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Erhard Strohm - One of the best experts on this subject based on the ideXlab platform.

  • 'Candidatus Streptomyces philanthi', an endosymbiotic streptomycete in the antennae of Philanthus digger wasps.
    International journal of systematic and evolutionary microbiology, 2020
    Co-Authors: Martin Kaltenpoth, Wolfgang Goettler, Gudrun Herzner, Colin Dale, J William Stubblefield, Kerstin Roeser-mueller, Erhard Strohm
    Abstract:

    Symbiotic interactions with bacteria are essential for the survival and reproduction of many insects. The European beewolf (Philanthus triangulum, Hymenoptera, Crabronidae) engages in a highly specific association with bacteria of the genus Streptomyces that appears to protect beewolf offspring against infection by pathogens. Using transmission and scanning electron microscopy, the bacteria were located in the antennal glands of female wasps, where they form dense cell clusters. Using genetic methods, closely related streptomycetes were found in the antennae of 27 Philanthus species (including two subspecies of P. triangulum from distant localities). In contrast, no endosymbionts could be detected in the antennae of other genera within the subfamily Philanthinae (Aphilanthops, Clypeadon and Cerceris). On the basis of morphological, genetic and ecological data, 'Candidatus Streptomyces philanthi' is proposed. 16S rRNA gene sequence data are provided for 28 ecotypes of 'Candidatus Streptomyces philanthi' that reside in different host species and subspecies of the genus Philanthus. Primers for the selective amplification of 'Candidatus Streptomyces philanthi' and an oligonucleotide probe for specific detection by fluorescence in situ hybridization (FISH) are described.

  • Nitric oxide radicals are emitted by wasp eggs to kill mold fungi
    bioRxiv, 2018
    Co-Authors: Erhard Strohm, Martin Kaltenpoth, Gudrun Herzner, Joachim Ruther, Tobias Engl
    Abstract:

    Detrimental microbes caused the evolution of a great diversity of antimicrobial defenses in plants and animals. Here we show that the eggs of a solitary digger wasp, the European beewolf Philanthus triangulum , emit large amounts of the gaseous free radical nitric oxide (NO . ) to protect themselves and their provisions, paralyzed honeybees, against mold fungi. Despite the extraordinary concentrations of nitrogen radicals (NO . and its oxidation product NO 2 . ) in the brood cells (~1500ppm), NO . is synthesized from L-arginine by an NO-synthase (NOS) as in other animals. The beewolf NOS gene revealed no conspicuous differences to related species. However, due to alternative splicing, the NOS-mRNA in beewolf eggs lacks a 144bp exon near the regulatory domain. This preventive external application of high doses of NO . by seemingly defenseless wasp eggs represents an evolutionary key innovation that adds a remarkable novel facet to the array of functions of the important biological effector NO . .

  • mycobiota in the brood cells of the european beewolf Philanthus triangulum hymenoptera crabronidae
    European Journal of Entomology, 2016
    Co-Authors: Tobias Engl, Bettina Bodenstein, Erhard Strohm
    Abstract:

    Mass provisioning insects have to cope with microbial spoilage of their food supplies. As their fitness is directly linked to the availability of high quality food for their offspring, they have evolved various mechanisms for preserving these resources. The European beewolf, Philanthus triangulum, uses several mechanisms to not only preserve the food for their larvae, paralyzed workers of the European honeybee, Apis mellifera, but also protect the larvae that develop on the stored food. To assess the spectrum of fungi that pose a threat to beewolf brood cells, we manipulated brood cells by removing the insect defenses. We monitored the subsequent fungal infestations that would have been prevented by the beewolf defense mechanisms and isolated and identified the mold fungi. The cosmopolitan and highly competitive species of Aspergillus, in particular A. flavus, dominated the mold in beewolf brood cells. All other infestations could also be attributed to generalist mold fungi that are commonly found in soil and also on insects. Our findings indicate that beewolf brood cells can be colonized by a broad range of opportunistic soil mold fungi. Thus, it seems highly adaptive that beewolves employ general, broad spectrum defense mechanisms.

  • Comparative morphology of the postpharyngeal gland in the Philanthinae (Hymenoptera, Crabronidae) and the evolution of an antimicrobial brood protection mechanism.
    BMC Evolutionary Biology, 2015
    Co-Authors: Katharina Weiss, Martin Kaltenpoth, Erhard Strohm, Gudrun Herzner
    Abstract:

    Background Hymenoptera that mass-provision their offspring have evolved elaborate antimicrobial strategies to ward off fungal infestation of the highly nutritive larval food. Females of the Afro-European Philanthus triangulum and the South American Trachypus elongatus (Crabronidae, Philanthinae) embalm their prey, paralyzed bees, with a secretion from a complex postpharyngeal gland (PPG). This coating consists of mainly unsaturated hydrocarbons and reduces water accumulation on the prey’s surface, thus rendering it unfavorable for fungal growth. Here we (1) investigated whether a North American Philanthus species also employs prey embalming and (2) assessed the occurrence and morphology of a PPG among females of the subfamily Philanthinae in order to elucidate the evolution of prey embalming as an antimicrobial strategy.

