Snails of a different coil

By Miriam Chacko
chacko.miriam@gmail.com

WHILE WALKING through the rainforest, the rustling sound of fallen leaves and the movement of the canopy above never fail to stir my attention. But it takes a keen eye and a seasoned guide to point out and explain the unique features of a species of plant or animal.

Snail Shells

The coiling direction of the shell influences the entire anatomy of the snail, dividing snails into dextral (clockwise) and sinistral (anti-clockwise) snails.

More than once, I have had the good fortune of trekking into Lambir National Park (LNP) with friends that are nature enthusiasts and knowledgeable of forest trivia. Stick insects, tarantulas, walking palm and giant ants in LNP are some of the things I had seen for the very first time. My most recent first sighting at LNP was that of a peculiar looking snail.

The snail was ordinary in size and pace but its shell was distinct. When I noticed the whirl on the shell was anti-clockwise, I realized that I had expected quite the opposite. In a dizzying moment, I wondered if only I was seeing it differently. But before I could put my foot in my mouth, Musa Musbah; the President of the Malaysian Nature Society confirmed that it was in fact a peculiar looking gastropod.

My knowledge of land snails before my interest piqued was that:
• they have a keen sense of smell but cannot hear,
• they are hermaphrodites,
• they are slimy and generally slow.

So first things first, I gathered as much literature as I could about the land snails of Borneo. Then I keyed in the unfamiliar scientific terminologies into Google and took note of all the different meanings. It must be obvious, by now that I am a student of the Arts.

In my efforts to unravel the truth about land snails, I have been convinced that their ways are sometimes stranger than fiction. For instance, despite being hermaphrodites, snails need another to mate and reproduce. And an interesting mating initiation rite is the piercing of a calcified love dart into the skin of the other snail. These love darts seem to stimulate the other snail into exchanging sachets of sperm. How bizarre! Then again, the more you get to know someone, the stranger they seem.

I also stumbled upon some interesting concepts of Science which when simplified are almost poetic. Chirality, for example, is when an object is not identical to its mirror image. The word chirality derives from the Greek word, cheir which means ‘hand’ and is a fitting example of chirality. A person’s hands are chiral in the same way sinistral (anti-clockwise) and dextral (clockwise) coiled shells are chiral. One cannot be mapped to the other by rotation.

Sinistral and dextral species coexist and are often found chilling on the same tree. But mating between the two can be difficult. The coiling direction of the shell influences the entire anatomy of the snail. The sinistral individuals carry their genital pore on the left-hand side of the head, whereas dextrals carry it on the right-hand side. This makes mating between sinistral and dextral species impossible in the case of globular shells and physically difficult but possible for snails with taller shells.

My search for sinistral species had me scanning through a glossary of long winded family names. Most of the names had a supercalifragilisticexpialidocious ring to it. One such family name was Camaenidae but it caught my attention because it includes the Amphidromus genus, which in turn includes the Amphidromus Martensi (A. Martensi) species. Now, A. Martensi is a chirally dimorphic species (having both sinistral and dextral species) and is endemic to Borneo.

Keeping in mind their bed troubles, sexual selection would have one type dominating the other, creating a common morph and a rarer morph within the same population. Therefore, the maintenance of both sinistral and dextral species on an even keel in natural populations of A. Martensi or even, Amphidromus Inversus intrigues evolutionary biologists. Without leaving much to conjecture, researchers study this paradox extensively, as it could provide unprecedented insight into evolution, in general.

Theories about external factors such as predation behavior and endogenous factors such as reproductive anatomy have been tested to explain stable dimorphism trends within the Amphidromus genus.

Another important area of study is land snail endemism. Such studies reveal the biogeographical uniqueness of the endemic habitat and the criticality of conserving such areas. Karsts (geological formations of limestone), usually riddled with caves and sinkholes, are considered hotspots for land snail endemism and speciation. Unfortunately, such regions are also likely targets for quarrying activities. And well, when commercial benefits can be had, the odds are rarely in favour of ecological endemism. But hope against hope, we shall.

Between love darts, coil morphism and endemism, there is a lot to know about land snails. Personally, I would not consider keeping one for a pet, nor would I, ever mange des escargots du beurre but studying them in their natural habitat would be time well spent in my books.


Miriam Chacko is essentially an environmentalist. After completing her postgraduate degree in Environment and International Development from the University of East Anglia, she got involved in projects promoting environmental awareness. Drawing on her experience, she has written articles on climate change and conservation.

A keen traveller, she has visited many countries in and around Asia and her love of the outdoors and interest in different cultures comes through in her writing.

Miriam has been writing for The Borneo Post SEEDS since 2013.

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