The
body plan of a sponge is simple: a single
outer layer of cells, the pinacoderm, separates the inner cellular
region known as the mesohyl from the outside. The pinacoderm lines
the internal canals and is eventually replaced by the choanoderm, a
layer of flagellated collar cells (choanocytes) grouped
in chambers. Choanocytes make up the principle ‘pump’ and’ filter’ of
the system, driving water, suspended bacteria and other particulate food through the sponge, which is
then digested.
The flow of water inside a sponge is one-way: the water is drawn
in through tiny pores (ostia) in the pinacoderm and exits through one
or more larger openings (osculae). The pumping system of a sponge
is usually supported by a combination of one or both of these skeletal
elements: mineral spicules (either calcareous or siliceous) and special
protein fibers (spongin). Adapted from the Tree of Life - Porifera
The Cretaceous sponges reported from New Jersey come from one of the following three families: |