daphnia

例句：

1. 1.Daphnia are tiny, aquatic creatures that play an important role in the ecosystem.
   水蚤是微小的、水生生物，它们在生态系统中起着重要的作用。
2. 2. The study of daphnia is crucial for understanding the impact of pollution on marine life.
   研究水蚤对于理解污染对海洋生物的影响至关重要。
3. 3. The researchers collected samples from different lakes to study the diversity and abundance of daphnia.
   研究人员从不同湖泊收集样本，以研究水蚤的多样性和数量。