Physiological Entomology最新文献

Anthropogenic climate change is thought to present a significant threat to biodiversity, in particular to tropical ectotherms, and the effects of long-term developmental heat stress on this group have received relatively little research attention. Here, we studied the effects of experimentally raising developmental temperatures on a tropical butterfly. We measured survival, development time, adult body mass and wing size of Heliconius erato demophoon (Linnaeus) (Lepidoptera: Nymphalidae) across three temperature treatments. Egg survival was lower in the hotter treatments, with 84%, 73% and 49% of eggs hatching in the 20–30°C (fluctuating temperature with 12 h at 20°C followed by 12 h at 30°C), 23–33°C and 26–36°C treatments, respectively. Larval survival was three times lower in the 26–36°C treatment (8%) compared with the 20–30°C treatment (26%), and we did not detect differences in pupal survival across treatments due to high mortality in earlier stages. Under a moderately increased temperature at 23–33°C, larvae developed faster and adults had a higher body mass and wing loading, but this was not seen in the hottest treatment (26–36°C). Females were also heavier than males in the 23–33°C treatment, but there was no associated increase in wing size. This may suggest a different developmental response to moderately elevated temperatures between the sexes. In summary, high developmental temperatures are particularly lethal for eggs and less so for larvae and also affect adult morphology. This highlights the importance of understanding the effects of temperature variation across ontogeny in tropical ectotherms.

A detailed effect of continuous exposure of Cd on an important pest of crops like Helicoverpa armigera is lacking in the current literature. The cadmium was provisioned at 1.25, 2.5 and 5 mg/kg in the artificial diet and fed to newly hatched larvae for at least three subsequent generations. The total developmental period and fecundity were severely affected with no larval hatching in treated insects. Total haemocyte count and differential haemocyte count (i.e., granulocytes and plasmatocytes) were decreased significantly compared to controls in treated insects. The antioxidant system (i.e., catalase, glucose-6-phosphate dehydrogenase, superoxide dismutase and peroxidase), and the two detoxifying agents glutathione-s-transferase showed increased activity compared to controls. The results of the acetylcholinesterase assay showed a decrease in activity. Increased rate of aspartate aminotransferase, alanine aminotransferase, uric acid and decreased rate of alkaline phosphatase and lactate dehydrogenase in the first generation but showing an increasing trend in next two generations. The acid phosphatase activity was increased in the first two generations but significantly reduced in the third generation. The discrepancy in all physiological activities corresponded with the histological study of midgut infrastructure. It is inferred from the obtained results that cadmium continuous exposure affects every system of any organism that may perform irreparable damages.

A detailed effect of continuous exposure of Cd on an important pest of crops like Helicoverpa armigera is lacking in the current literature. The cadmium was provisioned at 1.25, 2.5 and 5 mg/kg in the artificial diet and fed to newly hatched larvae for at least three subsequent generations. The total developmental period and fecundity were severely affected with no larval hatching in treated insects. Total haemocyte count and differential haemocyte count (i.e., granulocytes and plasmatocytes) were decreased significantly compared to controls in treated insects. The antioxidant system (i.e., catalase, glucose-6-phosphate dehydrogenase, superoxide dismutase and peroxidase), and the two detoxifying agents glutathione-s-transferase showed increased activity compared to controls. The results of the acetylcholinesterase assay showed a decrease in activity. Increased rate of aspartate aminotransferase, alanine aminotransferase, uric acid and decreased rate of alkaline phosphatase and lactate dehydrogenase in the first generation but showing an increasing trend in next two generations. The acid phosphatase activity was increased in the first two generations but significantly reduced in the third generation. The discrepancy in all physiological activities corresponded with the histological study of midgut infrastructure. It is inferred from the obtained results that cadmium continuous exposure affects every system of any organism that may perform irreparable damages.

Specialist and generalist insect herbivores evolved different strategies to process host-plant metabolites. We explored frass composition in Laothoe populi (L.) caterpillars (Lepidoptera: Sphingidae), a specialist moth species that is closely associated with plants of the Salicaceae (Mirb.) family. We fed the caterpillars with leaves from three willow species (Salix caprea L., S. purpurea L. and S. viminalis L.), one willow hybrid (S. x rubens Schrank) and one poplar species (Populus tremula L.). Using untargeted metabolomics, we compared the chemical composition and variation among leaf and frass samples. We quantified the chemical variation using either a simple index based on the presence and concentration of metabolites (i.e., Bray-Curtis) or an index that additionally accounts for chemical structural-compositional similarity (CSCS) among metabolites. Due to the high degree of dietary specialisation, we expected low host-specific variation in frass composition among the caterpillars. Based on literature, we further hypothesised that ingested salicinoids will be largely modified in the caterpillar gut while flavonoids will be often passively excreted. Finally, we compared chemical variation among the samples when quantified with Bray-Curtis or CSCS metrics. As expected, we found relatively low host-specific variation in the chemical composition of caterpillar frass. Our results further suggest that flavonoids were largely passively excreted by the caterpillars, while salicinoids were metabolised in the gut. Finally, we found that chemical composition measures based on Bray-Curtis overestimated the differences in chemical composition between frass and leaves, suggesting that for these type of samples CSCS measures are better suited to reflect metabolic changes more realistically.

