Slug

 

Slug

                                    Dusky slug (Arion subfuscus)
                                        Image courtesy Wikimedia Commons

Slug is an unappealing word, whether as a noun or a verb. It has associations of heaviness and slowness.

Garden slugs are not very attractive. As much as I tell myself they’re just snails without external shells, I cannot persuade myself of their intrinsic value. They must have some worth, surely, and yes! they are detritivores. Who wouldn’t want to claim that name for themselves? They are the refuse collectors of the natural world, as well as tasty morsels for some animals.

They generally come in quite muted shades, though yellow and bright orange are not uncommon. However, compared to sea slugs, they are very modestly dressed. They are not closely related to sea slugs, though both are molluscs.

There are more than three thousand known species of sea slugs or nudibranchs, many of them brightly coloured. Some of them take the stinging cells from prey such as jellyfish, reusing them for their own protection. Others take in the poisons from sea anemones and sponges, which are then exuded as defensive slime. They are not a threat to humans but could cause skin irritation if handled.

Some are so small as to be almost unnoticeable, only able to be studied under magnification, while the largest can measure about fifty centimetres. They can be found in all the oceans of the world, in shallow waters and the deeps.

Nudibranchs are common in UK rockpools, easily noticeable at low tide. They range in size from less than one or two centimetres (Diaphorodoris alba, which can be found in poor light) to twelve centimetres, (Doris pseudoargus, Sea lemon)

                                Rainbow sea slug (Babakina anadoni)

Image courtesy Wikimedia Commons

A rainbow sea slug (Babakina anadoni) was discovered recently in a rockpool in Devon. They are usually found in the warm Mediterranean waters around Portugal, Spain, and France. At less than two centimetres, this tiny animal was a happy find for a volunteer with the Rock Pool Project.