The Amphipod’s Unique Escape

James 4:7
“Therefore submit to God. Resist the devil and he will flee from you.”

The hunted are smart to stay upwind of the hunter. Many predators hunt using scent, at least in part. The same principle works in water. Many predators smell chemicals given off by their prey and use that scent to help them locate their prey. If you were predator in a stream you would be smart to stay downstream from your prey. The prey won’t smell you. In addition, you might be able to smell him if he gets too close.

Amazingly, the little shrimp‑like amphipod seems to be able to smell predators even downstream. Researchers from Lund University in Sweden have discovered that amphipods can even smell a brown trout downstream and try to avoid it. Scientists designed an artificial stream that divided into two branches. Down one branch was a brown trout, while no predator waited down the other branch. Then amphipods were placed upstream of the branch and allowed to go downstream. When the amphipods came to the branch, they avoided the branch with the trout. To check whether the amphipods were actually smelling scents from downstream, researchers put trout scents in the downstream water. This was enough to cause the amphipods to avoid that branch. Yet, when trout were placed in one of the downstream branches in glass tubes, keeping their scent from entering the water, the amphipods did not respond to the sight of the trout.

We, too, are being hunted as prey by the devil and his forces. We would do well to learn how to sense where the devil lies in wait for us, and like the amphipods, flee from him.

Prayer: Dear Father, I confess that I have not fled the devil when I should have. Forgive me through Jesus Christ. Amen.

Author: Paul A. Bartz

Ref: S.M., Downstream trout swim but can’t hide, Science News, v.154, p.91. Photo: Courtesy of Uwe Kils. (CC BY-SA 3.0.