Bath sponge

The bath sponge is one of the simplest animals in the whole sea. It has no brain, no heart, and no bones — not even a face! It looks like a soft, lumpy blob resting on the rocky seabed of the warm Mediterranean Sea. If you gave it a gentle squeeze underwater, it would feel springy and full of tiny holes.

So how does such a simple animal live? A sponge is a champion filter-feeder. Its whole body is covered in little holes, and it pulls seawater in through them all day long. As the water flows through, the sponge catches tiny specks of food and bits of floating bacteria, then pushes the clean water back out. It never has to chase a meal.

Bath sponges live stuck to rocks and the seabed, from shallow sunny spots down to water deeper than a swimming pool is long. They stay in one place their whole lives, gently swaying as the currents wash past. Grown-ups can be as big as a football, growing in rounded, lumpy shapes with a rust-coloured surprise hidden inside.

People have loved natural sponges for a very long time. Long ago in ancient Greece, and then all across Europe, people used soft bath sponges for washing themselves and cleaning their homes. That is exactly how the bath sponge got its name. The very same kind of sponge has been helping people stay clean for thousands of years.

Sponges are among the oldest and simplest animals on Earth, and they are surprisingly tough. If a sponge breaks into pieces, the pieces can often grow into brand-new sponges. People can use this ability to grow sponge fragments on underwater farms, a method that may reduce some harvesting pressure on wild sponges. Protecting healthy sponge grounds still matters, especially as warming water and disease can cause local die-offs.