25 September 2008

Is it a slug? Is it a ghost? It's Selenochlamys ysbryda

B. ROWSON & W. 0. C. SYMONDSON (2008). Selenochlamys ysbryda sp. nov. from Wales, UK: a Testacella-like slug new to western Europe (Stylommatophora: Trigonochlamydidae) Journal of Conchology, 39, 537-552

Back in July, the discovery of a bizarre carnivorous slug in Wales was in the news. The formal description of Selenochlamys ysbryda got published in the June issue of the Journal of Conchology that I received a couple of days ago and read this morning.

Selenochlamys ysbryda. Picture from National Museum Wales.

Selenochlamys ysbryda is a long (up to 110 mm) and narrow (up to 10 mm wide) colorless to milk white slug with a tiny (~2 mm long) internal vestigial shell near its rear end. It has a "very small" mantle covering its rear end. What about its lung?
Pulmonary cavity sunken below mantle, its volume difficult to establish, and without obvious venation.
How on earth does it absorb the oxygen from the air it breathes? Perhaps, oxygen just diffuses in thru the walls of the organs and the heart, which is described as "large", and carbon dioxide diffuses out.

Like its shell, the eyes of S. ysbryda are also small and vestigial. And the slug is nocturnal. Captive individuals of S. ysbryda were apparently eating live earthworms, although the authors never actually saw a slug in the process of doing so. However, they note that "earthworms regularly disappeared from the containers, and faeces appeared every 2-6 days...They contained numerous sigmoid earthworm chaetae."

Selenochlamys ysbryda going after earthworms. The red arrow (my addition) points at the vestigial shell. Fig. 7 from Rowson & Symondson.

The species name ysbryda means "a ghost or spirit" in Welsh. This is how the authors explain the name:
The name alludes to the species' ghostly appearance, nocturnal, predatory behaviour and the element of mystery surrounding its origin.
The provenance of the slug is indeed a mystery. Its type location is given as an "urban domestic garden" in Cardiff, Wales in the United Kingdom. However, the genus Selenochlamys have previously been known only from a few museum specimens coming from the western Caucasus of Georgia, southern Russia and the adjacent parts of Turkey. The authors speculate that in the wild S. ysbryda may live deep in the soil. This implies that the slugs may have been dispersed by humans in soil and plants.

No comments: