Allochthonous resources are less important for faunal communities on highly productive,small tropical islands

Ecosystems are interconnected by energy fluxes that provide resources for the inhabiting organisms along the transition zone. Especially where in situ resources are scarce, ecosystems can become highly dependent on external resources. The dependency on external input becomes less pronounced in systems with elevated in situ production, where only consumer species close to the site of external input remain subsidized, whereas species distant to the input site rely on the in situ production of the ecosystem. It is largely unclear though if this pattern is consistent over different consumer species and trophic levels in one ecosystem, and whether consumer species that occur both proximate to and at a distance from the input site differ in their dependency on external resource inputs between sites. Using stable isotope analysis, we investigated the dependency on external marine input for common ground‐associated consumer taxa on small tropical islands with high in situ production. We show that marine input is only relevant for strict beach‐dwelling taxa, while the terrestrial vegetation is the main carbon source for inland‐dwelling taxa. Consumer species that occurred both close (beach) and distant (inland) to the site of marine input showed similar proportions of marine input in their diets. This supports earlier findings that the relevance of external resources becomes limited to species close to the input site in systems with sufficient in situ production. However, it also indicates that the relevance of external input is also species‐dependent, as consumers occurring close and distant to the input site depended equally strong or weak on marine input.     

N-Acetylhistidine, Glutamate, and β-Alanine Are Concentrated in a Receptor Cell Layer of the Trout Inner Ear

An epithelial sheet isolated from the trout saccular macula, highly enriched in acousticolateralis receptor cells (hair cells), has been analyzed for primary amine-containing compounds. The hair cell preparation, compared to the saccular nerve, was found to contain elevated levels of the presumptive receptoneural transmitter, glutamate, as well as beta-alanine, and components eluting in the positions of the standards phosphoserine and phosphoethanolamine on cation-exchange HPLC. Saccular nerve contained a different spectrum of primary amines and was elevated specifically in carnosine/homocarnosine. Acid hydrolysis of perchlorate extracts of both hair cell and nerve fractions yielded large amounts of histidine. For the saccular nerve fraction, production of histidine by acid hydrolysis was matched by production of beta-alanine and gamma-aminobutyric acid (GABA) and disappearance of carnosine/homocarnosine. The dipeptides carnosine and homocarnosine have been chromatographically resolved by expanded HPLC and found to be present in saccular nerve in a ratio of approximately 10:1, respectively. Production of histidine in the hair cell extract was not coupled with production of beta-alanine and GABA. The hair cell histidine-containing unknown, present in millimolar concentration, has been identified as N-acetylhistidine by the hydrolysis and rechromatography of fractions from cation-exchange HPLC. The large and specific presence of N-acetylhistidine in the hair cell preparation, together with electrophysiological evidence for its facilitatory action on afferent fibers in the frog semicircular canal, is suggestive of a role for this molecule as well as glutamate in acousticolateralis receptoneural transmission.     

Influenza H5N1 virus infection of polarized human alveolar epithelial cells and lung microvascular endothelial cells

Background

Highly pathogenic avian influenza (HPAI) H5N1 virus is entrenched in poultry in Asia and Africa and continues to infect humans zoonotically causing acute respiratory disease syndrome and death. There is evidence that the virus may sometimes spread beyond respiratory tract to cause disseminated infection. The primary target cell for HPAI H5N1 virus in human lung is the alveolar epithelial cell. Alveolar epithelium and its adjacent lung microvascular endothelium form host barriers to the initiation of infection and dissemination of influenza H5N1 infection in humans. These are polarized cells and the polarity of influenza virus entry and egress as well as the secretion of cytokines and chemokines from the virus infected cells are likely to be central to the pathogenesis of human H5N1 disease.

Aim

To study influenza A (H5N1) virus replication and host innate immune responses in polarized primary human alveolar epithelial cells and lung microvascular endothelial cells and its relevance to the pathogenesis of human H5N1 disease.

Methods

We use an in vitro model of polarized primary human alveolar epithelial cells and lung microvascular endothelial cells grown in transwell culture inserts to compare infection with influenza A subtype H1N1 and H5N1 viruses via the apical or basolateral surfaces.

Results

We demonstrate that both influenza H1N1 and H5N1 viruses efficiently infect alveolar epithelial cells from both apical and basolateral surface of the epithelium but release of newly formed virus is mainly from the apical side of the epithelium. In contrast, influenza H5N1 virus, but not H1N1 virus, efficiently infected polarized microvascular endothelial cells from both apical and basolateral aspects. This provides a mechanistic explanation for how H5N1 virus may infect the lung from systemic circulation. Epidemiological evidence has implicated ingestion of virus-contaminated foods as the source of infection in some instances and our data suggests that viremia, secondary to, for example, gastro-intestinal infection, can potentially lead to infection of the lung. HPAI H5N1 virus was a more potent inducer of cytokines (e.g. IP-10, RANTES, IL-6) in comparison to H1N1 virus in alveolar epithelial cells, and these virus-induced chemokines were secreted onto both the apical and basolateral aspects of the polarized alveolar epithelium.

Conclusion

The predilection of viruses for different routes of entry and egress from the infected cell is important in understanding the pathogenesis of influenza H5N1 infection and may help unravel the pathogenesis of human H5N1 disease.     

