Re: Deep-sea UV fish vision?

["Thomas H. Hogan" <flzhgn@xxxxxxxxxxxxx>]

Most fish have excellent color vision!  Goldfish for instance have
the color receptive cone cells distributed throughout the retina, they
also have several types of the color receptive cone cells that we humans
do not (double and triple cone cells).  These cone cells are responsible
for color vision and detailed vision.  There are also rod cells which
are
primarily sensitive to blue light and are responsible for night and
motion vision.  All these cells are hooked up through several distinct
layers of cells which "process" the information gathered by the rods and
cones which are the light receptors.  (By the way, this processing is
in some ways similar to the development of film using a dilute
developer,
to increase sharpness where nearby grains of silver halide inhibit the 
development of thier nearest neighbors)  But, to get back to fish
vision and light penetration:  Ultraviolet light penetrates both fresh
and salt water to about the same extent that visible blue light does
and scuba divers sometimes report getting a sunburn while diving.

Many deep sea fish like the midshipman have luminescent organs, so do
squid, for the most part these luminescent organs are lit by 
photobacterium which uses the luciferin/luciferase method to convert
ATP chemical energy into light by a similar reaction to that of the 
firefly insect.

I actually took an infrared picture of a fish in its natural
environment--
it was jumping out of the water and happened to jump into the picture
that I was taking with a 500mm mirror lens, #87 filter at 1/1000 sec!
I'll post it to my web site at http://www.pic.net/~flzhgn/ if anyone
is interested.

Hank Hogan

------------------------------

Topic No. 8