7th February 2015 (weekly review)

It’s been a snowy, icy, wet, muddy week and these are not ideal conditions for seeking snails. Or even to encourage me to find snails.

Nevertheless, despite the less-than-desirable weather, I struck out on my quest and found two new species for my total, bringing me up to 14 species. A passable amount so early in the year, I hope. My new species were:

Trucatellina cylindrica, The Cylindrical Whorl Snail

My first species of the week was Trucatellina cylindrica, a species I was so excited about that I wrote a blog post specifically devoted to it. I’ll try not to repeat myself too much.

Truncatellina cylindrica Grahame Madge1

With a maximum width of 0.9 mm and maximum height of 2mm, this is the smallest snail I have found so far this year. It is also the rarest, with it only being known to survive at three sites in Britain. It was formerly much more widespread, with archaeological records from Cambridgeshire, Northumberland, Kent, Herefordshire and Northamptonshire being easily found on a quick google search.

Truncatellina cylindrica Grahame Madge12

Clearly, this species was once more widespread, but how does a species this small ever distribute itself anyway? Does it rely on unbroken habitats and thousands of years to spread? Perhaps not. This paper makes the claim that small snails – including Truncatellina species – could be distributed between neighbouring islands by wind.

Cochlodina laminata, The Plaited Door Snail

The door snails are one of my favourite groups – possibly because they deviate so much from the ‘typical’ form that most people associate snails with. The door snails get their name from the fact that they have an internal structure that they can move to close the mouth of the shell – like a door. This is presumably used to deter the attention of predators, but I wonder if it also serves a purpose in retaining moisture during periods of dryness. This internal structure is called a ‘clausilium’ and from this comes the name for the door snail family: Clausiliidae, of which there are eight species in the UK. Cochlodina laminata is probably the second most common species in Britain – but relatively uncommon and localised in Ireland –  and can be found amongst leaf litter and around fallen logs; it occasionally climbs up trees in damp weather. It can grow to a hearty 17mm long.

Cochlondina laminata

Juvenile shells are very glossy and translucent and can look like a different species to a fully mature individual, which are opaque and often have worn or bleached areas to the shell.

Cochlondina laminata juv

Note: The clausilium is not to be confused with an operculum which, whilst possibly serving the same sorts of purposes, is a completely separately evolved feature. Only two terrestrial snails in the UK possess opercula – Pomatias elegans and Acicula fusca.

I’ll be travelling a bit next week. This could either make snail-hunting difficult, or expose me to different species in a different area. We’ll see!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s