Effects of realistic doses of atrazine, metolachlor, and glyphosate on lipid peroxidation and diet-derived antioxidants in caged honey bees (Apis mellifera)

Impaired associative learning after chronic exposure to pesticides in young adult honey bees

Neonicotinoids are the most widespread insecticides in agriculture, preferred for their low toxicity to mammals and their systemic nature. Nevertheless, there have been increasing concerns regarding their impact on non-target organisms. Glyphosate is also widely used in crops and, therefore, traces of this pesticide are likely to be found together with neonicotinoids. Although glyphosate is considered a herbicide, adverse effects have been found on animal species, including honey bees. Apis mellifera is one of the most important pollinators in agroecosystems and is exposed to both these pesticides. Traces can be found in nectar and pollen of flowers that honey bees visit, but also in honey stores inside the hive. Young workers, which perform in-hive tasks that are crucial for colony maintenance, are potentially exposed to both these contaminated resources. These workers present high plasticity and are susceptible to stimuli that can modulate their behaviour and impact on colony state. Therefore, by performing standardised assays to study sublethal effects of these pesticides, these bees can be used as bioindicators. We studied the effect of chronic joint exposure to field-realistic concentrations of the neonicotinoid imidacloprid and glyphosate on gustatory perception and olfactory learning. Both pesticides reduced sucrose responsiveness and had a negative effect on olfactory learning. Glyphosate also reduced food uptake during rearing. The results indicate differential susceptibility according to honey bee age. The two agrochemicals had adverse effects on different aspects of honey bee appetitive behaviour, which could have repercussions for food distribution, propagation of olfactory information and task coordination within the nest.

Foraging in maize field areas: A risky business?

In Quebec, Canada, the cultivation of maize dominates the agricultural territory. This crop requires a sustained supply of fertilizers from different sources: chemical, natural or from residual materials (sludge). These amendments contain metallic trace elements, which may lead to metal-contaminated maize pollen, a possible source of prooxidants for the foraging bees. Our objective was to determine whether maize fields environment influences the oxidation processes and the accumulation of metals in bees. A few days prior to pollen shedding, beehives were installed in maize fields: one organically grown (site A) and three conventionally grown (sites B, C and D). Soil, maize pollen and bees were analyzed for metal content. Every 15days, bees were collected and analyzed for peroxidation of lipids, metallothionein-like proteins (MTLPs), proteins, retinoids and lipophilic antioxidants (carotenoids and α-tocopherol). The compound β-carotene was the most abundant in bees from all sites, followed by α-carotene, β-cryptoxanthin, α-cryptoxanthin, zeaxanthin and lutein. Retinaldehyde and retinol varied according to times and sites without demonstrating clear trends. However, significant differences between sites were noted in 13-cis-retinoic acid and two retinoic acid metabolites measured in bees, suggesting alteration in the reduction-oxidation processes. In line with these results, the level of lipid peroxidation was globally higher in sites B, C and D compared with the organic site. Higher concentrations of metals were observed in soil and pollen from the field A, but bees metal contents were equal or less than those measured in bees from other sites. Higher bee MTLP levels were measured in sites B, C and D. For most sampling times, the discriminant analysis revealed that the conditions were distinguished by the oxidation processes in bees. Our data suggest that bees foraging in conventionally grown maize fields are at risk of increased oxidative damages which can alter the fine regulation of retinoids.

Lipophilic antioxidants and lipid peroxidation in yellow perch subjected to various anthropogenic influences along the St. Lawrence River (QC, Canada)

In Lake Saint-Pierre (LSP), the last great widening of the St. Lawrence River (province of Québec, Canada), the yellow perch has been experiencing a significant decline since the mid-1990s. The combined effect of several stressors (deterioration of habitats appropriate for reproduction and growth, invasive species and poor water quality) seems to exert considerable influence on the yellow perch population in LSP, characterized by low recruitment. To better understand possible stressor effects at the biochemical level, LSP yellow perch were compared with other sites along a gradient of increasing human influences from upstream to downstream along the St. Lawrence River. Morphometry (size, weight, circumference and Fulton's condition factor) and biomarkers associated to the peroxidation of lipids, lipophilic antioxidants (α-tocopherol and carotenoids), along with retinoids (vitamins A1and A2) and proteins were compared between sites at the larval, juvenile and adult stages. Fulton's condition factor was similar between sites for juveniles but was significantly lower in LSP adults, suggesting a weakened physiological condition. In most contaminated sites as LSP, lipid peroxidation tended to be higher in juveniles and adults whereas the lipophilic antioxidant lycopene and proteins content were lower. Retinyl esters were significantly lower for LSP fish compared to other sites, not only in larvae but also in the livers of juveniles and adults. These results are consistent with possible altered metabolism in the retinoid system of LSP yellow perch. The overall results reflect the "pressure" gradient tested, where the yellow perch from the most affected sites located downstream had impaired physiological and biochemical conditions compared to the upstream sectors.

