Garden Snail Parade

Since I started this blog, I have been surprised by the diversity of land snails about in the city. As I have managed to get most of them on white background, I decided to write a post and display them all together.

Moss snail, Lauria cylindracea, a tiny, easily overlooked species which gives birth to live offspring. 

Garden Snails, Helix aspersa (=Cantareus aspersus), unashamedly mate in the middle of your garden  path throwing darts at each other. 

Girdled Snails, Hygromia cinctella, like walls. An introduced species since 1950, still expanding across Europe from the Mediterranean.

Kentish snail, Monacha cantiana prefers drier places. This species, introduced in the UK during Roman times, is a very common snail in my local Wildlife Garden. They can be darker with pale speckling.

Glass Snails, Oxychilus draparnaudi, are carnivorous snails that have caused havoc on native snails when introduced outside the UK.

Amber Snails, Succinea putris usually live in very damp places, but can be also found away from water. They cannot completely retract their bodies inside their shells.

Brown Lipped Snails, Cepaea nemoralis are very polymorphic in colour and pattern.You might be lucky to have these beauties in the garden.  

Have you noticed all the snails are facing to the right? This is because most (90%) of all snail species have right-handed shells (dextral). Occasionally a left-handed individuals appear in populations of right handed snails. These face a problem when trying to mate, as the genital opening will face away from most other snails in the population. The genetics of shell handedness has been elucidated in some species and appears to be determined by mutations in a single gene, but the left-handedness trait is expressed not in the mutant, but in the resulting offspring.

More information

Visit the Molluscs posts in Bugblog.

Terrestrial Mollusc Tool. A wonderful resource for US molluscs. Contains also lots of info on introduced European slugs and snails.

A blue glass snail

When lifting a pot to plant out today, I found this Glass Snail. There are four British species, and I think this is Oxychilus draparnaudi, given its relatively large size (a mighty 15 mm). Glass snails are named after their shiny, fragile and translucent shells when alive. After weathering the shells rapidly lose their lustre. Oxychilus shells are rather flat, which makes it easier for them to hide under pots or stones.

Given their small size - and their association with pots, nurseries and greenhouses - it is not surprising that several European Glass Snail species have been inadvertently introduced in temperate or subtropical regions around the world, including New Zealand, Australia and the U.S. and Canada. What perhaps is unexpected is that many Glass Snails, including O. draparnaudi are predators and their diet include other snails and slugs and their eggs, in addition to worms, and dead insects. They have even been reported to eat Garden Snails. When predating on snails, they attack the snail's body first with their radula and when they cannot access more flesh from the outside, they drill a hole on the shell to finish off their meal. The introduced populations, however, can be a threat for the native snail fauna and reductions or losses of local snail populations have been reported in areas with these predatory snails when compared with patches where they were absent in the U.S and New Zealand.

References
Barker, G.M. (2004). Natural enemies of terrestrial molluscs. CABI. DOI: 10.1079/9780851993195.0279. Here.
Karin Mahlfeld, Karin. Impact of introduced gastropods on molluscan communities, northern North Island. here.

The log pile revisited

We made a couple of log piles in the garden last year. Today I dismantled one of them to check what was in it. This was a very 'untidy', and relatively dry log pile, with the logs having been covered on branches from pruning bushes around the garden and the location being under a large Philadelphus bush. The first finding was that a lovely crumbly pile of compost had accumulated around the logs. There was a lot of bug activity in the pile. The most abundant form of -visible- life were woodlice, especially the common rough woodlouse, Porcellio scaber, which made the compost move as they were so many, also some smooth woodlouse, Oniscus asellus and common striped woodlice Philoscia muscorum. I found three species of snails: many common garden snails, Helix aspersa (=Cornu aspersum) most of them hibernating; a yellow banded snail Cepaea (one of 5 specimens we released in the garden a couple of years ago), and several Glass Snails Oxychilus draparnaldi (photo above). Several yellow slugs Limax flavus crawled around. There were quite a few spiders, amongst then a very large Tegenaria and possibly an Amaurobius, which rapidly disappeared amongst the logs. I also found some Blunt-tailed Snake Millipede (Cylindroiulus punctatus), which coiled into a spiral when disturbed. I saw some new springtails, but I couldn't get a decent photo. As for insects, a Harlequin seemed to be hibernating on a log. By far the most shocking thing was a couple of enormous earthworms, Lumbricus terrestris, which I found while they abandoned the log pile - possibly feeling the disturbance - by creeping on the ground. One of them was so large that at first I thought it was a snake! Big fun examining this log pile, I am sure I forgot to mention some bugs. I didn't even go through the whole of it but it yielded quite a number of interesting finds.

A banded snail, some woodlice and an earthworm

Garden Snails

Three species of woodlouse can be seen in the image

A specimen of the millipede Cilindroiulus punctatus

The largest earthworm I've seen in my garden, creeping on the ground

The same earthworm being held, just for scale

A yellow slug, Limax flavus