Social wasp parasites affect the nestmate recognition abilities of their hosts (<Emphasis Type="Italic">Polistes atrimandibularis</Emphasis> and <Emphasis Type="Italic">P. biglumis</Emphasis>, Hymenoptera,Vespidae)

Summary. Queens of the parasitic social wasp, Polistes atrimandibularis, temporarily mimic the odor of their host species, Polistes biglumis, but their offspring have parasite-specific odors. As a consequence, in parasitized colonies individuals with different odors co-inhabit the colony and host workers, who are responsible for colony defense, accept wasps with different odors. In order to verify whether this particular condition causes a change in recognition abilities of hosts, we tested nestmate/non-nestmate discrimination in field colonies invaded by social parasites (and in non-parasitized colonies as controls). Results show that parasitized colonies distinguish between nestmates and non-nestmates, distinguish their parasite queen from those that usurped alien colonies, and accept their parasite's non-mimetic offspring but make more recognition errors than non-parasitized colonies. The optimal acceptance threshold model predicts that when the frequency of encountering non-kin increases, residents become less permissive towards intruders. However, my data show that parasitized colonies are more permissive towards non-nestmates with respect to non-parasitized colonies but they are also more aggressive towards nestmates, suggesting that host workers' learning abilities are impaired.     

Alarm communication in <Emphasis Type="Italic">Ropalidia</Emphasis> social wasps

Summary Alarm pheromones, chemical substances produced by social insects to alert the colony to threat, are the principal means by which colony defence is co-ordinated. We present the results of a study on alarm behaviour in 5 swarming species of wasps belonging to the genus Ropalidia. These species show a remarkably efficient strategy of alarm communication, including visual display and attack synchronization. We show that pheromones released from the venom gland play an important role in alarm recruitment in species belonging to the Ropalidia flavopicta group, but not in Ropalidia sumatrae. We analysed the contents of the venom reservoirs content of four of the studied species by gas chromatography-mass spectrometry. Glands were found to contain a complex mixture of volatile compounds as well as spiroacetals of higher molecular weight. Interestingly, despite all species producing similar chemical compounds from the venom gland, these were found to elicit alarm behaviour in only those species that build nest envelopes, suggesting a link between chemical release of alarm behaviour and the evolution of nest architecture in Ropalidia wasps.Received 19 August 2003; revised 29 February 2004; accepted 10 March 2004     

Nesting Habit and Alarm Pheromones in Polistes gallicus (Hymenoptera, Vespidae)

Alarm pheromones are used in many social insects to elicit an alarm response of nestmates towards disturbances. This chemical alarm channel is especially used by species nesting in closed environments. Polistes gallicus paper wasps typically found their nests on open substrates where visual and vibrational stimuli could be more important than the chemical one to alarm the colony. We investigated, through field bioassays, if, also in this species, workers venom is still the source of alarm pheromones. Our results show that venom volatiles are able to increase the colony defence reaction stimulating more individuals to attack and sting the object of disturbance. Therefore our results suggest the hypothesis that chemical alarm is independent of nesting habit (concealed vs exposed) within the Polistes genus.     

Evidence of alarm pheromones in the venom of Polistes dominulus workers (Hymenoptera: Vespidae)

Abstract.  The active and coordinating capacity of defending the nest is a key feature of social insects. The present study investigates the presence of alarm pheromones in the venom of workers of the social wasp, Polistes dominulus . Laboratory experiments were performed with caged colonies of P. dominulus using a wind tunnel apparatus to test the behavioural response of workers to venom released by other workers and to venom extracts. Contrary to that previously reported for European paper wasps, the present results show that the venom is the source of alarm pheromones. Field experiments combining a visual (black target) and a chemical stimulus (venom extract) were performed to test the effect of the venom on the reaction of colonies. Wasps leave the nest, land on the visual target and attack the target significantly more once exposed to venom extract plus target than to solvent plus target. This work shows that the venom of P. dominulus workers elicits an alarm response, reduces the threshold for attack and acts as an attractant on targets. These results using P. dominulus indicate that, in both American and European species, colony defence is based on the same features, suggesting that chemical alarm is a widespread trait in the genus Polistes .     

