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1.
J Insect Physiol ; 119: 103952, 2019.
Article in English | MEDLINE | ID: mdl-31568763

ABSTRACT

Due to its huge invasion potential and specialization in honeybee predation, the invasive hornet Vespa velutina nigrithorax represents a high-concern species under both an ecological and economical perspective. In light of the development of specific odorant attractants to be used in sustainable control strategies, we carried out both behavioural assays and chemical analyses to investigate the possibility that, in the invasive population of V. velutina nigrithorax, reproductive females emit volatile pheromones to attract males, as demonstrated in a Chinese non-invasive population. We focused on the secretions produced by sternal and venom glands; because of the volatility and complexity of their composition, both of them could potentially allow an attraction and a species-specific response, decreasing therefore non-target species by-catches. Results of chemical analyses and behavioural assays showed that venom volatiles, although population-specific, are unlikely candidates as male attractants since they do not differ in composition or in quantity between reproductive females and workers and do not attract males. Conversely, sternal gland secretion differs between female castes for the presence of some ketoacids exclusive of gynes already reported as sex pheromones for the non-invasive subspecies V. velutina auraria. Despite such a difference, males are attracted by the sternal gland secretion of both workers and gynes. These results provide a first step to understand the reproductive biology of V. velutina nigrithorax in its invasive range and to develop effective and sustainable management strategies for the species.


Subject(s)
Sex Attractants/chemistry , Wasps/chemistry , Wasps/physiology , Animals , Exocrine Glands/chemistry , Female , Introduced Species , Male , Sex Attractants/physiology , Sexual Behavior, Animal/physiology , Wasp Venoms/chemistry
2.
Environ Pollut ; 218: 826-834, 2016 Nov.
Article in English | MEDLINE | ID: mdl-27528187

ABSTRACT

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.


Subject(s)
Bees/drug effects , Cadmium/adverse effects , Environmental Exposure/adverse effects , Environmental Pollutants/adverse effects , Immunocompetence/drug effects , Adaptation, Physiological , Animals , Antioxidants/metabolism , Bees/immunology , Bees/metabolism , Europe , Metallothionein , Pesticides , Stress, Physiological , United States , Zinc/metabolism
3.
J Exp Biol ; 217(Pt 17): 2998-3001, 2014 Sep 01.
Article in English | MEDLINE | ID: mdl-25165133

ABSTRACT

Honeybee disappearance is one of the major environmental and economic challenges this century has to face. The ecto-parasitic mite Varroa destructor represents one of the main causes of the worldwide beehive losses. Although halting mite transmission among beehives is of primary importance to save honeybee colonies from further decline, the natural route used by mites to abandon a collapsing colony has not been extensively investigated so far. Here, we explored whether, with increasing mite abundance within the colony, mites change their behaviour to maximize the chances of leaving a highly infested colony. We show that, at low mite abundance, mites remain within the colony and promote their reproduction by riding nurses that they distinguish from foragers by different chemical cuticular signatures. When mite abundance increases, the chemical profile of nurses and foragers tends to overlap, promoting mite departure from exploited colonies by riding pollen foragers.


Subject(s)
Animal Distribution/physiology , Bees/parasitology , Host-Parasite Interactions , Varroidae/physiology , Animals , Bees/chemistry , Behavior, Animal , Integumentary System/physiology
4.
J Exp Biol ; 213(3): 453-8, 2010 Feb 01.
Article in English | MEDLINE | ID: mdl-20086130

