bicycle.  The urchin in the 4th picture has been particularly clever, and is camouflaging itself inside of pieces of shell from another urchin.


Keeled Heart Urchin

Brissus latacarinatus

These usually live under the sand.  I've only seen their skeletons:
 
(1: Pipe Dreams, Kona / 2: Turtle Canyons, Oahu)

This one has been partially eaten by a horned helmet snail:
(1: Amber's Arches, Kauai)


Long-Spined Urchin

Diadema paucispinum

       
(1: Mala Pier, Maui / 2-3: Harbor Ledges, Kauai / 4: Kahalu'u Beach Park, Kona / 5: Garden Eel Cove, Kona / 6-7: Hale O Honu, Kauai / 8: Pahoehoe Beach, Kona)


Needle-Spined Urchin

Echinostrephus aciculatus

      
(1: The Dome, Kona / 2-3: Sheraton Caverns, Kauai / 4: Tortugas, Kauai / 5: Stone House, Kauai / 6: Turtle Canyons, Oahu / 7: End of the World, Molokini)


Oblong Urchin

Echinometra oblonga

 
(1: Black Rock, Maui / 2: Kahalu'u Beach Park, Kona)

These like to hide in crevices during the day.


Pebble Collector Urchin

Pseudoboletia indiana

  
(1: Shark Fin, Lanai / 2: St. Anthony Wreck, Maui / 3: Kaloko Arches, Kona)

Note the fine white tentacles in the first picture; that's how pebble collector urchins grab pebbles and move them to their back for camouflage.


Red Pencil Urchin

(aka Slate Pencil Urchin)
Heterocentrotus mamillatus

       
(1: Kaloko Arches, Kona / 2: Pentagon, Kona / 3: Horseshoe Reef, Oahu / 4: Mala Pier, Maui / 5-6: Olowalu, Maui / 7-8: Black Rock, Maui)

Common at shallower depths.

This is a juvenile, less than an inch across:
(1: Hoover's, Kona)

When they die their spines fall off, and what's left is the test (skeleton):
(1: Sheraton, Kona)


Rock-Boring Urchin

Echinometra mathaei

       
(1-2: Kealia Beach, Maui / 3: Hoover's, Kona / 4: Kahalu'u Beach Park, Kona / 5: Mario World, Oahu / 6: Black Rock, Maui / 7: Dog Beach, Kona / 8: Sheraton, Kona)

These fluoresce under UV light:
(1: Kahalu'u Beach Park, Kona)


Rough-Spined Urchin

Chondrocidaris gigantea

     
(1: First Cathedral, Lanai / 2-3: Garden Eel Cove, Kona / 4: Hoover's, Kona / 5: Sheraton, Kona / 6: Turtle Heaven, Kona)

In the second picture, the rough-spined urchin is to the right; the smoother-spined urchin to the left is a red pencil urchin.


Thomas's Urchin

Actinocidaris thomasi

(1: Barge Harbor North, Lanai)