Typically, the animal is endemic to the west coast shores of the North and South Islands, where wave action is increased.

The planktotrophic larval stage for S. australis will last about 6 months, with larvae typically settling any time from May through July.

Both M. insigne and the juvenile starfish are limited to the lower levels of the ecosystems as they have low tolerances for desiccation.

[5] The growth of arms occurs in a clockwise pattern when viewing the animal aborally, the side containing the buttocks of the organism.

[citation needed] Juveniles, until reaching about 0.8 cm in diameter, when they are about 7 to 8 months old, feed purely on M. insigne.

The starfish, as it increases in size to about 2 to 2.5 cm in diameter and begins to mature, will then solely feed on the mussels.

The diet of this starfish during the adult stage consists mainly of Perna canaliculus, the New Zealand green mussel.

This carnivorous shift in diet is consistent with a relocation from the nursery algal spaces to close reefs containing dense populations of P.

[citation needed] This predatory relationship between starfish and mussels in this intertidal zone was studied by Robert T. Paine in a paper published in 1971.