MadSci Network: Zoology |
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,
James
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