Temperature-dependent chemical components accumulation in Hippodamia variegata (Coleoptera: Coccinellidae) during overwintering

The supercooling point depression is the leading cold tolerance strategy for the variegated ladybug, [Hippodamia variegata (Goezel)]

The variegated ladybug, Hippodamia variegata is one of the most effective predators of various pests that hibernate as adult beetles. During the overwintering period from April 2021 to March 2022, we examined the supercooling point (SCP), cold tolerance, and physiological adaptations of beetles in Kerman, Iran. The beetles exhibited their greatest cold tolerance (63.4% after 24 h at -5°C) when their SCP was lowest (-23.2°C). Conversely, from April to October 2021, the SCP reached its peak (approximately -13.0°C), while cold tolerance was at its lowest level (6.7% after 24 h at -5°C). Cryoprotectant content (trehalose, glycerol, and glucose) was at its highest level in September (11.15, 10.82, and 6.31 mg/g, respectively). The critical thermal minimum (CTmin) reached its lowest point of -2.2°C in January and February. The lowest point of the lower lethal temperature (LLT) coincided with the lowest level of the SCP and the highest level of cold tolerance (in February, LT50 = -5.3°C, SCP = -23.2°C, and survival = 77.78% at -4°C/24 h). Chill-coma recovery time (CCRT) was examined at five different temperatures and two different exposure durations. The CCRT increased with a decrease in exposure temperature and time (68.0 s at -2°C after 2 h and 102.0 s at -2°C after 4 h). As the majority of the overwintering beetle's mortality occurred at temperatures significantly higher than SCP, the adults of H. variegata are chill-susceptible insects that primarily rely on a depressed supercooling point to cope with unfavorable conditions during the overwintering period.

Effect of cold storage on some biological and physiological performance of Adalia decempunctata L

Adalia decempunctata (L.) is a common predator in agro ecosystems. Here, the effects of low-temperature storage on biological parameters, energy reserves, and antioxidant enzymes were investigated. Eggs, larvae, and pupae of this predator were maintained for 1-4 weeks and adults for different days (20, 35, 50, and 65 d) at 4, 7, and 10 °C in darkness and 70 ± 5% R.H. After storage of 20 days, the survival rate in male and female insects was >90% in 4, 7, and 10 ± 1 °C. In 65 days, the highest survival rate for adult insects was recorded at 4 °C. Effect of cold storage on the performance of adult's A. decempunctata was not statistically different for periods up to 35 days, but decreased longer duration (65 days). The female adults were able to tolerate the cold storage period by producing higher amounts of glucose and antioxidant enzymes, thus displaying a high survival rate. Based on our results, maintaining A. decempunctata adults at low temperatures (i.e. 4, 7, and 10 °C) for 20 or 35 days performed best without loss of quality.

Fruit Fly in a Challenging Environment: Impact of Short-Term Temperature Stress on the Survival, Development, Reproduction, and Trehalose Metabolism of Bactrocera dorsalis (Diptera: Tephritidae)

An understanding of physiological damage and population development caused by uncomfortable temperature plays an important role in pest control. In order to clarify the adaptability of different temperatures and physiological response mechanism of B. dorsalis, we focused on the adaptation ability of this pest to environmental stress from physiological and ecological viewpoints. In this study, we explored the relationship between population parameters and glucose, glycogen, trehalose, and trehalose-6-phosphate synthase responses to high and low temperatures. Compared with the control group, temperature stress delayed the development duration of all stages, and the survival rates and longevity decreased gradually as temperature decreased to 0 °C and increased to 36 °C. Furthermore, with low temperature decrease from 10 °C to 0 °C, the average fecundity per female increased at 10 °C but decreased later. Reproduction of the species was negatively affected during high-temperature stresses, reaching the lowest value at 36 °C. In addition to significantly affecting biological characteristics, temperature stress influenced physiological changes of B. dorsalis in cold and heat tolerance. When temperature deviated significantly from the norm, the levels of substances associated with temperature resistance were altered: glucose, trehalose, and TPS levels increased, but glycogen levels decreased. These results suggest that temperature stresses exert a detrimental effect on the populations' survival, but the metabolism of trehalose and glycogen may enhance the pest's temperature resistance.

