Coscinasterias muricata Click to enlarge image
Eleven-armed Sea Star, Coscinasterias muricata Image: Dr Isobel Bennett
© Australian Museum

Fast Facts

  • Classification
    Species
    muricata
    Genus
    Coscinasterias
    Family
    Asteriidae
    Order
    Forcipulatida
    Class
    Asteroidea
    Phylum
    Echinodermata
    Kingdom
    Animalia
  • Size Range
    40 cm

Introduction

The Eleven-armed Sea Star is the largest species of sea star in Sydney and is commonly seen at low-tide levels, either on the rocky shore or in sandy bays.

Identification

The upper surface of the Eleven-armed Sea Star is covered in small spines.The number of arms varies from seven to 14 but, as the name suggests, it is usually found with 11 arms.

Habitat

The Eleven-armed Sea Star lives in intertidal rocky shores, coastal waters to a depth of 150 m.

Distribution

The Eleven-armed Sea Star is found in Southern Queensland, New South Wales, Victoria, South Australia, Western Australia and Tasmania. Also found in New Zealand.

Feeding and diet

The Eleven-armed Sea Star feeds on small crabs or marine worms.

Other behaviours and adaptations

Using a hand lens, you can see small protuberances like miniature jaws around the spines on the body of the Eleven-armed Sea Star. These are called pedicellariae, and they not only defend the sea star from predators, but also move up and down to catch food, which usually consists of small crabs or worms. These tiny jaws hang on until the prey is dead or until it can be reached by an arm or tube feet and passed to the mouth.