Bryosoans
203
5.7 Bryozoans
The bryozoans are a key component of the reef cryptofauna. They dwell in
sheltered habitats under stones, coral colonies, in trenches, in caves on the
steep cliffs of the fore-reef zone, in rubble and in dead corals on the bottom
of deep lagoons (Cuffey 1973). Bryozoans are colonial tentacular animals.
The skeleton of their colonies is formed by fine but firm branches consisting
of mycopolysaccharide polymer incrusted with carbonate material. The size
of their colonies is 2-lOcm, and that of the animal's zooids 0.1-0.3mm.
The form of their colonies varies from bushes, fans, mushroom and funnels
to crusts, fine moss-like coatings and nets (Cuffey 1977; Kubanin and
Murachveri 1980). When the animal's zooid is active, it displays its complex
filtering appatus - a halo of tentacles covered with ciliated epithelium. They
filter out detritus and phytoplankton. Some bryozoans catch small
zooplankton (Bugula). The bryozoans themselves are grazed by shrimps and
crabs, by some nudibranchs and some surgeon-fish (Soule and Soule 1976).
The total number of species of bryozoans inhabiting reefs exceeds 300.
Within a particular reef system it could be from 30 to 200 species: in the
Hawaiian reefs around 200 (Soule and Soule 1977), in the Red Sea more
than 80 (Dumont 1981), on the Bahamas 40 (Cuffey 1974, 1977). Most of
the reef bryozoans belong to the families Actidae and Reteporidae (order
Cyclostomata). They are the calcified bryozoans. Their colonies are
incrusted with calcium carbonate (Cuffey 1973). Predominating form of
their colonies are thin flat crusts. Some of them have bushy colonies with
firm thick branches (Cigliscula, Crisina, Retoporella, Neviakopora) or with a
fine branches (Scrupocellaria, Margaretta); mushroom-like colonies are
peculiar to Lichenopora. The most abundant bryozoan populations were
found in deeper poorly illuminated zones of outer and lagoonal reef slopes,
as well as in caves and in tunnels of outer slopes and in trenches and holes
within the patch reefs (Cuffey 1974, 1977; Logan 1984). There dominate the
incrusting forms of Cheilostomata: Celloporaria, Crassimarginata,
Parasmittina, Microporella, Schizoporella, Bugula, Canda, and Epistomia.
Their incrusting colonies cover the back surfaces of sponges, the walls of
holes, trenches and tunnels, and the foot parts of coral colonies. In deep
dark bottom biotopes the bryozoans overgrow the surfaces of molluscan
shells, dead corals, rubble, and the thalli of seaweeds. The most common
taxa in such biotopes are the cyclostomes Crisia, Idmonea, Nevianopora,
Lichenopora. They form mostly bush-like, moss-like or mushroom-like
colonies (Jackson 1984).
The bryozoans are important reef builders. On ancient reefs they were
sometimes the main agents of reef growth. The tripostome bryozoans, which
had massive branching colonies, were basic frameworkers in reef-like
biostrome constructions during the Early Paleozoic. During the Late
Paleozoic the same function of frameworkers and also the role of
203
5.7 Bryozoans
The bryozoans are a key component of the reef cryptofauna. They dwell in
sheltered habitats under stones, coral colonies, in trenches, in caves on the
steep cliffs of the fore-reef zone, in rubble and in dead corals on the bottom
of deep lagoons (Cuffey 1973). Bryozoans are colonial tentacular animals.
The skeleton of their colonies is formed by fine but firm branches consisting
of mycopolysaccharide polymer incrusted with carbonate material. The size
of their colonies is 2-lOcm, and that of the animal's zooids 0.1-0.3mm.
The form of their colonies varies from bushes, fans, mushroom and funnels
to crusts, fine moss-like coatings and nets (Cuffey 1977; Kubanin and
Murachveri 1980). When the animal's zooid is active, it displays its complex
filtering appatus - a halo of tentacles covered with ciliated epithelium. They
filter out detritus and phytoplankton. Some bryozoans catch small
zooplankton (Bugula). The bryozoans themselves are grazed by shrimps and
crabs, by some nudibranchs and some surgeon-fish (Soule and Soule 1976).
The total number of species of bryozoans inhabiting reefs exceeds 300.
Within a particular reef system it could be from 30 to 200 species: in the
Hawaiian reefs around 200 (Soule and Soule 1977), in the Red Sea more
than 80 (Dumont 1981), on the Bahamas 40 (Cuffey 1974, 1977). Most of
the reef bryozoans belong to the families Actidae and Reteporidae (order
Cyclostomata). They are the calcified bryozoans. Their colonies are
incrusted with calcium carbonate (Cuffey 1973). Predominating form of
their colonies are thin flat crusts. Some of them have bushy colonies with
firm thick branches (Cigliscula, Crisina, Retoporella, Neviakopora) or with a
fine branches (Scrupocellaria, Margaretta); mushroom-like colonies are
peculiar to Lichenopora. The most abundant bryozoan populations were
found in deeper poorly illuminated zones of outer and lagoonal reef slopes,
as well as in caves and in tunnels of outer slopes and in trenches and holes
within the patch reefs (Cuffey 1974, 1977; Logan 1984). There dominate the
incrusting forms of Cheilostomata: Celloporaria, Crassimarginata,
Parasmittina, Microporella, Schizoporella, Bugula, Canda, and Epistomia.
Their incrusting colonies cover the back surfaces of sponges, the walls of
holes, trenches and tunnels, and the foot parts of coral colonies. In deep
dark bottom biotopes the bryozoans overgrow the surfaces of molluscan
shells, dead corals, rubble, and the thalli of seaweeds. The most common
taxa in such biotopes are the cyclostomes Crisia, Idmonea, Nevianopora,
Lichenopora. They form mostly bush-like, moss-like or mushroom-like
colonies (Jackson 1984).
The bryozoans are important reef builders. On ancient reefs they were
sometimes the main agents of reef growth. The tripostome bryozoans, which
had massive branching colonies, were basic frameworkers in reef-like
biostrome constructions during the Early Paleozoic. During the Late
Paleozoic the same function of frameworkers and also the role of