Live-bearing seastar

Phylum: Echinodermata

Scientific name: Patiriella vivipara

Distribution: endemic to south eastern Tasmania

Description: This small orange-yellow seastar has a maximum arm radius of 15mm. It is pentagonal in shape and is one of the smallest seastars found in the world.

Habitat: sheltered rocky shores, low intertidal zone

Ecology: Live-bearing seastars are grazers, feeding on the microscopic algae growing on rocks in the intertidal zone. They are slow moving and occur only in sheltered bays where the wave action will not dislodge them.

Photo: Edgar

Interesting Facts: The live-bearing seastar is one of only three species in the world that gives birth to live young. They are hermaphroditic, meaning each individual is both male and female. They fertilise themselves and the young (up to five at a time) develop in a sac inside the parent. When they are ready, the young emerge from an opening on the parents’ back and crawl off onto the rocks. The young seastars, at only 1-6 mm across, are tiny miniatures of their parents.

Status: Common within its range which is quite limted. All the known populations occupy less than 3 hectares. They are restricted to rocky reefs in the tidal zone and seem to prefer living under rocks near the high tide mark, this puts them at great risk from changes to their habitat. Patiriella vivipara is listed as endangered under the Tasmanian Threatened Species Protection Act 1995.