Crickets in the spotlight: exploring the impact of light on circadian behavior

Identification and functional analyses of the CmdsRNase5 and CmdsRNase6 genes in rice leaffolder Cnaphalocrocis medinalis

RNA interference (RNAi) is a promising method for pest control; however, some studies have showed that the degradation of double-stranded RNA (dsRNA) by dsRNA-degrading nucleases (dsRNases) is one of the factors that may reduce RNAi efficiency in lepidopteran insects. In this study, we cloned two dsRNase genes named CmdsRNase5 and CmdsRNase6 from rice leaffolder Cnaphalocrocis medinalis, a notorious insect pest of rice. Open reading frames (ORFs) of CmdsRNase5 and CmdsRNase6 are 1317 and 1185 bp in length, encoding 438 and 394 amino acids, respectively. These two genes were expressed at the highest level in the third-instar larvae throughout developmental stages and highly expressed in the midgut and hemolymph of C. medinalis. RNAi efficiencies of CmdsRNase5 and CmdsRNase6 were 57.44 % and 63.94 % on day 3, respectively. The RNAi efficiency of a target gene CmCHS (chitin synthase from C. medinalis) was 58.70% on day 5 and this efficiency was 87.63 % after co-silencing of CmCHS + CmdsRNase5 + CmdsRNase6. The findings suggested that co-silencing of CmdsRNases alongside CmCHS mitigated the degradation of dsCmCHS and enhanced the RNAi efficiency in C. medinalis, leading to phenotypic deformities, increased mortality, and a significant reduction in both egg production and hatching rate. Transcriptome analysis indicated CmdsRNase5 or CmdsRNase6 knockdown affected the expression of many important functional genes, thereby hindering the growth and development of C. medinalis. The concurrent silencing of both CHS and dsRNases provides a novel strategy for RNAi-mediated green control of C. medinalis and other lepidopteran pests.

Light alters calling-song characteristics in crickets

Communication is crucial for mate choice and thus for the survival and fitness of most species. In the cricket, females choose males according to their calling-song attractiveness and, exhibiting positive phonotaxis, they approach the chosen male. Light has been widely reported to induce changes in crickets' daily activity patterns, including the males' stridulation behavior. It had remained unknown, however, whether light also affects the calling-song properties and thus may consequently also alter female choice. Here, we present a novel semi-automated process, enabling the analysis of calling-song properties in an extremely large sample size of recording sections from males subjected to lifelong light:dark (LD) or constant light (LL) conditions. Our findings revealed that the LD calling songs consisted of longer chirps, longer inter-syllable intervals and a higher proportion of 4-syllable chirps compared with those of LL males. We also conducted some preliminary female choice experiments suggesting that females (reared in LD conditions) exposed to playbacks of male calling songs exhibit a preference towards LD over LL recordings. We therefore conclude that illumination conditions such as constant light affect the male crickets' calling-song properties in a manner that may be discernible to the females. It remains unclear, however, how and to what extent female mate choice and the species' overall fitness are affected by these changes.

Current evidence in support of insect-friendly lighting practices

Anthropogenic light pollution is an emerging threat to natural ecosystems with myriad effects on insects in particular. Insect conservationists are increasingly interested in mitigating this driver of insect declines via sustainable lighting practices. Current recommendations often follow the five principles for responsible outdoor lighting developed by DarkSky International, a nonprofit organization founded by astronomers. While these principles unquestionably increase star visibility, their ecological costs and benefits remain relatively unexplored. Herein, we review recent research into the effects of each principle on insect fitness broadly defined. Most studies test the efficacy of spectral tuning, followed by dimming, although both mitigation methods seem generally ineffective in practice. In contrast, both shielding and motion detectors show promise as mitigation methods but remain remarkably understudied. Nonetheless, a preponderance of evidence now demonstrates that removing unnecessary light sources from natural habitats can reverse their varied impacts on diverse insect taxa and greatly benefit insect conservation.

When night becomes day: Artificial light at night alters insect behavior under semi-natural conditions

Light is the most important Zeitgeber for temporal synchronization in nature. Artificial light at night (ALAN) disrupts the natural light-dark rhythmicity and thus negatively affects animal behavior. However, to date, ALAN research has been mostly conducted under laboratory conditions in this context. Here, we used the field cricket, Gryllus bimaculatus, to investigate the effect of ALAN on insect behavior under semi-natural conditions, i.e., under shaded natural lighting conditions, natural temperature and soundscape. Male crickets were placed individually in outdoor enclosures and exposed to ALAN conditions ranging from <0.01 to 1500 lx intensity. The crickets' stridulation behavior was recorded for 14 consecutive days and nights and their daily activity patterns were analysed. ALAN impaired the crickets' stridulation rhythm, evoking a change in the crickets' naturally synchronized daily activity period. This was manifested by a light-intensity-dependent increase in the proportion of insects demonstrating an intrinsic circadian rhythm (free-run behavior). This also resulted in a change in the population's median activity cycle period. These ALAN-induced effects occurred despite the crickets' exposure to almost natural conditions. Our findings provide further validity to our previous studies on ALAN conducted under lab conditions and establish the deleterious impacts of ALAN on animal behavioral patterns. TEASER: Artificial light at night alters cricket behavior and desynchronizes their stridulation even under near-natural conditions.

Centennial issue

The Journal of Comparative Physiology A, also known as JCPA, was founded by Karl von Frisch and Alfred Kühn in 1924, then under its German title Zeitschrift für vergleichende Physiologie. During the 100 years of its history, it became the leading international journal in comparative physiology and its daughter discipline, neuroethology. As such, it had a major impact on the development of these disciplines. In celebration of this achievement and the nearly 10,000 articles that appeared during the last 100 years, this Centennial Issue is published. Its authors reflect on the history of JCPA and the early pioneers, including women scientists, of comparative physiology; share the impact that the Journal had on their careers; discuss the benefit of the enormous taxonomic diversity of model systems used in studies published in JCPA; contrast this philosophy with the strategy of a limited number of standard biomedical model systems; review popular and trending research topics covered in JCPA; and, by interrogating the past, take a peek into the future of neuroethology.