By Fred Gralenski
I like water. Not because I’m especially clean, but where there is water there is usually a good supply of critters for me to marvel at. Now where I live I have a good opportunity to study that big piece of water that stretches over to the old world, but that puddle is overwhelming. For one thing it keeps moving up and down. I know the basics of why it does this, but not the particulars, and I know a little of some of the critters, but WOW! The concept of the whole system and the interactions of the plants and animals are just so mind boggling that one must take leave of the ocean periodically and watch something simpler, like freshwater pools. I think it was with this in mind that soon after we moved to Pembroke we built a few small puddles on our property. I mean what could be simpler than watching a hole fill up with water? HAH! After 15 years I’m still confused. Why did the wood frogs prosper in one pond for a few years then leave? Why do the cattails threaten to take over three of the ponds but have not appeared in the biggest? How did the bladderwort get in one pond and not the others? I also do a little observing elsewhere. Why are there so many leeches in Dudley swamp in the Baring division of Moosehorn? Why are there only two ponds with fairy shrimp in that whole area, and how did they get there? And lastly, how did the fingernail clams get into the roadside ditches of Leighton Point Road?
Fingernail clams, probably of the Pisidium genus. Backdrop is a paper clip.
Few people but lots of ducks realize that fingernail clams exist at all. There are about 21 species of these bivalves that live in the puddles, ponds, lakes, streams and rivers in New England, however here in the Quoddy region we only have a few species. The available literature is scarce because the clams are of seemingly little economic value. The clams that I found are probably of the Pisidium genus. They have a reasonably good tolerance of the roadside pollution, that is, the salt and oil fumes that go with the location. There are often enough survivors after a standard roadside ditching disturbance to maintain a viable population, providing it is not too severe and the puddle returns. These clams are very similar in shape to the hard shell clam Mercenaria mercenaria, only much smaller. Like any other clam they have a foot for limited mobility and dual siphons for water intake and exhaust. They eat algae and any other teeny tiny critters that they can filter out. Fingernail clams propagate sexually and reach maturity in only a year or two depending on conditions, but can survive long periods of hibernation if the puddle dries up. Under the right conditions, typically in early summer, they will spawn, and the females will send out eggs into the water to be fertilized by the males. There is no larval stage for fingernail clams, and when the eggs hatch they look like very tiny adults, and quickly settle in to the happy life of being a clam. This Eden is often messed up by predatory insects, like dragonfly larva or diving beetles, or by ducks. Ducks, like Mallards or Blacks, find fingernail clams especially yummy. It is interesting to watch ducks work the mud and shores harvesting any and all available food. They will stick their beak into the substrate and, with a clever motion of their beak and tongue, the slurry is pumped up and the solids are filtered out and the water goes out the sides of their beak. However ducks do help fingernail clams find new territory. Fingernail clams are sort of sticky and will adhere to the feathers and legs of ducks and get a free ride to some remote pond or roadside ditch and set up a new population for some naturalist to ponder.
Lupine stem loaded with aphids. Where are all those Lady Beetles I boarded all winter?