Physiological Entomology最新文献

Cacopsylla permixta and Cacopsylla bidens are major pests of pears in Iran. They are commonly sprayed with various insecticides up to 12 times a year but control by these means is no longer reliable, suggesting the evolution of resistance. Here, we report about 60-fold variation in diazinon susceptibility both among five geographic populations of C. bidens and among three geographic populations of C. permixta, as well as 12- to 14-fold variations in imidacloprid susceptibility in these populations. The levels of resistance to the two compounds were highly correlated in the different populations. Esterase, cytochrome P450, and glutathione S-transferase activities all varied by about two-fold among the different populations and were also highly correlated with population resistance to the two insecticides, implying differences in metabolism contribute to the differences in resistance. Bioassays with inhibitors of each class of enzyme indicated all three, but particularly the esterases, contributed to the variation in diazinon resistance, while esterase and, in particular, cytochrome P450 activities contributed to the variation in imidacloprid resistance. The most resistant populations of each species also showed some resistance to chlorpyrifos and acetamiprid, suggesting there may be wide cross resistance to organophosphates and neonicotinoids in these populations. The sampled psyllid populations showed lower levels of resistance to representatives of two other classes of insecticides currently used in Iran, spirotetramat and abamectin, though resistance to spirotetramat was detectable and was correlated with diazinon and imidacloprid resistance across populations. We conclude that metabolic resistance to a range of insecticides is now evolving in field populations of both species in Iran, warranting timely development of resistance management plans.

Winter in climatic regions with low temperatures is a challenge for overwintering insects. They are exposed to temperature extremes, which directly cause mortality or lead to energy depletion. The winter hibernaculum of paper wasp gynes protects from predators and rain, but only poorly from ambient temperature. In order to detect physiological adaptations to differing climates, we compared the respiratory metabolism of overwintering gynes of two polistine species from the Mediterranean climate in Italy (Polistes dominula and Polistes gallicus), and of one species from the temperate climate in Austria (Polistes dominula). The wasps' CO₂ emission was measured with stop-flow respirometry in a temperature range from 2.5 to 20 °C. The mass-specific standard (resting) metabolic rate, the main type of metabolism of the dormant insects during overwintering, increased exponentially with ambient temperature but was suppressed in comparison to individuals measured in the summer, which conserves the energy stores. In addition, it was lower in the Mediterranean species (P. dominula and P. gallicus) in comparison to the temperate species (P. dominula), especially at higher temperatures. The active metabolic rate was suppressed to a similar amount. The suppressed metabolism of the overwintering Mediterranean gynes could be an adaptation to the higher winter temperatures to prevent a premature depletion of the energy resources.

The South American tomato pinworm, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is an economically important insect pest of tomatoes. Since its discovery in Burkina Faso in 2016, the use of synthetic insecticides was favored, with many cases of treatment failure. To explore alternative control methods, we conducted a screening of the 12 main tomato varieties produced in the country to test two hypotheses: (i) Some tomato varieties are less likely to attract gravid females and be used as oviposition site; (ii) Some varieties are unsuitable host plants as they allow slower development and lead to higher mortality. The varieties tested include RomaVF, KanonF1, Cobra 26 F1, FBT1, FBT2, FBT3, RaissaF1, JampacktF1, Mongal, Rio Grande, Tropimech, and Petomech. T. absoluta fitness was largely impacted by the tomato variety, especially egg incubation time and larval and pupal stage durations. As a result, the total T. absoluta life cycle was slower on Cobra 26 F1 and Kanon F1 (24.6 ± 1.8 and 25.8 ± 3.3 days, respectively) and faster on FBT1 and Rio grande (22.6 ± 3.0 and 22.8 ± 2.6 days, respectively). None of the varieties impacted the adult lifespan. All varieties were accepted as hosts by gravid females during multiple-choice oviposition assays. The number of eggs laid per female was statistically similar among the varieties. We conclude that two varieties, Kanon F1 and Cobra 26 F1, have better abilities to slow T. absoluta development, limiting the number of generations while increasing the probability that natural enemies find and kill their prey.

The diamondback moth (DBM), Plutella xylostella, is one of the most destructive insect pests on cruciferous plants, which causes huge economic losses annually across the world. Due to its resistance to all classes of insecticides, new effective management approaches are urgently needed. The innexin genes encode gap junction proteins in invertebrates, which play critical roles in cell-to-cell interactions for electrical currents, small molecules and ions. Zero population growth (zpg), one germline-specific innexin protein, is required for survival of differentiating early germ cells during gametogenesis in many insect species. In this study, nine innexin genes were identified from the P. xylostella genome, and named as Pxylinx1.1, Pxylinx1.2, Pxylinx2, Pxylinx3, Pxylinx4, Pxylinx7.1, Pxylinx7.2, PxylshakB.1 and PxylshakB.2. The expression profiles of P. xylostella innexin genes in different developmental stages and tissues were examined, revealing Pxylinx4 was specifically expressed in eggs and female ovaries, which is the candidate zpg gene in P. xylostella. RNA interference (RNAi) was utilized to investigate the functions of Pxylinx4 in egg-laying and egg-hatching. The results showed that RNAi treatment on Pxylinx4 in female P. xylostella, lead to the decrease of the egg-laying but not the egg-hatching. This study improves our understanding of P. xylostella innexin genes and provides a candidate molecular target (Pxylinx4) for developing new approaches to control this economically important pest.

