Closely related to sea stars, the sea urchins are segmented into five sections. This species has short robust spines and slender purple tube feet interspersed between them, it resembles a rolled up hedgehog! It is the largest of our native urchins. It camouflages itself by holding bits of weed, shell and gravel on it’s upper surface, a behaviour known as “hatting”.
Found in the low intertidal in northern NZ. Common subtidally throughout NZ.
As grasers, they feed mainly on kelp. They have an elaborate feeding structure, Aristotle’s Lantern,and leave behind a star shaped hole in large kelp fronds.
Sea urchins can live in very dense aggregations, where these are found often the rocks are bare of algae and it is often wondered what they eat.
They were eaten by early maori and are considered a delicacy in many countries throughout the world. NZ has not managed to successfully break into this international market as the gonads (reproductive organs) often taste bitter and their colour ranges from bright orange, through yellow and brown. There has been a lot of research happening with sea urchins in NZ to try and improve these factors. There has been success in improving the bitter taste with artificial diets but the colour remains irregular. Approximately one in five have the lovely orange gonad that is sought after overseas.References
A Guide to the Plants and Animals of the New Zealand Marine Studies Centre: McKinnon