A high quality method for hemolymph collection from honeybee larvae

Enantioselective toxicity of the neonicotinoid dinotefuran on honeybee (Apis mellifera) larvae

The threat of neonicotinoids to insect pollinators, particularly honeybees (Apis mellifera), is a global concern, but the risk of chiral neonicotinoids to insect larvae remains poorly understood. In the current study, we evaluated the acute and chronic toxicity of dinotefuran enantiomers to honeybee larvae in vitro and explored the mechanism of toxicity. The results showed that the acute median lethal dose (LD50) of S-dinotefuran to honeybee larvae was 30.0 μg/larva after oral exposure for 72 h, which was more toxic than rac-dinotefuran (92.7 μg/larva) and R-dinotefuran (183.6 μg/larva). Although the acute toxicity of the three forms of dinotefuran to larvae was lower than that to adults, chronic exposure significantly reduced larval survival, larval weight, and weight of newly emerged adults. Analysis of gene expression and hormone titer indicated that dinotefuran affects larval growth and development by interfering with nutrient digestion and absorption and the molting system. Analysis of hemolymph metabolome further revealed that disturbances in the neuroactive ligand-receptor interaction pathway and energy metabolism are the key mechanisms of dinotefuran toxicity to bee larvae. In addition, melatonin and vitellogenin are used by larvae to cope with dinotefuran-induced oxidative stress. Our results contribute to a comprehensive understanding of dinotefuran damage to bees and provide new insights into the mechanism of enantioselective toxicity of insecticides to insect larvae.

A blood test to monitor bee health across a European network of agricultural sites of different land-use by MALDI BeeTyping mass spectrometry

There are substantial concerns about impaired honey bee health and colony losses due to several poorly understood factors. We used MALDI profiling (MALDI BeeTyping®) analysis to investigate how some environmental and management factors under field conditions across Europe affected the honey bee haemolymph peptidome (all peptides in the circulatory fluid), as a profile of molecular markers representing the immune status of Apis mellifera. Honey bees were exposed to a range of environmental stressors in 128 agricultural sites across eight European countries in four biogeographic zones, with each country contributing eight sites each for two different cropping systems: oilseed rape (OSR) and apple (APP). The full haemolymph peptide profiles, including the presence and levels of three key immunity markers, namely the antimicrobial peptides (AMPs) Apidaecin, Abaecin and Defensin-1, allowed the honey bee responses to environmental variables to be discriminated by country, crop type and site. When considering just the AMPs, it was not possible to distinguish between countries by the prevalence of each AMP in the samples. However, it was possible to discriminate between countries on the amounts of the AMPs, with the Swedish samples in particular expressing high amounts of all AMPs. A machine learning model was developed to discriminate the haemolymphs of bees from APP and OSR sites. The model was 90.6 % accurate in identifying the crop type from the samples used to build the model. Overall, MALDI BeeTyping® of bee haemolymph represents a promising and cost-effective "blood test" for simultaneously monitoring dozens of peptide markers affected by environmental stressors at the landscape scale, thus providing policymakers with new diagnostic and regulatory tools for monitoring bee health.

DEVELOPMENT OF A HEMOLYMPH COLLECTION TECHNIQUE AND REPORT OF BIOCHEMICAL PARAMETERS OF HEMOLYMPH IN A MANAGED POPULATION OF FEMALE THORNY DEVIL STICK INSECTS (EURYCANTHA CALCARATA)

Insects are increasingly common in households, zoological collections, research, and food industries. Increased knowledge of insect health parameters is necessary to ensure proper welfare. The study goal was to develop a hemolymph collection technique and report hemolymph serum biochemical parameters for the thorny devil stick insect (Eurycantha calcarata). Clinically healthy adult stick insects (5 males and 14 females, 15.1-24.7 g) were enrolled. Four collection techniques were evaluated. Hemolymph collection was unsuccessful in males, but was successful in females by using a single technique. The insect was manually restrained in an elevated position and an 18-ga × 2.54-cm needle was used to puncture the membrane just caudal to the third pair of legs. With the puncture site directed ventrally, ≤1 ml of hemolymph was collected via gravity and allowed to visibly clot. The sample was then centrifuged, and the serum was separated. Serum samples were individually analyzed (Avian/Reptilian Profile Plus, VetScan VS2, Abaxis, Inc, Union City, CA 94587, USA). Fourteen samples (0.2-1.0 ml) were collected from 14 females. Median (minimum-maximum) parameters included the following: aspartate aminotransferase 12 (0-45) U/L, creatinine kinase 25 (0-76) U/L, uric acid 7.5 (3.1-13.7) mg/dl, glucose 12 (8-22) mg/dl, calcium 18.6 (17.2-19.4) mg/dl, phosphorus 15.0 (n = 1) or >30.0 (n = 13) mg/dL, total protein 2.7 (1.6-2.9) g/dL, albumin 0.9 (0.2-1.2) g/dL, globulin 1.7 (1.6-1.8) g/dL (n = 6) or not quantified (n = 8), potassium 10.6 (9.0-11.8) mmol/L, sodium < 100 mmol/L, and bile acids 0 lmol/L. This is the first report of biochemistry parameters in clinically healthy female stick insects. Larger sample sizes are needed to establish statistically valid reference ranges. Hemolymph collection techniques for male stick insects warrant further investigation.

