Effects of food availability on microsporidiosis and alkaloid production in the two-spotted lady beetle, Adalia bipunctata L

Efficacy and biosafety assessment of neuropeptide CAPA analogues against the peach-potato aphid (Myzus persicae)

Insect CAPA neuropeptidesare considered to affect water and ion balance by mediating the physiological metabolism activities of the Malpighian tubules. In previous studies, the CAPA-PK analogue 1895 (2Abf-Suc-FGPRLamide) was reported to decrease aphid fitness when administered through microinjection or via topical application. However, a further statistically significant decrease in the fitness of aphids and an increased mortality could not be established with pairwise combinations of 1895 with other CAPA analogue. In this study, we assessed the topical application of new combinations of 1895 with five CAPA-PVK analogues on the fitness of aphids. We found that 1895 and CAPA-PVK analogue 2315 (ASG-[β³ L]-VAFPRVamide) was statistically the most effective combination to control the peach potato aphid Myzus persicae nymphs via topical application, leading to 72% mortality. Additionally, the combination (1895+2315) was evaluated against a selection of beneficial insects, that is, a pollinator (Bombus terrestris) and three natural enemies (Chrysoperla carnea, Nasonia vitripennis, and Adalia bipunctata). We found no significant influence on food intake, weight increase, and survival for the pollinator and the three representative natural enemies. These results could facilitate to further establish and generate CAPA analogues as alternatives to broad spectrum and less friendly insecticides.

Fungal ectoparasites increase winter mortality of ladybird hosts despite limited effects on their immune system

Winter represents a challenging period for insects inhabiting temperate regions. A plethora of studies have investigated how environmental conditions such as temperature affect insect overwintering success. However, only a few studies have focused on biotic factors and the mechanisms affecting the overwintering performance of insects. Here, we investigated the effects of the parasitic fungus Hesperomyces virescens on the overwintering performance and immune system functioning of the invasive ladybird Harmonia axyridis. Winter survival was significantly lower for infected than for uninfected ladybirds. Body mass loss during overwintering tends to be higher for infected individuals compared to uninfected ones and for larger ladybirds. In addition, parasitic infection reduced post-winter longevity without food in male but not female ladybirds. Total haemocyte and protein concentration as well as antimicrobial activity against Escherichia coli significantly decreased during ladybird overwintering. However, haemolymph parameters were only poorly affected by Hesperomyces infection, with the exception of antimicrobial activity against E. coli that tended to be higher in infected ladybirds. Interestingly, none of the pre-winter haemolymph parameters were good predictors of ladybird winter survival. Overall, our results indicate that energy exhaustion unrelated to immune system challenge is the most probable explanation for increased overwintering mortality in infected ladybirds.

How Diet Leads to Defensive Dynamism: Effect of the Dietary Quality on Autogenous Alkaloid Recovery Rate in a Chemically Defended Beetle

The impact of different diets on chemical defense has been extensively studied in animals that sequester defensive chemicals from food. However, there are fewer studies of diet-mediated variation in autogenously produced defenses. Ladybird beetles, which use autogenously synthesized defensive alkaloids, are used as models in a wide diversity of studies of chemical defense, specifically in studies of intraspecific variation in color pattern and chemical defense. Many aphidophagous ladybirds consume a wide diversity of aphid prey, which vary in quality and thus could affect the synthesis of chemical defense. We measured alkaloid recovery rate after reflex bleeding by the ladybird Adalia bipunctata on two different aphid diets, the high quality Acyrthosiphon pisum and the lower quality Aphis fabae. Alkaloids reaccumulated in ladybirds more slowly when they were fed A. fabae than when they were fed A. pisum and females generally had more alkaloid than males, but reaccumulated alkaloid more slowly. Recovery times were more than 12 days. There appeared to be a weak positive relationship between alkaloid level and time since reflex bleeding for eggs of A. pisum- but not A. fabae-fed females. Our findings on diet and alkaloid synthesis in ladybirds suggest that chemical defense levels are very dynamic, indicating that studies conducted at a single point in time, such as those focused on ladybird color pattern, fail to consider a wide diversity of temporal variation that occurs in the field. This is likely true for many autogenously produced chemical defense systems in a diversity of other organisms.

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

The 9-azabicyclo[3.3.1]nonane ring system is present in several insect- and plant-derived alkaloids. (-)-Adaline (1) and (+)-euphococcinine (2), found in secretions of Coccinelid beetles, and (+)-N-methyleuphococcinine (3), isolated from the Colorado blue spruce Picea pungens, are members of this alkaloid family. Their unique bicyclic system with a quaternary stereocenter, and the potent biological activity exerted by these homotropane alkaloids, make them attractive synthetic targets. This work aims briefly to review the chemical ecology of Adalia bipunctata and the recent methodologies to obtain adaline (1), euphococcinine (2), and N-methyleuphococcinine (3).