Understanding the major mechanisms that allow an alien species to become invasive is crucial for ... more Understanding the major mechanisms that allow an alien species to become invasive is crucial for limiting the impact of such species, and individual immunity seems to be a crucial trait for their large range colonization when introduced to a new area. Indeed, a high resistance to pathogens and parasites could favour the establishment and proliferation of an alien species in a newly colonized region. A striking example of recent successful invasion is represented by the Asian hornet, Vespa velutina nigrithorax, which has invaded Western Europe threatening bees and beekeeping activities. Investigating the biology of this species is fundamental to understand how V. velutina nigrithorax has become invasive in Europe and this knowledge could be crucial for limiting its impact. Here, by performing bacterial challenge bioassays, we compare the immune competence of different castes and sex of a population of the invasive Asian hornet, V. velutina nigri thorax, and of the native European hornet, V. crabro. Our results demonstrate that the two species differ in their immunocompetence with respect to caste: a higher level of immunocompetence was found in the reproductive females of the Asian hornet which were resistant to bacterial challenge when compared to workers and males of both species and to reproductive females of the native European hornet. The high pathogen resistance in reproductive females of the Asian hornet, might therefore represent a key factor contributing to the ecological success and spread of this invader.
Simple Summary Social insects use cuticular hydrocarbons for chemical recognition and communicati... more Simple Summary Social insects use cuticular hydrocarbons for chemical recognition and communication. Cuticular hydrocarbons can also be exploited by parasites to their advantage for undermining host recognition systems. The small hive beetle (SHB) is a parasite of honey bee colonies but can also infest nests of other bee species. However, its chemical profile is still not known. For the first time, the present study investigated the SHB chemical profile and compared it with that of its honey bee host. The results show that the SHB has a low chemical profile that is similar to its honey bee host’s. However, while honey bees had a clear colony-specific chemical profile, SHBs did not. The generic chemical profile of the SHB is most likely linked to its free-flying behaviour in the field as these parasites are known to switch between host colonies, possibly limiting the acquisition of a colony specific chemical profile. Our findings also suggest that SHBs do not exploit any finely tuned...
Vespa velutina Lepieltier, 1836 (Hymenoptera: Vespidae) is an invasive predator of honeybees acci... more Vespa velutina Lepieltier, 1836 (Hymenoptera: Vespidae) is an invasive predator of honeybees accidentally introduced into Europe from eastern Asia. It was observed for the first time in southwest France in 2004 and in the following years it rapidly spread almost all over the country. In 2013 it was officially reported in Italy, in the region Liguria, near the border with France. In three years it invaded the whole province of Imperia and it was occasionally reported also in the South Western of Piedmont and in one locality in South Eastern Piedmont. The VELUTINA project was funded in 2014 by the Italian Ministry of Agriculture, with the aim of finding effective control methods against the predator. It includes both research and surveillance: adult and nest monitoring; development of methods for nest detection; development of protocols for nest destruction; studies on wasp chemical communication. Adult monitoring was performed in 5 Italian regions – the two where the hornet is alread...
In previous researches severe damages induced by Cadmium (an ubiquitary environmental pollutant w... more In previous researches severe damages induced by Cadmium (an ubiquitary environmental pollutant whose intracellular oxidative effects are increasingly lethal) exposure in human have been demonstrated. Morphologic effects were observed in Central Nervous System, liver, kidney, placenta. Recently, the involvement of immune system in Cadmium intoxication was demonstrated in mammalians; we, therefore, tried to evidence such effect in a simple model as Apis Mellifera. In this animal the immune system is represented by “fat bodies” which produce proteins active in defense against pathogenic agents. It is important to stress out that a dangerous syndrome causing the collapse of Apis mellifera hives has intensified recently, in Europe and North America. Current research in this field is oriented towards identifying a synergy of contributing factors to the weakening of the hive. In this paper, we aim to determine whether contamination by cadmium may have an immunosuppressive effect on the in...
• Vespa velutina is an alien hornet of high ecological and economic concern in Europe. • Its gut ... more • Vespa velutina is an alien hornet of high ecological and economic concern in Europe. • Its gut microbiome has been characterized through meta-genomics. • We investigated the effect of ontogeny, phenotype and similarity with environment. • Fungal and bacterial community's abundance depends on ontogeny and phenotype. • Microbiome characterization is a springboard for management strategies.