Incipient morphological castes in <Emphasis Type="Italic">Polistes gallicus</Emphasis> (Vespidae,Hymenoptera)

The occurrence of a pre-imaginal caste determination represents a sort of “point of no return” to eusociality. In some social insect taxa, including Polistes species, the occurrence of distinct queen and worker castes is still debated. Before this report, no clear morphological differences between reproductive and non-reproductive individuals were known. Here we show that several pre-imaginal morphological differences of the Van der Vecht organ occur between foundresses (queens) and workers. Geometric morphometrics revealed that queens are characterized by shape deformations of this organ, which is responsible for a typical allometric growth of the secretory area. This organ is predicted to be larger in foundresses compared to workers because its secretion is involved in defense against ants, in nestmate recognition and in preventing workers from challenging for direct reproduction. The results presented here indicate the existence of an incipient morphological caste determination Polistes gallicus and suggest that this species may have passed the “point of no return” for eusociality.     

Species and Colony Components in the Recognition Odor of Young Social Wasps: Their Expression and Learning (Polistes biglumis and P. atrimandibularis; Hymenoptera: Vespidae)

In Polistes, nestmate recognition relies on the learning of recognition cues from the nest. When wasps recognize nestmates, they match the template learned with the odor of the encountered wasp. The social wasp Polistes biglumis use the homogeneous odor of their colony to recognize nestmates. When these colonies become host colonies of the social parasite P. atrimandibularis, colony odor is no longer homogeneous, as the parasite offspring have an odor that differs from that of their hosts. In trying to understand how the mechanism of nestmate recognition works in parasitized colonies and why parasite offspring are accepted by hosts, we tested the responses of resident Polistes biglumis wasps from parasitized and unparasitized colonies to newly emerged parasites and to nestmate and non-nestmate conspecifics. The experiments indicate that immediately upon eclosion both young parasites and young hosts lack a colony odor and that colony odor can be soon acquired from the accepting colony. In addition, while residents of nonparasitized colonies recognize only the odor of their species, resident hosts of parasitized colonies have learned a template that fits the odors of two species.     

Recognition of social parasites as nest-mates: adoption of colony-specific host cuticular odours by the paper wasp parasite Polistes sulcifer.

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.     

Social interactions between an inquiline ant, <Emphasis Type="Italic">Ectatomma parasiticum</Emphasis>, and its host, <Emphasis Type="Italic">Ectatomma tuberculatum</Emphasis> (Formicidae,Ectatomminae)

Inquilines, workerless social parasites, frequently show advanced adaptations to their parasitic life style that indicate a long co-evolutionary history with their host. Ectatomma parasiticum, the first inquiline described in the poneromorph group, usurps established colonies of E. tuberculatum and produces only sexuals. In laboratory colonies, parasites were specifically attacked by the host workers, showing a failure in their social integration. Social interactions were frequent between parasites and their hosts, especially antennation, interpreted as attempts to promote colonial odor transfer. Inquilines destroyed eggs laid by the other queens (67 out of 209 eggs laid), including conspecific parasites, which is unusual. Such partial integration into the host colony and potential parasite virulence argue for a recent evolution of social parasitism in E. tuberculatum.     

Extreme Polygyny: Multi-seasonal “Hypergynous” Nesting in the Introduced Paper Wasp <Emphasis Type="Italic">Polistes dominulus</Emphasis>

In temperate climates, female paper wasps typically initiate new colonies in the spring. Several nest-founding tactics have been documented in Polistes species, including solitary nest initiation, joining a cooperative association, usurping an existing nest, or adopting an abandoned nest. Occasionally, exceptionally large groups of females have also been found reusing nests from the previous season. Here we report this phenomenon in introduced populations of the Eurasian species Polistes dominulus. We describe in detail the demographic and genetic characteristics of one such spring colony from Los Angeles, California, USA, which was collected with 84 associated adults and all stages of developing brood in its 613 cells. Genetic and morphological data indicate the presence of multiple reproductively active females of varying relatedness, as well as many nonbreeding females, including probable early-produced offspring. Despite some evidence of chaotic social conditions, the colony appeared to have been highly productive. Additional observations of similar colonies are needed to determine how control is maintained within such a large breeding aggregation.     