Mixtures of herbicides and metals affect the redox system of honey bees

The increasing loss of bee colonies in many countries has prompted a surge of studies on the factors affecting bee health. In North America, main crops such as maize and soybean are cultivated with extensive use of pesticides that may affect non-target organisms such as bees. Also, biosolids, used as a soil amendment, represent additional sources of metals in agroecosystems; however, there is no information about how these metals could affect the bees. In previous studies we investigated the effects of environmentally relevant doses of herbicides and metals, each individually, on caged honey bees. The present study aimed at investigating the effects of mixtures of herbicides (glyphosate and atrazine) and metals (cadmium and iron), as these mixtures represent more realistic exposure conditions. Levels of metal, vitamin E, carotenoids, retinaldehyde, at-retinol, retinoic acid isomers (9-cis RA, 13-cis RA, at-RA) and the metabolites 13-cis-4-oxo-RA and at-4-oxo-RA were measured in bees fed for 10 days with contaminated syrup. Mixtures of herbicides and cadmium that did not affect bee viability, lowered bee α- and β-carotenoid contents and increased 9-cis-RA as well as 13-cis-4-oxo-RA without modifying the levels of at-retinol. Bee treatment with either glyphosate, a combination of atrazine and cadmium, or mixtures of herbicides promoted lipid peroxidation. Iron was bioconcentrated in bees and led to high levels of lipid peroxidation. Metals also decreased zeaxanthin bee contents. These results show that mixtures of atrazine, glyphosate, cadmium and iron may affect different reactions occurring in the metabolic pathway of vitamin A in the honey bee.

Pollen Contaminated With Field-Relevant Levels of Cyhalothrin Affects Honey Bee Survival, Nutritional Physiology, and Pollen Consumption Behavior

Honey bees are exposed to a variety of environmental factors that impact their health, including nutritional stress, pathogens, and pesticides. In particular, there has been increasing evidence that sublethal exposure to pesticides can cause subtle, yet important effects on honey bee health and behavior. Here, we add to this body of knowledge by presenting data on bee-collected pollen containing sublethal levels of cyhalothrin, a pyrethroid insecticide, which, when fed to young honey bees, resulted in significant changes in lifespan, nutritional physiology,and behavior. For the first time, we show that when young, nest-aged bees are presented with pollen containing field-relevant levels of cyhalothrin, they reduce their consumption of contaminated pollen. This indicates that, at least for some chemicals, young bees are able to detect contamination in pollen and change their behavioral response, even if the contamination levels do not prevent foraging honey bees from collecting the contaminated pollen.

Complete nutrient content of four species of commercially available feeder insects fed enhanced diets during growth

Commercially raised feeder insects used to feed captive insectivores are a good source of many nutrients but are deficient in several key nutrients. Current methods used to supplement insects include dusting and gut-loading. Here, we report on the nutrient composition of four species of commercially raised feeder insects fed a special diet to enhance their nutrient content. Crickets, mealworms, superworms, and waxworms were analyzed for moisture, crude protein, fat, ash, acid detergent fiber, total dietary fiber, minerals, amino acids, fatty acids, vitamins, taurine, carotenoids, inositol, and cholesterol. All four species contained enhanced levels of vitamin E and omega 3 fatty acids when compared to previously published data for these species. Crickets, superworms, and mealworms contained β-carotene although using standard conversion factors only crickets and superworms would likely contain sufficient vitamin A activity for most species of insectivores. Waxworms did not contain any detectable β-carotene but did contain zeaxanthin which they likely converted from dietary β-carotene. All four species contained significant amounts of both inositol and cholesterol. Like previous reports all insects were a poor source of calcium and only superworms contained vitamin D above the limit of detection. When compared to the nutrient requirements as established by the NRC for growing rats or poultry, these species were good sources of most other nutrients although the high fat and low moisture content of both waxworms and superworms means when corrected for energy density these two species were deficient in more nutrients than crickets or mealworms. These data show the value of modifying the diet of commercially available insects as they are growing to enhance their nutrient content. They also suggest that for most insectivores properly supplemented lower fat insects such as crickets, or smaller mealworms should form the bulk of the diet.