kuento@kuhub.cc.ukans.edu (05/25/91)
In article <anderson.675093533@xray1.cshl.org>, anderson@cshl.org (John Anderson) writes: > lucyc@suite.sw.oz.au (Lucy Chubb) writes: > >>I have a frog (common Australian green tree frog - littoria >>coerelia (sp?)) and have observed it changing colour on a >>number of occasions. The colour changing could be a protective >>adaptation to help the frog blend into the background (although >>the colour changes seem to have nothing at all to do with the >>colour of the frogs surroundings). Does anyone know what sort >>of situations cause this type of frog (or other types of frog) >>to change colour when it is not threatened by a predator? > >> Lucy Chubb. Work by K. E. Linsenmaier on some North African grass frogs showed that in the case he observed, the frogs changed color in order to increase or decrease their reflectance (albedo) so as to reflect or absorb greater or lesser degrees of incoming radiation - in particular, during the dry season, they turned almost white, and highly UV-reflective, to minimize the effects of prolonged exposure to the sun. Probably not the same thing as in your Aussie frog, but who can say? > How do frogs (and chameleons, octopuses, anole lizards, etc) "know" > what color to change to to blend into the background? > > -- > John Anderson > Cold Spring Harbor Laboratory > anderson@cshl.org I seem to recall studies along these lines which showed the animals could perceive "relevant" colors (even if not sensitive to the full visible spectrum) and adjust their chromatophores accordingly. At least in the case of octopi and other cephalopods (which have visual systems comparable to our own, if not superior in many respects), I find this quite easy to believe. An interesting side note is that the animals do not have to see *themselves* in order to make the correct changes - just the background is needed (at least in the case of flounders/flukes, which often lie partially buried and *can't* see themselves much of the time). Pretty neat stuff... -------(please include "DY" in subj header of mail to this user)-------- Doug "Speaker-To-Insects" Yanega "UT!" Bitnet: KUENTO@UKANVAX My card: 0 The Fool (Snow Museum, Univ. of KS, Lawrence, KS 66045) "Ev-ry-bo-dy loves the Michigan RAAAAaaaaag!" - The Singing Frog