Patiriella regularis

Patiriella regularis
Scientific classification
Kingdom:	Animalia
Phylum:	Echinodermata
Subphylum:	Eleutherozoa
Class:	Asteroidea
Order:	Spinulosida
Suborder:	Leptognathina
Family:	Echinasteridae
Genus:	Patiriella
Species:	P. regularis
Binomial name
Patiriella regularis (Verrill, 1867)

Patiriella regularis, or New Zealand common cushion star, is a sea star of the family Echinasteridae, endemic to New Zealand. It has an armspread of up to 60 mm.

Patiriella regularis, the commonest sea star in New Zealand, inhabits the lower shore, under rocks and ledges to depths of about 5 metres. Coloration is most commonly bluish green, but some specimens are coloured black, orange or red. It feeds mainly on small barnacles, encrusting seaweeds and fine organic debris, although it sometimes eats larger prey such as gastropods and the half crab, Petrolisthes elongatus.

In shape, it is roughly similar to Stegnaster inflatus, except that it is concave between the arm points. It is rough to the touch and, when immersed, is covered with small, thin-walled bladders called papulae, which are respiratory structures.

Patiriella regularis is also found from the Derwent Estuary to the D'Entrecasteaux Channel in Tasmania, Australia, where it is dominant in intertidal regions and appears to outcompete other grazing sea stars. It is believed to have been introduced into Tasmania from New Zealand with shipments of live oysters early in the twentieth century.

References

• Miller M & Batt G, Reef and Beach Life of New Zealand, William Collins (New Zealand) Ltd, Auckland, New Zealand 1973
• Woodbridge