Parasites and pathogens can follow different patterns of infection depending on the host developm... more Parasites and pathogens can follow different patterns of infection depending on the host developmental stage or sex. In fact, immune function is energetically costly for hosts and trade-offs exist between immune defences and life history traits as growth, development and reproduction and organisms should thus optimize immune defence through their life cycle according to their This article is protected by copyright. All rights reserved. developmental stage. Identifying the most susceptible target and the most virulent pathogen is particularly important in the case of insect pests, in order to develop effective control strategies targeting the most vulnerable individuals with the most effective control agent. Here, we carried out laboratory tests to identify the most susceptible target of infection by infecting different stages of the red palm weevil Rhynchophorus ferrugineus (larvae, pupae, male and female adults) with both a generic pathogen, antibiotic-resistant Gram-negative bacteria Escherichia coli XL1-Blue, and two specific strains of entomopathogenic nematodes (EPNs), Steinernema carpocapsae ItS-CAO1 and Heterorhabditis bacteriophora ItH-LU1. By evaluating bacterial clearance, host mortality and parasite progeny release, we demonstrate that larvae are more resistant than adults to bacterial challenge and they release less EPNs progeny after infection despite a higher mortality compared to adults. Considering the two EPN strains, S. carpocapsae was more virulent than H. bacteriophora both in terms of host mortality and more abundant progeny released by hosts after death. The outcomes attained with unspecific and specific pathogens provide useful information for a more efficient and sustainable management of this invasive pest.
1. Invasive alien species are a major threat to biodiversity. In addition to predation and parasi... more 1. Invasive alien species are a major threat to biodiversity. In addition to predation and parasitism, native species might suffer from competition when invasive alien species occupy a similar ecological niche. 2. We focused on the potential interspecific interaction between two hornets: the Asian yellow-legged hornet, Vespa velutina, a high-concern invasive alien species recently arrived in Europe, and the native European hornet, Vespa crabro. The two species share a similar ecological niche and V. velutina is rapidly expanding across Europe, which suggests that V. crabro might suffer from competition. 3. We investigated, under laboratory controlled conditions, two life history traits that might cause the two species to compete: i) the ability of workers to find food sources and their flexibility in exploiting them (through individual food item choice tests and exploration assays), and ii) the worker resistance to pathogens (through immune challenge tests). 4. We show that trophic preference of both species highly overlaps, with a marked dietary preference for honeybees compared to other insect prey and non-prey protein items. No differences have been observed in the exploratory behaviour of both species. Finally, constitutive antibacterial activity was greater in workers of the native species than in workers of the invasive hornet. 5. Our laboratory study provides a first assessment under controlled conditions of the factors affecting competition between workers of two hornet species and proposes a framework to assess, in wild contexts, the magnitude of the competition and the impact of the introduced V. velutina on the native V. crabro.
Honeybee colonies are under the threat of many stressors, biotic and abiotic factors that strongl... more Honeybee colonies are under the threat of many stressors, biotic and abiotic factors that strongly affect their survival. Recently, great attention has been directed at chemical pesticides, including their effects at sub-lethal doses on bee behaviour and colony success; whereas the potential side effects of natural biocides largely used in agriculture, such as entomopathogenic fungi, have received only marginal attention. Here, we report the impact of the fungus Beauveria bassiana on honeybee nestmate recognition ability, a crucial feature at the basis of colony integrity. We performed both behavioural assays by recording bee guards’ response towards foragers (nestmate or non-nestmate) either exposed to B. bassiana or unexposed presented at the hive entrance, and GC-MS analyses of the cuticular hydrocarbons (CHCs) of fungus-exposed versus unexposed bees. Our results demonstrated that exposed bees have altered cuticular hydrocarbons and are more easily accepted into foreign colonies ...
