Mollusks on the Prairie?!?

Mollusks on the Prairie?!?

What is this? It looks like a tiny clam. But it’s in a temporary stock pond in shortgrass prairie.

One little mollusk is lying quietly in the upper left portion of the video by 3-4 seconds in. Two or three others swim through.

Where did these come from, and where did they go? This is in a 6,000-foot elevation temporary stock pond in the shortgrass prairie (primarily blue grama and buffalo grass with fringed sage, lupine, curly-cup gumweed, and some kind of wormwood) of eastern Colorado.

The ponds contain water only for a short while after a heavy thunderstorm. The night of the storm, croaking of prairie spadefoot toads can be heard as they gather at the pond to find a mate and lay their eggs. Tadpoles hatch after about a week, and mature over the next two to three weeks. If the weather is dry and the pond would dry up, I run water in until the tadpoles mature and leave the water. This year there were a lot of dragon flies and damsel flies also mating and depositing eggs in the pond. None of the minnow-looking youngsters that I believe turn into tiger salamanders, this year. But mollusks???

As far as a water source, this is a closed system with nothing flowing in or out – ever. There are no sources of surface water for miles and miles. Arrival is across semi-arid prairie-land or by air.

I’ve been watching over tadpoles in this pond for 25 years, and never before noticed wee clams swimming with them. Their swimming pattern and speed blends in with the tadpoles. But the little toads left, leaving 100 to 200 of these tiny hard-shelled critters that look like tiny clams. When they’re not swimming, they lie quietly on the bottom of the pond atop the mud – and look like clams. Some of them have grown green algae on their shells.

This video is from yesterday (August 31, 2020). Last night there was about 1/10th of an inch of rain. Today, the pond’s water is muddy and the wee clams are nowhere to be seen. It doesn’t seem likely that a coyote or raccoon splashed about in the small, shallow pond until it caught and ate them all. Does it? Doesn’t that mean that they must have come out of the mud, and dug back into the mud? And they’ll hibernate or go dormant down in the mud for how many years until they come back out to swim among the tadpoles?

This is a new visitor for me. Please send a message if you have some enlightening news about what these are, their life-cycle, and how they would have gotten here.

Stock Pond, Sept. 1, 2020


Stock pond and field beyond

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