The many, and unexpected, uses of mucus for a snail
by Paul Cormacain
DRAGGING itself over the ground was a huge, slow moving slug, some 15 cms long. Slugs do not corn much bigger in this country!
Details were taken, and afterwards the books came out at home to help with identification. Having come across these creatures before, I remembered something funny about the name.
This large slug was brick-red in colour, and officially it is called the great black slug. Perhaps we should use the scientific name, Arion ater, as that would certainly make more sense. A red slug called black, indeed.
The books do concede that the great black slug comes in a variety of colours. It is more likely to be completely black in the north of its range, but I have seen black ones here in the past.
The creature is quite common in Scotland, except in the north, and frequents Ireland, Wales and England. It lives in west Europe from the Mediterranean north to the north of Denmark, and is quite common. Further north in the Scandinavian countries it becomes rarer.
In Sweden the black slug is liable to be black, in France or Spain the Arion ater could be red. But it could be also grey. In the Netherlands it could be orange.
The Arion ater we saw was in the open, and slowly crawling along. It must have been so obvious to a passing bird! Slugs come with a layer of sticky mucus over their bodies, and it is believed this can help when hungry birds come along. The mucus makes it hard for the bird to grip the insect.
The large slug represented such a large meal for a bird, I do not believe that the mucus would be much of a deterrent. So I interfered with Nature. I lifted the slug and placed it in some bushes where it would be much safer, and might live a bit longer.
When the creature was lifted, it went into a defensive mode. This would be the usual defence against birds, where the slug would contract into a semicircular lump. The compressed skin would present a much harder surface than when the insect is crawling along.
I don't know whether this persuades the birds to move along and leave the slug alone, or not. As far as I am concerned, the life of Arion ater was saved, by me.
We have a dozen types of slug here, with another few turning up infrequently. Across the water there are nearly twice as many varieties, and of course, if you head over to Europe there are many, many more.
I mentioned the mucus earlier, and how it is seen as a bird deterrent. As slugs have no shells they could have a problem of drying out. So the mucus also acts to prevent this happening.
If the Arion ater is moving over sharp objects, again the mucus helps by protecting the body, and makes movement easier. It acts as a lubricant. The mucus is also sticky, so it helps the creatures to move up steep slopes
Mucus has such a versatile facility, perhaps humans should have it!
Coming Events
Monday 27 October- Lisburn RSPB and visitors will hear about Archaeology of the Birds of Ireland, at 7.30 in Friends School. Details from 9260 1864
Thursday 30 October - Birdwatch Morning at Castle Espie, more from 9187 4146
Friday 31 October - Wildlife and spooky stickers at CastleEspie, details from 9187 4146
Saturday 1 November - Many different birds will have returned to Lough Neagh from the north. Why not go see them, 10am to 12am? Contact Oxford Island on 3832 2205
Sunday 2 November - Gorse Grappling, the Wildlife Trust calls it, and the Trust is looking for help in clearing Inishargy Bog, why not call Malachy Martin on 4483 0282.
Ulster Star
24/10/2003
