Broadband Photoreceptors Are Involved in Violet Light Preference in the Parasitoid Fly Exorista Japonica

High-quality genome of the zoophytophagous stink bug, Nesidiocoris tenuis, informs their food habit adaptation

The zoophytophagous stink bug, Nesidiocoris tenuis, is a promising natural enemy of micro-pests such as whiteflies and thrips. This bug possesses both phytophagous and entomophagous food habits, enabling it to obtain nutrition from both plants and insects. This trait allows us to maintain its population density in agricultural fields by introducing insectary plants, even when the pest prey density is extremely low. However, if the bugs' population becomes too dense, they can sometimes damage crop plants. This dual character seems to arise from the food preferences and chemosensation of this predator. To understand the genomic landscape of N. tenuis, we examined the whole genome sequence of a commercially available Japanese strain. We used long-read sequencing and Hi-C analysis to assemble the genome at the chromosomal level. We then conducted a comparative analysis of the genome with previously reported genomes of phytophagous and hematophagous stink bugs to focus on the genetic factors contributing to this species' herbivorous and carnivorous tendencies. Our findings suggest that the gustatory gene set plays a pivotal role in adapting to food habits, making it a promising target for selective breeding. Furthermore, we identified the whole genomes of microorganisms symbiotic with this species through genomic analysis. We believe that our results shed light on the food habit adaptations of N. tenuis and will accelerate breeding efforts based on new breeding techniques for natural enemy insects, including genomics and genome editing.

Expression and function of opsin genes associated with phototaxis in Zeugodacus cucurbitae Coquillett (Diptera: Tephritidae)

BACKGROUND

Zeugodacus cucuribitae is a major agricultural pest that causes significant damage to varieties of plants. Vision plays a critical role in phototactic behavior of herbivorous insects. However, the effect of opsin on the phototactic behavior in Z. cucuribitae remains unknown. The aim of this research is to explore the key opsin genes that associate with phototaxis behavior of Z. cucurbitae.

RESULTS

Five opsin genes were identified and their expression patterns were analyzed. The relative expression levels of ZcRh1, ZcRh4 and ZcRh6 were highest in 4-day-old larvae, ZcRh2 and ZcRh3 were highest in 3rd-instar larvae and 5-day-old pupae, respectively. Furthermore, five opsin genes had the highest expression levels in compound eyes, followed by the antennae and head, whereas the lower occurred in other tissues. The expression of the long-wavelength-sensitive (LW) opsins first decreased and then increased under green light exposure. In contrast, the expression of ultraviolet-sensitive (UV) opsins first increased and then decreased with the duration of UV exposure. Silencing of LW opsin (dsZcRh1, dsZcRh2, and dsZcRh6) and UV opsin (dsZcRh3 and dsZcRh4) reduced the phototactic efficiency of Z. cucurbitae to green light by 52.27%, 60.72%, and 67.89%, and to UV light by 68.59% and 61.73%, respectively.

CONCLUSION

The results indicate that RNAi inhibited the expression of opsin, thereby inhibiting the phototaxis of Z. cucurbitae. This result provides theoretical support for the physical control of Z. cucurbitae and lays the foundation for further exploration of the mechanism of insect phototaxis. © 2023 Society of Chemical Industry.

Negative phototaxis of jumping cocooned parasitoid wasp larvae against short wavelengths and physicochemical properties of the cocoon shell

The parasitoid wasp Bathyplectes anurus (Hymenoptera: Ichneumonidae: Campopleginae) is a successful biocontrol agent against the alfalfa weevil, Hypera postica. This weevil is a serious pest of beneficial fabaceous plants such as alfalfa and Chinese milk vetch. One of the possible reasons for the success of this wasp in hot climates may be the ability of its cocooned larvae to repeatedly jump and roll until they relocate themselves away from detrimental sunlight and heat. It is not yet known which wavelengths of light trigger this avoidance behavior or the microstructure of the cocoon shell that might allow light transmission. Here, the response of the cocooned larvae to different wavelengths, and the microstructure, hardness, and elemental components of the cocoon shell were studied. A population of cocooned larvae were introduced on the boundary line between illuminated and shaded areas with blue, green, red, or near-infrared light-emitting diodes. The cocoons moved away from the blue and green light. The distance from the boundary to the cocoons in the shaded area was longer under these long wavelengths, followed by the red light and shortest under the near-infrared light and nil under darkness. No difference was found in mortality between different wavelengths after three days of illumination. Scanning electron microscope observations of the surface of the cocoon shell revealed that the belt-like central ridge was porous, which likely allows ventilation and light transmission. The surface of the cocoon shell showed a uniform distribution of sulfur, potentially aiding in the capture of green wavelengths. The ridge had twice the thickness of the main body and was 1.9 times harder than the main body. These results may be applied to better understand the individual responses of this biological control agent to modifications to their environment, including light pollution.

