Exploring the hormetic effects of radiation on the life table parameters of Spodoptera frugiperda.

BACKGROUND: Spodoptera frugiperda, a global agricultural pest, can be effectively controlled through the sterile insect technique. However, exposure to low-dose radiation below the sterilization threshold may induce hormetic effects. Here, the biphasic aspects of the fertile progeny population of S. frugiperda were analyzed using an age-stage, two-sex life table after dosing male and female pupae with 10-350 Gy gamma radiation. RESULTS: The parental sterilizing dose for 6-day-old female and male pupae was 200 and 350 Gy, respectively. The total longevity, pre-adult survival rate, net reproduction rate, and intrinsic growth rate of the offspring population increased with decreasing radiation doses from 250 to 10 Gy. Offspring population of parents treated with low doses of 10-100 Gy showed better life table parameters compared to non-irradiated controls. Females and males fecundity irradiated with 10, 50, and 100 Gy and 10 Gy, respectively, exceeded controls, producing 2339.4, 2726.4, 2311, and 2369 eggs, as opposed to 1802.9 eggs produced by the controls. Males irradiated with 10 Gy displayed the highest intrinsic rates of increase and net reproduction rate, at 0.1709 and 682.3, respectively. Projections from the survival rate and fecundity indicated that female and male S. frugiperda populations after 10 Gy irradiation may grow considerably faster than the controls. CONCLUSION: This study explores the hormetic effects of low-dose radiation on S. frugiperda through life table analysis, while providing enhancements for utilizing substerilizing gamma dose in a modified F1 sterility technique. © 2023 Society of Chemical Industry.

Genomes of 12 fig wasps provide insights into the adaptation of pollinators to fig syconia.

Figs and fig pollinators are one of the few classic textbook examples of obligate pollination mutualism. The specific dependence of fig pollinators on the relatively safe living environment with sufficient food sources in the enclosed fig syconia implies that they are vulnerable to habitat changes. However, there is still no extensive genomic evidence to reveal the evolutionary footprint of this long-term mutually beneficial symbiosis in fig pollinators. In fig syconia, there are also non-pollinator species. The non-pollinator species differ in their evolutionary and life histories from pollinators. We conducted comparative analyses on 11 newly sequenced fig wasp genomes and one previously published genome. The pollinators colonized the figs approximately 66.9 million years ago, consistent with the origin of host figs. Compared with non-pollinators, many more genes in pollinators were subject to relaxed selection. Seven genes were absent in pollinators in response to environmental stress and immune activation. Pollinators had more streamlined gene repertoires in the innate immune system, chemosensory toolbox, and detoxification system. Our results provide genomic evidence for the differentiation between pollinators and nonpollinators. The data suggest that owing to the long-term adaptation to the fig, some genes related to functions no longer required are absent in pollinators.

Comparative Performance of the Fall Armyworm (Lepidoptera: Noctuidae) Reared on Various Cereal-Based Artificial Diets.

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera, Noctuidae), is a polyphagous and highly destructive agricultural pest that invaded mainland China in 2019. To facilitate research on this pest, it is important to formulate and formalize a suitable artificial diet based on local ingredients. In this study, the life histories of fall armyworm reared on corn leaves and four artificial diets were recorded. The four artificial diets used were: soybean and sucrose-based (SS), soybean and wheat germ-based (SW), chickpea and wheat germ-based (CPW), and corn and soybean-based (CNS). The intrinsic rates of increase were 0.1957, 0.1981, 0.1816, 0.1748, and 0.1464 per day in the fall armyworm populations fed corn leaves, CNS, SW, CPW, and SS, respectively. The highest fecundity (F = 1225.4 eggs per female) and net reproduction rate (R0 = 544.7 offspring per individual) were observed for the fall armyworm reared on the CNS diet. Moreover, the developmental rate, survival rate, and fecundity were used to calculate the projection of the population growth. Projection results showed that the fall armyworm populations can increase considerably faster when fed the CNS diet compared with the other diets. In addition, the mass-rearing system showed that the most efficient and economical strategy would be to rear the fall armyworm on the CNS diet. The results indicated that the CNS diet was the most suitable diet for the fall armyworm mass rearing.

