The
phylum Bryozoa is made up of more than 4000 species, all of which are
sedentary colonial animals. Individual animals are called zooids and are
no larger than 1mm. They secrete a protective shelter around themselves
called a zooecium. Specialized muscles are used to draw the zooid in and
out of its zooecium. The muscles function by increasing or decreasing
the amount of water pressure surrounding the animal. The zooid is equipped
with a crown of tentacles that surround the mouth and can be extended
through the opening of the zooecium. The tentacles are funnel-shaped and
ciliated. The cilia create currents in the water which draw food particles,
mainly single-celled plants and bacteria, into the funnel. In certain
species, the tentacles are used to transport the food particles to the
mouth. An individual zooid may lie within a zooecium that is a part of,
or fused with, the zooecium of adjacent colony members. The zooecium can
be chitinous, limey, rubbery, membranous or gelatinous. The colony form
may be bushy, creeping, encrusting, leafy, fleshy or branching and some
may reach a size of a few meters across. The sizeof the colony increases
asexually while new colonies are formed by sexual reproduction.
The
phylum Bryozoa is made up of more than 4000 species, all of which are
sedentary colonial animals. Individual animals are called zooids and are
no larger than 1mm. They secrete a protective shelter around themselves
called a zooecium. Specialized muscles are used to draw the zooid in and
out of its zooecium. The muscles function by increasing or decreasing
the amount of water pressure surrounding the animal. The zooid is equipped
with a crown of tentacles that surround the mouth and can be extended
through the opening of the zooecium. The tentacles are funnel-shaped and
ciliated. The cilia create currents in the water which draw food particles,
mainly single-celled plants and bacteria, into the funnel. In certain
species, the tentacles are used to transport the food particles to the
mouth. An individual zooid may lie within a zooecium that is a part of,
or fused with, the zooecium of adjacent colony members. The zooecium can
be chitinous, limey, rubbery, membranous or gelatinous. The colony form
may be bushy, creeping, encrusting, leafy, fleshy or branching and some
may reach a size of a few meters across. The sizeof the colony increases
asexually while new colonies are formed by sexual reproduction.