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Pteraster militaris (O.F. Müller, 1776)
Wrinkled Star
Family: Pterasteridae
Extracted from Sea Stars of British Columbia, Southeast Alaska and Puget Sound by Philip Lambert.
Introduction to the Echinoderms of BC

Photograph

© Neil McDaniel     (Photo ID #15911)

Map

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Distribution of Pteraster militaris in British Columbia in British Columbia

Introduction


Family Description:

The aboral side of body is inflated and the oral side flat. A supra dorsal membrane supported by the spines of the paxillae covers the true aboral surface to create a nidamental chamber. In the centre of this membrane is a large opening (osculum). Many smaller spiracles pierce the rest of the membrane. On each side of the ambulacral furrow is a wide actinolateral membrane supported by long spines; between the spines are small holes, each guarded by an operculum, which lead to the nidamental chamber; water enters here and is expelled through the osculum. No oral intermediate plates.

Illustration

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Illustration Source: : Sea Stars of British Columbia, Southeast Alaska and Puget Sound by Philip Lambert

Species Information

Pteraster militaris is a stubby-armed, pale yellow sea star with a wrinkled aboral surface bearing a large pore (osculum) in the centre. Its colour can vary from creamy white to yellow or pink. Its five arms can grow up to 7.5 cm long. The ratio of arm to disc is 2.0 to 2.5. The aboral surface is a soft, fleshy, wrinkled, supradorsal membrane covering the aboral pseudopaxillae, which consist of a low base, slightly higher than it is wide, with 3 to 5 slender spinelets radiating from the top. Under magnification, tiny calcareous bodies can be seen in the membrane but no muscle bands as in Diplopteraster multipes. The adambulacrals of P. militaris have a transverse webbed comb of 6 to 9 spines, the proximal spine being the smallest. Extending horizontally from the outer end of the plate is a large spine (about three times length of the plate) embedded in the actinolateral membrane. The free outer edge of this membrane almost delineates the edge of the arm when viewed from the aboral side. Each mouth plate has 6 to 8 slender marginal spines joined by a membrane. A single large glassy-tipped suboral spine stands near the suture on each plate.

Characteristics



Similar Species

Pteraster militaris has longer arms and a softer, more wrinkled skin than its close relative, Pteraster tesselatus. The fans of marginal spines on adjoining mouth plates are not joined together by a continuous membrane as in P. tesse

Biology


Pteraster militaris eats the sponge Iophon pattersoni and the hydrocorals Allopora verrilli and A. petrograpta (N. McDaniel personal comment). The Atlantic form begins breeding in October. The female retains some eggs in the nidamental chamber and releases others. Large females brood a smaller proportion of spawned eggs than small females. Sperm enters through ambulacral pores to fertilize the eggs in the chamber. Thirty or forty juveniles grow to an arm's length of 4.5 mm in this chamber. While in the chamber, they feed on maternal skin, faecal material, mucus, aborted larvae and, possibly, dissolved organic matter. The sexes are separate and females have a continuous breeding season with a slight decrease in spring. Male gonads usually ripen in synchrony with those in other males, but female gonads do not.

Distribution

Distribution

Circumboreal; in the North Pacific, from the Bering Sea to northern Oregon and to the Sea of Japan; in the North Atlantic, on the Norwegian coast and to Cape Cod, U.S.A. Found at depths of 10 to 1100 metres, usually on mud, but in less than 30 metres on rocky substrates. In the Arctic, it is found on rock and a mixture of rock and mud.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)		COSEWIC
UnlistedUnlistedUnlistedUnlisted



BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

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