The removal response ofApis mellifera L. colonies to brood in wax and plastic cells after artificial and natural infestation withVarroa jacobsoni Oud. and to freeze-killed brood

LikeApis cerana colonies,A. mellifera colonies also show removal response toVarroa-infested brood cells. Infested worker brood cells of artificially and naturally infested combs were detected by the worker bees to various degrees in all types of comb-material used.The bees uncap brood cells and remove larvae or pupae infested with one or two mites. The removal response of worker bees was stronger towards brood cells containing two mites than cells with one mite.The specific signals which cause the removal of brood cells infested withVarroa mites are unknown. Removal response toVarroa-infested brood cells in plastic comb-material (Jenter-and ANP-comb) was significantly higher than to brood in wax combs. Up to now we do not know to what extent this tolerance mechanism is influenced by genetic and environmental factors.Our experiments comparing the removal of freeze-killed brood with the removal of brood infested withVarroa mites demonstrate positive correlations. Considering the time-consuming method of the artificial infestation with living mites, the hygienic behaviour-including the removal of brood cells infested with mites-of large series of colonies can be tested using freeze-killed brood.     

Grooming behaviour ofApis cerana,Apis mellifera andApis dorsata and its effect on the parasitic mitesVarroa jacobsoni andTropilaelaps clareae

OneApis mellifera and oneApis cerana observation hive were used to test the response to individually introducedVarroa jacobsoni mites. Within 60s, 88.6% of the involved cerana worker bees (n=44) showed auto-grooming behaviour. Within 5 min, allo-grooming behaviour, involving up to four nestmates, was observed in 33.3% of the infested bees. Successful mite removal was observed in 75% of the not-prematurely discontinued observations (n=36); 32% of the mites removed were caught with the mandibles.For mellifera auto-grooming behaviour was observed in most cases but delayed in comparison to cerana, and allo-grooming behaviour was rarely observed. Within 5 min, 48% of the mites in notprematurely discontinued observations (n=25) were removed, but none of the mites was caught with the mandibles.ForApis dorsata auto-grooming behaviour in response to the infestation withTropilaelaps clareae andVarroa mites is reported for the first time.Varroa was removed at a higher rate thanTropilaelaps. The higher survival chance ofTropilaelaps seems to be due to differences in mite behaviour and the preference for certain parts of the bee-body.     

Der Einfluss von Umweltbedingungen auf die Bildung von Gynandromorphen bei der HonigbieneApis mellifica L.

Zusammenfassung Schwankungen des Gynandromorphen-Anteils in der Brut einer Königin aus einer speziellen, Gynandromorphen erzeugenden Linie wurden in den Monaten Juli und August untersucht und Verschiebungen auf Grund von Umweltänderungen (Nektarangebot, Reizfütterung, Käfigung der Königin) festgestellt.Von insgesamt 16375 kontrollierten Bienen waren 2590 (15,9%) Gynandromorphen. Anregung zur Eiablage hatte Erhöhung des Gynandromorphen-Anteils auf 32,5% zur Folge, Hemmung der Königin während der Eiablage ein Absinken auf 6,0%.Die Entwicklungsdauer der Gynandromorphen lag zwischen 21 und 24 Tagen.Die Annahme einer polygenen Basis und Prädetermination des Eies bei Gynandromorphismus konnte durch Versuchsergebnisse gefestigt werden.Als wichtige Komponente bei der Erzeugung von Gynandromorphen muss bei entsprechender genetischer Grundlage und ausreichender Pflegefähigkeit der Ammenbienen die durch die Umwelteinflüsse geförderte oder gehemmte Eiablage-Intensität der Königin angesehen werden.

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Summary Fluctuations in the percentage of gynandromorphic bees in the brood of one queen from a specific gynandromorphs producing strain were observed and brought into connection with changes in the environment (nectar flow, sugar sirup feeding, caging of the queen).From a total of 16375 checked bees 2590 (15,9%) were gynandromorphs. Stimulation of egg deposition resulted in an increase of the gynandromorph fraction to 32,5%, hampering of the queen during egg deposition was followed by a decrease to 6%.The period of development of gynandromorphic individuals takes from 21–24 days.Further indications for a poligenic basis and a predetermination of the egg in gynandromorph occurrence were given by these experiments.Beside a specific genetic background and sufficient nursing bees for brood rearing one has to regard as an important prerequisite for the production of gynandromorphs the through environmental conditions stimulated or hampered intensity of egg deposition of the queen.

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Résumé Pendant les mois de juillet et d'août, des variations dans le pourcentage des gynandromorphes pondus par une reine issue d'une lignée spécialisée dans la production des gynandromorphes ont été étudiées et des modifications causées par des changements de milieu (la miellée, le nourrissement spéculatif, mise en cage de la reine) observées.Sur 16375 abeilles contrôlées, on a trouvé 2590 (15,9%) gynandromorphes. La stimulation à la ponte avait pour conséquence une augmentation du pourcentage s'élevant à 32,5%, alors que des obstacles mis à la ponte provoquaient une diminution pouvant descendre à 6%.La durée du développement des gynandromorphes oscillait de 21 à 24 jours.L'hypothèse d'une base polygène et d'une prédétermination de l'uf dans le cas de gynandromorphisme pouvait être confirmée par les résultats des expériences.L'intensité de la ponte stimulée ou freinée par les influences du milieu doit être considérée comme un facteur important de la production des gynandromorphes, à condition d'avoir une base génétique appropriée et une aptitude nourricière suffisante chez les nourrices.

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Meinem Lehrer, Herrn Prof. Dr.B. Rensch, zum 65. Geburtstag gewidmet.