  • Morphology, chemistry and function of the postpharyngeal gland in the South American digger wasps Trachypus boharti and Trachypus elongatus.
    PLOS ONE, 2013
    Co-Authors: Gudrun Herzner, Martin Kaltenpoth, Johannes Kroiss, Katharina Weiss, Theodor Poettinger, Dirk Koedam, Erhard Strohm
    Abstract:

    Microbes pose severe threats to animals as competitors or pathogens and strongly affect the evolution of life history traits like parental care. Females of the European beewolf Philanthus triangulum, a solitary digger wasp, provision their offspring with paralyzed honeybees and embalm them with the secretion from large postpharyngeal glands (PPG) that contain mainly unsaturated hydrocarbons. This coating changes the physico-chemical properties of the prey surface, causes a reduction of water condensation and retards growth of mold fungi. Here we examined the closely related South American genus Trachypus, which shows a life-history similar to Philanthus. We investigated whether Trachypus spp. also possess PPGs and embalm larval provisions. Using histological methods and 3D reconstructions we show that Trachypus boharti and T. elongatus possess PPGs that are similar to P. triangulum but somewhat smaller. The ultrastructure of the gland epithelium suggests that the gland content is at least partly sequestered from the hemolymph. Chemical analyses using gas chromatography / mass spectrometry revealed that both the cuticle and PPGs of Trachypus contain mainly unsaturated long-chain hydrocarbons. The gland of T. boharti additionally contains long-chain ketones. The hydrocarbons from the PPG of T. elongatus occurred on prey bees excavated from nests in the field but not on conspecific control bees. While the embalming only slightly elevated the amount of hydrocarbons on prey bees, the proportion of unsaturated hydrocarbons, which is crucial for the antifungal effect, was significantly increased. The Trachypus species under study possess PPGs that are very similar to the PPG of P. triangulum with regard to morphology, ultrastructure and chemistry. Moreover, we provide clear evidence that T. elongatus females embalm their prey, presumably as a means of prey preservation. The observed differences among Trachypus and Philanthus in gland size and prey embalming may have evolved in response to divergent ecological conditions.

Gudrun Herzner - One of the best experts on this subject based on the ideXlab platform.

  • 'Candidatus Streptomyces philanthi', an endosymbiotic streptomycete in the antennae of Philanthus digger wasps.
    International journal of systematic and evolutionary microbiology, 2020
    Co-Authors: Martin Kaltenpoth, Wolfgang Goettler, Gudrun Herzner, Colin Dale, J William Stubblefield, Kerstin Roeser-mueller, Erhard Strohm
    Abstract:

    Symbiotic interactions with bacteria are essential for the survival and reproduction of many insects. The European beewolf (Philanthus triangulum, Hymenoptera, Crabronidae) engages in a highly specific association with bacteria of the genus Streptomyces that appears to protect beewolf offspring against infection by pathogens. Using transmission and scanning electron microscopy, the bacteria were located in the antennal glands of female wasps, where they form dense cell clusters. Using genetic methods, closely related streptomycetes were found in the antennae of 27 Philanthus species (including two subspecies of P. triangulum from distant localities). In contrast, no endosymbionts could be detected in the antennae of other genera within the subfamily Philanthinae (Aphilanthops, Clypeadon and Cerceris). On the basis of morphological, genetic and ecological data, 'Candidatus Streptomyces philanthi' is proposed. 16S rRNA gene sequence data are provided for 28 ecotypes of 'Candidatus Streptomyces philanthi' that reside in different host species and subspecies of the genus Philanthus. Primers for the selective amplification of 'Candidatus Streptomyces philanthi' and an oligonucleotide probe for specific detection by fluorescence in situ hybridization (FISH) are described.

  • Nitric oxide radicals are emitted by wasp eggs to kill mold fungi
    bioRxiv, 2018
    Co-Authors: Erhard Strohm, Martin Kaltenpoth, Gudrun Herzner, Joachim Ruther, Tobias Engl
    Abstract:

    Detrimental microbes caused the evolution of a great diversity of antimicrobial defenses in plants and animals. Here we show that the eggs of a solitary digger wasp, the European beewolf Philanthus triangulum , emit large amounts of the gaseous free radical nitric oxide (NO . ) to protect themselves and their provisions, paralyzed honeybees, against mold fungi. Despite the extraordinary concentrations of nitrogen radicals (NO . and its oxidation product NO 2 . ) in the brood cells (~1500ppm), NO . is synthesized from L-arginine by an NO-synthase (NOS) as in other animals. The beewolf NOS gene revealed no conspicuous differences to related species. However, due to alternative splicing, the NOS-mRNA in beewolf eggs lacks a 144bp exon near the regulatory domain. This preventive external application of high doses of NO . by seemingly defenseless wasp eggs represents an evolutionary key innovation that adds a remarkable novel facet to the array of functions of the important biological effector NO . .

