Do you have a sponge in your bathroom? When I was young, practically every family had a bath sponge. These days shower mops made of netting are all the rage and the bath sponge has perhaps had its heyday. Which is no bad thing, considering that sponges are animals.
At one time sponges were thought to be plants. That isn’t so surprising really given that they look more like plants than animals. Of all animal life, sponges are the simplest. However they are unusual in that, whilst most animals move through their habitat, sponges are immobile. They are attached to solid surfaces and they feed by setting up currents of water from which they filter out particles of food. So, rather than moving through their environment, they make their environment move through them.
Sponges have no nerve cells and very few muscle cells – in fact their bodies are very different to that of other animals. But they do have skeletons. The skeleton is made of a network of fibres, called spicules, which are made of silicon dioxide, calcium carbonate or spongin. There are four classes of sponge and these are classified according to the type of spicules a sponge has.
Some sponges are carnivorous, but not much is known about these types given that they live in very deep waters, over 5 miles down.
Calcareous sponges have skeletons made from calcium carbonate. These sponges are usually small and quite dull to look at.
Glass sponges have skeletons made from silicon dioxide. These are much bigger than the calcareous variety with widths of over 1m and reaching heights of 1m. They are pretty to look at, rather like lace, but their skeletons are very delicate and often collapse when they are dredged up to the surface.
Demosponges are the biggest and most colourful of sponge life. They also make up 90% of all sponge species and include the recognisable bath sponge. They can be over 1m in both height and breadth and if clumped together, create a beautiful coloured underwater garden that can rival corals for their stunning hues.
Deep ocean life is fascinating and there’s bound to be so much more we have yet to discover. Find out more about invertebrates in our other blogs about these creatures.