An initiative of Earthwatch Institute

  1. Hairy_urchin3_steve_smith Purple with orange spikes by S Smith
  2. Hairy_urchin__graham_edgar 10-15cm in diameter and spine length is max 1.5cm by G Edgar
  3. Hairy_urchin2_steve_smith Covered in kelp by S Smith

Collector Urchin

Tripneustes gratilla


  • Urchins are round ball like animals covered in sharp spines that move on very small tube-like feet.
  • Collector urchins are usually bluish-purple with white spines. However they can vary in colour, and some individuals have orange tipped spines while others are sometimes fully orange.
  • The spines are generally short compared to most other urchins (up to 1.5cm long) and are never longer than the width of the shell (adults 15 cm).
  • They are often partially covered in algae, pebbles or shell fragments, making them distinct from other urchins.
  • Size: Adult skeleton reaches 10-15cm in diameter, spine length 1.5cm.

What to Observe

Search area for 30 minutes and record under the following categories-

  • Abundant - found easily with little searching
  • Frequent - found with minimal searching
  • Rare - only 1 or 2 individuals found with intensive searching
  • Not found - not present during search

ClimateWatch Science Advisor

As a result of climate change, warm tropical ocean currents are expected to strengthen and persist for longer periods in southern coastal area normally dominated by cooler waters. The consequent increases in water temperature are likely to result in unfavourable conditions for sea urchin species. Climate change may also alter the chemical properties of sea water, making it harder for urchins to grow and reproduce. 

When To Look

Throughout the year

Where To Look

  • In rock pools and in crevices near low tide mark.
  • Tropical Australia to southern NSW and Southern WA. 
  • WA, QLD, NSW

  1. Search Species

  1. What Else?

    There are several other urchin species in the same family (Temnopleuridae) that have short or soft looking spines and look similar to the collector urchin (T.  gratilla), however, these are normally difficult to find (being cryptic), and live mainly in the curled fronds of kelp. The collector urchin can be distinguished from most of these by its common behaviour of collecting algae, pebbles and shell fragments and placing these on its body (hence their other name, collector sea urchins).  

  1. Did You Know?

    Commonly found in the Indo-Pacific, Hawaii, off the coast of Mozambique and The Red Sea.

    Once an individual dies or is taken out of the water it loses its bright colours.

    Their main predators are puffer fish, octopus and humans.

    Human exploitation of this species has caused a sharp decline in population.