Invertebrate of the Week: Helmet Urchin

Also known as shingle urchins, or hāʻukeʻuke in Hawaiian,  helmet urchins have evolved to resist strong wave action and drying out (which is why they can tolerate being exposed to air).  This huge south swell would be no problem for a helmet urchin!  Its unique design allows it to stay firmly in place on rocks while being pounded by wind and waves.  Its modified spines aren’t sharp like other urchins.  Instead, they are flat and smooth – well adapted to the environment in which they live.  Unlike most other sea urchins, helmet urchins prefer to feed on periwinkles and coralline algae, although they eat algae as well.  Because this urchin often occurs on rocky areas with high wave action, it can be really hard to get to, but it is harvested as food and can be quite tastey!

Periwinkles

Helmet Urchin (Photo: Ryan Tabata)