Philosophical Transactions of the Royal Society B: Biological Sciences, 2019
Insect societies play a crucial role in the functioning of most ecosystems and have fascinated bo... more Insect societies play a crucial role in the functioning of most ecosystems and have fascinated both scientists and the lay public for centuries. Despite the long history of study, we are still far from understanding how insect societies have evolved and how social cohesion in their colonies is maintained. Here we suggest inquiline social parasites of insect societies as an under-exploited experimental tool for understanding sociality. We draw on examples from obligate inquiline (permanent) social parasites in wasps, ants and bees to illustrate how these parasites may allow us to better understand societies and learn more about the evolution and functioning of insect societies. We highlight three main features of these social parasite–host systems—namely, close phylogenetic relationships, strong selective pressures arising from coevolution and multiple independent origins—that make inquiline social parasites particularly suited for this aim; we propose a conceptual comparative framew...
Reproductive and task partitioning in large colonies of social insects suggest that colony member... more Reproductive and task partitioning in large colonies of social insects suggest that colony members belonging to different castes or performing different tasks during their life (polyethism) may produce specific semiochemicals and be differently sensitive to the variety of pheromones involved in intraspecific chemical communication. The main peripheral olfactory organs are the antennal chemosensilla, where the early olfactory processes take place. At this stage, members of two different families of soluble chemosensory proteins [odorant-binding proteins (OBPs) and chemosensory proteins (CSPs)] show a remarkable affinity for different odorants and act as carriers while a further family, the Niemann-Pick type C2 proteins (NPC2) may have a similar function, although this has not been fully demonstrated. Sensillar lymph also contains Odorant degrading enzymes (ODEs) which are involved in inactivation through degradation of the chemical signals, once the message is conveyed. Despite their importance in chemical communication, little is known about how proteins involved in peripheral olfaction and, more generally antennal proteins, differ in honeybees of different caste, task and age. Here, we investigate for the first time, using a shotgun proteomic approach, the antennal profile of honeybees of different castes (queens and workers) and workers performing different tasks (nurses, guards, and foragers) by controlling for the potential confounding effect of age. Regarding olfactory proteins, major differences were observed between queens and workers, some of which were found to be more abundant in queens (OBP3, OBP18, and NPC2-1) and others to be more abundant in workers (OBP15, OBP21, CSP1, and CSP3); while between workers performing different tasks, OBP14 was more abundant in nurses with respect to guards and foragers. Apart from proteins involved in olfaction, we have found that the antennal proteomes are mainly characterized by castes and tasks, while age has no effect on antennal protein profile. Among the main differences, the strong decrease in vitellogenins found in guards and foragers is not associated with age.
In the last decades a dramatic loss of Apis mellifera hives has been reported in both Europe and ... more In the last decades a dramatic loss of Apis mellifera hives has been reported in both Europe and USA. Research in this field is oriented towards identifying a synergy of contributing factors, i.e. pathogens, pesticides, habitat loss and pollution to the weakening of the hive. Cadmium (Cd) is a hazardous anthropogenic pollutant whose effects are proving to be increasingly lethal. Among the multiple damages related to Cd contamination, some studies report that it causes immunosuppression in various animal species. The aim of this paper is to determine whether contamination by Cd, may have a similar effect on the honey bees' immunocompetence. Our results, obtained by immune challenge experiments and confirmed by structural and ultrastructural observations show that such metal causes a reduction in immunocompetence in 3 days Cd exposed bees. As further evidence of honey bee response to Cd treatment, Energy Dispersive X-ray Spectroscopy (X-EDS) has revealed the presence of zinc (Zn) in peculiar electron-dense granules in fat body cells. Zn is a characteristic component of metallothioneins (MTs), which are usually synthesized as anti-oxidant and scavenger tools against Cd contamination. Our findings suggest that honey bee colonies may have a weakened immune system in Cd polluted areas, resulting in a decreased ability in dealing with pathogens.
Nervous tissue is one of the most metabolically expensive animal tissues, thus evolutionary inves... more Nervous tissue is one of the most metabolically expensive animal tissues, thus evolutionary investments that result in enlarged brain regions should also result in improved behavioural performance. Indeed, large-scale comparative studies in vertebrates and invertebrates have successfully linked differences in brain anatomy to differences in ecology and behaviour, but their precision can be limited by the detail of the anatomical measurements, or by only measuring behaviour indirectly. Therefore, detailed case studies are valuable complements to these investigations and have provided important evidence linking brain structure to function in a range of higher-order behavioural traits, such as foraging experience or aggressive behaviour. Here, we show that differences in the size of both lower and higher-order sensory brain areas reflect differences in the relative importance of these senses in the foraging choices of hawk moths, as suggested by previous anatomical work in Lepidopteran...