Baculoviruses, like their holometabolous host insects, comprise a monophyletic clade and, since the evolutionary origin of this virus family, have coevolved with their hosts. Despite this intimate coevolutionary relationship, baculoviruses have occasionally diverged independently of the host phylogeny by acquiring new infection mechanisms. Given that current baculovirus genomes contain various anti-apoptotic genes and pseudogenes, the possibility arises that ancient baculoviruses had the genetic means to counter antiviral host apoptosis mechanisms. In this review, we propose an evolutionary scenario for baculovirus diversification in which the development of novel antiviral apoptosis mechanisms in host insects provided the necessary pressure to produce new baculovirus lineages possessing novel anti-apoptotic genes. This apoptotic arms race and subsequent viral host adaptation likely play a crucial role in the establishment of baculovirus diversity.

Trade-offs between negatively associated traits underlie life history evolution. Immune function is often involved in life history trade-offs, because of the energetic and nutritional costs of mounting and maintaining immune responses. Reproductive strategies exist on a continuum between semelparity and iteroparity. While immune function is often downregulated in semelparous organisms because they do not have to account for future survival or reproduction, those organisms that also provide parental care may retain the strength of immune responses. Wolf spiders (family: Lycosidae) are semelparous yet provide parental and provide a good system to evaluate trade-offs between immune responses and reproductive effort. We measured encapsulation response and reproductive effort of female wolf spiders from three reproductive classes: nongravid, gravid, and carrying young. To our knowledge, this is the first investigation of the immune responses of female wolf spiders carrying young. We hypothesized female T. georgicola derive the allocate resources to reproduction at the expense of immune function. However, we found reproductive effort had no relationship with encapsulation response in spiders carrying young. There was also no difference in the encapsulation response between reproductive classes. Individual differences in resource acquisition may explain the lack of a relationship between reproductive effort and encapsulation in spiders carrying young. Spiders with larger resource pools have more resources to devote to reproduction and immunity. Maintaining resources to mount immune responses across reproductive stages could also increase the fitness of female wolf spiders because they must survive to carry and disperse the young, which reduces kin competition among spiderlings.

Surface features of plants can influence the searching efficiency and survival of predatory insects. Surfaces act as barriers preventing attachment of both phytophages and also their insect predators. In this regard, we focused on the oviposition site selection and the attachment ability of all life stages (eggs, larvae, imagines) of two common ladybird species, Propylea quatuordecimpunctata and Harmonia axyridis (Coleoptera: Coccinellidae), on artificial and natural substrates with different surface features and properties (roughness, wettability). Both species preferred a hydrophilic surface as the oviposition site and this can be correlated with the better performance of both larvae and adults on these substrates compared with hydrophobic ones. The egg glue of both ladybird species can wet hydrophobic surfaces such as those of many plant leaves and also with prominent 3D wax coverage. The surface roughness has an important role in the oviposition site selection in P. quatuordecimpunctata, but not in H. axyridis. The oviposition preference for smooth surfaces in P. quatuordecimpunctata could be due to better performance of larvae on smooth substrates compared with rough ones. The egg glue of both species can adapt to artificial and natural surfaces characterized by different asperity sizes faithfully replicating their shape, except for very high asperity sizes or big trichomes. The results of the present research can shed light on the mechanical ecology of the evolutionary successful Coccinellidae and may aid in the development of suitable substrates for coccinellid egg-laying, in order to improve the mass rearing technique of species used in biological control.

This study investigated the behavioural and electrophysiological responses of the thrips Liothrips jatrophae to conspecific extracts and some of its identified compounds. We integrated four constituents of the insect's chemical communication: identification of the compounds from L. jatrophae extract, behavioural response to extracts and synthetic blends, morphology of the main olfactory receptors (antennae), and electrophysiological response of the main olfactory receptors of the antennae to extracts and to individual synthetic compounds and synthetic blends. Analysis by GC–MS revealed that the L. jatrophae extract contains a mixture of 11 compounds (perillene, tridecane, β-acaridial, tetradecane, pentadecane, heptadecane, heptadecene, dodecyl isobutyrate, tridecyl isobutyrate, tetradecyl isobutyrate and hexadecyl isobutyrate). The major compounds were tridecane, pentadecane, tetradecyl isobutyrate and hexadecyl isobutyrate. When the thrips were exposed to the extracts, they exhibited an escape response, accompanied by other behavioural responses, such as rapid sideways movement and lifting of the abdomen and secretion of a drop at the tip of the abdomen. Morphology and distribution of the L. jatrophae antennal sensilla were examined with a scanning electron microscope (SEM). The antenna consists of a scape, pedicel and six flagella. The microphotographs showed two types of sensilla: basiconica and trichoidea. Single sensillum recording (SSR) showed that the sensilla basiconica located in segment IV of the antenna were the most sensitive to the L. jatrophae extracts and to a synthetic blend, whereas the sensilla trichoidea did not exhibit electrophysiological response.

The study of desiccation resistance and its underlying traits is key to understanding species responses to changes in water availability, especially in the context of predicted increases in the frequency and severity of droughts due to climate change. We performed laboratory experiments using dung beetles, important ecosystem service providers, to investigate variations in physiological traits within species, both at population and individual levels. Desiccation resistance, water loss tolerance and water content were measured in lowland and mountain populations to investigate whether physiological traits vary (i) according to elevation across four species, and (ii) according to sex or male morphology (minor and major morphs) in two species, and if these responses were consistent across species. Our results showed that desiccation resistance of dung beetles varies both at individual and population levels. We found that desiccation resistance varied between lowland and mountain populations, but no differences were found for other traits such as water loss tolerance. Moreover, differences in individual physiological responses between females, major and minor males suggest that females were more resistant to desiccation than minors and majors, but these responses were species-dependent. Our analysis at two hierarchical levels, individual and population, emphasizes the importance of considering within-species variability in predictions of how species may respond to future climatic conditions. Predictions of the responses of species to environmental change may produce different conclusions if they rely on observations from single populations or take into account only a limited range of phenotypes per population.