Atlas of Common Fouling Bryozoans

Fouling bryozoans are those species found on ships' hulls, piers, pilings, buoys, and other artificial structures (including the panels so popular with marine ecologists).   Many of these species are eurytopic, tolerant of changes in temperature and salinity, and found in fouling communities in many harbors and estuaries around the world.  Others are only known from one or a few studies or geographic regions.

Some fouling species are cryptogenic -- meaning we don't know what their original distributions may have been.   Others are clearly not native to the area in which they are now found, but are  invaders, exotic or non-indigenous species.  The goal of these pages is to describe and illustrate as many of these species as possible for the benefit of those who are working on surveys of coastal marine habitats and assessments of potential marine invaders in those habitats.  

Characters used in identification

Colony Form

In terms of how they occupy space on a fouling panel or natural surface bryozoans can be encrusting, branching, or runner-like.  Encrusting forms vary from tiny dot or spot colonies, large flat sheets or multilayered mounds.   Branching colonies may be flexible or rigid, with branches varying from a single zooid (individual) wide fronds.   Runner-like colonies have zooids arrayed singly or in groups along an encrusting stolon, but masses of stolons and zooids may be so dense that they form a mossy mat on the substratum surface.   For this reason although colony form is useful in identifying species, bryozoan taxonomists rely more heavily on the characteristics of individual zooids.  

Runners

Encrusters

Dots

Sheets

Mounds

Erect branching

Bushes

Trees

Broad branching

Zooid Form

In general terms zooids are either tubular or box-like and calcified (walls reinforced with calcium carbonate) or uncalcified 

Zooids of ctenostome bryozoans can be tubular or box-like, but are uncalcified (outer layer is chitinized to a greater or lesser degree). 

Zooids of cheilostome bryozoans are boxes  with a trap-door like operculum in the frontal wall, have at least the side walls of the box calcified and often elaborate patterns of calcification, ranging from nodulles, granules, pores, ridges, ribs, and spines.  Cyclostome bryozoans are curved, calcified tubes.   Bryozoan morphology is described in more detail in Taxonomy and Morphology.   Other characters useful in identification include presence and nature of heterozooids, brood chambers, ovicells, avicularia, and vibracula, early growth pattern and ancestrula (first zooid produced by metamorphosis of settled larva, often different from later zooids of colony in size and shape.  In studies of the early stages of fouling, sometimes it may be the only zooid present on a panel)

Atlas of Common fouling Bryozoans

The following are the most common fouling genera.  In some genera many species occur, and the problem of identification is confounded by the fact that they are not yet all described and named.  This especially true for fouling communities in tropical regions.  However, other genera have only one or a few species represented in fouling communities.  

Ctenostomes

Walls not calcified, Zooids tubular to box or sac-like,  No operculum, ovicells, or avicularia.

Bowerbankia

Colony made of branching stolons, along which the ovoid zooids are clustered.  Zooids bud off stolons, but arise separately from it. Dense mats of stolons may develop in some species,  others may develop free branches.  Polypides with 8 or 10 equal, evenly arrayed tentacles.

Zoobotryon

Colony composed of Small tubular zooids arrayed along a thick, gelatinous, trifurcately branching stolon.  May form very large colonies.  Polypides with 8 tentacles

Victorella 

Colony made up of chains tubular zooids with stolon-like basal portions.  At first glance look like Bowerbankia, but close examination shows that "stolon" is not separated from rest of zooid by a diaphragm as in Bowerbankia or Zoobotryon.  Also forms dense mats, and, in these conditions, zooids may bud secondary zooids, forming tall clusters.  Polypide with 8 tentacles, two of them bent away from each other giving the lophophore a bilateral symmetry.  May occur in very low salinities.

Alcyonidium

Amathia

Anguinella

Cheilostomes

Aetea

Scruparia

Electra

Membranipora

Conopeum

Callopora

Tegella

Bugula

Scrupocellaria

Celleporina

Hippothoa

Schizoporella

Cryptosula

Watersipora

Hippoporina

Celleporaria

Parasmittina

Savignyella

Rhynchozoon

Synnotum

Vittaticella

Thalamoporella

Cyclostomes

Crisia

Disporella

Lichenopora

Tubulipora