Musings: Fish eyes

This is a supplementary page, for Where are the eyes? (December 16, 2009).

As a reminder, here is the picture:
Fish picture: Where are the eyes?

So where are the eyes? That's easy enough: those green things at the top (near the front). Actually, the green hemispheres are the eye lenses. (You weren't distracted by the nares? The nares are olfactory organs, something like nostrils -- and are those circular dark spots just above the mouth.)

So far, not new. The fish and its upward-pointing eyes have been known for decades. But there has been a mystery. How does this fish eat if it can't see its mouth region? The fish lives at a depth where there is some light -- but very little. Upward pointing eyes are good for such a fish; upward is where they might find food. But upward is not where the mouth is. If it sees something "up there", how does it gets its mouth to the prey? What the new work shows is that when the fish turns upward to attack its prey, the eyes stay aimed at the food. That is, the eyes rotate within the head. Rotate "forward". Whether the fish can actually see its mouth is not clear, but maybe close enough. The work is based on observations of the fish in the wild, from robotic submersible vessels, followed by some observations in the lab.

Here are two news stories. The first is the one Borislav came across; it has good pictures and a link to a video. The second may offer a more complete discussion.
* Weird Fish With Transparent Head. (February 22, 2009.) (Note that the main figure is part of a series; click on Next for more. The figure shown at the start of this post is #1 from this set.)
* Mystery Of Deep-Sea Fish With Tubular Eyes And Transparent Head Solved. (Science Daily, February 26, 2009.)

Here is the paper, which I think you may find worth a browse. Macropinna microstoma and the Paradox of Its Tubular Eyes. (B H Robison & K R Reisenbichler, Copeia 2008, No. 4, 780-784.) In particular, Figure 2 shows the eyes pointing upward (part A) and pointing forward (part B).

Any of you who have ever bought anything with the HP logo on it have contributed to this work. The work was done at the Monterey Bay Aquarium and Research Institute (MBARI), about 100 miles south of San Francisco. The Institute was founded by HP's P, and is funded by the David and Lucile Packard Foundation.

More from MBARI: Quiz: What is it? (October 31, 2012). See the answer.

Return to this item on main page: Where are the eyes? (December 16, 2009).

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