MOSS ANIMALS (Bryozoans)

 Existing as a colony of very tiny, nearly independent individuals called zooids, a bryozoan or moss animal is often symmetrical of pattern. The name “moss animals” results from the resemblance between encrusting bryozoans and thin patches of moss found on rock. Colonies are sessile (attached) and through asexual budding or “cloning” of zooids may spread out mat-like or stack up like a mini high-rise building, depending on the species. Superficially some bryozoans resemble other, very different organisms such as hydroids, hydrocorals or even seaweeds!
Three basic colony designs, shown here, are noticeable to the naturalist: encrusting or flat (photograph A, orange encrusting bryozoan BZ7), erect, branching and flexible (articulate) (photograph B, stick bryozoan BZ18) and erect, branching and calcified (inarticulate) (photograph C, fluted bryozoan BZ24).
Each zooid secretes an often highly ornamented house (chamber) made of calcium carbonate—species-specific of design—around itself. Normally the worm-like zooid body extends about halfway out of the house, revealing a ring of tentacles surrounding the lophophore. The filter-feeding lophophore uses millions of tiny beating hairs or cilia to propel tiny particles of food (such as bacteria, tiny algae and detritus) toward the gullet. The mouth is inside the incomplete circle of tentacles, and the anus is located outside and below—thus the name “ectoproct” (outside anus).
At least 300 species of bryozoans or moss animals live in the marine waters of the Pacific Northwest.