Sponges
Sponges are the simplest form of multi-cellular animals. A sponge is a
bottom-dwelling creature which attaches itself to something solid in a
place where it can find enough food to grow. The scientific name for
sponges is "Porifera," which translates into "pore-bearing."
A sponge exists by pumping water through its body. A sponge is covered
with tiny pores which lead internally to a system of canals and eventually out to one or more larger
holes. These canals exist to move water through the sponge's body. Lining these canals are special
collar cells. The collar cells force water through the sponge which brings oxygen and nutrients
while removing carbon dioxide and waste. The collar cells are how sponges feed. The water brings
with it bacteria and other organisms which the cells capture and filter out.
How Do Sponges Reproduce?
Most sponges are both male and female. During mating, one sponge plays the male role while the
other plays the female role, even though both are capable of playing either role. A sponge may play
a female role one time and a male role the next time. Sperm is released by the "male" sponge and
enters the "female" sponge. After internal fertilization, larvae is released. After floating around for
a few days, they settle down and start growing.
The Two Types of Sponges
There are many different types of beautiful and colorful sponges. The two basic types of sponges
are: encrusting or free-standing. However, these are not part of the true classification of sponges (it
just makes it easier for us to categorize them).
Encrusting sponges are similar to moss because they tend to cover the surfaces of rocks.
Free-standing sponges have lots of inner volume compared with their surface area. Sometimes,
they grow into strange shapes and gigantic sizes.
Because of their strange and large shapes, free standing sponges are best known to people. The
barrel sponge, a tropical sponge, can grow large enough to fit a person inside of it. Tube sponges
are well known for very varied coloration.
Sponge
Sponges are very slow-moving animals that are found across the sea floor. Although many sponges actually
move less than a millimetre a day, some adult sponges are actually sessile, which means that they are fixed onto
something and do not move at all.
Sponges are thought to have evolved around 500 million years ago, and today there are more than 5,000 known
species of sponge with another 5,000 species thought to have not yet been discovered. Most sponges live in a
salt water environment, attached to objects on the sea floor. Less than 200 sponge species inhabit freshwater
habitats.
The body of the sponge is made up of a jelly-like substance that is supported by a thin layer of cells on either
side. The body of the sponge contain thousands of pores which allow water to keep flowing through it.
Sponges have no organs, and obtain their nutrition from the water that is continuously flowing through them.
Sponges can be found in variety of different sizes and shapes tubes, fans, cups, cones and blobs.
Sponges are omnivorous animals that obtain their nutrition from the food particles in the water. Sponges
primarily eat bacteria, phytoplankton and bits out of the water. A number of sponge species are known to have a
more carnivorous diet, eating small fish and crustaceans on the reefs.
Due to the abundance and variety of sponges, they are preyed upon by many animals. The fact that sponges
move so slowly, if at all, means that they cannot avoid being eaten. Sea turtles, crustaceans, fish and
echinoderms all prey on sponges.
Sponges are hermaphrodites, which means that they have both male and female reproductive organs.
Fertilisation occurs inside many sponges, and sometimes externally when sperm are released into the water. The
tiny sponge larvae are able to move through the water and eventually settle on the sea floor as they get bigger,
and begin to move very little. Sponges can also regenerate. Pieces of a sponge that are broken off will
eventually grow into full adults if given enough time. Gemmules are also used for dispersing sponges
themselves. Gemmules are aggregates of several types of cells that are surrounded by a protective coating in
sponges .