Co-Expression Network Analysis: A Future Approach for Pest Control Target Discovery

The striped stem borer (SSB, Chilo suppressalis Walker) is a major pest of rice worldwide. Double-stranded RNAs (dsRNAs) targeting essential genes can trigger a lethal RNA interference (RNAi) response in insect pests. In this study, we applied a Weighted Gene Co-expression Network Analysis (WGCNA) to diet-based RNA-Seq data as a method to facilitate the discovery of novel target genes for pest control. Nieman-Pick type c 1 homolog b (NPC1b) was identified as the gene with the highest correlation values to hemolymph cholesterol levels and larval size. Functional characterization of the gene supported CsNPC1b expression with dietary cholesterol uptake and insect growth. This study revealed the critical role of NPC1b for intestinal cholesterol absorption in lepidopteran insects and highlights the utility of the WGCNA approach for identifying new pest management targets.

An Efficient and Simple Method for Collecting Haemolymph of Cerambycidae (Insecta: Coleoptera) Adults

Cerambycid beetles (Cerambycidae) are major forest pests, posing a serious threat to the security of forest resources worldwide. Extensive research has focused on the control of cerambycid beetles from physiological and biochemical perspectives. Despite the important roles of insect haemolymph in physiological processes, efficient collection methods for Cerambycidae are lacking. For the efficient and easy collection of large amounts of pure haemolymph from adult cerambycid beetles, a new method, named net centrifugation, was developed. Three species of cerambycid beetles with large differences in size, Anoplophora chinensis, Monochamus saltuarius and Saperda populnea, were selected for the study. Haemolymph was collected by the newly developed net centrifugation method-in which an inner nylon net is used during centrifugation under optimised conditions, and a relatively small wound is generated on the insect-as well as the traditional tearing method and double centrifugation method. Among the three methods evaluated, the net centrifugation method caused the least damage to cerambycid beetles during the whole operation. This method resulted in the most haemolymph from a single beetle, with the lowest turbidity, mostly pure haemocytes in the precipitate, the clearest haemolymph smears by microscopy and the highest quality of RNA extracted from haemocytes. The net centrifugation method has a high collection efficiency, providing important technical support for haemolymph extraction and entomological research.

A systematic review of research conducted by pioneer groups in ecotoxicological studies with bees in Brazil: advances and perspectives

Brazil presents the most threatened endemic or rare species among neotropical regions, with the Hymenoptera order, to which bees belong, classified as a high-risk category. In Brazil, the main cause of bee death is the indiscriminate use of pesticides. In this context, groups such as Bee Ecotoxicology and Conservation Laboratory (LECA in Portuguese) and Bees and Environmental Services (ASAs in Portuguese) have become a reference in studies evaluating the impacts of pesticides on bees since 1976. Thus, the objective of this review was to conduct a quantitative and qualitative review of the studies conducted by these groups to evaluate and compile the advances made over the years, identify potential knowledge gaps for future studies, and support the sensitivities of stingless bees when compared to the species Apis mellifera. The quantitative analyses showed that most studies were carried out in the genus Apis, under laboratory conditions. However, more recently (since 2003), studies have also focused on stingless bees and the neonicotinoid class of insecticides. The most relevant gaps identified were the lack of studies under field conditions and on bee biology. The qualitative analyses indicated that Brazilian stingless bees are more susceptible to pesticides than A. mellifera and require a much lower average dose, concentration, or lethal time to display morphological and behavioral damage or decreased lifespan. Thus, future studies should work towards establishing more representative protocols for stingless bees. Furthermore, public policies must be created for the protection and conservation of bees native to Brazil.

Impact of low temperatures on the immune system of honeybees

Changes in temperature resulting from climate change can impact the distribution and survival of species, including bees, where temperature may also affect their immune system. Evaluation of immune system activity is often performed by the total count of circulating hemocytes in the hemolymph. However, there are few studies on bees examining the relationship between the amount of circulating hemocytes and temperature. This study evaluated changes of circulating hemocytes in Apis mellifera hemolymph at different temperatures and development stages. Total hemocytes of bees were determined at - 8, 16, 24, and 32 °C - and at different development stages - in vivo larvae, in vitro larvae, newly emerged, and forager bees. A. mellifera larvae had a greater number of circulating hemocytes compared to the other development stages (newly emerged and foragers). Additionally, temperature was an important factor explaining variation of circulating hemocytes in the hemolymph, according to principal component analyses (PCA), as the number of circulating hemocytes was greater at higher temperatures. Therefore, extreme events arising from climate change, such as variation in temperature, can directly impact the immune system of bees, both individually and at the colony level, threatening the distribution and survival of several species.