Invasive alien pest insect species represent a major threat for agriculture and biodiversity. Bec... more Invasive alien pest insect species represent a major threat for agriculture and biodiversity. Because chemical treatments employed to contrast such pests elicit serious environmental and human health problems, a great effort is currently directed to develop long term and environmentally friendly biological control strategies. However, the successful application of some promising techniques, such as the Sterile Insect Technique (SIT), requires a deep knowledge of the pest basic biology. Here, we argue that understanding pest sexual biology using a social network approach can significantly improve the performance of control strategies. For example, SIT may benefit from understanding how individuals interact and how males accede to reproduction, in order to target the most reproductively active and polygamic males. In this paper we studied the socio-sexual networks of the Asian red palm weevil (RPW) Rhynchophorus ferrugineus, a worldwide invader which is causing heavy economic impacts ...
Differences in male and female phenotypes are often the results of sexual selection. Over the yea... more Differences in male and female phenotypes are often the results of sexual selection. Over the years, a vast number of studies investigated how and why the 2 sexes differ in their physical appearance, reaching the conclusion that peculiar visual traits, signals, or ornaments usually evolve under the pressure of sexual selection to mediate intrasexual competition and mate choice. In social contexts, however, males and females can hold different roles and social interactions may depend on the individual gender. The femaledominated hymenopteran societies represent a fascinating scenario to investigate recognition and communication among individuals of different genders outside a common sexual selection framework because sterile female workers typically do not mate and are not attracted to males. Here, we used laboratory bioassays (lure presentation experiments) to evaluate the ability of Polistes dominula workers to discriminate between individuals of the 2 genders, investigating the relevance of the chemical and visual cues potentially involved in such process. Our results showed that P. dominula workers are able to discriminate between the sexes and visual cues rather than chemical ones are responsible for such discrimination.
Behavioural variability at the individual level can be traced down to both internal (genetic, phy... more Behavioural variability at the individual level can be traced down to both internal (genetic, physiologic) and external (environmental, social) determinants. Individual variance can be partly explained with the existence of personalities, i.e. the presence of traits which, at the individual level are constant over time and not bound to a specific context. Inside social insects, the study of personality is still in its infancy and it is complicated by the presence of reproductive and morphological castes, temporal polyethism and a complex social environment. Investigating the existence of personalities inside insect societies is fundamental especially considering the importance that individual personalities may have at the colonial level. We aimed to test the existence of personalities in the paper wasp Polistes dominula and its possible influence on individual reproductive success. We evaluated whether workers individual behaviour was constant over time (two sessions ten days spaced...
The ability to discriminate between friends and foes is a central feature of social life. In soci... more The ability to discriminate between friends and foes is a central feature of social life. In social insects, nestmate recognition is mediated by colony specific cuticular hydrocarbons (CHCs) (label) that are perceived by an individual and compared with its neural representation of the colony odour (template). Although numerous advances have been made in understanding the identity, origin and production of recognition cues in social hymenoptera, relatively little is known about the ontogeny of nestmate recognition, and the learning processes that might be involved. It appears that wasps and bees learn the recognition cues required for template formation from their nest/comb odour, while ants learn principally from their nestmates. In general, the referent template is learned during the early stages of adult life, although pre-imaginal learning might play a role. The CHC blend can change over time; cue-exchange among nestmates is therefore needed to reduce chemical variability among individuals and to integrate environmental compounds into the colony odour. As a result of this process, the referent template is updated during life. This relative plasticity of the recognition system can be exploited by insect social parasites to integrate themselves within the host colonies and to fool host workers about their real identity. By studying the chemical integration strategies of social parasites new insights on the ontogeny of nestmate recognition could be acquired. However, further studies are needed to reveal the neural substrates implicated in learning and memory at different stages of social insect life to better understand how and when template formation occurs.