Molecular studies on odorant receptors (ORs), odorant-binding proteins (OBPs) and the functioning of the receptor and pheromone signal transduction in fruit fly Bactrocera species have expanded exponentially during the past few decades. OBPs contribute to the sensing of the olfactory system (OS) via the transduction of odorants through the sensillum lymph. However, ORs, a family of G-protein-coupled receptors in Bactrocera and various other species, exhibit heightened responsiveness to multiple chemical odours such as hormones, sensory stimuli and neurotransmitters. The apparent mechanism involves a combinatorial code encompassing both peripheral and antennal lobe processing, facilitating the reception of sexual pheromones and environmental cues. The OS is specifically designed to recognize and process information from volatile chemical signals, and these chemical signals play an important function in various flies. Insects rely on these chemicals to navigate and comprehend their surroundings. A mature insect OS is composed of two pairs of sensillae-covered palps, antennae and two primary pairs of olfactory appendages on the anterior head. It has been shown that chemosensory gene families contribute in odour perception. These include various neuroreceptor families, such as OBPs, chemosensory proteins and sensory neuron membrane proteins. Additionally, there are three divergent chemoreceptors, namely ORs, ionotropic receptors and gustatory receptors. Methods based on systematic biology, molecular biology and bioinformatics tools have rapidly emerged to investigate the insect communication systems and provide new insights for the management of many agricultural pest. Several aromatic compounds, including semiochemicals and pheromones, have been employed to defend crops and animals from destructive fruit flies and other invasive and frugivorous species. To promote the expansion of the cropping system, the utilization of phytochemical lures can be convenient for sustainable agriculture production and enhance food security. Hence, this review examined the state of the art in chemical communication of insects with a focus on fruit fly pest species to identify OS and their semiochemical receptors, protein receptors and chemosensory receptors (CSRs), as well as their practical applications for biological control and integrated pest management are highlighted.

Worldwide spread in the incidence of diabetes justified the need of extensive research in an appropriate model system to develop an effective treatment strategy for diabetology. In recent years, because of animal ethical issues and limitations, the silkworm (Bombyx mori) has emerged as a perfect invertebrate model for various biomedical experiments. However, there are several issues related to induce hyperglycaemia in the mammalian system that have not been studied in the silkworms. In the present study, we investigated the consequences of induced hyperglycaemia by oral and intravascular administration of streptozotocin (STZ) and glucose in the silkworms. Interestingly, results confirmed the competence of STZ to induce hyperglycaemia when administered through intravascular route, but suppress the glucose concentration if administrated orally in the silkworms. Comparatively, the severity of induced hyperglycaemia in the silkworms remained nearly the same in response to the oral and intravascular administration of glucose. Furthermore, prolonged administration of STZ has recorded negative effect on the growth rate of the silkworms, whereas a drastic decline in the same was reported in the silkworms administered with glucose. Notably, these results confirm that the response shown by the silkworms to STZ is very similar to that of mammals, making it an excellent model to study diabetic complications and consequences associated with STZ in diabetology.

Ectotherm predators and their prey could potentially respond differently to habitat temperatures. Predators might select higher temperatures to increase their probability of capture while prey could select lower or higher temperatures that may enhance their escape capability. We used a combination of field and laboratory analyses to characterise the thermal niches of predator species and their potential arthropod prey. We studied a predator–prey system in northern Chile using a common desert-dwelling spider Loxosceles laeta and three potential prey: a tenebrionid beetle Psammetichus costatus (Coleoptera), Pycnoscelus surinamensis (Blattodea) and Porcellio laevis (Isopoda). Results showed that the predator L. laeta selects warmer temperatures (T_p = 27.22 ± 4.87°C) in laboratory and lower temperatures in field conditions (T_s = 20.8 ± 1.59°C), with low temperatures in the morning and high temperatures at night. The three prey species had lower and different preferred temperatures than the predator in laboratory conditions. However, we found a high overlap in the thermal niche between the predator and their prey in field conditions, whereby the predator selected similar temperatures to its prey, one exception being P. laevis that chooses completely different habitat temperatures. This suggests that predators look for their prey in places with low temperatures that are not thermally suitable for them, whereas the prey may use this strategy of selecting low temperatures to evade potential predators.

