Porifera
Sponges are the most primitive of the multicellular invertebrates.
They lack a mouth and gut. The bodies are organized around a system of
water canals. Sponges feed, breath, reproduce, and excrete by means of
pumping water through their body. Their size is related to ocean current
velocity and other factors such as availability of space.. They have a
wide variety in coloration (red, orange, blue, yellow, purple, etc.) and
the spicules occur as many different shapes. Spicules are tiny,
hard particles often shaped like spikes and stars. These traits are
helpful in identifying the sponge species. The diagrams below show
some of the sponge's body plan., which resembles a hollow tube. The
opening at the top is called the osculum. Along the inside
of the sponge are collar cells, which beat like flagellate draw
water into the cavity and move water through the pores and canals.
Sponges of the family
Cladorhizidae are especially unusual in that they typically feed by capturing
and digesting whole animals. That's right, these sponges are actually carnivorous!
They capture small crustaceans with their spicules which act like Velcro
when they come in contact with the crustacean exoskeletons. Cells then
migrate around the helpless prey and digestion takes place outside the
shell.
FEEDING
Sponges are characterized by the possession of a feeding system unique
among animals. Poriferans don't have mouths; instead, they have tiny pores
in their outer walls through which water is drawn. Cells in the sponge
walls filter goodies from the water as the water is pumped through the
body and out other larger openings. The flow of water through the sponge
is unidirectional, driven by the beating of flagella which line the surface
of chambers connected by a series of canals. This type of feeding
is referred to as filter feeding. Sponge cells perform a variety
of bodily functions and appear to be more independent of each other than
are the cells of other animals.
Sponges in the Greek
and Roman times were used, when dried, to clean a person's body. Today
we still use products much like that. The sponges we use today are mostly
artificial. Some natural sponges for cleaning can still be found.
REPRODUCTION
Sponges reproduce by both asexual and sexual means. Most poriferans
that reproduce by sexual means are hermaphroditic, which means they
produce eggs and sperm at different times. Sperm are frequently "broadcast"
into the water column. That is, sperm are created, concentrated and sent
out the excurrent openings. These sperm are subsequently captured by female
sponges of the same species. Inside the female, the sperm are transported
to eggs by special cells called archaeocytes. Sponges that reproduce
asexually produce buds or, more often, gemmules, which are packets
of several cells of various types inside a protective covering. Fresh water
sponges of the Spongillidae often produce gemmules prior to winter. Over
the winter, the conditions often become harsh and the adult sponges don't
survive. The gemmules then develop into adult sponges beginning the
following spring.
Research is being
done on sponge's chemicals that keep bacteria from over-growing on them.
Scientists have found these chemicals are powerful antibiotics that may
help prevent or cure some diseases. Leukemia, arthritis, and strep throat
are among the diseases that the sponges' chemicals may help to cure. Scientists
hope that they will soon be ready for human use.
http://www.ucmp.berkeley.edu/porifera/porifera.html
http://www.oceanoasis.org/fieldguide/sponges.html
http://mareco.org/spongepage/calcarea.htm
http://www4.d25.k12.id.us/phs/biology/porifera.html