Selenochlamys ysbryda (Ghost Slug)

Selenochlamys ysbryda (Ghost Slug)

A ghost slug (Selenochlamys ysbryda), is a predatory air-breathing land slug. It is a shell-less pulmonate gastropod mollusc in the Trigonochlamydidae family.

The species was first recognized from various sites in Wales and was formally described and named in 2008 by Ben Rowson, a taxonomist at the National Museum of Wales (Amgueddfa Cymru) and Bill Symondson, an ecologist at Cardiff University.

Subsequently, it has appeared at numerous other sites in South Wales and a few in England, but it is assumed to have been introduced in the United Kingdom, mostly in gardens.

Scientific classification

Kingdom:Animalia
Phylum:Mollusca
Class:Gastropoda
Superfamily:Parmacelloidea
Family:Trigonochlamydidae
Subfamily:Trigonochlamydinae
Genus:Selenochlamys
Species:S. ysbryda

Specimens likely to be this species have now also been identified from two sites in Crimea’s natural mountain forest, indicating that the Crimean mountains are within its native range.

The strange Ghost Slug (Selenochlamys ysbryda) made headlines in 2008 when it was described as a new species from the Cardiff Garden. Very little was known about this animal when the first specimens were found.

Since then, the story has linked our collections and specialized expertise to prominent members of the British public, taxonomists in Europe, recording networks, and the media to show how a picture is emerging.

The bloodthirsty Ghost Slug (Selenochlamys ysbryda) of Cardiff, which preys on earthworms in flower pots, has been named one of the world’s “top 10” newly discovered species.

The Arizona State University’s International Institute for Species Exploration, gave the killer slug a place in The State of Observed Species, its annual report.

The report highlights thousands of new plants, animals and other specimens officially designated as new species in 2008.

The ghost slug was named Selenochlamys ysbryda (partly the Welsh word for ghost, ysbryd) and is thought to be the first beast to have Welsh in its scientific name.

Experts called it the Ghost Slug of Cardiff, even though the first one was spotted in Caerphilly on October 29, 2006.

A year later, another slug was discovered by a gardener in Cardiff who alerted the National Museum of Wales. Biology experts at the Museum and the University of Cardiff officially designated a new species last year.

The slug lies in flower beds waiting to suck unsuspecting “like spaghetti” worms.

With bladed teeth, they can eat earthworms, and biologists are now trying to find out how “alien” species have invaded Welsh gardens.

Ben Rowson, a biologist at the Cardiff National Museum, said, “Selenochlamys ysbryda seemed appropriate for this nocturnal hunter and indicated where it was first found.”

Bill Symondson, an ecologist at Cardiff University, said: “The lack of eyes and body-colour could indicate the species that have evolved in the cave system.

Entomologist Quentin Wheeler, director of the International Institute for Species Exploration at Arizona State University, said: “Most people do not realize just how incomplete our knowledge of the Earth’s species is, or the steady pace at which taxonomists are exploring that diversity.”

He added: “The tracing of the species of the world and their unique attributes are essential parts of the understanding of the history of life.”

Species

Selenochlamys ysbryda (Ghost Slug)

Emphasizing its spooky nature, we have given the species the scientific name Selenochlamys ysbryda, based on the Welsh word ysbryd, meaning ghost or spirit. The common name of “Ghost Slug (Selenochlamys ysbryda)” soon became well known.

Adding it with the obscure genus Selenochlamys was a specialized task and required the dissection of several specimens, including our holotype. (Incidentally, Selenochlamys already combines Greek words with Selene, the goddess of the moon, but “Moon-Cloaked Ghost Slug” sounded a little too melodramatic.)

In many respects, The Ghost Slug (Selenochlamys ysbryda) is very strange. It is extremely elusive, living in the soil up to a meter deep, visiting the surface rarely. In large numbers, it seldom occurs.

This makes it a typical difficult slug to look for, particularly in the gardens of other people or other places that can not be excavated.

It’s very distinctive, too. After examining one, most agree that it will be unmistakable in the future (haunting, perhaps?).

The slug is ghostly white, almost eyeless. It kills and eats earthworms whose burrows it may enter with its extremely extensible body.

This differs from most other slugs in the fact that they have a breathing hole right at the tail, and that they retract like the finger of a glove, appearing to suck their own head inside out.

Unlike some British slugs, a good photograph can be identified with certainty. The pictures here show some similar species that are often confused with it.

This combination of elusiveness and distinctiveness makes the species perfect for a public recording project.

Scientists need to know more, not just out of curiosity, but because the species could pose a threat to the populations of earthworms. It appears to have been introduced from abroad, i.e. to be alien or non-native species, the spread of which may be of concern.

We would like to thank the then Countryside Council for Wales (now part of Natural Resources Wales) for funding early survey work and dissemination of information in 2009 and others who have spread the word.

Contributions by the public

Responses from more than 300 people across the UK (and a few from overseas) have been received and responded to since 2008.

A large proportion of these They were mistaken identifications, but many were correct, and now more than 25 Ghost Slug (Selenochlamys ysbryda) populations are known. These verified records were submitted to the National Biodiversity Network through the Conchological Society of Great Britain and Ireland. 

The Ghost Slug (Selenochlamys ysbryda) can be found in two sites in Bristol and in south-east Wales in all the main valleys and in the cities of Newport and Cardiff.

However, it remains rare or absent in some nearby areas (such as Swansea) and does not occur in any way throughout the region. Virtually all records come from gardens, settlements, or nearby roads and riversides in populated areas.

This is also true of the unexpected outlier reported in May 2013 from Wallingford, Oxfordshire, which may indicate an eastward spread. The species is evidently well established in Britain and has survived the unusually cold, dry, or wet winters of the last five years.

Contributions by specialists

This species has been scattered around Britain for at least ten years but has not yet been seen elsewhere in Western Europe. The first records are from Brecon Cathedral in 2004 (in the 2009 paper by German taxonomists) and from Caerphilly in 2006 (in the pet invertebrates forum).

It was expected to originate in the Caucasus Mountains of Georgia and Russia, or in northern Turkey, where other Selenochlams were present. However, a 2012 paper by a taxonomist based in Ukraine described a museum specimen of S. Ysbryda was found in 1989 in Crimea.

Which can be expected – Crimea has a number of endemic molluscs, and several alien species in Britain were originally described in the region. The United Kingdom also has a history of conflict and trade with Crimea (there is even Sebastopol near the slug population in Cwmbran!), making a direct, accidental introduction plausible.

DNA was sequenced from six specimens of Ghost Slug, Cardiff, Newport, Bristol, and Talgarth as part of our recent British Slug studies. The sequences were all but similar, supporting the theory that the species is not native to the United Kingdom.

If you are going to report a sighting, please make sure your slug is a true Ghost Slug (Selenochlamys ysbryda). You can verify this this by looking at the mantle and the eyes.

The mantle looks like a layer of skin through which the breathing hole is often evident. This Ghost Slug (Selenochlamys ysbryda) has a tiny, disk-shaped mantle on the back of his body.

There are no eyespots on its tentacles. Other white or pale slug species have a huge, cloak-like mantle over their shoulders near the front of their bodies. They have black eyespots on the tips of two of their tentacles. 

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