Frozen section and electron microscopy studies of the infection of the red palm weevil, Rhynchophorus ferrugineus (coleoptera:curculionidae) by the entomopathogenic fungus Metarhizium anisopliae.

This study determined the pathogenicity of Metarhizium anisopliae strain SD-3 against invasive red palm weevil (RPW), Rhynchophorus ferrugineus Olivier (coleoptera:curculionidae) larvae in Hainan Province, China. Inoculation of 1 × 108 conidia/mL caused 100 % mortality of R. ferrugineus, indicating that the conidia of strain SD-3 were highly virulent. The process of invasion mechanism was showed by scanning electron microscopy (SEM) and frozen section as follows. Once R. ferrugineus was infected by strain SD-3, M. anisopliae hyphae first invaded the cuticular and body cavity of R. ferrugineus. Secondly, well-developed muscles, fat, tracheaes and digestive tube tissues in the abdomen of R. ferrugineus were then decomposed and absorbed by M. anisopliae hyphae, leading to the total destruction of the larvae. Finally, M. anisopliae hyphae reproduced, resulting in a large number of conidia in the body of RPW. The SEM and frozen section are convenient tools to observe the mode of action of entomopathogenic fungi and to observe how M. anisopliae is able to colonize and infect the host.

Screening of tropical isolates of Metarhizium anisopliae for virulence to the red palm weevil Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae).

The red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) is a serious pest of the palm tree in tropical regions of the world. One strain of Metarhizium sp. ZJ-1, isolated from Chinese soils, was evaluated for growth characteristics, and screened for its virulence to R. ferrugineus larvae in laboratory conditions. An approximately 685-bp fragment was amplified by ITS (ITS1-5.8S-ITS2) PCR from strain ZJ-1, further phylogenetic analysis revealed that 93 % similarity to Metarhizium anisopliae. Inoculation of 1 × 10(8) conidia/mL caused 100 % mortality of R. ferrugineus, LT50 levels of ZJ-1 were 1.66 days (1 × 10(8) conidia/mL), indicating that the conidia of strain ZJ-1 were highly virulent. These results suggest that M. anisopliae ZJ-1 has potential as an effective and persistent biological control agent for R. ferrugineus.

Large proportion of genes in one cryptic WO prophage genome are actively and sex-specifically transcribed in a fig wasp species.

BACKGROUND: Cryptic prophages are genetically defective in their induction and propagation, and are simply regarded as genetic remnants. There are several putative cryptic WO prophages in the sequenced Wolbachia genomes. Whether they are lytic is unclear and their functions are poorly understood. Only three open reading frames (ORFs) in cryptic WO prophages have been reported to be actively transcribed. RESULTS: In this study, we comprehensively examined the transcription of the only cryptic WO prophage (WOSol) in a Wolbachia strain that infects a fig wasp, Ceratosolen solmsi (Agaonidae, Chalcidoidea). By analyzing the transcriptions of all the ORFs of WOSol in both sexes of C. solmsi, using qualitative and quantitative methods, we demonstrated that i) a high percentage of ORFs are actively transcribed (59%, 17/29); ii) the expression of these ORFs is highly sex-specific, with a strong male bias (three in females and 15 in males); iii) an ank (ankyrin-domain-containing) gene actively transcribed in both wasp sexes is more highly expressed in males. CONCLUSIONS: A large proportion of the genes in the cryptic WO prophage WOSol are expressed, which overturns the concept that cryptic prophages are simply genetically defective. The highly sex-specific expression patterns of these genes in the host suggest that they play important roles in Wolbachia biology and its reproductive manipulation of its insect host, particularly through the males.

Adaptive evolution of the circadian gene timeout in insects.