Nocturnal mosquito Cryptochrome 1 mediates greater electrophysiological and behavioral responses to blue light relative to diurnal mosquito Cryptochrome 1

Nocturnal Anopheles mosquitoes exhibit strong behavioral avoidance to blue-light while diurnal Aedes mosquitoes are behaviorally attracted to blue-light and a wide range of other wavelengths of light. To determine the molecular mechanism of these effects, we expressed light-sensing Anopheles gambiae (AgCRY1) and Aedes aegypti (AeCRY1) Cryptochrome 1 (CRY) genes under a crypGAL4-24 driver line in a mutant Drosophila genetic background lacking native functional CRY, then tested behavioral and electrophysiological effects of mosquito CRY expression relative to positive and negative CRY control conditions. Neither mosquito CRY stops the circadian clock as shown by robust circadian behavioral rhythmicity in constant darkness in flies expressing either AgCRY1 or AeCRY1. AgCRY1 and AeCRY1 both mediate acute increases in large ventral lateral neuronal firing rate evoked by 450 nm blue-light, corresponding to CRY's peak absorbance in its base state, indicating that both mosquito CRYs are functional, however, AgCRY1 mediates significantly stronger sustained electrophysiological light-evoked depolarization in response to blue-light relative to AeCRY1. In contrast, neither AgCRY1 nor AeCRY1 expression mediates measurable increases in large ventral lateral neuronal firing rates in response to 405 nm violet-light, the peak of the Rhodopsin-7 photoreceptor that is co-expressed in the large lateral ventral neurons. These results are consistent with the known action spectra of type 1 CRYs and lack of response in cry-null controls. AgCRY1 and AeCRY1 expressing flies show behavioral attraction to low intensity blue-light, but AgCRY1 expressing flies show behavioral avoidance to higher intensity blue-light. These results show that nocturnal and diurnal mosquito Cryptochrome 1 proteins mediate differential physiological and behavioral responses to blue-light that are consistent with species-specific mosquito behavior.

UV-LED lights enhance the establishment and biological control efficacy of Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae)

The zoophytophagous mirid Nesidiocoris tenuis (Hemiptera: Miridae) is one of the biological control agents against the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae), a major pest of greenhouse crops. The successful establishment of a biological control agent and its co-occurrence with the target pests increases the efficacy of biological control programs in greenhouses. In this study, we explored the effects of different wavelengths of LED light on establishment of N. tenuis in laboratory condition, with the goal of enhancing the biological control of B. tabaci in greenhouse crops. Nesidiocoris tenuis was most strongly attracted by LED light at a wavelength of 385 nm. This same wavelength was also highly attractive to B. tabaci in Y-tube experiments with lights of specific wavelengths provided is each arm of the apparatus. In trials in growth chambers, we verified the attraction of N. tenuis to 385 nm wavelength. When LED light at a wavelength of 385 nm was used in a growth chamber for 6 hours out of 24 hours, it significantly increased the remaining number of N. tenuis in growth chamber and level of predation compared to treatment with white LED light or without LED light. In conclusion, UV-LED light at a wavelength of 385 nm attracts both B. tabaci and N. tenuis. Thus, it would be used for enhancing early establishment of this mirid bug, better spatial congruence of both mirid bug and whitefly, and better control of the whitefly.

Have artificial lighting and noise pollution caused zoonosis and the COVID-19 pandemic? A review

Where did the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) come from? Did it spread to 'patient zero' through proactive human-animal contact? Why did humans faced an increasing number of zoonotic diseases in the past few decades? In this article, we propose a new theory by which human pollution such as artificial lighting and noise accentuate pathogen shedding from bats and other wild habitants in urban environments. This theory differs from the current hypothesis that wildlife trades and bushmeat consumption largely contribute to the spillover of zoonotic pathogens to humans. As natural reservoirs, bats harbor the greatest number of zoonotic viruses among all mammalian orders, while they also have a unique immune system to maintain functioning. Some bat species roost in proximity with human settlements, including urban communities and surrounding areas that are potentially most impacted by anthropogenic activities. We review the behavioral changes of wild habitants, including bats and other species, caused by environmental pollution such as artificial lighting and noise pollution, with focus on the spillover of zoonotic pathogens to humans. We found that there is a strong positive correlation between environmental stress and the behavior and health conditions of wild species, including bats. Specifically, artificial lighting attracts insectivorous bats to congregate around streetlights, resulting in changes in their diets and improved likelihood of close contact with humans and animals. Moreover, many bat species avoid lit areas by expending more energies on commuting and foraging. Noise pollution has similar effects on bat behavior. Bats exposed to chronic noise pollution have weakened immune functions, increased viral shedding, and declined immunity during pregnancy, lactation, and vulnerable periods due to noised-induced stress. Other wild species exposed to artificial lighting and noise pollution also show stress-induced behaviors and deteriorated health. Overall, evidence supports our hypothesis that artificial lighting and noise pollution have been overlooked as long-term contributors to the spillover of zoonotic pathogens to humans in urban environments.