  • Comparative morphology of the postpharyngeal gland in the Philanthinae (Hymenoptera, Crabronidae) and the evolution of an antimicrobial brood protection mechanism.
    BMC Evolutionary Biology, 2015
    Co-Authors: Katharina Weiss, Martin Kaltenpoth, Erhard Strohm, Gudrun Herzner
    Abstract:

    Background Hymenoptera that mass-provision their offspring have evolved elaborate antimicrobial strategies to ward off fungal infestation of the highly nutritive larval food. Females of the Afro-European Philanthus triangulum and the South American Trachypus elongatus (Crabronidae, Philanthinae) embalm their prey, paralyzed bees, with a secretion from a complex postpharyngeal gland (PPG). This coating consists of mainly unsaturated hydrocarbons and reduces water accumulation on the prey’s surface, thus rendering it unfavorable for fungal growth. Here we (1) investigated whether a North American Philanthus species also employs prey embalming and (2) assessed the occurrence and morphology of a PPG among females of the subfamily Philanthinae in order to elucidate the evolution of prey embalming as an antimicrobial strategy.

  • Morphology, chemistry and function of the postpharyngeal gland in the South American digger wasps Trachypus boharti and Trachypus elongatus.
    PLOS ONE, 2013
    Co-Authors: Gudrun Herzner, Martin Kaltenpoth, Johannes Kroiss, Katharina Weiss, Theodor Poettinger, Dirk Koedam, Erhard Strohm
    Abstract:

    Microbes pose severe threats to animals as competitors or pathogens and strongly affect the evolution of life history traits like parental care. Females of the European beewolf Philanthus triangulum, a solitary digger wasp, provision their offspring with paralyzed honeybees and embalm them with the secretion from large postpharyngeal glands (PPG) that contain mainly unsaturated hydrocarbons. This coating changes the physico-chemical properties of the prey surface, causes a reduction of water condensation and retards growth of mold fungi. Here we examined the closely related South American genus Trachypus, which shows a life-history similar to Philanthus. We investigated whether Trachypus spp. also possess PPGs and embalm larval provisions. Using histological methods and 3D reconstructions we show that Trachypus boharti and T. elongatus possess PPGs that are similar to P. triangulum but somewhat smaller. The ultrastructure of the gland epithelium suggests that the gland content is at least partly sequestered from the hemolymph. Chemical analyses using gas chromatography / mass spectrometry revealed that both the cuticle and PPGs of Trachypus contain mainly unsaturated long-chain hydrocarbons. The gland of T. boharti additionally contains long-chain ketones. The hydrocarbons from the PPG of T. elongatus occurred on prey bees excavated from nests in the field but not on conspecific control bees. While the embalming only slightly elevated the amount of hydrocarbons on prey bees, the proportion of unsaturated hydrocarbons, which is crucial for the antifungal effect, was significantly increased. The Trachypus species under study possess PPGs that are very similar to the PPG of P. triangulum with regard to morphology, ultrastructure and chemistry. Moreover, we provide clear evidence that T. elongatus females embalm their prey, presumably as a means of prey preservation. The observed differences among Trachypus and Philanthus in gland size and prey embalming may have evolved in response to divergent ecological conditions.

  • Cryptic combat against competing microbes is a costly component of parental care in a digger wasp
    Animal Behaviour, 2011
    Co-Authors: Gudrun Herzner, Tobias Engl, Erhard Strohm
    Abstract:

    Microorganisms are ubiquitous and key selective agents in parental care behaviour. Various animal species have thus evolved diverse means to prevent and combat detrimental effects of microbial competitors and pathogens on their offspring. The European beewolf, Philanthus triangulum, is a solitary crabronid wasp that stores paralysed honeybees as larval provisions in subterranean nests. In the soil the highly nutritious provisions can be attacked by a large number of microorganisms. We investigated the effect of fungal infestations of larval provisions on the reproductive success of beewolves. Although fungal infestations reduced larval survival, female beewolves largely eliminated this effect by embalming larval provisions with ample amounts of hydrocarbons. However, this came at the cost of a reduced ability to apply hydrocarbons to the provisions of future offspring. This reduced investment in embalming resulted in a higher risk of mould infestations. Embalming of the prey in P. triangulum thus meets the criterion of parental investment and females have to balance this investment of hydrocarbons in current and future offspring to maximize their lifetime reproductive success.

Martin Kaltenpoth - One of the best experts on this subject based on the ideXlab platform.

