T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Snail (Common Garden) Cornu aspersum

Kingdom:   Animalia
Phylum:     Mollusca
Class:        Gastropoda
(unranked):        clade Heterobranchia
clade Euthyneura
clade Panpulmonata
clade Eupulmonata
clade Stylommatophora
informal group Sigmurethra
Superfamily:       Helicoidea
Family:      Helicidae
Genus:      Cornu
Species:     C. aspersum
Binomial name: Cornu aspersum
Synonym: Helix aspersa 
Common name: Brown Garden Snail

Cornu aspersum is an invasive alien snail with shells up to 32 mm in diameter and is originally from Europe and is, widespread in New Zealand.  Active at night or during wet weather it is  Slow moving, using a slime trail. It has a well developed sense of smell and /taste.
Each mature snail will mate several times in a single season and egg laying starts 3–6 days after first mating, but can occur within hours of subsequent matings. Cornu aspersum deposit their eggs into pockets in moist soil. These pockets are usually excavated by the snails themselves through movement of the head and anterior foot, though occasionally natural cavities will be used.  After oviposition the nests are covered with soil and abandoned. The number of eggs in each clutch varies from 10 to 170.  The incubation period of the eggs  vary according to the relative humidity of the incubation environment.. The average is 13 to 19 days. The young hatchling snails remain in the nest for 1–16 days . During this time, cannibalism on sib eggs can occur.
There is concern of this snails effect indigenous biodiversity through selective feeding on foliage of herbaceous plants and the seedlings of a range of species, Cornu aspersum represents a significant threat to natural processes of  vegetation regeneration.  Many of the introduced terrestrial molluscs brought with them to New Zealand a range of parasites, including mites, ciliate protozoa, microsporidia, and nematodes.. With increasing contact between the alien and indigenous species, there is potential for transmission of these parasites and pathogens to our indigenous fauna. This transmission has already occurred in the case of the parasitic mite Riccardoella limacum in urban areas and in Egmont National Park .Cantareus aspersus provides a reservoir of Riccardoella that is likely to infest sympatric indigenous species Cornu aspersum snails can live live for 2-3 years.

Cornu aspersum snail on patrol 



A juvenile snail 5mm shell.


A young juvenile.

 

Cornu aspersum is a hermaphrodite, meaning it has male and female reproductive organs. It needs a partner to create juveniles. The snails 'hook up' on the right sides of their heads, this can last for up to 12 hours. They inject each other with spermatozoa and both will become impregnated.
Once they are fertilized, they lay up to 100 tiny little eggs, each containing little snails. These are usually buried in soil, but if it is too wet, these can be attached to the side of a plant. These small eat their eggs to gain the calcium needed to harden their shell. A snail can reproduce about once a month.  

Below is a diagrammatic transverse view of the buccal cavity of a snail showing the radula and how it is used. The rest of the body of the snail is shown in green. The food is shown in blue. Muscles that control the radula are shown in brown. The surface of the radula ribbon, with numerous teeth, is shown as a zig-zag line.

The snails rows of chitinous, recurved teeth leave a distinctive zigzag pattern in their feeding trails as seen in photos below.
 

A close up of the freeding trail patterns.