Cuticular Hydrocarbon Profile of Parasitic Beetles, Aethina tumida (Coleoptera: Nitidulidae)

Cuticular hydrocarbons (CHCs) cover insects’ bodies and play important roles in chemical communication, including nestmate recognition, for social insects. To enter colonies of a social host species, parasites may acquire host-specific CHCs or covertly maintain their own CHC profile by lowering its quantity. However, the chemical profile of small hive beetles (SHBs), Aethina tumida, which are parasites of honey bee, Apis mellifera, colonies, and other bee nests, is currently unknown. Here, adults of SHB and honey bee host workers were collected from the same field colonies and their CHC profiles were analysed using GC-MS. The chemical profiles of field-sampled SHBs were also compared with those of host-naive beetles reared in the laboratory. Laboratory-reared SHBs differed in their CHC profiles from field-sampled ones, which showed a more similar, but ten-fold lower, generic host CHC profile compared to host workers. While the data confirm colony-specific CHCs of honey bee workers, the profile of field-collected SHBs was not colony-specific. Adult SHBs often commute between different host colonies, thereby possibly preventing the acquisition of a colony-specific CHC profiles. An ester was exclusive to both groups of SHBs and might constitute an intraspecific recognition cue. Our data suggest that SHBs do not use any finely tuned chemical strategy to conceal their presence inside host colonies and instead probably rely on their hard exoskeleton and defence behaviours

Co-exposition effects on honey bee Apis meliffera olfactory learning performance

In the last ten years honey bee (Apis mellifera) colonies have been in decline. There are multiple causes that contribute to that rapid downtrend. Among them are pests and pathogens, land-use intensification, habitat loss and fragmentation. In most of the cases, the consequences of co-exposition are unknown as only few studies addressed these questions so far. Here we would like to investigate the impact of co-expositon between a pathogen and a neonicotinoid on honey bee survival and learning performances. Yet all the studies about the influence of pesticides on learning and memory abilities are conducted on honey bees that were exposed to pesticide after emergence. But it is known that neonicotinoids are also stored inside the hives in pollen, nectar and brood is exposed to it. In our work we exposed honey bee larvae to American Foulbrood and to sub-lethal doses of Thiamethoxam (chronic exposure). First we hypothesise that the application of two treatments may have synergistic effect and induce higher mortality rates on larvae. We also tested the impact of this co-exposition, during the larval stage, on impairment of learning and memory abilities as well as the social behaviour of the honey bee workers. We used the standard olfactory conditioning procedure that is based on Proboscis Extension Response (PER) to study the changes in learning and memory abilities caused by the co-exposition effect

Cuticular Hydrocarbon Profile of Parasitic Beetles, Aethina tumida (Coleoptera: Nitidulidae)

Cuticular hydrocarbons (CHCs) cover insects’ bodies and play important roles in chemical communication, including nestmate recognition, for social insects. To enter colonies of a social host species, parasites may acquire host-specific CHCs or covertly maintain their own CHC profile by lowering its quantity. However, the chemical profile of small hive beetles (SHBs), Aethina tumida, which are parasites of honey bee, Apis mellifera, colonies, and other bee nests, is currently unknown. Here, adults of SHB and honey bee host workers were collected from the same field colonies and their CHC profiles were analysed using GC-MS. The chemical profiles of field-sampled SHBs were also compared with those of host-naive beetles reared in the laboratory. Laboratory-reared SHBs differed in their CHC profiles from field-sampled ones, which showed a more similar, but ten-fold lower, generic host CHC profile compared to host workers. While the data confirm colony-specific CHCs of honey bee workers, the profile of field-collected SHBs was not colony-specific. Adult SHBs often commute between different host colonies, thereby possibly preventing the acquisition of a colony-specific CHC profiles. An ester was exclusive to both groups of SHBs and might constitute an intraspecific recognition cue. Our data suggest that SHBs do not use any finely tuned chemical strategy to conceal their presence inside host colonies and instead probably rely on their hard exoskeleton and defence behaviours

