Perception of solar UVB radiation by phytophagous insects: Behavioral responses and ecosystem implications

Abstract

Most of our present knowledge about the impacts of solar UVB radiation on terrestrial ecosystems comes from studies with plants. Recently, the effects of UVB on the growth and survival of consumer species have begun to receive attention, but very little is known about UVB impacts on animal behavior. Here we report that manipulations of the f lux of solar UVB received by field-grown soybean crops had large and consistent effects on the density of the thrips (Caliothrips phaseoli, Thysanoptera: Thripidae) populations that invaded the canopies, as well as on the amount of leaf damage caused by the insects. Solar UVB strongly reduced thrips herbivory. Thrips not only preferred leaves from plants that were not exposed to solar UVB over leaves from UVBexposed plants in laboratory and field choice experiments, but they also appeared to directly sense and avoid exposure to solar UVB. Additional choice experiments showed that soybean leaf consumption by the late-season soybean worm Anticarsia gemmatalis (Lepidoptera: Noctuidae) was much less intense in leaves with even slight symptoms of an early thrips attack than in undamaged leaves. These experiments suggest that phytophagous insects can present direct and indirect behavioral responses to solar UVB. The indirect responses are mediated by changes in the plant host that are induced by UVB and, possibly, by other insects whose behavior is affected by UVB.Depletion of stratospheric ozone (1) is a cause of concern because the biological impacts of an increase in solar UVB (290-320 nm) are unknown. Most studies to date on ecological effects of solar UVB have been carried out on plants (2-4); however, there is growing awareness in the UVB research community (2-7), as well as among those studying other aspects of global environmental change (8), about the limitations of impact predictions that result from up-scaling information obtained in studies of a single organism or trophic level. The concentration of the research effort on plants is in part a consequence of the assumption that the effects of UVB on ecosystem functioning are largely mediated by its effects on the primary producers (6).Recent studies on animal consumers have focused on those effects of UVB on consumer growth and survival that are mediated by changes in host chemistry (9-11) and on direct damaging effects of UVB. In the latter regard, it has been shown that certain animal species (particular instars), such as juvenile forms of some aquatic organisms, are not well protected from UV radiation and are damaged by prolonged exposure to present-day levels of UVA (320-400 nm) and UVB (4, 12, 13) radiation. Damaging effects of acute exposures on zooplanktonic organisms have also been documented in studies carried out in Antarctic waters under ozone-hole episodes (14). Interestingly, one of the few studies that included more than one trophic level has shown that direct damaging effects of solar UV radiation on phytophagous insect larvae can counterbalance the negative impact of UV on algal photosynthesis an...

The Mechanistic Underpinnings of anago1-Mediated, Environmentally Dependent, and Stochastic Phenotype

“…Our study also links light conditions to JA signaling, which is supported by several previous studies. Specifically, solar UV-B radiation renders plants more resistant to herbivory, primarily due to up-regulation of the JA pathway (Ballare et al, 1996;Mazza et al, 1999;Demkura et al, 2010). Consistent with these prior findings, the ago1-dependent lesions were much less frequent in filtered light conditions that exclude UV-B radiation (Stasinopoulos and Hangarter, 1990).…”

“…The three phytohormones SA, ET, and JA are the canonical defense hormones. As previous results link light conditions (UV-B) with defense hormone response (A-H- Mackerness et al, 1999;Mazza et al, 1999), we set out to examine whether the SA, JA, and JA/ET pathways were responsible for the lesions on ago1 cotyledons. We measured the expression of marker genes for SA, JA, or JA/ET signaling in 10-dold cotyledons of wild-type, ago1-46, ago1-27, and ago1-25 mutant seedlings grown in the lesion-inducing, full-spectrum light condition.…”

Evaluación de la viabilidad de huevos de abeja Apis mellifera L. sometidos a radiación ultravioleta

“…Aquí las viabilidades disminuían a medida que aumentaba el tiempo de exposición. Mazza et al (1999), en experimentos realizados en insectos detectaron una sensibilidad de éstos a la radiación UV-B, ya que los insectos evitan la exposición solar UV-B.…”

“…Igualmente, se han observado efectos sobre la corteza del suelo, disminuyendo la productividad y aumentando la mortalidad biológica de los suelos (Belnap et al, 2007). En organismos acuáticos la exposición prolongada a la radiación UV-B ha provocado daños (Mazza et al, 1999), como aumento de la mortalidad embrionaria en especies de anfibios (Anzalone et al, 1998), mortalidad significante en huevos de bacalao atlántico (Béland et al, 1999), daños y mortalidad en invertebrados de agua dulce (Hurtubise et al, 1998;Cywinska et al, 2000). Los efectos de la radiación UV también se han observado en insectos, como por ejemplo fotosensibilidad a la radiación UV en Caliothrips phaseoli (Mazza et al, 2002) y el género Deleatidium (Johansson y Nyström, 2004), reactivación biológica y desaparición de alrededor de 7x10 9 dímeros de pirimidina del ARN total por huevos de Smittia sp.…”

Effects of Solar Radiation on Animal Thermoregulation

“…Other plants such as soybeans also receive reduced herbivorous damage when exposed to UVB (Zavala et al, 2000). Thrips, insects that feeds on plant leaves, actually avoid exposure to UVB solar radiation, suggesting that insects can behaviorally respond to that particular wavelength presence (Mazza et al, 1999). UVB can also have an indirect effect upon some species of insect larvae, as those who eat UVB radiated plant material are found to have decreased growth rates and suffer more mortalities versus larvae that feed on non-radiated plant matter (McCloud & Berenbaum, 1994).…”