Understanding the major mechanisms that allow an alien species to become invasive is crucial for ... more Understanding the major mechanisms that allow an alien species to become invasive is crucial for limiting the impact of such species, and individual immunity seems to be a crucial trait for their large range colonization when introduced to a new area. Indeed, a high resistance to pathogens and parasites could favour the establishment and proliferation of an alien species in a newly colonized region. A striking example of recent successful invasion is represented by the Asian hornet, Vespa velutina nigrithorax, which has invaded Western Europe threatening bees and beekeeping activities. Investigating the biology of this species is fundamental to understand how V. velutina nigrithorax has become invasive in Europe and this knowledge could be crucial for limiting its impact. Here, by performing bacterial challenge bioassays, we compare the immune competence of different castes and sex of a population of the invasive Asian hornet, V. velutina nigri thorax, and of the native European hornet, V. crabro. Our results demonstrate that the two species differ in their immunocompetence with respect to caste: a higher level of immunocompetence was found in the reproductive females of the Asian hornet which were resistant to bacterial challenge when compared to workers and males of both species and to reproductive females of the native European hornet. The high pathogen resistance in reproductive females of the Asian hornet, might therefore represent a key factor contributing to the ecological success and spread of this invader.
Simple Summary Social insects use cuticular hydrocarbons for chemical recognition and communicati... more Simple Summary Social insects use cuticular hydrocarbons for chemical recognition and communication. Cuticular hydrocarbons can also be exploited by parasites to their advantage for undermining host recognition systems. The small hive beetle (SHB) is a parasite of honey bee colonies but can also infest nests of other bee species. However, its chemical profile is still not known. For the first time, the present study investigated the SHB chemical profile and compared it with that of its honey bee host. The results show that the SHB has a low chemical profile that is similar to its honey bee host’s. However, while honey bees had a clear colony-specific chemical profile, SHBs did not. The generic chemical profile of the SHB is most likely linked to its free-flying behaviour in the field as these parasites are known to switch between host colonies, possibly limiting the acquisition of a colony specific chemical profile. Our findings also suggest that SHBs do not exploit any finely tuned...
Vespa velutina Lepieltier, 1836 (Hymenoptera: Vespidae) is an invasive predator of honeybees acci... more Vespa velutina Lepieltier, 1836 (Hymenoptera: Vespidae) is an invasive predator of honeybees accidentally introduced into Europe from eastern Asia. It was observed for the first time in southwest France in 2004 and in the following years it rapidly spread almost all over the country. In 2013 it was officially reported in Italy, in the region Liguria, near the border with France. In three years it invaded the whole province of Imperia and it was occasionally reported also in the South Western of Piedmont and in one locality in South Eastern Piedmont. The VELUTINA project was funded in 2014 by the Italian Ministry of Agriculture, with the aim of finding effective control methods against the predator. It includes both research and surveillance: adult and nest monitoring; development of methods for nest detection; development of protocols for nest destruction; studies on wasp chemical communication. Adult monitoring was performed in 5 Italian regions – the two where the hornet is alread...
In previous researches severe damages induced by Cadmium (an ubiquitary environmental pollutant w... more In previous researches severe damages induced by Cadmium (an ubiquitary environmental pollutant whose intracellular oxidative effects are increasingly lethal) exposure in human have been demonstrated. Morphologic effects were observed in Central Nervous System, liver, kidney, placenta. Recently, the involvement of immune system in Cadmium intoxication was demonstrated in mammalians; we, therefore, tried to evidence such effect in a simple model as Apis Mellifera. In this animal the immune system is represented by “fat bodies” which produce proteins active in defense against pathogenic agents. It is important to stress out that a dangerous syndrome causing the collapse of Apis mellifera hives has intensified recently, in Europe and North America. Current research in this field is oriented towards identifying a synergy of contributing factors to the weakening of the hive. In this paper, we aim to determine whether contamination by cadmium may have an immunosuppressive effect on the in...
• Vespa velutina is an alien hornet of high ecological and economic concern in Europe. • Its gut ... more • Vespa velutina is an alien hornet of high ecological and economic concern in Europe. • Its gut microbiome has been characterized through meta-genomics. • We investigated the effect of ontogeny, phenotype and similarity with environment. • Fungal and bacterial community's abundance depends on ontogeny and phenotype. • Microbiome characterization is a springboard for management strategies.