  • 'Candidatus Streptomyces philanthi', an endosymbiotic streptomycete in the antennae of Philanthus digger wasps.
    International journal of systematic and evolutionary microbiology, 2020
    Co-Authors: Martin Kaltenpoth, Wolfgang Goettler, Gudrun Herzner, Colin Dale, J William Stubblefield, Kerstin Roeser-mueller, Erhard Strohm
    Abstract:

    Symbiotic interactions with bacteria are essential for the survival and reproduction of many insects. The European beewolf (Philanthus triangulum, Hymenoptera, Crabronidae) engages in a highly specific association with bacteria of the genus Streptomyces that appears to protect beewolf offspring against infection by pathogens. Using transmission and scanning electron microscopy, the bacteria were located in the antennal glands of female wasps, where they form dense cell clusters. Using genetic methods, closely related streptomycetes were found in the antennae of 27 Philanthus species (including two subspecies of P. triangulum from distant localities). In contrast, no endosymbionts could be detected in the antennae of other genera within the subfamily Philanthinae (Aphilanthops, Clypeadon and Cerceris). On the basis of morphological, genetic and ecological data, 'Candidatus Streptomyces philanthi' is proposed. 16S rRNA gene sequence data are provided for 28 ecotypes of 'Candidatus Streptomyces philanthi' that reside in different host species and subspecies of the genus Philanthus. Primers for the selective amplification of 'Candidatus Streptomyces philanthi' and an oligonucleotide probe for specific detection by fluorescence in situ hybridization (FISH) are described.

  • Nitric oxide radicals are emitted by wasp eggs to kill mold fungi
    bioRxiv, 2018
    Co-Authors: Erhard Strohm, Martin Kaltenpoth, Gudrun Herzner, Joachim Ruther, Tobias Engl
    Abstract:

    Detrimental microbes caused the evolution of a great diversity of antimicrobial defenses in plants and animals. Here we show that the eggs of a solitary digger wasp, the European beewolf Philanthus triangulum , emit large amounts of the gaseous free radical nitric oxide (NO . ) to protect themselves and their provisions, paralyzed honeybees, against mold fungi. Despite the extraordinary concentrations of nitrogen radicals (NO . and its oxidation product NO 2 . ) in the brood cells (~1500ppm), NO . is synthesized from L-arginine by an NO-synthase (NOS) as in other animals. The beewolf NOS gene revealed no conspicuous differences to related species. However, due to alternative splicing, the NOS-mRNA in beewolf eggs lacks a 144bp exon near the regulatory domain. This preventive external application of high doses of NO . by seemingly defenseless wasp eggs represents an evolutionary key innovation that adds a remarkable novel facet to the array of functions of the important biological effector NO . .

  • Comparative morphology of the postpharyngeal gland in the Philanthinae (Hymenoptera, Crabronidae) and the evolution of an antimicrobial brood protection mechanism.
    BMC Evolutionary Biology, 2015
    Co-Authors: Katharina Weiss, Martin Kaltenpoth, Erhard Strohm, Gudrun Herzner
    Abstract:

    Background Hymenoptera that mass-provision their offspring have evolved elaborate antimicrobial strategies to ward off fungal infestation of the highly nutritive larval food. Females of the Afro-European Philanthus triangulum and the South American Trachypus elongatus (Crabronidae, Philanthinae) embalm their prey, paralyzed bees, with a secretion from a complex postpharyngeal gland (PPG). This coating consists of mainly unsaturated hydrocarbons and reduces water accumulation on the prey’s surface, thus rendering it unfavorable for fungal growth. Here we (1) investigated whether a North American Philanthus species also employs prey embalming and (2) assessed the occurrence and morphology of a PPG among females of the subfamily Philanthinae in order to elucidate the evolution of prey embalming as an antimicrobial strategy.

  • Morphology, chemistry and function of the postpharyngeal gland in the South American digger wasps Trachypus boharti and Trachypus elongatus.
    PLOS ONE, 2013
    Co-Authors: Gudrun Herzner, Martin Kaltenpoth, Johannes Kroiss, Katharina Weiss, Theodor Poettinger, Dirk Koedam, Erhard Strohm
    Abstract:

    Microbes pose severe threats to animals as competitors or pathogens and strongly affect the evolution of life history traits like parental care. Females of the European beewolf Philanthus triangulum, a solitary digger wasp, provision their offspring with paralyzed honeybees and embalm them with the secretion from large postpharyngeal glands (PPG) that contain mainly unsaturated hydrocarbons. This coating changes the physico-chemical properties of the prey surface, causes a reduction of water condensation and retards growth of mold fungi. Here we examined the closely related South American genus Trachypus, which shows a life-history similar to Philanthus. We investigated whether Trachypus spp. also possess PPGs and embalm larval provisions. Using histological methods and 3D reconstructions we show that Trachypus boharti and T. elongatus possess PPGs that are similar to P. triangulum but somewhat smaller. The ultrastructure of the gland epithelium suggests that the gland content is at least partly sequestered from the hemolymph. Chemical analyses using gas chromatography / mass spectrometry revealed that both the cuticle and PPGs of Trachypus contain mainly unsaturated long-chain hydrocarbons. The gland of T. boharti additionally contains long-chain ketones. The hydrocarbons from the PPG of T. elongatus occurred on prey bees excavated from nests in the field but not on conspecific control bees. While the embalming only slightly elevated the amount of hydrocarbons on prey bees, the proportion of unsaturated hydrocarbons, which is crucial for the antifungal effect, was significantly increased. The Trachypus species under study possess PPGs that are very similar to the PPG of P. triangulum with regard to morphology, ultrastructure and chemistry. Moreover, we provide clear evidence that T. elongatus females embalm their prey, presumably as a means of prey preservation. The observed differences among Trachypus and Philanthus in gland size and prey embalming may have evolved in response to divergent ecological conditions.

