The barrel eye fish a is a marvelous fish because they have a transparent covering over their head. It looks like the canopy of a jet fighter. Within that enclosure are a pair of tubular eyes with green spherical lenses sitting on top of two parallel tubes. The retinas are horizontal and so the animal is clearly looking up. What always bothered me, though, was that they had this funny little poochie mouth that that sticks out and is outside the field of view of the eyes and I was always bothered by the fact that they can't see what they're eating.
How do they feed if you can't see?
So one day when we were out here diving, we came across one of these rare but marvelous fishes. And as I was watching it, the eyes rotated downwards. I thought, that's it, the eyes can rotate. And then we were able to put together a reasonable scenario that these fish swim long underneath gelatinous predators, like big, long siphon rivers that have chains of curtains. So the fish looks up.
Sees the prey trapped in the tentacles, keeps its eyes locked on the food, pivots the body upwards, grabs the food, pivots back down, and swims along, looking for the next, the next, uh, food item in the buffet line. And that transparent covering over the eyes protects them from the stinging cells in the tentacles. And suddenly it all came together. That's what's going on. That's how this works. Those are the kinds of days in field science that you can't predict. But when they happen, it makes you really excited and happy. You think, yeah, I picked the right job. This is fun.