Parasites and pathogens can follow different patterns of infection depending on the host developm... more Parasites and pathogens can follow different patterns of infection depending on the host developmental stage or sex. In fact, immune function is energetically costly for hosts and trade-offs exist between immune defences and life history traits as growth, development and reproduction and organisms should thus optimize immune defence through their life cycle according to their This article is protected by copyright. All rights reserved. developmental stage. Identifying the most susceptible target and the most virulent pathogen is particularly important in the case of insect pests, in order to develop effective control strategies targeting the most vulnerable individuals with the most effective control agent. Here, we carried out laboratory tests to identify the most susceptible target of infection by infecting different stages of the red palm weevil Rhynchophorus ferrugineus (larvae, pupae, male and female adults) with both a generic pathogen, antibiotic-resistant Gram-negative bacteria Escherichia coli XL1-Blue, and two specific strains of entomopathogenic nematodes (EPNs), Steinernema carpocapsae ItS-CAO1 and Heterorhabditis bacteriophora ItH-LU1. By evaluating bacterial clearance, host mortality and parasite progeny release, we demonstrate that larvae are more resistant than adults to bacterial challenge and they release less EPNs progeny after infection despite a higher mortality compared to adults. Considering the two EPN strains, S. carpocapsae was more virulent than H. bacteriophora both in terms of host mortality and more abundant progeny released by hosts after death. The outcomes attained with unspecific and specific pathogens provide useful information for a more efficient and sustainable management of this invasive pest.
1. Invasive alien species are a major threat to biodiversity. In addition to predation and parasi... more 1. Invasive alien species are a major threat to biodiversity. In addition to predation and parasitism, native species might suffer from competition when invasive alien species occupy a similar ecological niche. 2. We focused on the potential interspecific interaction between two hornets: the Asian yellow-legged hornet, Vespa velutina, a high-concern invasive alien species recently arrived in Europe, and the native European hornet, Vespa crabro. The two species share a similar ecological niche and V. velutina is rapidly expanding across Europe, which suggests that V. crabro might suffer from competition. 3. We investigated, under laboratory controlled conditions, two life history traits that might cause the two species to compete: i) the ability of workers to find food sources and their flexibility in exploiting them (through individual food item choice tests and exploration assays), and ii) the worker resistance to pathogens (through immune challenge tests). 4. We show that trophic preference of both species highly overlaps, with a marked dietary preference for honeybees compared to other insect prey and non-prey protein items. No differences have been observed in the exploratory behaviour of both species. Finally, constitutive antibacterial activity was greater in workers of the native species than in workers of the invasive hornet. 5. Our laboratory study provides a first assessment under controlled conditions of the factors affecting competition between workers of two hornet species and proposes a framework to assess, in wild contexts, the magnitude of the competition and the impact of the introduced V. velutina on the native V. crabro.
Honeybee colonies are under the threat of many stressors, biotic and abiotic factors that strongl... more Honeybee colonies are under the threat of many stressors, biotic and abiotic factors that strongly affect their survival. Recently, great attention has been directed at chemical pesticides, including their effects at sub-lethal doses on bee behaviour and colony success; whereas the potential side effects of natural biocides largely used in agriculture, such as entomopathogenic fungi, have received only marginal attention. Here, we report the impact of the fungus Beauveria bassiana on honeybee nestmate recognition ability, a crucial feature at the basis of colony integrity. We performed both behavioural assays by recording bee guards’ response towards foragers (nestmate or non-nestmate) either exposed to B. bassiana or unexposed presented at the hive entrance, and GC-MS analyses of the cuticular hydrocarbons (CHCs) of fungus-exposed versus unexposed bees. Our results demonstrated that exposed bees have altered cuticular hydrocarbons and are more easily accepted into foreign colonies ...