Sex Ratio of Small Hive Beetles: The Role of Pupation and Adult Longevity

The sex ratio of sexually reproducing animal species tends to be 1:1, which is known as Fisher’s principle. However, differential mortality and intraspecific competition during pupation can result in a biased adult sex ratio in insects. The female-biased sex ratio of small hive beetles (SHBs) is known from both laboratory and field studies, but the underlying reasons are not well understood. Here, we used laboratory mass and individual pupation to test if differential mortality between sexes and/or intraspecific interactions can explain this sex ratio. The data show a significant female-biased adult sex ratio in both mass and individual rearing, even when assuming that all dead individuals were males. Our results therefore suggest that neither differential mortality during pupation nor intraspecific interactions are likely to explain the female-biased sex ratio of freshly emerged adult SHBs. We regard it as more likely that either competition during the larval feeding stage or genetic mechanisms are involved. In addition, we compared our data with previously published data on the sex ratio of both freshly emerged and field-collected SHBs to investigate possible gender differences in adult longevity. The data show a significantly greater female bias in the sex ratio upon emergence, compared to field-collected SHBs, suggesting that adult females have a shorter longevity

Larval exposure to thiamethoxam and American foulbrood: effects on mortality and cognition in the honey bee Apis mellifera

Here, we examined the in vitro effects of co-exposure to a pathogen and a common neonicotinoid on honey bee larvae survival and on adult learning behavior following a standard olfactory conditioning procedure based on the proboscis extension response paradigm. We exposed or co-exposed honey bee larvae to American foulbrood and to sub-lethal doses of thiamethoxam (chronic exposure). Our results revealed no additive effects between the two stressors on larval mortality. However, the present work provides the first evidence of impaired learning and memory in adult bees that were fed thiamethoxam (0.6 ng/bee) during the larval stage. We also show no alterations in learning and memory in bees after infection with American foulbrood at the larval stage. The present study contributes to our knowledge of the sub-lethal effects of neonicotinoids on honey bee larvae and adults.En este estudio se examinaron los efectos in vitro de la co-exposición a un patógeno y un neonicotinoide común en la supervivencia de las larvas de abejas melíferas y sobre el comportamiento de aprendizaje de adultos siguiendo un procedimiento de acondicionamiento olfativo estándar basado en el paradigma de la respuesta de extensión de la probóscide (PER por sus siglas en inglés). Expusimos o co-expusimos las larvas de abejas melíferas a la loque americana y a dosis sub-letales de thiamethoxam (exposición crónica). Nuestros resultados no revelaron efectos aditivos entre los dos estresores sobre la mortalidad larvaria. Sin embargo, el presente trabajo proporciona la primera evidencia de deterioro del aprendizaje y la memoria en abejas adultas que fueron alimentadas con thiamethoxam (0,6 38 ng / abeja) durante la fase larvaria. También mostramos que no hay alteraciones en el aprendizaje y la memoria en las abejas después de la infección con loque americana en la fase larvaria. El presente estudio contribuye a nuestro conocimiento de los efectos sub-letales de los neonicotinoides en larvas de abejas y en adultos

Multiple mating by both sexes in an invasive insect species, Aethina tumida (Coleoptera: Nitidulidae).

Multiple mating by both sexes is common among sexually reproducing animals. Small hive beetles (SHB), Aethina tumida, are parasites of bee nests endemic to sub-Saharan Africa and have become a widespread invasive species. Despite the considerable economic damages they can cause, their basic biology remains poorly understood. Here we show that male and female small hive beetles can mate multiple times, suggesting that costs for mating are low in this species. In an invasive A. tumida population in the USA, a combination of laboratory experiments for males and paternity analysis with eight polymorphic DNA microsatellite markers for field-caught females were used to estimate the number of mating by both sexes. The data show that females and males can mate multiple times - females mated with up to eight males, whereas males mated with at least seven females. The results also showed that A. tumida displayed a skewed paternity, although this was not consistent among the tested females. Thus, first or last male advantage seem to be unlikely in A. tumida. Our observations that individuals of both sexes of A. tumida can mate multiple times opens new research avenues for examining drivers of multiple mating and determining the role it may play in promoting biological invasions. This article is protected by copyright. All rights reserved