ABSTRACT

Social life offers animals increased fitness opportunities. However, the advantages are not evenly distributed and some individuals benefit more than others. The ultimate advantage of reaching the highest rank in a dominance hierarchy is the achievement of reproduction monopoly. In social insects, dominant individuals and queens keep their reproductive control through differential oophagy of unwanted eggs (egg policing). Egg recognition is the main proximate mechanism for maintaining reproductive dominance. In the social wasp Polistes dominulus, subordinate queens often lay eggs in the presence of the dominant individual. Combining gas chromatography-mass spectrometry (GC-MS) analysis and laboratory bioassays, we found that chemical differences between eggs of subordinate and dominant foundresses can explain the differential success in oophagy enjoyed by dominant individuals. We propose that dominance behaviour is an investigative behaviour as well as a ritualized agonistic behaviour. In fact, the frequency of dominance acts increases with the chemical similarity of the surfaces of dominant- and subordinate-laid eggs. Therefore, dominant individuals probably perform dominance behaviour to test the cuticular signatures of subordinates and so better assess the chemical profiles of subordinate eggs. Finally, we provide evidence that in particular social contexts, subordinate Polistes foundresses can develop ovaries as large as those of dominant individuals but nevertheless lay very few eggs. The subordinates probably lay a limited number of eggs to avoid unnecessary energy loss, as a result of efficient queen policing, but will start laying eggs as soon as the queen fails.


Subject(s)
Behavior, Animal/physiology , Hydrocarbons/metabolism , Ovulation/physiology , Social Dominance , Wasps/physiology , Animals , Female , Linear Models , Principal Component Analysis
5.
Proc Biol Sci ; 275(1639): 1189-96, 2008 May 22.
Article in English | MEDLINE | ID: mdl-18285281

ABSTRACT

To establish a dominance order, social animals often rely on indicators of fighting to avoid costly aggressive encounters. In some species, individuals use colour patterns to signal their social status. Recent studies claimed that facial markings in the eusocial paper wasp Polistes dominulus are status badges that allow co-foundresses to form a linear hierarchy based on individual quality. Here, we evaluated facial patterns in natural populations of P. dominulus, in its native range, to observe whether the marks reflect overall wasp quality in different contexts. We used the same measures of clypeus patterns used by earlier studies, but did not find that they functioned as status badges. Our analyses showed no evidence that visual markers are related to: (i) size, (ii) probability of surviving winter, (iii) social rank in spring associations, or (iv) health status (assessed by the presence of strepsipteran endoparasites). Size, however, is important. Larger wasps are more likely to survive the winter and to acquire the dominant position in spring associations. Larvae infected with endoparasites become smaller adult wasps. These findings suggest that body size is a reliable quality indicator on which wasps build their social networks, and that clypeus patterning is not involved.


Subject(s)
Behavior, Animal/physiology , Body Size/physiology , Color , Social Dominance , Wasps/physiology , Animals , Female , Seasons
6.
J Evol Biol ; 18(5): 1362-7, 2005 Sep.
Article in English | MEDLINE | ID: mdl-16135131

ABSTRACT

Parasites that exploit the parental behaviour of several host species may be selected to form distinct host-specific genetic lineages. This process is well documented in bird brood parasites, but not in insect social parasites. Polistes atrimandibularis is the only paper-wasp social parasite known to exploit four host species. It does not form genetically distinct host races according to analyses based on microsatellite loci. Also, there were no size-matching between parasites and host species. Instead, P. atrimandibularis queens seemed to be successful as parasites in this population only when they originated from nests of P. dominulus, the largest species. The other host species are a sink for P. atrimandibularis since adult females emerging from those nests appear too small to usurp colonies themselves. Traits that may help P. atrimandibularis infiltrate multiple species may include its nonaggressive usurpation tactics and its ability to acquire host cuticular hydrocarbon recognition labels.


Subject(s)
Genetic Variation , Genetics, Population , Social Behavior , Wasps/genetics , Wasps/parasitology , Analysis of Variance , Animals , Body Weights and Measures , Female , Gene Frequency , Genotype , Host-Parasite Interactions , Italy , Microsatellite Repeats/genetics , Phylogeny , Species Specificity
7.
Parasitology ; 129(Pt 5): 643-51, 2004 Nov.
Article in English | MEDLINE | ID: mdl-15552409

ABSTRACT

Chemical cues are so important in the recognition mechanism of social insects that most social parasites (which rely on hosts to rear their brood) have been documented as overcoming the mechanism by which colony residents recognize non-nestmates, by mimicking the odour of the usurped colony. We simulated in the laboratory the process by which the obligate social parasite, Polistes semenowi, invades nests of the host species, Polistes dominulus, in the field and analysed the epicuticular lipid layer before and after host nest usurpation. The experiment documents that P. semenowi social parasites have an epicuticular hydrocarbon pattern which is very similar to that of their host but, after entering host colonies, parasites mimic the odour of the colonies they invade, to the point that they perfectly match the hydrocarbon profile peculiar to the colony they entered. However, both before and after host nest invasion, parasites show a tendency to possess diluted recognition cues with respect to their hosts.