Philosophical Transactions of the Royal Society B: Biological Sciences, 2019
Insect societies play a crucial role in the functioning of most ecosystems and have fascinated bo... more Insect societies play a crucial role in the functioning of most ecosystems and have fascinated both scientists and the lay public for centuries. Despite the long history of study, we are still far from understanding how insect societies have evolved and how social cohesion in their colonies is maintained. Here we suggest inquiline social parasites of insect societies as an under-exploited experimental tool for understanding sociality. We draw on examples from obligate inquiline (permanent) social parasites in wasps, ants and bees to illustrate how these parasites may allow us to better understand societies and learn more about the evolution and functioning of insect societies. We highlight three main features of these social parasite–host systems—namely, close phylogenetic relationships, strong selective pressures arising from coevolution and multiple independent origins—that make inquiline social parasites particularly suited for this aim; we propose a conceptual comparative framew...
Reproductive and task partitioning in large colonies of social insects suggest that colony member... more Reproductive and task partitioning in large colonies of social insects suggest that colony members belonging to different castes or performing different tasks during their life (polyethism) may produce specific semiochemicals and be differently sensitive to the variety of pheromones involved in intraspecific chemical communication. The main peripheral olfactory organs are the antennal chemosensilla, where the early olfactory processes take place. At this stage, members of two different families of soluble chemosensory proteins [odorant-binding proteins (OBPs) and chemosensory proteins (CSPs)] show a remarkable affinity for different odorants and act as carriers while a further family, the Niemann-Pick type C2 proteins (NPC2) may have a similar function, although this has not been fully demonstrated. Sensillar lymph also contains Odorant degrading enzymes (ODEs) which are involved in inactivation through degradation of the chemical signals, once the message is conveyed. Despite their importance in chemical communication, little is known about how proteins involved in peripheral olfaction and, more generally antennal proteins, differ in honeybees of different caste, task and age. Here, we investigate for the first time, using a shotgun proteomic approach, the antennal profile of honeybees of different castes (queens and workers) and workers performing different tasks (nurses, guards, and foragers) by controlling for the potential confounding effect of age. Regarding olfactory proteins, major differences were observed between queens and workers, some of which were found to be more abundant in queens (OBP3, OBP18, and NPC2-1) and others to be more abundant in workers (OBP15, OBP21, CSP1, and CSP3); while between workers performing different tasks, OBP14 was more abundant in nurses with respect to guards and foragers. Apart from proteins involved in olfaction, we have found that the antennal proteomes are mainly characterized by castes and tasks, while age has no effect on antennal protein profile. Among the main differences, the strong decrease in vitellogenins found in guards and foragers is not associated with age.
In the last decades a dramatic loss of Apis mellifera hives has been reported in both Europe and ... more In the last decades a dramatic loss of Apis mellifera hives has been reported in both Europe and USA. Research in this field is oriented towards identifying a synergy of contributing factors, i.e. pathogens, pesticides, habitat loss and pollution to the weakening of the hive. Cadmium (Cd) is a hazardous anthropogenic pollutant whose effects are proving to be increasingly lethal. Among the multiple damages related to Cd contamination, some studies report that it causes immunosuppression in various animal species. The aim of this paper is to determine whether contamination by Cd, may have a similar effect on the honey bees' immunocompetence. Our results, obtained by immune challenge experiments and confirmed by structural and ultrastructural observations show that such metal causes a reduction in immunocompetence in 3 days Cd exposed bees. As further evidence of honey bee response to Cd treatment, Energy Dispersive X-ray Spectroscopy (X-EDS) has revealed the presence of zinc (Zn) in peculiar electron-dense granules in fat body cells. Zn is a characteristic component of metallothioneins (MTs), which are usually synthesized as anti-oxidant and scavenger tools against Cd contamination. Our findings suggest that honey bee colonies may have a weakened immune system in Cd polluted areas, resulting in a decreased ability in dealing with pathogens.
Nervous tissue is one of the most metabolically expensive animal tissues, thus evolutionary inves... more Nervous tissue is one of the most metabolically expensive animal tissues, thus evolutionary investments that result in enlarged brain regions should also result in improved behavioural performance. Indeed, large-scale comparative studies in vertebrates and invertebrates have successfully linked differences in brain anatomy to differences in ecology and behaviour, but their precision can be limited by the detail of the anatomical measurements, or by only measuring behaviour indirectly. Therefore, detailed case studies are valuable complements to these investigations and have provided important evidence linking brain structure to function in a range of higher-order behavioural traits, such as foraging experience or aggressive behaviour. Here, we show that differences in the size of both lower and higher-order sensory brain areas reflect differences in the relative importance of these senses in the foraging choices of hawk moths, as suggested by previous anatomical work in Lepidopteran...
