Silent Predators

31/01/2022

Flat, spiny and in the shape of a star one the most recognisable marine creatures are the sea stars. Coming in a range of sizes, shapes and number of arms Aotearoa is home to at least 184 species of sea star.

One funky and unique species endemic to (found only in) Aotearoa is the Ambush Star (Stegnaster inflatus). The ambush star can be found all around Aotearoa in the subtidal (underwater) zone and easily spotted due to its bright colour. This species of sea star is unusual because of how they catch their prey.

The ambush star arches its body so that it is standing on the tips of its arm, forming a cup-like shape with its body. The sea star then waits until an unsuspecting creature (e.g. small fish liked triplefins or rock fish) decides to take shelter under the cave made by the sea star’s body. The ambush star them collapses their body and suctions down, trapping the prey animal underneath it. At which point the sea star eats the captured animal. A diagram of this process from Grace, 1974 is shown below.

We were excited when this species was spotted on Auckland shores (Campbells Bay) in October 2019 and July 2020 during the Hauraki Gulf Monitoring Project.