Phylogenetic signal of sub-arctic beetle communities

Postglacial dispersal and colonization processes have shaped community patterns in sub-Arctic regions such as Churchill, Manitoba, and Canada. This study investigates evolutionary community structure within the beetle (Coleoptera) families of Churchill and tests whether biological traits have played a role in governing colonization patterns from refugial and southerly geographic regions. This study quantifies sub-Arctic beetle phylogenetic community structure for each family using the net relatedness index (NRI) and nearest taxon index (NTI), calculated using publicly available data from the Barcode of Life Data Systems (BOLD); compares patterns across families with different traits (habitat, diet) using standard statistical analysis (ANOVA) as well as phylogenetic generalized least squares (PGLS) using a family-level beetle phylogeny obtained from the literature; and compares community structure in Churchill with a region in southern Canada (Guelph, Ontario). These analyses were also repeated at a genus level. The dominant pattern detected in our study was that aquatic families were much better represented in Churchill compared to terrestrial families, when compared against richness sampled from across Canada and Alaska. Individually, most families showed significant phylogenetic clustering in Churchill, likely due to the strong environmental filtering present in Arctic environments. There was no significant difference in phylogenetic structure between Churchill and Guelph but with a trend toward stronger clustering in the North. Fungivores were significantly more overdispersed than other feeding modes, predators were significantly more clustered, and aquatic families showed significantly stronger clustering compared to terrestrial. This study contributes to our understanding of the traits and processes structuring insect biodiversity and macroecological trends in the sub-Arctic.

Reproductive Diapause in North American Populations of the Introduced Lady Beetle Hippodamia variegata (Coleoptera: Coccinellidae)

The Palearctic lady beetle species, Hippodamia variegata (Coleoptera: Coccinellidae), first collected in 1984 near Montreal, Quebec, Canada, is expanding its distribution into northeastern and north central portions of North America. Examination of responses to abiotic factors that influence the seasonal biology of H. variegata may provide insights into its potential range expansion in North America. The induction and duration of adult hibernal diapause in three North American populations of H. variegata, collected between 40°N and 44°N latitude, was determined at four constant photoperiods (L:D 16:8, 14:10, 12:12, and 10:14) at 22°C. Thirteen to twenty-one percent of females reared at L:D 16:8 entered diapause, whereas shorter photoperiods (L:D 12:12 and 10:14) induced diapause in 100% of females. Variation in the response to L:D 14:10 was observed among the three populations, 27-100% of females exhibited reproductive diapause. Pupae and young adults were sensitive to changes in constant photoperiods (L:D 16:8 ⇆ 10:14). Individuals reared at L:D 10:14 that were moved to L:D 16:8 on the day of pupation or the day of adult eclosion produced ovipositing females. Individuals reared at L:D 16:8 and transferred to L:D 10:14 on the day of pupation or the day of adult eclosion produced females that did not oviposit within 30 d of eclosion.

Comparative metabolomics analysis of Callosobruchus chinensis larvae under hypoxia, hypoxia/hypercapnia and normoxia

BACKGROUND

Insect tolerance to low oxygen (hypoxia) and high carbon dioxide (hypercapnia) is critical for insect control. On the basis of bioassay, metabolism profiles were built to investigate adaptive mechanisms in bean weevil under hypoxia (2% O₂ ), hypoxia/hypercapnia (2% O₂ + 18% CO₂ ) and normoxia (control, 20% O₂ + 80% N₂ ) using gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS).

RESULTS

The growth and development of bean weevils were significantly suppressed by the two hypoxia conditions; hypercapnia enhanced the mortality, but after 24 days of exposure, the surviving insects emerged as adults earlier than those under hypoxia only. Metabolism profiles also showed striking differences in metabolites among the treatment and control groups, both quantitatively and qualitatively. Pairwise comparisons of the three groups showed that 61 metabolites changed significantly, 40 in the hypoxia group and 37 in the hypoxia/hypercapnia group relative to the control group, while only 16 were shared equally by the hypoxia and hypoxia/hypercapnia groups. Increased metabolites were mainly carbohydrates, amino acids and organic acids, while free fatty acids were decreased. Furthermore, the changes were strengthened by the addition of hypercapnia, but excluding free fatty acids.

CONCLUSION

The findings show that bean weevil has high tolerance to hypoxia or even hypoxia/hypercapnia at biologically achievable levels and provide more direct evidence for stored product insect mechanism regulation under hypoxia stress, especially free fatty acid regulation by hypercapnia but not by hypoxia. © 2016 Society of Chemical Industry.