Scotopic colour vision in nocturnal hawkmoths

Abstract

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 x 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.

The composition and timing of flower odour emission by wild Petunia axillaris coincide with the antennal perception and nocturnal activity of the pollinator Manduca sexta

“…A study conducted with M. sexta has shown that there is synergy between odour and visual cues (Raguso and Willis 2002). In fact, colours can be distinguished by hawk moths even at night (Kelber et al 2002). Odours attract the moths from a distance, but at short distance from a flower they will feed on both scented and nonscented flowers (Raguso and Willis 2002).…”

A dual function of white coloration in a nocturnal spider Dolomedes raptor (Araneae: Pisauridae)

“…In addition to a prior study on a tree frog (Gómez et al, 2009), our present study on the fishing spider D. raptor suggests that color signals may be more broadly employed in the courtship of nocturnal animals than previously appreciated. Numerous nocturnal animals have good color vision and color cues have been demonstrated to be important in nonreproductive aspects of their lives, such as foraging (Kelber, Balkenius, & Warrant, 2002), navigation (Warrant & Dacke, 2011) and mutualistic interaction (Peng, Blamires, Agnarsson, Lin, & Tso, 2013). However, so far it is unknown whether in nocturnal animals a conspicuous body color can serve as disruptive coloration under dim night conditions.…”

Behavioral evidence illuminating the visual abilities of the terrestrial Caribbean hermit crab Coenobita clypeatus

“…Many species like the honeybee, butterfly, and parasitoid wasp rely on true color more than shape or brightness for object detection (Desouhant et al, 2010). A recent study indicates that even the nocturnal hawk moth Deilephila elpenor can use color vision to discriminate colored stimuli at intensities corresponding to dim starlight (Kelber et al, 2002). Terrestrial hermit crabs vary in colors on their body, legs, claws and shells, and sometimes they change color after molting.…”