Crepuscular and nocturnal illumination and its effects on color perception by the nocturnal hawkmoth Deilephila elpenor

Abstract

SUMMARY Recent studies have shown that certain nocturnal insect and vertebrate species have true color vision under nocturnal illumination. Thus, their vision is potentially affected by changes in the spectral quality of twilight and nocturnal illumination, due to the presence or absence of the moon,artificial light pollution and other factors. We investigated this in the following manner. First we measured the spectral irradiance (from 300 to 700 nm) during the day, sunset, twilight, full moon, new moon, and in the presence of high levels of light pollution. The spectra were then converted to both human-based chromaticities and to relative quantum catches for the nocturnal hawkmoth Deilephila elpenor, which has color vision. The reflectance spectra of various flowers and leaves and the red hindwings of D. elpenor were also converted to chromaticities and relative quantum catches. Finally, the achromatic and chromatic contrasts (with and without von Kries color constancy) of the flowers and hindwings against a leaf background were determined under the various lighting environments. The twilight and nocturnal illuminants were substantially different from each other, resulting in significantly different contrasts. The addition of von Kries color constancy significantly reduced the effect of changing illuminants on chromatic contrast, suggesting that, even in this light-limited environment,the ability of color vision to provide reliable signals under changing illuminants may offset the concurrent threefold decrease in sensitivity and spatial resolution. Given this, color vision may be more common in crepuscular and nocturnal species than previously considered.

Planetary targets in the search for extrasolar oxygenic photosynthesis

“…The photon flux density received on the Earth from our moon is estimated to be 0.5 nmol photon m −2 s −1 (Munz and McFarland 1973), 3 nmol photon m −2 s −1 (Salisbury 1981) and 5 nmol photon m −2 s −1 (Gorbunov and Falkowski 2002). Subsequent estimates are 3 nmol photon m −2 s −1 (Johnsen et al 2006) and 12 nmol photon m −2 s −1 (Cummings et al 2008). The mean of these values is less than the absolute minimum for photolithotrophic growth by O 2 -evolving organisms (10 nmol photon m −2 s −1 ), so that even the full moon on a cloudless night could not support photosynthetic growth of organisms.…”

Polarizing optics in a spider eye

“…Both measured and modeled data indicate that the polarizing effect of the tapetum is stronger for green than for UV light. In addition, both light intensity and polarization in the sky are higher at 500 nm than at 350 nm (Coulson, 1988), even under twilight conditions when the spiders are most active (Cronin et al, 2006;Dacke et al, 1999;Johnsen et al, 2006). One would thus expect that D. cupreus uses the green-receptors for polarized skylight navigation.…”

The blurred line between photic and aphotic environments: a large Mexican cave with almost no dark zone

“…Unlike the daily cycle of light and dark, which is well characterized with respect to light during the night (Johnsen et al, 2006;Johnson, 2012), the transition from light to dark at the entrance to a cave is not well described, nor is it considered of particular importance because of the relatively abrupt transition to total darkness. Typically, the transition zone is short (only a few meters) and there is in fact a distinct fauna of the twilight zone of cave entrances, one that is dominated by groups that are not found in the aphotic zone of caves, such as frogs (Graham, 1962) and moths (Graham, 1968;Taylor et al, 2010).…”

“…Light loss in litter is strong, but since the Beer-Lambert law is exponential, small amounts of light penetrate deep into the litter. Often, species in these habitats have enlarged eye size in order to retain the ability to form images (Warrant, 2006;Tierney et al, 2017). On the other hand, there are eyeless troglomorphic species known from twilight habitats (Prendini et al, 2009;Heads, 2010).…”