Most insects harbor two paralogous circadian genes, namely timeout and timeless. However, in the Hymenoptera only timeout is present. It remains unclear whether both genes, especially timeout in hymenopteran insects, have distinct evolutionary patterns. In this study, we examine the molecular evolution of both genes in 25 arthropod species, for which whole genome data are available, with addition of the daily expression of the timeout gene in a pollinating fig wasp, Ceratosolen solmsi (Hymenoptera: Chalcidoidea: Agaonidae). Timeless is under stronger purifying selection than timeout, and timeout has positively selected sites in insects, especially in the Hymenoptera. Within the Hymenoptera, the function of timeout may be conserved in bees and ants, but still evolving rapidly in some wasps such as the chalcids. In fig wasps, timeout is rhythmically expressed only in females when outside of the fig syconium but arrhythmically in male and female wasps inside the syconium. These plastic gene expressions reflect adaptive differences of males and females to their environment.

Delimitation and description of the immature stages of a pollinating fig wasp, Ceratosolen solmsi marchali Mayr (Hymenoptera: Agaonidae).

The mutualism between fig trees and their wasp pollinators is a model system for many ecological and evolutionary studies. However, the immature stages of pollinating fig wasps have rarely been studied. We monitored developing fig wasps of known ages and performed a series of dissections at 24 h intervals to identify key developmental traits of Ceratosolen solmsi marchali Mayr (Hymenoptera: Agaonidae), a pollinator of Ficus hispida L. (Moraceae). We identified where in the Ficus ovary eggs were deposited and time to hatch. We were also able to identify the timing and key underlying characters of five larval instars, three sub-pupal stages, and a single prepupal stage. We provide detailed morphological descriptions for the key stages and report some behavioral observations of the wasps in the several developmental stages we recorded. Scanning electron microscope images were taken.

Obligate mutualism within a host drives the extreme specialization of a fig wasp genome.

BACKGROUND: Fig pollinating wasps form obligate symbioses with their fig hosts. This mutualism arose approximately 75 million years ago. Unlike many other intimate symbioses, which involve vertical transmission of symbionts to host offspring, female fig wasps fly great distances to transfer horizontally between hosts. In contrast, male wasps are wingless and cannot disperse. Symbionts that keep intimate contact with their hosts often show genome reduction, but it is not clear if the wide dispersal of female fig wasps will counteract this general tendency. We sequenced the genome of the fig wasp Ceratosolen solmsi to address this question. RESULTS: The genome size of the fig wasp C. solmsi is typical of insects, but has undergone dramatic reductions of gene families involved in environmental sensing and detoxification. The streamlined chemosensory ability reflects the overwhelming importance of females finding trees of their only host species, Ficus hispida, during their fleeting adult lives. Despite long-distance dispersal, little need exists for detoxification or environmental protection because fig wasps spend nearly all of their lives inside a largely benign host. Analyses of transcriptomes in females and males at four key life stages reveal that the extreme anatomical sexual dimorphism of fig wasps may result from a strong bias in sex-differential gene expression. CONCLUSIONS: Our comparison of the C. solmsi genome with other insects provides new insights into the evolution of obligate mutualism. The draft genome of the fig wasp, and transcriptomic comparisons between both sexes at four different life stages, provide insights into the molecular basis for the extreme anatomical sexual dimorphism of this species.

Chaos of Wolbachia sequences inside the compact fig syconia of Ficus benjamina (Ficus: moraceae).

Figs and fig wasps form a peculiar closed community in which the Ficus tree provides a compact syconium (inflorescence) habitat for the lives of a complex assemblage of Chalcidoid insects. These diverse fig wasp species have intimate ecological relationships within the closed world of the fig syconia. Previous surveys of Wolbachia, maternally inherited endosymbiotic bacteria that infect vast numbers of arthropod hosts, showed that fig wasps have some of the highest known incidences of Wolbachia amongst all insects. We ask whether the evolutionary patterns of Wolbachia sequences in this closed syconium community are different from those in the outside world. In the present study, we sampled all 17 fig wasp species living on Ficus benjamina, covering 4 families, 6 subfamilies, and 8 genera of wasps. We made a thorough survey of Wolbachia infection patterns and studied evolutionary patterns in wsp (Wolbachia Surface Protein) sequences. We find evidence for high infection incidences, frequent recombination between Wolbachia strains, and considerable horizontal transfer, suggesting rapid evolution of Wolbachia sequences within the syconium community. Though the fig wasps have relatively limited contact with outside world, Wolbachia may be introduced to the syconium community via horizontal transmission by fig wasps species that have winged males and visit the syconia earlier.