Wavelength-Specific Behavior of the Western Flower Thrips (Frankliniella occidentalis): Evidence for a Blue-Green Chromatic Mechanism

The western flower thrips (Frankliniella occidentalis) is a serious pest in horticulture, feeding on leaf tissue and floral resources. Blue and yellow sticky traps are commonly used for monitoring and control in greenhouses. The mechanisms underlying the color preferences are largely unknown. The use of light-emitting diodes (LEDs) is a promising approach to increase the attractiveness of visual traps and to study the color choice behavior in insects. The color preferences of F. occidentalis were systematically investigated in a series of choice experiments with several LEDs from the ultraviolet (UV) and visible spectral range. Blue LEDs were most attractive, followed by green, while only a moderate attractiveness of UV was observed. Blue and green were identified as two separate attractive ranges. When light from blue and green LEDs was mixed, the attractiveness decreased compared to its single components. In conclusion, F. occidentalis exhibits two different wavelength specific behaviors towards blue and green. Compelling indications are provided that these behaviors are controlled by two photoreceptors maximally sensitive in the blue and green range with an inhibitory chromatic interaction between both. Since the known UV sensitive photoreceptor could be confirmed, a trichromatic photoreceptor setup is suggested for F. occidentalis. For advanced plant protection strategies, the results offer several opportunities to optimize monitoring or even develop mass trapping devices.

Circadian Regulation of Light-Evoked Attraction and Avoidance Behaviors in Daytime- versus Nighttime-Biting Mosquitoes

Mosquitoes pose widespread threats to humans and other animals as disease vectors [1]. Day- versus night-biting mosquitoes occupy distinct time-of-day niches [2, 3]. Here, we explore day- versus night-biting female and male mosquitoes' innate temporal attraction/avoidance behavioral responses to light and their regulation by circadian circuit and molecular mechanisms. Day-biting mosquitoes Aedes aegypti, particularly females, are attracted to light during the day regardless of spectra. In contrast, night-biting mosquitoes, Anopheles coluzzii, specifically avoid ultraviolet (UV) and blue light during the day. Behavioral attraction to/avoidance of light in both species change with time of day and show distinct sex and circadian neural circuit differences. Males of both diurnal and nocturnal mosquito species show reduced UV light avoidance in anticipation of evening onset relative to females. The circadian neural circuits of diurnal/day- and nocturnal/night-biting mosquitoes based on PERIOD (PER) and pigment-dispersing factor (PDF) expression show similar but distinct circuit organizations between species. The basis of diurnal versus nocturnal behaviors is driven by molecular clock timing, which cycles in anti-phase between day- versus night-biting mosquitoes. Observed differences at the neural circuit and protein levels provide insight into the fundamental basis underlying diurnality versus nocturnality. Molecular disruption of the circadian clock severely interferes with light-evoked attraction/avoidance behaviors in mosquitoes. In summary, attraction/avoidance behaviors show marked differences between day- versus night-biting mosquitoes, but both classes of mosquitoes are circadian and light regulated, which may be applied toward species-specific control of harmful mosquitoes.

Advances in insect phototaxis and application to pest management: a review

Many insects, especially nocturnal insects, exhibit positive phototaxis to artificial lights. Light traps are currently used to monitor and manage insect pest populations, and play a crucial role in physical pest control. Efficient use of light traps to attract target insect pests is an important topic in the application of integrated pest management (IPM). Phototactic responses of insects vary among species, light characteristics and the physiological status of the insects. In addition, light can cause several biological responses, including biochemical, physiological, molecular and fitness changes in insects. In this review, we discuss several hypotheses on insect phototaxis, factors affecting insect phototaxis, insect-sensitive wavelengths, biological responses of insects to light, and countermeasures for conserving beneficial insects and increasing the effect of trapping. In addition, we provide information on the different sensitivities to wavelengths causing positive phototactic behavior in > 70 insect pest and beneficial insect species. The use of advanced light traps equipped with superior light sources, such as light-emitting diodes (LEDs), will make physical pest control in IPM more efficient. © 2019 Society of Chemical Industry.

Effect of Different Light Spectrum in Helicoverpa armigera Larvae during HearNPV Induced Tree-Top Disease

Lepidopteran larvae upon infection by baculovirus show positive photo-tactic movement during tree-top disease. In light of many insects exploiting specific spectral information for the different behavioral decision, each spectral wavelength of light is an individual parsimonious candidate for such behavior stimulation. Here, we investigated the responses of third instar Helicoverpa armigera larvae infected by Helicoverpa armigera nucleopolyhedrovirus (HearNPV) to white (broad-spectrum), blue (450–490 nm), UVA (320–400 nm), and UVB (290–320 nm) lights for the tree-top disease. Our findings suggest that tree-top phenomenon is induced only when the light is applied from above. Blue, white and UVA lights from above induced tree-top disease, causing infected larvae to die in an elevated position compared to those larvae living in the complete dark. In contrast, UVB from above did not induce tree-top disease. Blue light exerted the maximum photo-tactic response, significantly (p < 0.01) higher than white light. The magnitude of the response decreased with decreasing wavelength to UVA, and no response at UVB. Our results suggested that the spectral wavelength of the light has a significant effect on the induction of the tree-top disease in H. armigera third instar larvae infected with HearNPV.