海洋生物會在水裡留下足跡，而科學家發現，海綿在過濾海水的同時，會把其他生物的DNA留在體內。海綿能在任何水域找到，本身不會遷移，而且亦有再生能力。科學家只要抽取部分樣本作測試，就可更有效地了解水域出末的動物。

marine creatures would leave DNA behinds in water, and scientist found out when sponges filter-feed, DNA of other creatures would be catch in in their tissues. Sponges can be found in all kind of aquatic habitat and they do not travel; they could already regenerate nicely after scientist take sample from them. With this process, scientists can identify and learn more about marine creatures in different areas in a more effective way.

https://www.natureworldnews.com/articles/41347/20190605/sponges-collect-penguin-seal-and-fish-dna-from-the-water-they-filter.htm