''Coscinasterias calamaria'', or the eleven-armed sea star, is a starfish in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Asteriidae The Asteriidae are a diverse family of Asteroidea (sea stars) in the order Forcipulatida. It is one of three families in the order Forcipulatida. Genera The World Register of Marine Species lists these genera within the family Asteriidae (in a ...

. It was thought to be

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to southern Australia and

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

but has since been documented as occurring in the

Cape Peninsula The Cape Peninsula ( af, Kaapse Skiereiland) is a generally mountainous peninsula that juts out into the Atlantic Ocean at the south-western extremity of the African continent. At the southern end of the peninsula are Cape Point and the Cape ...

as well. It is found around low tide levels and deeper, under rocks and wandering over seaweed in pools.

Description

''Coscinasterias calamaria'' is the largest starfish in southern Australia and New Zealand. Although called the eleven-armed sea star there can be any number of arms between seven and fourteen, but eleven is the most common number. These starfish are often found with arms of varying lengths. This is because arms sometimes become detached and new arms grow in their place. This starfish has rows of pincer-like

pedicellaria A pedicellaria (plural: pedicellariae) is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms (phylum Echinodermata), particularly in sea stars (class Asteroidea) and sea urchins (class Echi ...

e on both its upper and lower surface which gives it a prickly appearance. Its total diameter is up to .

Distribution

''Coscinasterias calamaria'' is native to the coasts of Australia and New Zealand. Its range extends from

Rottnest Island Rottnest Island ( nys, Wadjemup), often colloquially referred to as "Rotto", is a island off the coast of Western Australia, located west of Fremantle. A sandy, low-lying island formed on a base of aeolianite limestone, Rottnest is an A-class ...

in Western Australia round the southern coast to New South Wales and Point Dangar in Queensland, including Tasmania and

Lord Howe Island Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland P ...

Biology

''Coscinasterias calamaria'' mostly feeds on the

blue mussel The blue mussel (''Mytilus edulis''), also known as the common mussel, is a medium-sized edible marine bivalve mollusc in the family Mytilidae, the mussels. Blue mussels are subject to commercial use and intensive aquaculture. A species with a l ...

(''Mytilus edulis'') and other benthic invertebrates. It has been found that it seldom feeds on the blacklip abalone (''Haliotis rubra'') unless there is a scarcity of mussels. When this happens, aggregations of starfish do feed on it. This is despite laboratory feeding tests demonstrating that it prefers abalone. It seems that the abalone has some behavioural responses to attack that make it more likely to escape, one of which seems to be the production of a chemical deterrent by the mollusc. There are smell chemoreceptors on the tips of the arms, and the starfish can navigate accurately by smell towards a source of food. It then extends its stomach over its prey, secretes enzymes onto it and liquefies before returning the stomach to its normal position. When food is scarce, this starfish can exist for many weeks without food. ''Coscinasterias calamaria'' mainly reproduces by fissiparity (self division) by tearing itself in two pieces across the disc. It is capable of regenerating a whole new body from a single arm, but only if the arm includes part of the central disc. It can also reproduce sexually. It is difficult to establish the relative importance of the two forms of reproduction in this starfish but it has been shown that individuals in close proximity to one another have little genetic diversity while starfish collected at separations of as little as have widely different genetic composition, particularly so in the case of subtidal populations.

References

* Miller M & Batt G, ''Reef and Beach Life of New Zealand'', William Collins (New Zealand) Ltd, Auckland, New Zealand 1973 {{Taxonbar, from=Q2370571 Asteriidae Fauna of the Indian Ocean Fauna of the Pacific Ocean Echinoderms of New Zealand Fauna of Western Australia Animals described in 1840 Taxa named by John Edward Gray