  • Dynamics of symbiont-mediated antibiotic production reveal efficient long-term protection for beewolf offspring
    Frontiers in Zoology, 2013
    Co-Authors: Sabrina Koehler, Jan Doubský, Martin Kaltenpoth
    Abstract:

    BackgroundInsects have evolved a wide range of mechanisms to defend themselves and their offspring against antagonists. One of these strategies involves the utilization of antimicrobial compounds provided by symbiotic bacteria to protect the host or its nutritional resources from pathogens and parasites. In the symbiosis of the solitary digger wasp, Philanthus triangulum (Hymenoptera, Crabronidae), the bacterial symbiont ‘Candidatus Streptomyces philanthi’ defends the developing larvae against pathogens by producing a mixture of at least nine antimicrobial substances on the cocoon surface. This antibiotic cocktail inhibits the growth of a broad range of detrimental fungi and bacteria, thereby significantly enhancing the offspring’s survival probability.ResultsHere we show that the production of antimicrobial compounds by the beewolf symbionts is confined to the first two weeks after cocoon spinning, leading to a high concentration of piericidins and streptochlorin on the cocoon surface. Expression profiling of housekeeping, sporulation, and antibiotic biosynthesis genes indicates that antibiotic production coincides with morphological differentiation that enables the symbionts to survive the nutrient-limited conditions on the beewolf cocoon. The antibiotic substances remain stable on the cocoon surface for the entire duration of the beewolf’s hibernation period, demonstrating that the compounds are resistant against environmental influences.ConclusionsThe antibiotic production by the beewolf symbionts serves as a reliable protection for the wasp offspring against pathogenic microorganisms during the long and unpredictable developmental phase in the subterranean brood cells. Thus, the beewolf-Streptomyces symbiosis provides one of the rare examples of antibiotics serving as an efficient defense in the natural environment and may aid in devising new strategies for the utilization of antibiotic combination therapies in human medicine against increasingly resistant bacterial and fungal pathogens.

Thomas Schmitt - One of the best experts on this subject based on the ideXlab platform.

  • Hydrocarbons in the antennal gland secretion of female European beewolves, Philanthus triangulum (Hymenoptera, Crabronidae)
    Chemoecology, 2009
    Co-Authors: Martin Kaltenpoth, Thomas Schmitt, Erhard Strohm
    Abstract:

    The antennae of female European beewolves ( Philanthus triangulum , Hymenoptera: Crabronidae) contain unique gland reservoirs that are inhabited by the symbiotic bacterium ‘ Candidatus Streptomyces philanthi’. The reservoir content is secreted into the subterranean brood cells where it serves a dual function: (1) It provides the larvae with spatial information about the orientation of cocoon spinning, and (2) it supplies the larva with the symbiotic bacteria that are needed for the protection of the cocoon against pathogenic microorganisms. We analyzed the hydrocarbon composition of the antennal gland secretion (AGS) by solid phase micro-extraction–gas chromatography–mass spectrometry. We detected 28 substances, the majority of which were saturated and unsaturated hydrocarbons, with minor amounts of some branched alkanes, two ketones, and three unknown substances. There was a strong dimorphism in the chemical composition of the AGS among beewolf females. The two morphs had either ( Z )-9-pentacosene (C_25-type) or ( Z )-9-heptacosene (C_27-type) as the main component, and they differed significantly in the relative amounts of most of the other AGS substances. The hydrocarbon composition of the AGS is very similar to that of the postpharyngeal gland of female beewolves, suggesting that the hydrocarbons are universally used for different purposes and transported into the gland from the hemolymph. The putative function of the hydrocarbons in the AGS is discussed.