Behavioral defense strategies of the stingless bee, <Emphasis Type="Italic">Austroplebeia australis</Emphasis>, against the small hive beetle, <Emphasis Type="Italic">Aethina tumida</Emphasis>

Small hive beetle, Aethina tumida Murray, is a parasite of social bee colonies and has become an invasive species, raising concern of the potential threat to native pollinators in its new ranges. Here, we report the defensive behavior strategies used by workers of the Australian stingless bee, Austroplebeia australis Friese, against the small hive beetle. A non-destructive method was used to observe in-hive behavior and interactions between bees and different life stages of small hive beetle (egg, larva, and adult). A number of different individual and group defensive behaviors were recorded. Up to 97% of small hive beetle eggs were destroyed within 90 min of introduction, with a significant increase in temporal rate of destruction between the first and subsequent introductions. A similar result was recorded for 3-day-old small hive beetle larvae, with an increased removal rate from 62.5 to 92.5% between the first and second introductions. Of 32 adult beetles introduced directly into the 4 colonies, 59% were ejected, with the remainder being entombed alive in hives within 6 h. Efficiency of ejection also significantly increased between the first and third introductions. Our observations suggest that A. australis colonies, despite no previous exposure to this exotic parasite, have well developed hive defences that are likely to minimize entry and survival of small hive beetles.     

Fitness aspects of transgenic <Emphasis Type="Italic">Aedes fluviatilis</Emphasis> mosquitoes expressing a <Emphasis Type="Italic">Plasmodium</Emphasis>-blocking molecule

Vector-born diseases cause millions of deaths every year globally. Alternatives for the control of diseases such as malaria and dengue fever are urgently needed and the use of transgenic mosquitoes that block parasite/virus is a sound strategy to be used within control programs. However, prior to use transgenic mosquitoes as control tools, it is important to study their fitness since different biological aspects might influence their ability to disseminate and compete with wild populations. We previously reported the construction of four transgenic Aedes fluviatilis mosquito lines expressing a Plasmodium- blocking molecule (mutated bee venom phospholipase A₂–mPLA₂). Presently we studied two aspects of their fitness: body size, that has been used as a fitness-related status, and the expression of major enzymes classes involved in the metabolism of xenobiotics, including insecticides. Body size analysis (recorded by geometric wing morphometrics) indicated that both male and female mosquitoes were larger than the non-transgenic counterparts, suggesting that this characteristic might have an impact on their overall fitness. By contrast, no significant difference in the activity of enzymes related to metabolic insecticide resistance was detected in transgenic mosquitoes. The implication on fitness advantage of these features, towards the implementation of this strategy, is further discussed.     

Can venom volatiles be a taxonomic tool for Polistes wasps (Hymenoptera,Vespidae)?

In the present study, we investigated whether venom volatiles have a species-specific composition and could possibly be used to discriminate between related paper wasp species. We compared venom volatile chemical profiles, obtained through gas chromatography-mass spectrometry analyses, of three non-parasitic European Polistes species ( P. dominulus , P. gallicus and P. nimphus ). The results show that the venom volatile composition is indeed species specific and can thus be a useful systematic tool.     

Multiple host-ant use by the predatory social parasite <Emphasis Type="Italic">Phengaris</Emphasis> (=<Emphasis Type="Italic">Maculinea</Emphasis>) <Emphasis Type="Italic">arion</Emphasis> (Lepidoptera,Lycaenidae)

