Welsh Ghost Slug (Selenochlamys ysbryda)

Selenochlamys ysbryda Rowson & Symondson, 2008
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Welsh Ghost Slug (Selenochlamys ysbryda).
Photo: National Museum Wales (Source). ( Enlarge).		  
   

Radula and single radula tooth of Selenochlamys ysbryda.
EM picture: National Museum Wales (Source). ( Enlarge).		  
 
Systematics of Selenochlamys ysbryda
(Simplified!)
Order Stylommatophora
Suborder Helicina
Infraorder Limacoidei
Family Trigonochlamydidae
Selenochlamys ysbryda Rowson & Symondson, 2008

Source: MolluscaBase eds. (2025). Trigonochlamydidae Hesse, 1882.
The subterraneous lifestyle of predatory gastropods hunting earthworms underground made numerous adaptations necessary during their evolution. So, for example, the Daudebardias (Daudebardiinae) have their shell strongly reduced for the advantage of greater agility. This, however, came at the cost of their not being able anymore to withdraw into their shell. This tendency is even further progressed in the so-called rucksack snails (Testacellidae): Their shell is only a small mussel-shaped rest lest on the tail end of their back. It reminds of the shape of a, however noticeably larger, abalone (Haliotidae), an unusually shaped kind of marine gastropod. When they hunt underground, those semi-slugs withdraw their vulnerable tentacles inside the head, since they would not be able to see anything anyway.

Only in 2006, in Wales a snail species was discovered, which had eluded detection due to its subterraneous life, and which received the unusual scientific name Selenochlamys ysbryda Rowson & Symondson, 2008. The species name ysbryda is derived from the Welsh word ysbryd for a ghost and aptly so, since the slug is of a whitish and rather translucent colour, giving it a noticeably ghostly appearance.

The shell reduction in this Ghost Snail is progressed further than in semi-slugs: Selenochlamys is a shell-less snail or slug without any trace of an external shell. Contrary to other slugs native to Europe, the Ghost Slug has its breathing hole (pneumostome) located at the end of the foot, similar to rucksack snails. Additionally, the Ghost Slug's eyes, hardly beneficial underground, are reduced. Like other subterraneous snail species, such as the Blind Snail (Ceciliodes acicula), Selenochlamys does have four tentacles, but no eyes.

Similar to other predatory snail groups (e.g. Testacellids, Daudebardias or the Dalmatian Predator Snail (Poiretia cornea), see Nutrition of Gastropods Part II), the radula teeth of Selenochlamys ysbryda are equally adapted to their method of obtaining food: Radula teeth shaped like daggers make it easy for the snail to catch and keep hold of earth worms, to stop them from escaping and to pull them into the mouth. In Ghost Snails, as in Daudebardias, one may assume that the worm is swallowed whole.

The first specimen of Selenochlamys ysbryda was fittingly found in a churchyard in Brecon, Wales. Further specimens then were found in other locations throughout Wales. From there the Ghost Slug is extending its distribution area and it could even potentially become an agrarian pest due to it exterminating the earthworms, which on the other hand are necessary for maintaining and fertilizing ground matter (Sally Williams: Worm-eating 'ghost' slug is advancing across Wales. Wales Online (2012), accessed 13.09.2022).

Unexpectedly, it is assumed today that Selenochlamys ysbryda is, in fact, a neozoon - an introduced species, which might have come to Great Britain in potted plants. ( Finding Site in Wales - New window!). The nearest relatives of this slug species from the Trigonochlamydidae family are found in Turkey and in Georgia (Selenochlamys pallida). Specimens of Selenochlamys, which had been found on the Krim peninsula in Ukraine in 2012 and 2015, could be distinguished anatomically from Selenochlamys pallida, hence have been determined as Selenochlamys ysbryda and thus it is assumed that the species originated from the Krim peninsula.

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Latest Change: 25.10.2026 (Robert Nordsieck).