E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Orthasterias koehleri (de Loriol, 1897)
Rainbow Star
Family: Asteriidae

© Mike Edley  Email the photographer   (Photo ID #909)

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Distribution of Orthasterias koehleri in British Columbia
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Introduction


Family Description:

Five or more arms. At least one adambulacral is fused into an adoral carina. The adambulacrals are wider than their length. Crossed and straight pedicellariae are present, the former usually in dense tufts around the spines. The aboral skeleton is meshlike. The tube feet are arranged in four rows.

Species Information


Click on the image below to view an expanded illustration for this taxon. If more than one illustration is available for a species (e.g., two subspecies may be illustrated) then links to the separate images will be provided below.



Orthasterias koehleri is a strikingly colourful large long-armed sea star with reddish banding around the arms between white or cream patches and prominent white or purple spines. Some individuals are a plain straw colour or a shade of blue. O. koehleri has five arms up to 25 cm long and an arm-to-disc ratio of 6.5 to 10.0. The arms have a row of carinal spines, each 4 to 5 mm long, with two or three series of similar well-spaced rows of spines on each side of the carinals. The aboral spines have a wreath of crossed pedicellariae at the base. Lanceolate pedicellariae, which vary from straight and pointed to broad and toothed, occur between the spines. The papulae occur in groups of three to five. A regular series of 80 to 85 superomarginals, with spines similar to aborals, curves upward in the interradial region to meet the series from the adjacent arm. Each spine has a wreath of crossed pedicellariae. An obvious intermarginal channel, with occasional lanceolate pedicellariae, separates this series from the two series of stout inferomarginal spines each with a tuft of crossed pedicellariae on distal side only. Oral intermediates consist of a single row of stout spines between the inferomarginals and adambulacrals. The adambulacrals have two slender diverging spines at right angles to the furrow, with a lanceolate pedicellaria at the base. Three to five adambulacral plates fuse to form an adoral carina. The mouth plates are usually too sunken to be seen clearly.

Similar Species

Orthasterias koehleri is similar to Stylasterias forreri in the aboral spines and wreaths of pedicellariae, but the living colours distinguish them. S. forreri is only black or brown, never red, orange or white. O. koehleri<

Biology


In a study of 157 feeding individuals, 71 per cent ate the bivalve Humilaria, 10 per cent the rock jingle Pododesmus, 6 per cent the chiton Tonicella, 3 per cent the lamp shell Terebratalia, and 2 per cent the black chiton Katharina. Other feeding observations include sea squirts and bivalves (Entodesma, Hinnites and Saxidomus).

The species breeds from June to August. It elevates itself on arm tips to spawn from paired gonopores. Females produce translucent tangerine-coloured eggs (diameter 150 micrometres). After fertilization, these develop into plank to trophic bipinnaria larvae in 5 days at 10°C. Ripe female O. koehleri produce an unidentified chemical that attracts sperm. This may be a general phenomenon with other sea stars, but it has only been demonstrated with this species. The scale worm Arctonöe fragilis is commensal on O. koehleri.

Richard Carlson at the Auke Bay Lab in Juneau reported that a tagged individual that had lost an arm had regenerated only three quarters of it after six years, demonstrating that growth is quite slow. He also found that individuals live at least nine years and probably longer.

Distribution

Distribution

The eastern Aleutian Islands, Alaska, to Santa Rosa Island, California. Common on rock, pebbles, sand and mud in the intertidal zone to 230 metres deep.

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

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2017. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 21/07/2019 8:19:48 AM]
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