Snails as … pollinators (!?)

Always on the look-out for interesting and/or quirky plant stories, I was really pleased to have chanced upon this delightful item amongst one of the many sources I scour continually on your behalf to unearth such phyto-relevant material. And, believing it to be an up-to-date item – since it was brought to my notice on what I assumed to be an immediate, hot-off-the-press, instant-gratification news site – I duly started to pen this piece. It wasn’t anything that sensational, but it was an interesting addition to the seemingly ever-growing catalogue of animals that assist the pollination efforts of angiosperms. It was the straightforward account concerning the conclusive demonstration of malacophily (pollination by snails), which hitherto had apparently been a rare and obscure phenomenon, by Khoisnam Sarma et al.

They demonstrate that the Graceful Awlsnail, Lamellaxis gracile, pollinates Volvulopsis nummularium (in the Convolvulaceae, the sweet potato/morning glory family). Interestingly, they report that the flower is also pollinated by Asian honey bees (Apis cerana indica), which poses the obvious question: If it’s bee-pollinated, why bother with snails? To which the non-obvious answer is that the plant flowers for only half a day, when it might be raining. The advantage of dual pollinators is that the snails are able to mediate this important process on rainy days when the bees are not active, and vice versa. Continuity of pollination regardless of the weather, that’s a smart move on the plant’s part. So, although this report isn’t a world first for malacophily (the paper cites other works listing seven species in which this interaction occurs), it is a nice tale of ‘smart plants’. And it’s nice to show a good side to snails, many of which multitudinous, marauding molluscs seem to exist only to consume plants for their own selfish, life-sustaining purposes.

Furthermore, since I was unaware of the role of snails as pollinators, I thought it would be nice to share (which is not to imply that I’m assuming the same shameful level of ignorance amongst my readers!). But, given current – and future – concerns about decline in bee populations and pollination of crops,* maybe this research – and publicising thereof here – will inspire others to determine if there are additional/alternative pollinators to ensure continuity of food supply (and a degree of food security) for those of us dependent upon such food sources. And, after all, “A diverse … pollinator community is needed to maintain stable and high quality crop yields”.

But, have you spotted the ‘problem’ yet? The original item is dated 2007(!), which goes to show that you can’t assume that everything supplied nowadays on electronic ever-so-fast media is necessarily bang up-to-date(!)

Still, this cautionary tale is an excuse to share with you another pollen-related item that is much more timely. Regarding biotic agents of pollination, entomophily – pollination by insects – is probably the most important, and butterflies (psychophily) and bees (melittophily or hymenopterophily) are probably the most common exponents of this phenomenon. But, is one group of insects better – more efficient as a pollinator – than the other? Yes, according to Beyte Barrios et al. whose study can be neatly summarised by the paper’s title thus, “Butterflies visit more frequently, but bees are better pollinators: the importance of mouthpart dimensions in effective pollen removal and deposition”. So, now you know the ‘buzz’ about bees, butterflies, and … awlsnails** (whether graceful or otherwise).

* For a listing of crops pollinated by bees, go to Wikipedia.

** This is not a typographic error for all snails. As far as we know all snails don’t participate in pollination. Rather, the word is specific to a group of snails, and is presumably an allusion to the pointed shells looking like the tips of awls, tools for piercing small holes in materials such as wood or leather.

[Ed. – if you are now eager to engage in pollination biology research, or would like your students to do so, then this course manual on experimental biology by T. Miller and A. Winn of Florida State University (USA)’s Department of Biological Science could be just what the doctor ordered]

Reference List

Khoisnam Sharma, Rajesh Tandon, KR Shivanna, Mohan HY Ram, 2007. 'Snail-pollination in Volvulopsis nummularium', Current Science 93, pp. 826–831

Beyte Barrios, Sean R. Pena, Andrea Salas, Suzanne Koptur, 2016, 'Butterflies visit more frequently, but bees are better pollinators: the importance of mouthpart dimensions in effective pollen removal and deposition', AoB Plants, vol. 8, p. plw001