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Fatty acids (FAs) are important in metabolism and in the maintenance of Apis mellifera colonies. Our objective was to identify the variation in FA composition of the bodies of A. mellifera worker bees after immunological challenges with sterile injections and Paenibacillus larvae vegetative cells. The expression of the hymenoptaecin and abaecin genes was studied and the FAs were identified and quantified. After a challenge with P. larvae, the immune system was activated and abaecin and hymenoptaecin peptide genes were overexpressed. Also, the content of short-chain FAs such as caprylic, capric, and tridecylic acids increased significantly; on the contrary, oleic acid decreased. To the best of our knowledge, this is the first analysis of changes in the FA profile of honey bee workers after immune stimulation with P. larvae. Health status may be a key factor that alters FA composition. More research about the interaction with other stressors affecting the survival of honey bee colonies is needed. [ABSTRACT FROM AUTHOR]

Both the identity and prevalence of parasitoid dipterans associated with bumble bees (Bombus spp.) in southern South America are little known. Between 2009 and 2017, a total of 2978 bumble bees were individually collected in 63 localities from 11 provinces of the country. After dissections, the presence of parasitoids was observed in the native bumble bees Bombus pauloensis, B. bellicosus, B. opifex, and B. brasiliensis, plus in the exotic invasive species B. terrestris. A combination of both morphological and molecular analysis based on the COI gene allowed the isolation of two species of Physocephala (Conopidae) and one of Helicobia (Sarcophagidae), expanding their host range and geographic distribution. The second instar larva of Helicobia aurescens is described. [ABSTRACT FROM AUTHOR]

The high overwinter mortalities in the honey bee population of Apis mellifera have been linked to immunocompromised individuals experiencing nutritional limitations. Larval nutrition plays a crucial role in determining the successful development of adults, making them more susceptible to bacterial diseases when undernourished. One of the main intracellular signalling pathways in the larval immune system against bacterial diseases is the Toll receptor signalling pathway, which activates antimicrobial peptides like defensin. Inadequate nutrition also disrupts the redox balance on A. mellifera individuals, with superoxide dismutase and catalase being the key components of their antioxidant system. Vitellogenin is associated with the mobilization of nutrients in early A. mellifera bee stages. Considering that Saccharomyces cerevisiae is the second most significant by‐product of the brewing industry, it may serve as a valuable raw material. We investigated the impact of feeding larvae with live S. cerevisiae cells on the relative expression of their main immune and antioxidant‐related genes. To assess gene expression, we conducted RT‐qPCR, using RNA extracted from ten larvae per treatment on the seventh day when the feeding trial concluded. Importantly, the presence of S. cerevisiae did not affect larval survival compared to the control group. However, the relative expression of immune‐related gene toll18W and antioxidant‐related gene sod in larvae fed with live S. cerevisiae cells was significantly higher than in larvae that were not fed with them. This suggests that the inclusion of S. cerevisiae in their diet may provide larvae with a nutritional advantage. Additionally, the vitellogenin (vg) gene expression increased in treated larvae compared to the control group, potentially facilitating their access to nutrients and, consequently, enhancing their ability to cope with nutritional stress. [ABSTRACT FROM AUTHOR]