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

Leptasterias hexactis
Six-Armed Star
Family: Asteriidae

© Aaron Baldwin  Email the photographer   (Photo ID #2058)

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Distribution of Leptasterias hexactis 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


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Members of the Leptasterias hexactis complex have six arms 4 to 8 cm long, each with a distinct carinal row whose plates bear one to three spines apiece. This group of sea stars has arm-to-disc ratios ranging from 3.3 to 5.4. It generally appears to have short stubby arms with an obvious row of light coloured spines down the centre of the arm and widely spaced capitate, dorsolateral spines irregularly arranged in a loose reticulate pattern. The superomarginals have one or two spines, rarely three, and the inferomarginals two. The oral intermediates are usually in a single well-developed series extending beyond half the arm, but never two rows. The adambulacrals have one or two spines, with clusters of crossed pedicellariae on their distal sides.

Similar Species

Small Leptasterias may be confused with juveniles of Pisaster ochraceus or Evasterias troschelii, which occasionally have six arms. P. ochraceus has a single spine on each adambulacral, with a cluster of pedicellariae at the base but not on the spine. Leptasterias has one or two spines per plate with a cluster of pedicellariae on the spine itself. E. troschelii has pedicellariae on the adambulacrals but an arm-to-disc ratio of 5.0-7.6 and six similar rows of spines between the superomarginals and the furrow, made up of two inferomarginals and four oral intermediates. Leptasterias has no more than two oral intermediates.

Biology


Due to the taxonomic confusion that has existed for many years in the identification of Leptasterias, it is not clear if feeding observations in the literature attributed to a particular species are correct. Consequently, I am presenting all the biological observations that refer to intertidal species of Leptasterias.

Depending on place, time of year, and abundance of prey, the diet of L. hexactis includes barnacles (Balanus), sea cucumbers (Cucumaria), limpets (Acmaea), snails (Thais, Littorina and Calliostoma) and chitons (Katharina, Tonicella). It does not appear to detect prey from a distance. When prey is abundant, the sea star is more selective for larger individuals. The top snail Calliostoma ligatum shows an effective escape response to L. hexactis. The commensal slipper limpet Crepidula adunca attaches itself almost exclusively to C. ligatum, thereby taking advantage of its predator avoidance behaviour. The small pulmonate Onchidella borealis has glands along the edge of its body that repel L. hexactis. The Lacuna marmorata snail reacts to L. hexactis by twisting its shell, waving tentacles and dropping off the eelgrass blade that it was attached to. The Carinate Dovesnail (Alia carinata) repels L. hexactis by nipping its tube feet. The Balanus glandula barnacle appears to detect the chemical cues of this predator and stays closed much longer than if mechanically stimulated. L. hexactis tolerates low salinity (median tolerance limit: 12.9 parts per thousand) but its feeding and respiration rates drop in this environment.

L. hexactis aggregates to breed in January. Males discharge sperm into the water and females retain fertilized eggs under their arched bodies. The female produces from 50 to 1500 large yellow or orange eggs, which she broods for three months before the juvenile sea stars leave to lead independent lives. The scale worm Arctonöe fragilis is commensal on L. hexactis.

Distribution

Distribution

The Alaskan Peninsula to the Juan de Fuca Strait, Puget Sound and the Strait of Georgia. The small brooding forms of Leptasterias are commonly found on rocky shores under rocks, in crevices and in mussel beds; larger specimens are found subtidally.

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) 2019. 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: 19/11/2019 1:43:43 AM]
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