Maine Nature News

Archive for March, 2010

The “frost is coming out of the ground.”

This is a vole tunnel revealed when the snow melted.

Since time began I called those things clams; you know, the critters that crawl around on the bottom of the local swimming hole and the kids with masks and snorkels and swim fins would bring the mollusc up for an ID.  ‘That’s a clam,’ I’d say, ‘Nice one.’  The bad thing is it was really a mussel.  What’s the difference between a clam and a mussel?  Everyone in the Quoddy region knows the clam is a steamer, and has two fused siphons in its mantle and you peel the skin off these (the neck) before eating. With mussels you don’t have to do this.  Mussels also have byssal threads for attachment, and clams don’t.  Freshwater mussels have byssal threads as juveniles, but not as adults.

Watching a mussel is not very exciting but there are lots of mysteries and clever goings on in that little bivalve.  For example, how did they get here?  Towards the end of the last ice age, about 18,000 years ago, there was a mile or so of ice here, and no freshwater mussels. Sea level was several hundred feet lower than at present, but there were, however, mussels living in the exposed land that is now Grand Bank, Georges Bank, and the Middle Atlantic coastal plain and in the Midwest around southern Illinois and Indiana. Mussels had already developed means for long distance travel when conditions arose as the glaciers retreated.  When male and female mussels spawn the eggs are held by the female and develop into larvae called glochidia. The female waits until an opportune time to release the larvae in the presence of migratory fish.  The glochidia attach to the gills of the unsuspecting fish for a free ride to wherever, and colonize new territory.  Mussels may parasitize several types of fish (or even amphibians) for this endeavor, but usually have a preferred host. Maine, with only 10 species of mussels, was not heavily colonized, but New York, closer to the Midwest hub of mussel diversity, has about 50 species.

Once mussels set up shop in an area, they are preyed upon by almost everything, including birds, fish, otters, raccoons and especially muskrats. It is unusual for a rodent to have such a tendency to be a carnivore, but unfortunately for the mussels. Native Americans ate freshwater mussels, especially in the Midwest.  Shell middens on the Tennessee River accumulated over thousands of years and covered acres of land to a depth of over a hundred feet.  Freshwater mussels were eaten by Maine Indians but not to a great extent.  In my early years, working at a farm in Massachusetts in the Connecticut valley, some of my fellow workers were migrants from Haiti, and would eat the mussels from the contaminated river.  I tried, but their immune system was much better than mine, and a case of vomiting and diarrhea kept me home for a couple of days.

In the early 1800’s, freshwater mussel shells were first used commercially to make buttons, and as our population grew more and more buttons were required.  This industry peaked in the early 1900’s, when over 5.5 billion buttons were made annually, worth over $12,500,000. Freshwater mussels in New England tend to have thinner shells and are not good for buttons, so this industry was centered in the Midwest.  With the advent of plastics about 1920 the mussel shell button industry declined, but about that time it was discovered in Asia that a small piece of grit could be inserted beneath the mantle of a marine oyster and the oyster would secrete nacreous material over this irritation and produce a pearl.  It was also discovered that the best material for this piece of grit was a bead of freshwater mussel shell, and the best mussel shell came from our Midwest.  This industry peaked about 1988 when about 25,000 tons of mussel shells were exported, and as recently as 10 years ago prime mussel shells from the Midwest were fetching as much as $7 per pound.

So that’s a bit about our freshwater mussels, but much, much more can be found in the “Freshwater Mussels of Maine” from the Maine DIFW.  But do we have any freshwater clams in Maine?  Sure do, but that’s another story.  In the meantime, notice the flocks of robins, grackles, blackbirds and the Mourning cloaks and Commas and listen for the frogs.

Storm worn. It was a hard winter for this skiff.

Well, I would like to say that I saw our first woodchuck today. It was on the I95 in West Gardiner. Actually 2 about a mile apart, but one was casualty of being run over. DH

I noticed that one of my bird feeders–a clear plastic tube–was empty and flying around and inside it were what I think of as honeybees! I watched them come and go for about an hour. These bees were about an inch in length and had a brown/orange patch of color on the end of their bodies. Isn’t it early for them to be out and were they looking for a place to
settle? They are not around now. JB

Two butterflies today!  One was a orange and black, about the size of a nickle. The second was approximately 1″ wide with its wings spread, also orange and black. TF

This morning, the Solar and Heliospheric Observatory recorded a halo CME emerging from the vicinity of sunspot 1054: (movie at link). The cloud appears to be heading toward Earth and it could spark geomagnetic storms when it arrives on or about March 17th. High-latitude sky watchers should be alert for auroras. RE

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