Western pearlshell facts for kids
Quick facts for kids Western pearlshell |
|
|---|---|
| Conservation status | |
| Scientific classification | |
| Genus: |
Margaritifera
|
| Species: |
falcata
|
The western pearlshell (Margaritifera falcata) is a special type of freshwater bivalve. It is a pearl mussel, which means it's a kind of bivalve mollusk. These mussels can sometimes even make pearls!
You can find this species only in the United States and Canada. They mostly live in areas west of the Rocky Mountains.
Where Do Western Pearlshells Live?
This pearl mussel lives in rivers and streams that flow into the Pacific Ocean. You can find them from California all the way north to British Columbia and southern Alaska.
Sadly, some groups of these mussels near the coast and in big rivers are disappearing fast. However, the western pearlshell is still common in parts of the northern Rocky Mountains. Even there, some groups in Montana might be shrinking.
Crossing the Continental Divide
You can also find western pearlshells east of the Continental Divide. The Continental Divide is like a big line of mountains that separates rivers. Rivers on one side flow towards the Pacific Ocean, and rivers on the other side flow towards the Atlantic or Arctic Oceans. The mussels found east of this divide live in the headwaters (the very beginning) of the Missouri River.
Scientists first thought these mussels were a different kind, called Margaritifera margaritifera. But they recently confirmed that they are indeed M. falcata. This means the mussels somehow crossed the big divide!
How Mussels Crossed the Divide
The most likely way they crossed is through something called headwater capture. This happens when rivers change their paths over a very long time. For example, during the Pleistocene Ice Age, over 20,000 years ago, glaciers moved and changed how rivers flowed.
Scientists think that Westslope cutthroat trout crossed the Continental Divide from the west. They moved into the rivers that became the Missouri River. These trout are very important for young M. falcata mussels. The tiny baby mussels, called glochidia larvae, attach themselves to fish to travel. So, it's very likely that the mussels hitched a ride on these trout to cross the divide!
