Two Things You Never Knew About Molluscs
As the fall colours were fading in 2009, the Friends of Gatineau Park held their Annual General Meeting at the Visitor Centre in Old Chelsea.
One of the speakers that day was Dr. André Martel of the Canadian Museum of Nature, who has led several projects on the freshwater mussels in Gatineau Park during the past five years.
Dr. Martel’s is a malacologist, that is a scientist who studies molluscs.
Public talks about molluscs may not strike you as huge crowd pleasers but that only goes to prove Dr. Martel’s skill and enthusiasm because the fact is that he fascinated the audience for more than an hour.
His talk included information on endangered species, invaders like zebra mussels, and the high level of diversity among bivalve varieties in our region.
But since I can’t make such subjects seem as interesting as he can I’ll just report what he had to say about the reproductive or sex life of our native freshwater mussels, sometimes called ‘native clams’.
I bet you never even knew clams had a sex life.
Of course they do; otherwise where do you think all the little baby clams would come from.
In fact it’s not the sex life but the baby clams that are at the heart of the story because Dr. Martel explained the secret of how clams that obviously can’t swim are able to convince their offspring to make their way upstream.
If these molluscs never made it upstream over rapids and past rocky streambeds then they’d never have colonized inland lakes; but they have.
According to Dr. Martel the way that a native clam which can’t swim arranges for its children to get the benefits of swimming is to have them hitch a ride.
Fish swim and so baby clams hitch rides on passing fish.
In this case the word hitch is literal because the baby clams actually clamp their tiny shells onto the ends of the fish’s fins or gills and in some cases are equipped with tiny hooks to get a better grip.
The trick of course is for the mamma clam to get the fish to stop long enough to play school bus.
Like all good mothers some species of clams have their tricks. The most sophisticated trick, seen in clams called ‘’lampmussels’’ (genus Lampsilis), is to pretend she’s a minnow so a hungry fish will come and try to eat what is in effect a fishing lure; only to get hooked—not by an angler—but by a few microscopic clam babies who hang on for a few weeks or months and thus find their ways far and wide.
Other mother clams use other fishing techniques such as hanging their children out on long lines to snag a passing ride.
I want to thank Dr. Martel both for his fascinating talk and also for the use of his slides for this little video.
