MadSci Network: Zoology

Re: How do mudskipper's eyes focus in and out of the water?

Date: Mon Sep 11 09:49:12 2000
Posted By: James Cotton, Graduate Student, Molecular Evolution & Systematics
Area of science: Zoology
ID: 951425371.Zo

Dear KJ,

Since no-one else has tried to answer your question for a while, I thought i'd try and clear it up, even though i didn't know the answer. Mudskippers are a favourite example of how organisms evolve to live succesfully in an unusual environment - obviously, most fish are entirely water-based but the midskippers have evolved features that let them function very well amphibiously.

Because of this, i thought answering your question would be very easy, but i found very little information about it in internet searches and searches of the biological literature - a lot of work about how mudskippers live with changes in salt levels and temperature changes, but nothing about their vision. I'll share with you what i did find out online, of course..

There's a brilliant Australian site about mudskippers which tells you pretty much all you could want to know EXCEPT your question! The New Jersey state aquarium has a little page saying somethings about why mudskipper eyes are special, but not how they can focus. Houston Zoo just say that mudskippers can see 'in all directions on both land and water', but don't really say how. I even found the lyrics to a song about a mudskipper, but that doesn't really help (In fact, its actually wrong about them having segmented eyes - thats Anableps anableps, the four-eyed fish, which has something like bi-focal spectacles to allow it to see in and out of water.. mudskippers definitely don't do that).

After all these dead-ends I was beginning to get a little frustrated, but one website - an Iranian nature magazine, of all things, led me to what i think is the truth, saying that 'mudskippers are mainly adapted for aerial vision'. I e-mailed Richard Mleczko, who runs the Australian site i mentioned first, and he pretty much confirmed this - he doesn't pretend to be an expert, but he understands that mudskippers have pretty poor vision underwater, and can't focus well when submerged. When faced by aquatic threats, they either run into burrows or onto dry land.

Basically, then, the answer is that mudskippers can only focus properly in air, and only poorly underwater. Maybe they have lenses that can focus over a wider range than some organisms, but still not sufficiently for sharp vision in both environments. Hope this answers your question, and sorry i can't come up with any more convinvcing references or anything - i HAVE tried, i promise.

Thanks for asking - hope the next question you ask gets a more definitive answer, and sorry its taken so long for someone to reply to you, Yours,


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