Subject(s)
Host-Parasite Interactions , Hydrocarbons/analysis , Molecular Mimicry , Wasps/physiology , Animals , Cues , Female , Hydrocarbons/chemistry , Male , Multivariate Analysis , Odorants/analysis , Social Behavior , Species Specificity , Wasps/chemistry , Wasps/parasitology
8.
J Insect Physiol ; 50(2-3): 217-23, 2004.
Article in English | MEDLINE | ID: mdl-15019524

ABSTRACT

In multiple-foundress nests of the wasp Polistes dominulus, dominance hierarchies are established among foundresses, and only the dominant (=alpha) individual lays eggs. The alpha female can be distinguished from subordinate females and workers on the basis of the proportions of some hydrocarbons present on the cuticle, suggesting that chemical signaling of her reproductive status could occur. P. dominulus is also the host species of the obligate social parasite Polistes sulcifer. After aggressively usurping host colonies and behaviorally replacing the host alpha female, parasites are characterized by a change in the proportions of their cuticular hydrocarbons to match that of the host cuticular profile at both species and colony levels. In the current study, we demonstrate that P. sulcifer queens also modify their cuticular hydrocarbon proportions after usurpation to match that of the host alpha female. Parasite females, therefore, acquire the dominant rank in host colonies both reproductively and chemically by mimicking the typical alpha profile of the host. Parasite females were not able to fully inhibit ovary development in host foundresses, and 10 days after usurpation, parasites, alpha and beta foundresses show similar chemical profiles and ovarian development.


Subject(s)
Dominance-Subordination , Host-Parasite Interactions , Insect Proteins/analysis , Odorants , Pheromones/chemistry , Wasps/physiology , Animals , Discriminant Analysis , Female , Hydrocarbons/analysis , Molecular Mimicry , Pheromones/analysis , Social Environment , Species Specificity , Wasps/chemistry , Wasps/parasitology
9.
J Evol Biol ; 16(2): 254-9, 2003 Mar.
Article in English | MEDLINE | ID: mdl-14635864

ABSTRACT

The resolution of social conflict in colonies may accord with the interests of the most numerous party. In social insect colonies with single once-mated queens, workers are more closely related to the workers' sons than they are to the queens' sons. Therefore, they should prefer workers to produce males, against the queen's interests. Workers are capable of producing males as they arise from unfertilized eggs. We found Polistes gallicus to have colonies of single, once-mated queens, as determined by microsatellite genotyping of the workers, so worker interests predict worker male production. In colonies lacking queens, workers produced the males, but not in colonies with original queens. Thus worker interests were expressed only when the queen was gone. The high fraction of missing queens and early end to the colony cycle relative to climate so early in the season is surprising and may indicate a forceful elimination of the queen.


Subject(s)
Sex Ratio , Social Behavior , Wasps/physiology , Animals , Female , Italy , Likelihood Functions , Male , Microsatellite Repeats , Reproduction/physiology
10.
Proc Biol Sci ; 268(1482): 2253-60, 2001 Nov 07.
Article in English | MEDLINE | ID: mdl-11674873

ABSTRACT

Colonies of the polistine wasp Polistes dominulus are parasitized by the permanent worker-less social parasite Polistes sulcifer. After usurpation of the host colony, parasite females are characterized by a change in the relative proportions of their cuticular hydrocarbons to match those of the host species. In this paper we present evidence from field data and laboratory experiments that P. sulcifer females adopt a colony-specific host odour that facilitates their acceptance by host females of the usurped colony. Presentation experiments demonstrate that parasite females are recognized as foreign individuals by workers of other parasitized nests. We show that the modification of parasite cuticular compounds is sufficient for this recognition. This provides evidence that, after invasion, P. sulcifer queens do not require appeasement or propaganda substances for their acceptance by host colonies. Furthermore, multivariate discriminant analysis of the cuticular hydrocarbon proportions of the parasites after usurpation assigns the parasites together with P. dominulus females of their own host colony. To the authors' knowledge, this is the first confirmation that social parasites adopt colony-specific host odours.


