lives where the sponges grow thick

Size
Length: 8–12 cm
Lifespan
5–10 years
Diet
Carnivorous. Feeds on sponges and small invertebrates. A slow-moving predator that feeds on encrusting organisms on rocky reefs. Uses tube feet to move across reef and pull food towards mouth.
Habitat
Rocky reefs, kelp forests, and harbours from 5 to 50 metres depth. Often found on rocky bottoms with abundant sponge growth. Prefers areas with complex rocky structure and strong currents.
Range
Found in coastal waters of North and South Islands from Northland to Otago. Most common on rocky reefs and in harbours. Endemic to New Zealand waters. Distribution follows suitable rocky habitats.
Endemism
Endemic
Main Threats
No significant conservation threats. Climate change affecting marine habitats. Ocean acidification may impact larval development and survival of sponge populations, which are primary food source.
Population
Populations considered stable and widespread. Species is common on rocky reefs throughout New Zealand. No formal conservation assessment exists. Distinctive, angular shape makes it easy to identify among sea stars.
Conservation Status
Not Threatened
Human Risk
harmless
Handling Note
native sea star, harmless to humans, leave undisturbed
Conservation Note
Native marine invertebrate; not assessed by NZTCS as marine invertebrates are outside the scope of current threat classifications.
Te Ao Māori
The reef star has no traditional Māori name or significance. It was not a food source. Its distinctive, angular shape was likely noted by coastal Māori. But it was not gathered or used in traditional practices. In modern times, it is a common sight for divers on rocky reefs. It is one of New Zealand's many endemic sea stars. Its name reflects its preferred habitat. The rocky reef. Observation was keen. Use was absent. The star persists. It is unseen by history. It is seen by science. It belongs to the reef. It does not belong to the story. Yet. The name is English. The origin is descriptive. The presence is ancient. The recognition is new.
Angular and raised, its plates give it a geometric, almost architectural appearance. The reef star does not look like a typical sea star. The arms are short and broad. The surface is covered in large, raised plates that fit together like tiles. The colour is pale brown or grey. This provides camouflage against the rocky reef. Structure dictates form. Appearance aids concealment. The tile-like pattern breaks the outline. The predator misses. Rocky reefs are its preferred habitat. The reef star lives from five to fifty metres depth. It occurs on rocky bottoms with abundant sponge growth. It is most common in areas with strong currents. Here, sponges and other encrusting organisms are abundant. The current brings food. It carries away waste. Flow is essential. Stagnation is fatal. The environment supports the life. Slow-moving and methodical, it feeds on sponges. The reef star crawls across the reef. It grazes on encrusting sponges and other small invertebrates. It uses its tube feet to pull food towards its mouth. The mouth is on the underside of the disc. It is surrounded by five jaws. Movement is gradual. Consumption is steady. The process is efficient. The sponge is consumed. The rock stays clean. The raised plates provide protection. The reef star has a hard, armoured surface. This makes it difficult for predators to bite or swallow. The plates are covered in small spines. This adds another layer of defence. It is not a fast star. But it is a well-protected one. Armour replaces speed. Defence is structural. Survival is passive. The shell holds. The predator retreats. Endemic to New Zealand, it lives nowhere else on Earth. The reef star is found from Northland to Otago. It occurs on rocky reefs throughout the country. It is a common sight for divers who know where to look. They look on the walls and overhangs. Among the sponges and kelp. Uniqueness is geographic. Presence is local. The diver finds it. The star remains. Reproduction occurs in spring and summer. The reef star releases eggs and sperm into the water. Fertilisation occurs there. The larvae drift in the plankton for several weeks. They settle to the bottom. They are tiny at first. But they grow quickly in the food-rich waters of the reef. Growth is rapid. Survival is chance. The next generation arrives. The cycle continues. Climate change may affect it indirectly. Ocean acidification makes it harder for sponges to build their skeletons. If the sponge populations decline, the reef star may decline with them. For now, it remains common on rocky reefs. A geometric, angular presence on the walls and overhangs. Resilience is tested. Limits are unknown.