Suffolk Wildlife Trust: Sponge uses its loaf and lives deeper in the sea than plants

The breadcrumb sponge. Picture: SWT/R Spray

The breadcrumb sponge. Picture: SWT/R Spray

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Continuing series on species found in Suffolk and around its coasts, in association with Seasearch. This week, the breadcrumb sponge (Halichondria panacea).

We tend to associate sponges with more tropical waters but they do appear in UK seas. This is one of the most commonly seen sponges around the UK.

The name comes from its crumbly consistency, and some say it often looks like a loaf which has been left out in the rain!

If you find any on the beach they will still be spongy and full of small holes, if not quite bathroom ready. It can grow in a variety of shapes – thin crust, cushion or lobed forms. Sponges are filter feeders. Water passes through their bodies; in through their many, many small holes and out through the fewer larger ones.

Sponges are some of the very simplest animals. So simple that you might not have realised that they were animals at all.

While they don’t have the complicated bits we do – arms, eyes, ears or even internal organs – they do have to eat just like us. They definitely aren’t plants as they don’t use light to make their own food by photosynthesis. That’s an important distinction and it’s because of this that sea sponges can live much deeper than marine plants – the seaweeds – down beyond where light can penetrate.

Light fades as you go deeper and much of the seabed is covered with stationary animals rather than plants. In the shallows this sponge often takes on-board a population of algae – they are just stowaways – which mean that this normally beige to yellow sponge can appear quite green.

Although sponges seem soft, shapeless and springy they do actually have skeletons – they’re just not jointed like ours. Breadcrumb sponge, like many others, has a scattering of microscopic glassy bones (called spicules) which help hold its shape and make it hard and unappetising to eat! The shapes of these spicules can be extremely ornate and beautiful, although the breadcrumb sponge’s are simple curved needles.

For more information about Suffolk Wildlife Trust call 01473 890089 or visit www.suffolkwildlifetrust.org

The volunteer diving organisation Seasearch is run by the Marine Conservation Society and supported by The Wildlife Trusts. For details visit www.seasearch.co.uk