Species

Reef Sea Star

Stichaster australis, (Verrill, 1867)

marine

About Reef Sea Star

Stichaster australis, the reef starfish, is a species of starfish found in the shallow waters of the rocky intertidal of New Zealand. Typically, the animal is endemic to the west coast shores of the North and South Islands, where wave action is increased. They do not usually inhabit ecosystems that have reduced wave action and calm conditions as they prefer a higher-energy environment. These marine invertebrates range in color from pink to purple, but can also be orange. They typically have eleven arms, but sometimes they may have either ten or twelve. As full-grown adults, they are 8 to 10 cm in diameter.

Diet

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 will remain at the M. insigne nursery for about a year. This coralline alga is rich in calcium which is beneficial for the young starfish and its skeletal growth. After this stage, the diet of S. australis shifts to include, but is not limited to, P. canaliculus. 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. canaliculus. The mussel beds ultimately become the permanent home for this invertebrate.

Reproduction

The starfish engages in external fertilization in which the female releases the eggs and the male releases the sperm. Fertilization occurs in the water column. Its breeding season is the summer. During this time, male and female starfish can be found extremely close or even on top of one another. Consequently, spawning occurring several times from October through January.

Where to see it

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