Priority Marine Features (PMFs) are species and habitats that we consider to be conservation priorities in Scottish waters. Our coasts and seas are home to around 8,000 animal and plant species. The PMF list is used to help target future marine conservation work in Scotland.

In the second of a series of posts focusing on PMFs, Lisa Kamphausen from our marine team explains her attraction to sponges, which are an important component of several habitats on the list, such as Deep-sea sponge communities.

Yellow sponge with brittlestars, anemones and hydroids (c) Ben James/SNH

If you separate the cells of a sponge, by squeezing it through a sieve for example, the cells live on. What’s more, if you mix up the cells of a red and a yellow sponge and leave them, they will un-mix and re-assemble into a new red sponge and a new yellow sponge.

Black brittlestars with orange sponges and sea squirts, © Ben James/SNH

Fascinating – but you may ask why on Earth would you do such a thing in the first place? You’ll be glad to hear that this wasn’t just a random discovery by a marine biologist with time on their hands; there was good reason for putting the sponges through this process and it relates to immunology.

Close-up of the large sponge Suberites ficus, © Ben James/ SNH

This classic experiment was first carried out over a hundred years ago and it shows that sponge cells are able to discriminate between ‘self’ and ‘non-self’ cells, through some basic immune functions. This is seen in the way the cells reorganised into their original groups, rejecting the ‘non-self’ cells.

A rugose squat lobster with a boring yellow sponge on a flame shell bed (boring as in it bores tiny holes in shells), © Marine Scotland

You can see individual sponge cells re-form into a new sponge in this short clip narrated by David Attenborough. The clip is taken from the BBC’s First Life documentary: it’s thought that the way the sponge cells regroup and reform may provide an insight into the origins of life on Earth.

The immune system of sponges may be basic but it is highly effective. Sponges are never seen covered in other organisms, as are many other marine creatures, because they produce substances which deter other organisms and prevent them from being smothered. Some of these substances are of great interest to medical scientists: they could potentially be used in cancer treatment drugs for instance.

Reef community of dead man’s fingers, Haliclona viscosa sponge, anemones and hydroids, © SNH/Ben James

Many different species of sponge can be found in Scotland’s seas and they are important components of several types of seabed communities. For example, they provide shelter for a wide range of other animals and elevated perches for filter feeders, such as brittlestars. They also help to filter water, a vital process for maintaining clean and healthy seas.

Goblet sponge, © SNH/Ben James

The UK’s largest known grouping of sponges was discovered at the end of 2014, near the extinct underwater volcano Rosemary Bank, reminding us of the treasures that still await discovery in our seas.

Sponges are some of the oldest organisms on Earth, so whatever their immune system is doing, it is clearly working extremely well; otherwise they would have died out.

You can find more information about Scotland’s Priority Marine Features on our website.