  • Low level of cuticular hydrocarbons in a parasitoid of a solitary digger wasp and its potential for concealment
    Entomological Science, 2009
    Co-Authors: Johannes Kroiss, Thomas Schmitt, Erhard Strohm
    Abstract:

    Insect cuticular hydrocarbons (CHC) play a role as semiochemicals in many host–parasite systems and chemical mimicry or camouflage is a well-known mechanism of parasites to evade detection by the host. The cuckoo wasp Hedychrum rutilans (Hymenoptera, Chrysididae) is a parasitoid of larvae of the European beewolf Philanthus triangulum (Hymenoptera, Crabronidae). Females chemically mimic the cuticular hydrocarbons of their hosts to avoid detection and countermeasures when entering the host nest for oviposition. Here we report on a possible second mechanism of the chrysidid wasp H. rutilans to evade detection: the amount of CHC/mm2 of cuticle is only approximately one-fifth compared to its beewolf host. Furthermore, we show that surprisingly large amounts of CHC of beewolf females can be found on the walls of the underground nest. Potentially, these hydrocarbons might constitute a background odor against which the cuckoo wasps or their chemical traces have to be perceived by the beewolf. The reduction in the amount of CHC of the cuckoo wasps might be equivalent to a dilution of recognition cues, especially against the background odor of the nest walls, and might provide a means to escape detection within the nest due to “chemical insignificance”.

  • The Chemistry of the Postpharyngeal Gland of Female European Beewolves
    Journal of Chemical Ecology, 2008
    Co-Authors: Erhard Strohm, Martin Kaltenpoth, Gudrun Herzner, Klaus Peschke, Peter Schreier, Wilhelm Boland, Sven Geiselhardt, Thomas Schmitt
    Abstract:

    Females of the European beewolf, Philanthus triangulum , possess a large glove-shaped gland in the head, the postpharyngeal gland (PPG). They apply the content of the PPG to their prey, paralyzed honeybees, where it delays fungal infestation. Here, we describe the chemical composition of the gland by using combined GC-MS, GC-FTIR, and derivatization. The PPG of beewolves contains mainly long-chain unsaturated hydrocarbons (C23–C33), lower amounts of saturated hydrocarbons (C14–C33), and minor amounts of methyl-branched hydrocarbons (C17–C31). Additionally, the hexane-soluble gland content is comprised of small amounts of an unsaturated C25 alcohol, an unknown sesquiterpene, an octadecenylmethylester, and several long-chain saturated (C25, C27) and unsaturated (C23–C27) ketones, some of which have not yet been reported as natural products. Surprisingly, we found a dimorphism with regard to the major component of the PPG with some females having ( Z )-9-pentacosene, whereas others have ( Z )-9-heptacosene as their predominant component. The biological relevance of the compounds for the prevention of fungal growth on the prey and the significance of the chemical dimorphism are discussed.

  • A cuckoo in wolves' clothing? Chemical mimicry in a specialized cuckoo wasp of the European beewolf (Hymenoptera, Chrysididae and Crabronidae)
    Frontiers in Zoology, 2008
    Co-Authors: Erhard Strohm, Johannes Kroiss, Gudrun Herzner, Peter Schreier, Claudia Laurien-kehnen, Wilhelm Boland, Thomas Schmitt
    Abstract:

    Background Host-parasite interactions are among the most important biotic relationships. Host species should evolve mechanisms to detect their enemies and employ appropriate counterstrategies. Parasites, in turn, should evolve mechanisms to evade detection and thus maximize their success. Females of the European beewolf (Philanthus triangulum, Hymenoptera, Crabronidae) hunt exclusively honeybee workers as food for their progeny. The brood cells containing the paralyzed bees are severely threatened by a highly specialized cuckoo wasp (Hedychrum rutilans, Hymenoptera, Chrysididae). Female cuckoo wasps enter beewolf nests to oviposit on paralyzed bees that are temporarily couched in the nest burrow. The cuckoo wasp larva kills the beewolf larva and feeds on it and the bees. Here, we investigated whether H. rutilans evades detection by its host. Since chemical senses are most important in the dark nest, we hypothesized that the cuckoo wasp might employ chemical camouflage.

  • A cuckoo in wolves' clothing? Chemical mimicry in a specialized cuckoo wasp of the European beewolf (Hymenoptera, Chrysididae and Crabronidae)
    Frontiers in Zoology, 2008
    Co-Authors: Erhard Strohm, Johannes Kroiss, Gudrun Herzner, Peter Schreier, Claudia Laurien-kehnen, Wilhelm Boland, Thomas Schmitt
    Abstract:

