What are those dark purple lumps on the rocks below? The sea urchins, Colobocentrotus atratus, have earned several nicknames for their distinctive body shape, including “helmet urchin” and “shingle urchin.” Unlike other urchins covered in long, sharp spines, C. atratus have a smooth body and flattened spines. Their unique body plan helps them withstand pounding waves and cling onto rocks in the rough surf zone where they live; their Hawaiian name is hāʻukeʻuke kaupali, meaning “cliff-perching sea urchin.” You can find them dotting rocky coasts of the Indo-Pacific Ocean and grazing on encrusting red algae.

[Photo* and caption by Jessica Schaefer]

*Photo taken during a citizen science survey by the OPIHI program at a rocky intertidal site on Oʻahu in June 2017.

For more info check out The Waikiki Aquarium and The University of Hawaii at Mānoa.

[Edited by Karli Chudeau]