Last Friday I gave you this rather interesting looking object to identify, preferably using a rhyme:
Believe it or not the photographs show either side of the same object – on one side it just looks like a rugose lump and on the other it shows a rather nice natural spiral.
Aside from some great humorous comments by 4utu and Henrik Nielsen, there were some of you who worked out that this is the operculum from a marine snail and even managed to explain that in rhyme – so very well done to Barbara, Chris and especially Lee Post who upped the ante by writing a full verse:
oh purr Q lum from foreign shores
possibly from a near ites door
side door -back door does not exist
main door -strong door , built to resist
Flick Baker went a step further (taxonomically) by identifying that this operculum is from a snail in the genus Turbo with the rhyme: “Gives your engine serious puff, even when she’s running rough“.
More specifically, this operculum is from the South African Turban Shell Turbo sarmaticus Linnaeus, 1758.
The operculum is a part of many snails that is often forgotten about – it forms a protective trapdoor that the snail closes behind itself when it retreats inside its shell (‘operculum’ means ‘cover’ or ‘lid’ in Latin). This trapdoor helps prevent desiccation in land snails and helps protect against predators in marine snails.
When the animal dies the operculum will often fall off as the body of the animal decays or is eaten, so often it won’t find its way into a museum collection with the rest of the shell. However, opercula can be quite distinctive and are sometimes more useful for identifying a species than the rest of the shell – a handy point to remember.
Since the two sides are so very different (rugose and spiralled), which is outside and which is inside when the door is closed?
The rugose side is on the outside. Presumably additional armour to defend against some pretty determined predators.