Bryozoans: Mother Nature’s Look-Alikes

Ever look at a horse and wonder if it was a pig or a cat? Me neither. I have however, looked at dozens of my photos and wondered if they were actually bryozoans and not the hydroids, corals or seaweeds they resembled. 

Mother Nature turned trickster when she created bryozoans. She gave them many different forms and colors. On land, an animal that looks like a horse is very probably a horse. Underwater, an animal that looks like a hydroid, coral or seaweed may just be a bryozoan (or vice versa).
Bryozoa is Latin for “moss animal” and many bryozoans look like moss. Among the characteristics they share is a circle or u-shaped crown of ciliated tentacles called a lophophore. They feed by extending these tentacles into the water to catch bacteria, plankton and detritus. 
There are about 4,000 species of bryozoans and about 300 of them live off the California coast. Colonies can be a few inches to several feet wide. The largest ones can contain many millions of tiny, interconnected individuals called zooids, each a millimeter or less in size. 
The colonies also contain autozooids, which supply food to nonfeeding zooids and eliminate waste. Some colonies contain specialist autozooids that brood fertilized eggs or defend the colony. Although bryozoans are considered sessile animals, some can move (albeit very slowly) by using spiny defensive zooids as legs. Bryozoans are apparently quite tasty and nudibranchs, fish, sea urchins, crustaceans, sea spiders and sea stars dine on them.
The majority of bryozoan species belong to the order Cheilostomata, which has the largest variety of specialist zooids. Three of the bryozoans discussed here are members of Cheilostomata, which have mineralized exoskeletons. 
Most bryozoans are hermaphrodites. Colonies grow by asexual budding. But they can also reproduce sexually, with the majority of species brooding their eggs after fertilizing them with sperm captured by zooids. The larvae that hatch from the fertilized eggs swim for a while before settling on the substrate and morphing into a zooid that is the beginning of a new colony. 
Whether you see bryozoans in a positive or negative light depends upon the circumstances. If you own an ocean-going boat, you probably consider them a nuisance. The more than 125 species that grow on the bottoms of ships (as well as on pilings, piers and docks) affect the maneuverability and speed of their hosts and must be removed periodically. But if you are a scientist studying the large variety of chemical compounds some bryozoans produce in hopes they may prove beneficial to humans some day, you probably think of them in a positive way. 
The bryozoans chosen for this article are common off the West Coast and can be identified without lab work. Most do not have common names.
Diaperoforma californica: This is the only one in this article that is not a member of the order Cheilostomatida. The flat branches can be pale yellow or tan. The colonies can be two to three inches thick, more than 11 inches across and are home a variety of small invertebrates. D. californica is found from British Columbia to Baja.
Celleporella sp. This undescribed species resembles a stony coral. It can be four inches tall and is white or cream colored. Celleporella are common and prefer to live on rocks in areas with moderate to strong water motion.
Phidolopora pacifica (lacy bryozoan): This is a common, abundant bryozoan that prefers a rocky location. When I was a new diver we called it lace coral and it does, indeed, have a delicate, lacey look. It comes in shades of orange. The colonies can be eight inches in diameter and four inches tall. P. pacifica is found from very shallow intertidal waters to about 665 foot depths and from British Columbia to the Galapagos Islands.
Watersipora subtorquata: Two years ago off Santa Cruz Island I came across this bryozoan that has a bat star feeding on it. The bright color and size of the colony made it stand out underwater. It looked like the common bryozoan I now know to be Hippoporina insculpta only the latter is yellow, tan or pale orange and has more folds. The guidebooks say H. insculpta isn’t as fragile as Watersipora. There is an encrusting base that forms leaf-like folded sheets as it grows upward. Parts of this bryozoan are thought to die periodically, leaving gray patches that can be seen in the photo. Watersipora subtorquata is a worldwide species not native to California. It is becoming increasingly common not only in kelp forests but also in harbors and on wharf pilings. 
The author wishes to thank Genny and Shane Anderson for their assistance with this article. 
Bryozoan
Stats
Phylum: Bryozoa
Class: Gymnolaemata (Celleporella sp., Phidolopora pacifica, Watersipora subtorquata) Stenolaemata (Diaperoforma californica)
Order: Cheilostomatida (Celleporella sp., Phidolopora pacifica, Watersipora subtorquata) Cyclostomatida (Diaperoforma californica)
Family: Diastoporidae (Diaperoforma californica) Phidoloporidae (Celleporella sp.) Reteporidae (Phidolopora pacifica) Watersiporidae (Watersipora subtorquata
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