Seanet High Intertidal

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Oscarella carmela Muricy & Pearse 2004
Phylum Porifera, Class Demospongiae, Order Homosclerophorida, Family Plakinidae

Encrusting sponge; skeleton absent (no spiclules); thin soft slimy crust 2-3 mm thick, raised into small lumps or lobes; superficially resembles a compound ascidian; color tan to light brown or pale reddish orange; ovoid choanocyte chambers (only visible under a microscope).

Very patchy, on sides and underneath boulders submerged in tidepools in the high intertidal zone; also in aquarium facilities.

Geo Range: central California,  north at least to Vancouver
Similar species: Halisarca sp. also lacks spicules but possesses elongate tubular choanocyte chambers.

Image: from underside of a boulder; white spots are spirorbid polychaetes.