    Background Host-parasite interactions are among the most important biotic relationships. Host species should evolve mechanisms to detect their enemies and employ appropriate counterstrategies. Parasites, in turn, should evolve mechanisms to evade detection and thus maximize their success. Females of the European beewolf ( Philanthus triangulum , Hymenoptera, Crabronidae) hunt exclusively honeybee workers as food for their progeny. The brood cells containing the paralyzed bees are severely threatened by a highly specialized cuckoo wasp ( Hedychrum rutilans , Hymenoptera, Chrysididae). Female cuckoo wasps enter beewolf nests to oviposit on paralyzed bees that are temporarily couched in the nest burrow. The cuckoo wasp larva kills the beewolf larva and feeds on it and the bees. Here, we investigated whether H. rutilans evades detection by its host. Since chemical senses are most important in the dark nest, we hypothesized that the cuckoo wasp might employ chemical camouflage. Results Field observations suggest that cuckoo wasps are attacked by beewolves in front of their nest, most probably after being recognized visually. In contrast, beewolves seem not to detect signs of the presence of these parasitoids neither when these had visited the nest nor when directly encountered in the dark nest burrow. In a recognition bioassay in observation cages, beewolf females responded significantly less frequently to filter paper discs treated with a cuticular extract from H. rutilans females, than to filter paper discs treated with an extract from another cuckoo wasp species ( Chrysis viridula ). The behavior to paper discs treated with a cuticular extract from H. rutilans females did not differ significantly from the behavior towards filter paper discs treated with the solvent only. We hypothesized that cuckoo wasps either mimic the chemistry of their beewolf host or their host's prey. We tested this hypothesis using GC-MS analyses of the cuticles of male and female beewolves, cuckoo wasps, and honeybee workers. Cuticle extracts of Hedychrum nobile (Hymenoptera: Chrysididae) and Cerceris arenaria (Hymenoptera: Crabronidae) were used as outgroups. There was little congruence with regard to cuticular compounds between H. rutilans females and honeybees as well as females of C. arenaria and H. nobile . However, there was a considerable similarity between beewolf females and H. rutilans females. Beewolf females show a striking dimorphism regarding their cuticular hydrocarbons with one morph having ( Z )-9-C25:1 and the other morph having ( Z )-9-C27:1 as the major component. H. rutilans females were more similar to the morph having (Z)-9-C27:1 as the main component. Conclusion We conclude that H. rutilans females closely mimic the composition of cuticular compounds of their host species P. triangulum . The occurrence of isomeric forms of certain compounds on the cuticles of the cuckoo wasps but their absence on beewolf females suggests that cuckoo wasps synthesize the cuticular compounds rather than sequester them from their host. Thus, the behavioral data and the chemical analysis provide evidence that a specialized cuckoo wasp exhibits chemical mimicry of the odor of its host. This probably allows the cuckoo wasp to enter the nest with a reduced risk of being detected by olfaction and without leaving traitorous chemical traces.

Johannes Kroiss - One of the best experts on this subject based on the ideXlab platform.

  • Morphology, chemistry and function of the postpharyngeal gland in the South American digger wasps Trachypus boharti and Trachypus elongatus.
    PLOS ONE, 2013
    Co-Authors: Gudrun Herzner, Martin Kaltenpoth, Johannes Kroiss, Katharina Weiss, Theodor Poettinger, Dirk Koedam, Erhard Strohm
    Abstract:

    Microbes pose severe threats to animals as competitors or pathogens and strongly affect the evolution of life history traits like parental care. Females of the European beewolf Philanthus triangulum, a solitary digger wasp, provision their offspring with paralyzed honeybees and embalm them with the secretion from large postpharyngeal glands (PPG) that contain mainly unsaturated hydrocarbons. This coating changes the physico-chemical properties of the prey surface, causes a reduction of water condensation and retards growth of mold fungi. Here we examined the closely related South American genus Trachypus, which shows a life-history similar to Philanthus. We investigated whether Trachypus spp. also possess PPGs and embalm larval provisions. Using histological methods and 3D reconstructions we show that Trachypus boharti and T. elongatus possess PPGs that are similar to P. triangulum but somewhat smaller. The ultrastructure of the gland epithelium suggests that the gland content is at least partly sequestered from the hemolymph. Chemical analyses using gas chromatography / mass spectrometry revealed that both the cuticle and PPGs of Trachypus contain mainly unsaturated long-chain hydrocarbons. The gland of T. boharti additionally contains long-chain ketones. The hydrocarbons from the PPG of T. elongatus occurred on prey bees excavated from nests in the field but not on conspecific control bees. While the embalming only slightly elevated the amount of hydrocarbons on prey bees, the proportion of unsaturated hydrocarbons, which is crucial for the antifungal effect, was significantly increased. The Trachypus species under study possess PPGs that are very similar to the PPG of P. triangulum with regard to morphology, ultrastructure and chemistry. Moreover, we provide clear evidence that T. elongatus females embalm their prey, presumably as a means of prey preservation. The observed differences among Trachypus and Philanthus in gland size and prey embalming may have evolved in response to divergent ecological conditions.

  • male territoriality and mating system in the european beewolf Philanthus triangulum f hymenoptera crabronidae evidence for a hotspot lek polygyny
    Journal of Ethology, 2010
    Co-Authors: Johannes Kroiss, Klaus Lechner, Erhard Strohm
    Abstract:

    The evolution of the mating system of a species is strongly influenced by the spatial and temporal distribution of females and/or resources. Here, we describe aspects of the territorial behavior of males of a solitary digger wasp, the European beewolf (Philanthus triangulum) and characterize the mating system. We show that beewolf males establish small territories that do not contain any resources essential to females. These territories are intensively scent-marked with a pheromone from a cephalic gland and are defended against intruders in combat flights. We provide evidence that scent-marking constitutes a chemical display and that the pheromone serves to attract receptive females and, thus, represents a sex pheromone. Using spatial statistics, we show that beewolf territories are clumped in space both with respect to other male territories and, more importantly, with respect to female nesting sites. Additionally, the proportion of days a territory is occupied by a male is correlated with the number of female nests in the vicinity. Taking into account that beewolf males do not defend or provide resources essential to females, but merely display chemically to attract females for mating in an aggregation of territories close to female nesting sites, we conclude that the European beewolf exhibits a hotspot lek polygyny with female nesting sites constituting “hotspots” for lek formation.

