[Coral-List] Color vision in fishes
reedkc at comcast.net
Mon Jun 5 18:22:13 EDT 2006
Though my comments may not be of interest to many of the coral professionals out there, I feel compelled to make some statements that I hope you will find pertinent to your work, and perhaps of interest to anyone working with animal light sensors of any wavelength in the marine environment; whether the animal is an anthozoan, cubozoan, teleost or a fish in the class chondrichthyes.
Before one gets to the lab or experimental design, here's the basic expectations for an animal's visual sensor on this planet: Since about 50% of the wavelengths in the electromagnetic spectrum of our nearest star arrive at sea level (after filtration through a variable atmosphere), then it stands to reason that terrestrial animals and animals near the surface of the water (coastal) may see some of the hues of what humans perceive as 'color vision', approx' 400-700 nanometers wavelengths of energy. Every biologist knows however, that many vertebrate animals have only dichromatic color vision (two cone receptor types or opsins), most New World monkeys only have dichromatic color vision, most Old World Apes and humans have trichromatic color perception (three functional cone types), but many remarkable birds and goldfish/carp (Cyprinids) have four functional cone types! The fourth color vision receptor in goldfish turned out to be in the near ultraviolet wavelength of the upper 300 nanometer range (Neumeyer, 1985 & 1988).
The answer to your question is: I'm sure that different species of shallow water marine fish have color perception to differing degrees. I can't give you a species list that states which ones are dichromats, trichromats, or perhaps tetrachromatic like the freshwater goldfish. I'd love to see that list if any researcher has gone there (especially in a scleractinian munching scarid).
Now, remember that blue shift in the ocean (red wavelengths are filtered out at shallow depths) if you are trying to hypothesize about which colors in the reef environment our tropical coral fish should see. I'll demonstrate with the attachments of the 'blue rice coral', Montipora flabellata, that I photographed in shallow water at Hanauma Bay, Oahu: without a strobe, the naked eye sees a bluish colony; but, in the strobe photo blue rice coral actually is a pinkish color (sorry, the two photos are different magnification).
Of course if the marine animal is from the abyss, or terrestrial animal is strongly nocturnal, there's not as much need (if any) for color vision. Consequently, the retina from those species demonstrate less cone receptor types and the rod receptors start to predominate. Thus, one shouldn't expect a deep water fish to have as much color perception as a shallow water coral reef fish.
If I interpreted Baker & Smith's 1982 figure (Solar spectral irradiance at different depths, z, in clear ocean water) correctly, then about 90% of UVA & UVB combined (400 to 290 nm) is filtered out in the near surface waters/first 3.5 meters of depth. So, may not need to look too hard for UV receptor in coral reef fish eyes--even the diurnally active ones.
If anyone is still reading this, let's go one visual step beyond the fishes' color perception (variable by species) to another visual sense: polarized light perception. Dr. Craig Hawryshyn who works on salmon perception at the University of Victoria, was working with McFarland about twenty years ago when he discovered that carp/goldfish were able to detect polarized ultraviolet light (not just ultraviolet 'color'). Reminder--the degree of polarization of light penetrating the coastal or reef crest water depends on the angle of the sun above the horizon. Hawryshyn and a team of divers showed that significant, detectable levels of polarized light penetrated at least 60 feet in cloudy water (article by Joseph Alper in Sea Frontiers). I believe in the ocean, polarization varies from 50 to 90 percent.
I would love to have my statements above corrected/updated by researchers as my current interests are in yet another coral direction.
A footnote of embarrassment: I once confused 'opsin' with 'opsonin'--don't! The visual proteins are opsins. An antibody facilitating phagocytosis by leukocytes is an 'opsonin'.
Keven Reed, O.D.
Orange Park, FL 32003
----- Original Message -----
From: Kristen Hoss
To: coral-list at coral.aoml.noaa.gov
Sent: Saturday, May 27, 2006 10:04 AM
Subject: [Coral-List] Color vision in fishes
I have had conflicting reports about color vision in fishes. From the resources I have read it seems to me that coral reef fishes have color vision which is designed to enhance detection of conspecifics and certain morphological patterns contrasting with the reef; whereas nocturnal fishes see in black and white.
First I would like to know if this general statement is accurate. Second I would like to know more about color vision in deep water fishes, pelagic fishes and if possible freshwater fishes. Any references would be appreciated as would general statements about if they see in color or black and white and why.
I am a wildlife biologist, marine ecologist and an educator. The purpose of this question is to clear up misconceptions between my colleagues and myself about what we have learned over the years, thus to provide a better education for the students and ourselves.
Thank you for your time-
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