Invasive alien pest insect species represent a major threat for agriculture and biodiversity. Bec... more Invasive alien pest insect species represent a major threat for agriculture and biodiversity. Because chemical treatments employed to contrast such pests elicit serious environmental and human health problems, a great effort is currently directed to develop long term and environmentally friendly biological control strategies. However, the successful application of some promising techniques, such as the Sterile Insect Technique (SIT), requires a deep knowledge of the pest basic biology. Here, we argue that understanding pest sexual biology using a social network approach can significantly improve the performance of control strategies. For example, SIT may benefit from understanding how individuals interact and how males accede to reproduction, in order to target the most reproductively active and polygamic males. In this paper we studied the socio-sexual networks of the Asian red palm weevil (RPW) Rhynchophorus ferrugineus, a worldwide invader which is causing heavy economic impacts ...
Differences in male and female phenotypes are often the results of sexual selection. Over the yea... more Differences in male and female phenotypes are often the results of sexual selection. Over the years, a vast number of studies investigated how and why the 2 sexes differ in their physical appearance, reaching the conclusion that peculiar visual traits, signals, or ornaments usually evolve under the pressure of sexual selection to mediate intrasexual competition and mate choice. In social contexts, however, males and females can hold different roles and social interactions may depend on the individual gender. The femaledominated hymenopteran societies represent a fascinating scenario to investigate recognition and communication among individuals of different genders outside a common sexual selection framework because sterile female workers typically do not mate and are not attracted to males. Here, we used laboratory bioassays (lure presentation experiments) to evaluate the ability of Polistes dominula workers to discriminate between individuals of the 2 genders, investigating the relevance of the chemical and visual cues potentially involved in such process. Our results showed that P. dominula workers are able to discriminate between the sexes and visual cues rather than chemical ones are responsible for such discrimination.
Behavioural variability at the individual level can be traced down to both internal (genetic, phy... more Behavioural variability at the individual level can be traced down to both internal (genetic, physiologic) and external (environmental, social) determinants. Individual variance can be partly explained with the existence of personalities, i.e. the presence of traits which, at the individual level are constant over time and not bound to a specific context. Inside social insects, the study of personality is still in its infancy and it is complicated by the presence of reproductive and morphological castes, temporal polyethism and a complex social environment. Investigating the existence of personalities inside insect societies is fundamental especially considering the importance that individual personalities may have at the colonial level. We aimed to test the existence of personalities in the paper wasp Polistes dominula and its possible influence on individual reproductive success. We evaluated whether workers individual behaviour was constant over time (two sessions ten days spaced...
The ability to discriminate between friends and foes is a central feature of social life. In soci... more The ability to discriminate between friends and foes is a central feature of social life. In social insects, nestmate recognition is mediated by colony specific cuticular hydrocarbons (CHCs) (label) that are perceived by an individual and compared with its neural representation of the colony odour (template). Although numerous advances have been made in understanding the identity, origin and production of recognition cues in social hymenoptera, relatively little is known about the ontogeny of nestmate recognition, and the learning processes that might be involved. It appears that wasps and bees learn the recognition cues required for template formation from their nest/comb odour, while ants learn principally from their nestmates. In general, the referent template is learned during the early stages of adult life, although pre-imaginal learning might play a role. The CHC blend can change over time; cue-exchange among nestmates is therefore needed to reduce chemical variability among individuals and to integrate environmental compounds into the colony odour. As a result of this process, the referent template is updated during life. This relative plasticity of the recognition system can be exploited by insect social parasites to integrate themselves within the host colonies and to fool host workers about their real identity. By studying the chemical integration strategies of social parasites new insights on the ontogeny of nestmate recognition could be acquired. However, further studies are needed to reveal the neural substrates implicated in learning and memory at different stages of social insect life to better understand how and when template formation occurs.
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Papers by Rita Cervo