  • Male territoriality and mating system in the European beewolf Philanthus triangulum F. (Hymenoptera: Crabronidae): evidence for a “hotspot” lek polygyny
    Journal of Ethology, 2009
    Co-Authors: Johannes Kroiss, Klaus Lechner, Erhard Strohm
    Abstract:

    The evolution of the mating system of a species is strongly influenced by the spatial and temporal distribution of females and/or resources. Here, we describe aspects of the territorial behavior of males of a solitary digger wasp, the European beewolf (Philanthus triangulum) and characterize the mating system. We show that beewolf males establish small territories that do not contain any resources essential to females. These territories are intensively scent-marked with a pheromone from a cephalic gland and are defended against intruders in combat flights. We provide evidence that scent-marking constitutes a chemical display and that the pheromone serves to attract receptive females and, thus, represents a sex pheromone. Using spatial statistics, we show that beewolf territories are clumped in space both with respect to other male territories and, more importantly, with respect to female nesting sites. Additionally, the proportion of days a territory is occupied by a male is correlated with the number of female nests in the vicinity. Taking into account that beewolf males do not defend or provide resources essential to females, but merely display chemically to attract females for mating in an aggregation of territories close to female nesting sites, we conclude that the European beewolf exhibits a hotspot lek polygyny with female nesting sites constituting “hotspots” for lek formation.

  • Low level of cuticular hydrocarbons in a parasitoid of a solitary digger wasp and its potential for concealment
    Entomological Science, 2009
    Co-Authors: Johannes Kroiss, Thomas Schmitt, Erhard Strohm
    Abstract:

    Insect cuticular hydrocarbons (CHC) play a role as semiochemicals in many host–parasite systems and chemical mimicry or camouflage is a well-known mechanism of parasites to evade detection by the host. The cuckoo wasp Hedychrum rutilans (Hymenoptera, Chrysididae) is a parasitoid of larvae of the European beewolf Philanthus triangulum (Hymenoptera, Crabronidae). Females chemically mimic the cuticular hydrocarbons of their hosts to avoid detection and countermeasures when entering the host nest for oviposition. Here we report on a possible second mechanism of the chrysidid wasp H. rutilans to evade detection: the amount of CHC/mm2 of cuticle is only approximately one-fifth compared to its beewolf host. Furthermore, we show that surprisingly large amounts of CHC of beewolf females can be found on the walls of the underground nest. Potentially, these hydrocarbons might constitute a background odor against which the cuckoo wasps or their chemical traces have to be perceived by the beewolf. The reduction in the amount of CHC of the cuckoo wasps might be equivalent to a dilution of recognition cues, especially against the background odor of the nest walls, and might provide a means to escape detection within the nest due to “chemical insignificance”.

  • Hydrocarbons in the nest material of a solitary digger wasp represent a kairomone for a specialized cuckoo wasp
    Animal Behaviour, 2008
    Co-Authors: Johannes Kroiss, Susanne Bordon, Erhard Strohm
    Abstract:

    Cuticular hydrocarbons (CHCs) can be found on the cuticle of insects and they primarily serve to reduce desiccation. Additionally, they constitute important cues for species, kin and nestmate recognition. In paper wasps, these CHCs can also be found on the nest material and facilitate nestmate recognition. We analysed whether the nest material of a solitary digger wasp, the European beewolf, Philanthus triangulum (Hymenoptera, Crabronidae), also contains CHCs and whether these might provide cues for the host search of a specialized cuckoo wasp (Hedychrum rutilans). Ejected nest material contained 3.6 ± 2.1 μg of CHCs/g. The composition of these nest hydrocarbons (NHCs) was very similar to the CHC composition of the cuticles of beewolf females. In particular, there were two distinct chemomorphs occurring in the European beewolf that could be unambiguously distinguished by means of the NHCs. Because of these large amounts of NHCs, females of the specialized parasitoid H. rutilans (Hymenoptera, Chrysididae) may use these NHCs as kairomones to locate and identify the host nest. Bioassays showed that females of this cuckoo wasp are able to recognize nest mounds of their host visually and are able to discriminate between host and nonhost nest material by using qustatory cues. Furthermore, in olfactometer assays, H. rutilans females stayed significantly longer in the segment supplied with an airflow that passed over beewolf nest material than in a control segment. Our results suggest that the beewolf NHCs provide important olfactory cues for a chrysidid parasitoid for host localization.