Vladimir Nabokov

NABOKV-L post 0007027, Tue, 5 Nov 2002 18:51:23 -0800

Fw: Big Bug Surprise:"VN, Mimicry, & Moth Nocturnal Color Vision!
----- Original Message -----
From: Johnson, Kurt
To: Vladimir Nabokov Forum
Sent: Tuesday, November 05, 2002 9:10 AM
Subject: RE: Big Bug Surprise

This post will interest all the people who debate this topic of Nabokov and mimicry. This scientific paper appeared in the most recent issue of Nature (one of top 2 journals in science in the world) and elaborates night time color vision in moths. This has a dramatic effect on arguments about natural selection working for selection of detail in mimicry, and other, Lepidoptera-related phenomena. You'll remember that some of Nabokov's examples about detail in mimicry, which he did not feel could be directed by natural selection alone, were examples from nocturnal moths, esp. Saturnidae. If indeed, moths have nightime color vision, with regard to any selection pressures that effect "recognition" in relation to details of pattern, particularly with regard to sexual identification, there are rather revolutionary implications (compared to the assumption that such color and detail in moths did not come into play with regard to recognition). However, how this would play with predator selection with regard to differential survival and mimicry is trickier since, as you know, I mentioned that it is estimated that 80% or more of invertebrate predation is from other invertebrates, the rest by birds, amphibians, reptiles etc. and it appears that there is as yet no data (at least that I know of) regarding nighttime color vision in these others, or other invertebrates. However, this research would suggest that (1) nightime color vision has been active in the INTRAspecific channels regarding natural selection in moths for millenia and (2) these data invite further suspicion that such phenomena may be far more universal in nature than anticipated.

I guess its a lesson about not assuming to much about the limitations of nature itself. Below in the info. on the paper, and the Abstract.

Scotopic colour vision in nocturnal hawkmoths

ALMUT KELBER, ANNA BALKENIUS & ERIC J. WARRANT http://www.nature.com/nlink/v419/n6910/abs/nature01065_fs.html

here is the Abstract

Nature 419, 922 - 925 (2002); doi:10.1038/nature01065


Scotopic colour vision in nocturnal hawkmoths


Department of Cell and Organism Biology, Vision Group, Lund University, Helgonavägen 3, S-22362 Lund, Sweden

Correspondence and requests for materials should be addressed to A.K. (e-mail: almut.kelber@zool.lu.se).

Humans are colour-blind at night, and it has been assumed that this is true of all animals. But colour vision is as useful for discriminating objects at night as it is during the day. Here we show, through behavioural experiments, that the nocturnal hawkmoth Deilephila elpenor uses colour vision to discriminate coloured stimuli at intensities corresponding to dim starlight (0.0001 cd m-2). It can do this even if the illumination colour changes, thereby showing colour constancy-a property of true colour vision systems. In identical conditions humans are completely colour-blind. Our calculations show that the possession of three photoreceptor classes reduces the absolute sensitivity of the eye, which indicates that colour vision has a high ecological relevance in nocturnal moths. In addition, the photoreceptors of a single ommatidium absorb too few photons for reliable discrimination, indicating that spatial and/or temporal summation must occur for colour vision to be possible. Taken together, our results show that colour vision occurs at nocturnal intensities in a biologically relevant context.