Decollate Snail

The decollate snail is native to North Africa and the Mediterranean Region. It was inadvertently introduced into Southern California. They are thought to have spread from this point into more states overtime. Since it was introduced yet doesn't seem to be causing harm, it does not appear to be considered invasive in the United States at this time. Decollate snails can be spread readily in container plants and soil that are moved through human means. They are a carnivorous snail, mainly consuming animal matter. But are overall omnivorous in their feeding habits [3].

Taxonomy

Kingdom	Animalia
Phylum	Mollusca (mollusks)
Class	Gastropoda (gastropods)
Order	Stylommatophora (Air breathing snails + slugs)
Family	Subulinidae (Small, tropical snails)
Species	Rumina decollata

Land Snail Overview

All continents have land snails, they are especially prevalent everywhere in Eastern North America, where there are more than 500 native species. They live mostly in leaf litter of forests, old fields, and wetlands. They can also be found in more disturbed habitats such as active gardens and fields, river banks, suburbs, and even cities. The term ‘land snails’ includes snails and slugs, which have no obvious shell, they're shell is actually inside them. Most land snails feed upon a wide variety of organic material. But it is mainly consistent of green or dead herbaceous plants, rotting wood and fungi, bark and algae. They also consume empty snail shells, sap, animal scats and carcasses, and even rasp on limestone rock or cement [4].The radula (like in many mollusks,) has a rasping tongue as a mandible, they can use to ‘rasp’. It is full of horny teeth made of chitin and is used for scraping off particles of food from underneath [6]. Carnivorous snail species attack nematodes and other snails. Carnivorous snails are where the decollate snail lands on the feeding scale. Predators of land snails include invertebrates such as parasitic mites, nematodes, flies, beetle larvae, adult beetles, millipedes, and other snails like the decollate. Some other larger predators include salamanders, turtles, shrews, mice and other small mammals. Even birds, especially those who are ground-foragers. Both shelled snails and slugs can generally be categorized as decomposers. [4]

Identification

To identify a decollate snail, their spiraling shell is pinkish brown, elongated irregularly unlike most other land snails. It is tapered toward the end. Young snails can have a more pale-colored lighter brown shell. The shell can grow up to 1-3/5 inches (40 mm) long and 5/8 inch (14 mm) in diameter. When the shell grows, the tip of the shell breaks off and older whirls of the shell are dropped. Only four to seven whirls are retained in older snails, as the rest are discarded. Younger snails may retain up to 10 whirls of the shell, as they have not dropped those whorls yet. Their antennae, head, and foot are blackish to dark olive-gray. The decollate snail eggs are pale white in color, and are buried in the topsoil. They can be found in clusters or singularly [3]. To further identify them, we can look at the order they are classified in, Stylommatophora. Stylommatophora includes air-breathing land snails and slugs. Snails in Stylommatophora have lost their gills, and have an air-breathing organ with a lung on its roof. The two things that all Stylommatophora share are a long pedal gland placed beneath a membrane and retractile tentacles. Their eyes can also be found on the tips of two long tentacles, in this case, the decollate snails eye stalks. [7]

Habitat and Distribution

Decollate snails are native to North Africa and the Mediterranean Region. They were introduced into Southern California in the 1960s. They now occupy irrigated sites in Central and Southern California. They are considered introduced and not invasive, because they are non-native but do not seem to be causing harm. Because this snail is a burrowing species and the eggs and snails occur in topsoil, the snail can be spread easily by humans in plants and soil that are moved, leading to them being found in more states than California [3]. Currently, they are introduced in the United States, Bermuda and Mexico. It is widespread, but localized, in the Sun Belt from California east to Florida and north along the Atlantic coast to Pennsylvania [5]. As for their native habitats, In Europe they live in dry and open habitats, and prefer shady habitats in Portugal, between plants and under stones, or buried in the soil. They dislike sandy and loamy soils. In North Africa snails can be found up to 10 cm deep inside the soil, under stones, yet rarely in root systems of shrubs [1].

References

1] AnimalBase :: Rumina decollata species homepage. (2013). . http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/home/species?id=1293.

2] Cadmium in soils and groundwater: A review - PMC. (2020). . https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7147761/.

3] Decollate Snail / UC Statewide IPM Program (UC IPM). (n.d.). . https://ipm.ucanr.edu/natural-enemies/decollate-snail/.

4] Mollusks : Carnegie Museum of Natural History. (2005). . https://www.carnegiemnh.org/science/mollusks/landsnailecology.html.

5] snail eating snails. (n.d.). . https://entnemdept.ufl.edu/creatures/misc/gastro/snail_eating_snails.htm.

6] Snails. Germanfactsheet.pdf. (n.d) https://agresearch.montana.edu/wtarc/producerinfo/entomology-insect-ecology/EasternHeathSnail/GermanFactSheet.pdf

7] Classification. (n.d.). . http://bioweb.uwlax.edu/bio210/f2012/ravenscr_patr/classification.htm.