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Sponges, or poriferans,
are animals of the phylum Porifera. They are sessile, mostly marine,
waterdwelling filter feeders, pumping water through their matrix
and filtering out particulates of food matter. Sponges are among
the simplest of animals, with partially differentiated tissues
but without muscles, nerves, and internal organs. In some ways
they are closer to being a cell colony than multicellular organisms.
There are over 15000 modern species of sponges known, and more
are being discovered every day. The fossil record of sponges dates
back to the precambrian era. The structure of a sponge is simple:
it is shaped like a tube, with the end stuck to a rock or other
object. The open end is called the osculum, and the interior is
the spongocoel. The walls are perforated with microscopic pores
that allow water to flow through the spongocoel.
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Although animals,
sponges may also be considered multi-cellular colonies. A sponge
can be placed in a blender and the remaining living cells will
reform themselves into another sponge. If multiple sponges are
blended together, each species will recombine independently. It
is thought that the earliest animal life on Earth resembled sponges.
The earliest known multicelled animal fossils are sponges from
China that are roughly 600,000,000 years old. Sponges have not
been as extensively studied as some other phyla and there may
be some surprises still to be found. For example, it has recently
been shown that some sponges are not sessile and can move to more
favorable locations as rapidly as few cm a day. Another sponge,
the Venus Flower Basket has some newly discovered uses involving
fiber optics.
Above Images Come From The NOAA
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