在池塘水样中，我们发现了一个轮虫用它的纤毛轮快速游动。

In the pond water sample, we spotted a ___rotifer swimming swiftly with its ciliated wheel.

科学家们通过观察轮虫的数量来评估湖泊的生态健康状况。

Scientists assess the health of lake ecosystems by monitoring the population of ___rotifers.