November 2019

Slug or snail?

What is this mollusc? It was found in an area of regenerating bushland on the north side of Brisbane.


Fine-speckled Semi-slug, Stanisicarion virens. Photo courtesy of Brendan McIntyre. Iridescent Semi-slug, Ubiquitarion iridis. Photo by Jeff Wright. Transmission of Rat Lungworms between hosts.

This mollusc is a Semi-slug, which is a type of pulmonate gastropod (air-breathing snail equipped with a lung). Semi-slugs make up part of the Family Helicarionidae, and all members have thin, glassy shells. Semi-slugs differ from their more traditional snail relatives by having a much smaller, ear-shaped shell that is too small to completely cover the body. While they might appear to be an intermediate form between snails and slugs, semi-slugs are not closely related to any of the families of true slugs. There is a large diversity of semi-slug species in eastern Australia, and this can make identification difficult. Nine new species of semi-slug from eastern Queensland were named this year, so there’s obviously much more to discover about these amazing molluscs! Fortunately, we were able to access the Snail Whisperer, Dr John Stanisic for an identification. John thinks that this specimen is a Fine-speckled Semi-slug (Stanisicarion virens).

Although they look cute and can sometimes be found in home gardens, Semi-slugs are not suitable for keeping as pets. This is because they can act as intermediate hosts for the two species of Rat Lungworm (Angiostrongylus cantonensis and A. mackerrasae) that occur in eastern Australia. Ingestion of the larval stages of these worms by a human can result in severe neurological symptoms and, in some cases, death.

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