Subject(s)
Appetitive Behavior , Odorants , Wasps/physiology , Animals , Female , Host-Parasite Interactions
11.
Nature ; 405(6788): 784-7, 2000 Jun 15.
Article in English | MEDLINE | ID: mdl-10866197

ABSTRACT

High-resolution genetic markers have revolutionized our understanding of vertebrate mating systems, but have so far yielded few comparable surprises about kinship in social insects. Here we use microsatellite markers to reveal an unexpected and unique social system in what is probably the best-studied social wasp, Polistes dominulus. Social insect colonies are nearly always composed of close relatives; therefore, non-reproductive helping behaviour can be favoured by kin selection, because the helpers aid reproductives who share their genes. In P. dominulus, however, 35% of foundress nestmates are unrelated and gain no such advantage. The P. dominulus system is unlike all other cases of unrelated social insects, because one individual has nearly complete reproductive dominance over subordinates who could have chosen other reproductive options. The only significant advantage that subordinates obtain is a chance at later reproduction, particularly if the queen dies. Thus, P. dominulus societies are functionally unlike other social insects, but similar to certain vertebrate societies, in which the unrelated helpers gain through inheritance of a territory or a mate.


Subject(s)
Helping Behavior , Wasps/physiology , Animals , Female , Male
12.
Naturwissenschaften ; 87(4): 172-6, 2000 Apr.
Article in English | MEDLINE | ID: mdl-10840803

ABSTRACT

Obligate social parasites in the social insects have lost the worker caste and the ability to establish nests. As a result, parasites must usurp a host nest, overcome the host recognition system, and depend on the host workers to rear their offspring. We analysed cuticular hydrocarbon profiles of live parasite females of the paper wasp social parasite Polistes sulcifer before and after usurpation of host nests, using the non-destructive technique of solid-phase micro-extraction. Our results reveal that hydrocarbon profiles of parasites change after usurpation of host nests to match the cuticular profile of the host species. Chemical evidence further shows that the parasite queen changes the odour of the nest by the addition of a parasite-specific hydrocarbon. We discuss the possible role of this in the recognition and acceptance of the parasite and its offspring in the host colony.


Subject(s)
Social Behavior , Wasps , Animals , Female , Odorants
13.
Behav Processes ; 36(3): 213-8, 1996 Jun.
Article in English | MEDLINE | ID: mdl-24896870

ABSTRACT

Sometimes the nests of the paper wasp Polistes dominulus are parasitized by the obligate social parasite Polistes sulcifer. It is not known how, in the spring, this parasite searches for established nests of its host species. This study investigates the capacity to detect the host nest by olfactory cues alone. In laboratory experiments P. sulcifer females were allowed to choose different options hidden from view: host nest and dummy, various portions of the host nest (larvae, pupae and material), nests or immature brood pertaining to different sympatric species (P. dominulus, P. nimpha and P. gallicus). The parasites proved to be capable of perceiving nest odour and of discriminating between different species of Polistes. The odour of the immature host brood, rather than the nest material, elicits the greatest response in the parasites.

14.
Behav Processes ; 28(1-2): 51-8, 1992 Dec.
Article in English | MEDLINE | ID: mdl-24924790

ABSTRACT

The behaviour of stroking the abdomen over the nest surface has previously been described in females of only a few Polistes wasp species, and was considered to be associated with pheromonal release. This study examines abdomen stroking in solitary and multiple female laboratory colonies of Polistes dominulus during the pre-emergence period. In multiple female colonies stroking behaviour is related to hierarchy: alpha females stroking more than subordinates. However, after removal of the dominant female the subordinate increases her stroking rate. Solitary females also stroke but, unlike alpha females, they do so less during the egg-stage than in subsequent stages of the colonial cycle. It is hypothesized that abdomen stroking cues the immature brood as to which adult female is the dominant individual; this could lead to competition between females on the same nest. This function is also discussed in the context of intra- and inter-specific Polistes parasites, where the behaviour is particularly evident.

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