Egg-Laying Demand Induces Aversion of UV Light in Drosophila Females

Abstract

Summary Drosophila melanogaster females are highly selective about the chemosensory quality of their egg-laying sites [1–6], an important trait that promotes the survival and fitness of their offspring. How egg-laying females respond to ultraviolet light (UV) is not known, however. UV is a well-documented phototactic cue for adult Drosophila [7–13], but it is an aversive cue for larvae [14–17]. Here, we show that female flies exhibit UV aversion in response to their egg-laying demand. First, females exhibit egg-laying aversion of UV: they prefer to lay eggs on dark sites when choosing between UV-illuminated and dark sites. Second, they also exhibit movement aversion of UV: positional tracking of single females suggests that egg-laying demand increases their tendency to turn away from UV. Genetic manipulations of the retina suggest that egg-laying and movement aversion of UV are both mediated by the inner (R7) and not the outer (R1-6) photoreceptors. Finally, we show that the Dm8 amacrine neurons, a synaptic target of R7 photoreceptors and a mediator of UV spectral preference [12], are dispensable for egg-laying aversion but essential for movement aversion of UV. This study suggests egg-laying demand can temporarily convert UV into an aversive cue for female Drosophila, and that R7 photoreceptors recruit different downstream targets to control different egg-laying-induced behavioral modifications.

CRYPTOCHROME mediates behavioral executive choice in response to UV light

“…The ability to discern the changes in intensity, spectral content, timing, and exposure length of light provides valuable environmental information crucial to an organism's well-being and survival. UV lightavoidance behavior has been demonstrated in foraging larva and egg-laying activity in females (39,40). We demonstrate that the CRY/HK signaling pathway mediates UV light avoidance behavior in adult male Drosophila.…”

“…Many insects exhibit an innate spectral attraction to low-intensity UV light, as shown by phototaxis behavioral assays (36)(37)(38). In contrast, highintensity UV light induces avoidance behavior, particularly in larvae and egg-laying females (39,40), and reduces mating activity in adult male Drosophila (41).…”

Oviposition preferences for ethanol depend on spatial arrangement and differ dramatically among closely related Drosophila species

“…The adaptive significance of these behaviors remains to be determined, though reasonable hypotheses include choosing to oviposit in a place with fewer toxins, microbes, parasitoids, or large consumers, but which is near enough to the food source that larvae can find it. Regardless, initial investigation into the genes and neural circuits responsible for these behaviors illustrate the great potential to use oviposition as a model to study preferences and decision-making (Gou et al, 2014; Joseph and Heberlein, 2012; Joseph et al, 2009; Yang et al, 2008; Zhu et al, 2014). …”

A Bitter Taste of the Sun Makes Egg-Laying Flies Run

“…Previously, Chung-Hui Yang's group had found that UV avoidance emerges in Drosophila females that are in an egg-laying state (Zhu et al 2014). In an article in this issue of GENETICS, Yang and colleagues take advantage of the same behavioral paradigm to probe the functional relevance of TRPA1-mediated UV sensing and avoidance in more detail (Guntur et al 2016).…”

“…R7 photoreceptors, expressing Rh3 and Rh4 UV-sensitive rhodopsins, play a significant role in the eye (Zhu et al 2014). Bitter GRNs in the proboscis, expressing UV-sensitive dTrpA1, do so in the taste system (Guntur et al 2016).…”