The Asian citrus psyllid, Diaphorina citri, is a vector of the bacterial pathogen, Candidatus Liberibacter asiaticus (CLas) that is believed to cause huanglongbing (HLB), also known as citrus greening disease. This phytopathogen can manipulate its vectors directly by modifying behaviour and altering fitness and indirectly by reducing host plant quality, which may affect the predation efficiency of natural enemies. Little is known about how this phytopathogen may affect third tropic level predators. The purpose of this investigation was to determine if the CLas pathogen modifies interactions between D. citri and its predators. We tested whether CLas infection of psyllids indirectly affects fitness of a key predator, the lady beetle Harmonia axyridis. We provided ladybeetles with 10 infected or uninfected adult psyllids in choice bioassays and measured the consumption rate over 24 h. Similarly, 15 infected or uninfected adult psyllids were provided to ladybeetles in no-choice bioassays and feeding rates and net weight gain of male and female beetles were measured over 5 consecutive days. Fecundity and fertility of lady beetles feeding on CLas-infected D. citri was reduced compared with those feeding on uninfected D. citri, and oocyte development appeared diminished in those beetles feeding on infected compared with uninfected psyllids. However, in choice assays, beetles did not distinguish between CLas-infected and uninfected psyllids. We postulate that CLas may reduce the nutritional quality of psyllids diminishing fecundity and fertility of their predatory beetles. Our results lead us to speculate that under conditions of near 100% HLB infection, as occurs endemically in Florida, effectiveness of biological control for D. citri may benefit from provisioning ladybeetle predators with alternative hosts of higher nutritional quality or augmentative releases of laboratory-reared predators.

Heliothine moths represent some of the world's most important agricultural pest species. Helicoverpa zea (Corn Earworm) and Heliothis virescens (Tobacco Budworm) cause billions in damage and control costs worldwide each year. Given their economic importance, sex pheromones of many species have been studied for the development of management techniques such as trapping for population monitoring. The majority of pheromones identified and studied to date have been female-produced sex pheromones. Less emphasis has been placed on male sex pheromones, associated with abdominal hairpencil structures that often function in courtship or to attract females. The present study examines the composition, detection and behavioural role of male H. zea hairpencil compounds in male autodetection and in courtship. Comparative examination of the hairpencil effluvia of H. zea and H. virescens did not reveal distinct differences in pheromone blend composition produced by males of these species. Electrophysiological testing demonstrated broad antennal neuron response in both males and females of H. zea to nine key stimuli, with sexual dimorphism present in each species. Behavioural assays suggested that odours released by male hairpencils are important in mate acceptance by female H. zea and may play a role in mate choice and species isolation. Wind tunnel observations indicated that key H. zea hairpencil odours (hexadecanyl acetate and octadecanyl acetate) also function in mate competition, antagonising responses of downwind conspecific males following a synthetic female sex pheromone plume. This finding provides insight regarding male–male detection and response to hairpencil compounds in H. zea.

The biological complexity of leaf-cutting ants is determined in part by both positive and negative associations with microorganisms. These ants constantly face microorganisms that can compromise workers’ survival and the integrity of their symbiont fungus. The ability to produce antimicrobial compounds within the colony, both by the workers and by associated microorganisms, is an adaptive response that protects against these natural enemies. Atta cephalotes (Linnaeus, 1758) is an ecologically successful species with a great capacity to overcome pathogenic microorganisms. In contrast to the Acromyrmex genus, the evidence suggests that it does not maintain an association with antibiotic-producing actinobacteria raising the question of whether this species maintains associations with bacterial communities that can potentially protect the colony against prejudicial microorganisms. In this direction, the diversity and composition of the culturable bacterial microbiota associated with A. cephalotes developmental stages were evaluated, as well as their potential to inhibit the growth of the entomopathogenic fungus Metarhizium anisopliae and the mycoparasite Trichoderma sp. Six nests were collected, of which a total of 900 larvae, 900 pupae and 900 adult workers were analysed. Culture-dependent and molecular methods were used to identify the strains to genus level. To determine differences in bacterial composition in the development stages, analysis of the contribution to dissimilarity (SIMPER) were performed. Seventy-seven strains corresponding to 18 genera were documented. Acinetobacter was the dominant one. On the other hand, Acinetobacter, Bacillus, Enterobacter, Serratia and Microbacterium were maintained from the larval to the adult stage. Furthermore, except for Acinetobacter, different strains of these bacterial groups significantly inhibited pathogenic fungi growth. The results suggest the existence of a persistent association of A. cephalotes with strains of these bacterial genera and a potential role in defence at the collective level.