Garden snail

Cornu Aspersum, otherwise known as the garden snail, is likely the most widely known species of all terrestrial mollusks. It is in the family Helicidae which includes many of the most common land snails. It used to be under the classification Helix Aspersa, however the newer classification groups it into the genus Cornu.

It is widely regarded as a garden pest due to the accidental introduction of the organism into many areas, however in some parts of the world it is also desired as a food item.

A common garden snail crawling on vegetation

Taxonomy

Kingdom: Animalia

Phylum: Mollusca

Class: Gastropoda

Order: Stylommatophora

Family: Helicidae

Genus: Cornu

Species: Cornu aspersum

Description

Adults have a thin but hard calcareous shell that can be 1-1.5 inches in diameter and 1-1.375 inches high [1]. Their shells vary in color and shade but are typically a reticulated pattern of dark brown, brownish-golden, or chestnut with yellow stripes, flecks, or streaks. The body of the garden snail is soft, slimy, and brownish-gray in color. Its soft body is able to be fully retracted into its shell which it does whenever it is resting or feels threatened. Another mechanism the garden snail uses when threatened, injured, or irritated is a defensive froth of mucus that might repel some enemies or overwhelm aggressive small ants and other insects [4].

Picture showing the appearance and differences among Garden Snail shells

Unlike other species within the class Gastropoda, garden snails do not have a operculum which is a type of seal certain mollusks use in order to keep in moisture and for defense against small predators. Instead, during dry or cold weather garden snails seal the aperture of the shell with a thin membrane of dried mucus, called an epiphragm.

Life Cycle and Reproduction

Members of Cornu aspersum are [hermaphrodites], meaning they produce both male and female gametes [2]. Because of this reproduction is usually sexual, however self-fertilization can sometimes occur. Mating sessions often taken several hours in which sperm is shared between each snail; garden snails are also one of the species that use "Love Darts" in mating.

Two weeks after fertilization, garden snails lay around 80 spherical white eggs into small spaces in topsoil or even in spaces under rocks. Within the span of a year a garden snail can lay around six batches of eggs, with the eggs being about 4mm in diameter. Upon hatching young garden snails take one to two years to reach maturity and begin the reproductive cycle all over.

This picture depicts the spherical white Garden Snail eggs shown in the spaces in the topsoil in order to protect eggs from outside harm

Habitat

Cornu aspersum is native to the Mediterranean region and its present range stretches from northwest Africa and Iberia, eastwards to Asia Minor and Egypt and northwards to the British Isles. However there is an increasing non-native distribution to other regions of the world including Australia, North America, Costa Rica, and South America [3]. Due to their deliberate or accidental introduction into various regions it is now cosmopolitan in temperate zones, and has become naturalized in regions with climates that differ from the Mediterranean climate in which it evolved.

Human Importance

The common garden snail is a species most notably known to humans as an agriculture and garden pest, an edible delicacy, and also occasionally a household pet. When it comes to being used as a food source garden snails are used as the main ingredient when making escargot which is most commonly known for being a special French cuisine enjoyed worldwide. In attempts to reduce damage to crops and other plants, pesticides and other control options such as caffeine and copper are used in order to prevent garden snails from reaching foliage and fruit to consume. Even other species of snail such as the decollate snail are used as predators to prevent garden snails from infesting areas. Additionally, garden snails are used for their secretions as many of the compounds and chemicals are used in gels and moisturizers for human skin care [5].

References

[1] Garden Snail (cornu aspersum) n.d. iNaturalist. https://www.inaturalist.org/taxa/480298-Cornu-aspersum#Description

[2] Brown garden snail - cornu asperum (Müller). https://entnemdept.ufl.edu/creatures/misc/gastro/brown_garden_snail.htm

[3] CABI, 2015. Cornu aspersum (common garden snail). https://www.cabi.org/isc/datasheet/26821

[4] Ansart, A.; Vernon, P.; Daguzan, J. (2002). "Elements of cold hardiness in a littoral population of the land snail Cornu aspersum (Gastropoda: Pulmonata)". Journal of Comparative Physiology B. 172 (7): 619–625.

[5] Liu, Lucy; Sood, Anshum; Steinweg, Stephanie (2017). "Snails and Skin Care—An Uncovered Combination". JAMA Dermatol. 153 (7): 650. doi:10.1001/jamadermatol.2017.1383. PMID 28700796.

[6] Welter-Schultes, F. "Genus taxon summary for Cornu. version 12-01-2014". AnimalBase.