Phengaris (=Maculinea) arion is an endangered social parasite of Myrmica ants, and for a very long time was considered as specific to Myrmica sabuleti. Previous studies carried out in Poland suggested some discrepancies within this assumption, and therefore a much more intensive survey was undertaken. The host ant use of P. arion was studied at five sites in different types of biotopes in Poland, i.e. xerothermal grasslands where Thymus pulegioides was used as a larval food plant by the butterfly, and more or less sandy biotopes with Thymus serpyllum. Altogether nine Myrmica species were recorded, and considerable variation in species composition and density of nests was recorded. At four localities M. sabuleti proved to be the most common ant. A total of 529 Myrmica nests were examined, and only 20 of them contained larvae and pupae of P. arion. Host ants belonged to five different species, i.e. M. sabuleti, Myrmica scabrinodis, Myrmica schencki, Myrmica lobicornis and Myrmica hellenica. Only at one site (NE Poland) was a significant heterogeneity in parasitation rates among Myrmica species detected. M. lobicornis was the most often infested ant there, which may suggest local specialisation of the butterfly. Overall low parasitism rates may explain the vulnerability of P. arion in Central Europe but further studies are also necessary.     

Workers do not mediate the inhibitory power of queens in a termite, <Emphasis Type="Italic">Reticulitermes speratus</Emphasis> (Isoptera,Rhinotermitidae)

In social insects, the caste systems are based on reproductive division of labor; queens specialize in reproduction and workers primarily maintain the colony. Recently, a volatile pheromone containing n-butyl-n-butyrate and 2-methyl-1-butanol was identified as a termite queen pheromone that inhibits the differentiation of female neotenic reproductives (secondary queens). Although this volatile inhibitory pheromone regulates caste differentiation directly, the method by which it reaches members without direct contact with the queen in large colonies is not well understood. Therefore, additional mechanisms of indirect communication must exist, such as worker-mediated queen signal transport. We found that workers exposed to female reproductives did not mediate queens’ inhibitory signal in a termite Reticulitermes speratus. The experiment assessed worker transfer from direct to indirect contact groups and determined that the differentiation of new female reproductives in the indirect contact groups was not influenced by the direct contact groups, whereas direct contact with functional female reproductives and artificial queen pheromone did suppress neotenic differentiation. This suggests that worker transfer of the queen signal is unlikely and that for colony-wide inhibition direct contact by the majority of infertile members with reproductives or eggs, which emit the same volatiles as female reproductives, is necessary within a certain time interval.     

Pungent odor of the adult skipper butterfly <Emphasis Type="Italic">Erynnis</Emphasis><Emphasis Type="Italic">montanus</Emphasis> (Lepidoptera: Hesperiidae)

Adults of some butterfly species have odors, several components of which are known to have pheromonal or defensive functions. Little is known about the odors of hesperiid butterflies, however. Erynnis montanus (Hesperiidae), especially male adults, emit a pungent odor that is detectable by the human nose. Chemical analysis has revealed that crude extracts of wild individuals contained 10 volatile substances, of which docosane and heneicosane were the main components. Because males contain a significantly larger amount of p-cresol than females, this aromatic compound is characterized as a strong male odor. At the end of the adult occurrence period, p-cresol decreased substantially in each male. Benzothiazole, identified for the first time in lepidopteran adults, was present in both sexes in almost equal amounts. Among the 10 volatile substances detected in males, biased distribution in the wings rather than the body was observed for benzothiazole, heptanal, and p-cresol. Male adults have androconial organs in the costal part of the forewing on which benzothiazole and p-cresol tended to concentrate. However, these compounds were detected not only in other parts of the forewing but also in the hindwing and body, suggesting the presence of undiscovered scent-producing organs.     

Rank integration in dominance hierarchies of host colonies by the paper wasp social parasite Polistes sulcifer (Hymenoptera, Vespidae)

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.     

