Host egg pigmentation protects developing parasitoids from ultraviolet radiation

Ultraviolet-B radiation in relation to agriculture in the context of climate change: a review

Over the past few decades, the amount of ultraviolet-B radiation (UV-B) reaching the earth's surface has been altered due to climate change and stratospheric ozone dynamics. This narrow but highly biologically active spectrum of light (280-320 nm) can affect plant growth and development. Depletion of ozone and climate change are interlinked in a very complicated manner, i.e., significantly contributing to each other. The interaction of climate change, ozone depletion, and changes in UV-B radiation negatively affects the growth, development, and yield of plants. Furthermore, this interaction will become more complex in the coming years. The ozone layer reduction is paving a path for UV-B radiation to impact the surface of the earth and interfere with the plant's normal life by negatively affecting the plant's morphology and physiology. The nature and degree of the future response of the agricultural ecosystem to the decreasing or increasing UV-B radiation in the background of climate change and ozone dynamics are still unclear. In this regard, this review aims to elucidate the effects of enhanced UV-B radiation reaching the earth's surface due to the depletion of the ozone layer on plants' physiology and the performance of major cereals.

Photoprotective egg pigmentation reduces negative carryover effects of ultraviolet radiation on stink bug nymph survival

Solar ultraviolet radiation (UV) can have a wide range of negative effects on animal fitness that take place not only during, but also after exposure (carryover effects). UV-induced carryover effects and potential adaptations to avoid or mitigate them are understudied in terrestrial animals, including arthropods and their potentially most vulnerable life stages. The spined soldier bug, Podisus maculiventris, increases the emergence of its eggs that are exposed to UV radiation by coating them in sunscreen-like pigmentation, but consequences of these conditions of embryonic development for nymphs and adults are unknown. We measured stink bug nymph survival, adult size and sex ratio following exposure of differently pigmented eggs across a range of UV intensities. Nymph survival to adulthood decreased with higher intensity of embryonic UV exposure and this carryover effect decreased with higher level of egg pigmentation, similar to previously observed effects on embryonic survival. Nymph development time, adult size and sex ratio were not affected by embryonic exposure to UV radiation nor by photoprotective egg pigmentation. This study is the first to demonstrate the potential for lethal carryover effects of UV radiation in terrestrial insects, highlighting the need for more studies of how this pervasive environmental stressor can affect fitness across life stages.

Latitudinal variation in biophysical characteristics of avian eggshells to cope with differential effects of solar radiation

Solar radiation is an important driver of animal coloration, not only because of the effects of coloration on body temperature but also because coloration may protect from the deleterious effects of UV radiation. Indeed, dark coloration may protect from UV, but may increase the risk of overheating. In addition, the effect of coloration on thermoregulation should change with egg size, as smaller eggs have higher surface-volume ratios and greater convective coefficients than larger eggs, so that small eggs can dissipate heat quickly. We tested whether the reflectance of eggshells, egg spottiness, and egg size of the ground-nesting Kentish plover Charadrius alexandrinus is affected by maximum ambient temperature and solar radiation at breeding sites. We measured reflectance, both in the UV and human visible spectrum, spottiness, and egg size in photographs from a museum collection of plover eggshells. Eggshells of lower reflectance (darker) were found at higher latitudes. However, in southern localities where solar radiation is very high, eggshells are also of dark coloration. Eggshell coloration had no significant relationship with ambient temperature. Spotiness was site-specific. Small eggs tended to be light-colored. Thermal constraints may drive the observed spatial variation in eggshell coloration, which may be lighter in lower latitudes to diminish the risk of overheating as a result of higher levels of solar radiation. However, in southern localities with very high levels of UV radiation, eggshells are of dark coloration likely to protect embryos from more intense UV radiation. Egg size exhibited variation in relation to coloration, likely through the effect of surface area-to-volume ratios on overheating and cooling rates of eggs. Therefore, differential effects of solar radiation on functions of coloration and size of eggshells may shape latitudinal variations in egg appearance in the Kentish plover.