Multiporina unicornis (Johnston, 1847)
Household bleach was used on these preserved specimens to dissolve organic matter, leaving only the exoskeleton shown in these pictures taken with the scanning electron microscope.
This encrusting bryozoan is common in The San Francisco Estuary, though it was likely introduced by the importation of Atlantic oysters. In some references, it is still incorrectly referred to as Schizoporella unicornis, but it has been placed by authorities in the genus Multiporina.
The first photograph is of a colony growing on a cable at the Clipper Yacht Harbor in Sausalito. The red arrows point to some of the varieties of avicularia, and the blue arrow shows an ovicell, used for brooding developing larvae. There may be one, two or no avicularia present, and there may also be zooids without ovicells. The second photograph shows a zooid lacking both avicularia and ovicell.
Photos by Vic Smith