The surface topography of <Emphasis Type="Italic">Eudiplozoon nipponicum</Emphasis> (Monogenea) developmental stages parasitizing carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

Using scanning electron microscopy (SEM), the external morphology of all developmental stages (egg, oncomiracidium, diporpa, just fused juvenile and adult) of the parasite, Eudiplozoon nipponicum (Monogenea, Diplozoidae), from the gills of carp was studied. During the ontogeny, the tegument, tegumentary and sensory structures are subsequently developed. The tegument of free swimming oncomiracidium occurs in two types — the ciliated and non-ciliated with numerous uniciliated sensory structures. An attachment apparatus starts to form during the oncomiracidium stage. Further developmental stages are adapted to the environment of the gills. Tegumentary folds become more apparent later in development and assist to the parasite’s attachment. In connection with its reproductive strategy, the two morphological structures of diporpa (ventral sucker and dorsal papilla) appear to play important role. On the gills, two individuals need to meet and these structures mediate the fusion between two diporpae. The hindbody of adult parasite is highly modified for attachment. The haptor, folds and lobular extensions are most developed. The forebody is flexible and able to interact with host gill tissue via the mouth and associated mouth structures. The process of food intake of the parasite was discussed.     

The state of populations of <Emphasis Type="Italic">Lernaea cyprinacea</Emphasis> L. (copepoda: lernaeidae) and crucian carp <Emphasis Type="Italic">Carassius carassius</Emphasis> L. in Dlinnoye Lake

The state of populations of the crucian carp Carassius carassius L. and the copepod parasite Lernaea cyprinacea L. was studied after 10 years of a sharp decrease in their abundance. Only one generation of Lernaea cyprinacea species was recorded each year. The alteration of the parasite generation occurred in the second half of July. Changes in the age structure of the copepod population did not affect the distribution pattern of its abundance in the host population, but the values of the K exponent changed in accordance with alterations of the parasite generations. By 2007 the sex ratio in the population became equal, males and females differed in their lengths and weights, and three dimensional groups were found in the catches. It is thought that males and females of the crucian carp have different roles in the maintenance of the L. cyprinacea abundance. The dominating fish sizes and the level of the host infection by copepods remained the same as in 1997–2003.     

Influence of co-evolution with a parasite, <Emphasis Type="Italic">Nosema whitei,</Emphasis> and population size on recombination rates and fitness in the red flour beetle, <Emphasis Type="Italic">Tribolium castaneum</Emphasis>

The high prevalence of meiotic recombination—an important element of sexual reproduction—represents one of the greatest puzzles in biology. The influence of either selection by a co-evolving parasite alone or in combination with genetic drift on recombination rates was tested in the host-parasite system Tribolium castaneum and Nosema whitei. After eight generations, populations with smaller genetic drift had a lower recombination rate than those with high drift whereas parasites had no effect. Interestingly, changes in recombination rate at one site of the chromosome negatively correlated with changes at the adjacent site on the same chromosome indicating an occurrence of crossover interference. The occurrence of spontaneous or plastic changes in recombination rates could be excluded with a separate experiment.     

Survey of Helminth Parasites in Populations of <Emphasis Type="Italic">Alouatta palliata mexicana</Emphasis> and <Emphasis Type="Italic">A. pigra</Emphasis> in Continuous and in Fragmented Habitat in Southern Mexico

The 2 howler species that occur in southern Mexico, Alouatta palliata mexicana and Alouatta pigra are endangered, mainly as a result of habitat loss and fragmentation from human activity. Little is known about the gastrointestinal parasite communities affecting their populations, and lack of baseline information for populations of howler species in continuous forest habitats, makes evaluations of gastrointestinal parasite prevalence in populations in fragmented landscapes difficult. We report the results of a one-time broad survey of gastrointestinal parasites in fecal samples of individuals from several demographically stable populations of Alouatta palliata mexicana and A. pigra existing in continuous and/or protected forests. We further report similar data for populations of both species in human-fragmented landscapes. We detected 6 parasites for each howler monkey species, but only 3 of them (Trematode I, Controrchis biliophilus, Trypanoxyuris sp.) were common to both species. While parasitic prevalence in populations of both howler species was, in general, higher in the fragmented habitat than in continuous and/or protected forests. The difference is only marginally significant in Alouatta pigra. Some parasites (Coccidia and Strongylid) only appeared in populations in fragmented landscapes. Preliminary data suggest that adult males tended to have higher parasite prevalence values than those of adult females in both howler species. Parasite prevalence is associated to average group size, but not to population density in Alouatta pigra.