Snail taxonomy: when genitals matter

The ‘Australian Outback’ – for most of us this is a synonym for the red, hot, dry endlessness covering most of inland Australia. Who would associate this landscape with snails? And yet, land snails have managed to conquer large expanses of this semi-arid environment.

In order to survive in this harsh environment, offering months of heat and drought with only the occasional downpour, moisture-dependent land snails had to come up with several adaptations.

For one, land snail species living in the dry interior are spending most of their lives doing nothing. They survive long phases of otherwise inhospitable conditions by aestivating deep in the ground and resurface only during very infrequent days or weeks of rain, when they feed and reproduce hastily before the drought hits again.

Having a shell that enables snails to hide under rocks and in crevices and escape the eyes of predators is also an important adaptation to survive in the semi-desert. As a result, land snails have often evolved very similar looking shells. This similarity makes it difficult to tell species and even genera apart from each other.

To discriminate snails from each other we resort to other anatomical features: copulatory organs being the most informative ones. These organs are not constrained by environmental selection and are believed to play a role in kin recognition. Thus, they have evolved freely into many different shapes and forms.

When we routinely examined the genital anatomy of two ‘brown jobs’ (a term we use to describe pretty average looking snails) from Kimberley in Western Australia, we found that their genital anatomy differed dramatically from any known land snail in Australia. The only conclusion for us was that these species are not only new to science, but each represented a new genus of land snail. Genetic studies have subsequently confirmed our findings. With Cardiotrachia and Rachita we have named the 130th and 131th genus of the Australian land snail family Camaenidae.

The taxonomic distinctiveness of these two snails is rooted in their long history of evolutionary separation. Based on what little we know about their evolution, these rather inconspicuous animals have survived for millions of years in one of the most isolated and inhospitable places of the continent. Let’s make sure they also survive the environmental change ahead of them, caused by us humans.

Francesco Criscione
Post-Doctoral Researcher 

Frank Köhler
Research Scientist

More information:
Criscione, F. & Köhler, F. (2014) Cardiotrachia and Rachita – two new land snail genera from the East Kimberley, Western Australia (Eupulmonata: Camaenidae). Systematics and Biodiversity. Online First.