1,721,006 research outputs found
Cooperative behaviour in naked mole-rats (Heterocephalus glaber): Specialized castes or social plasicity?
No full textMaster thesis - University of Veterinary Medicine Vienna - 2020In cooperatively breeding vertebrates, non-reproductive group members assist in rearing offspring that is not their own and perform a variety of cooperative tasks such as foraging, nest building, and group defence. Investment in these activities varies between individuals according to state-dependent changes in fitness costs and benefits. The most extreme form of cooperative breeding is found in eusocial insects, where cooperative labour is divided among non-breeders via task specialisation, which leads to the formation of morphologically distinct permanent castes or temporal (age-based) castes. Naked-mole rats (Heterocephalus glaber) were the first mammals to be described as eusocial. Large group size and high reproductive skew make them unique among mammals and may have led to the development of a highly specialised social organisation similar to that of eusocial insects. The aim of the study was to clarify whether non-reproductive colony members of naked mole-rats are organised in a rigid caste system of behavioural specialisation or whether they show social plasticity similar to other cooperatively breeding mammals. We collected observational and body mass data from five naked mole-rat colonies over several months and employed multilevel, multinomial regression models to investigate task specialisation and the distribution of body mass and cooperative behaviour. Non-breeders did not specialise on specific tasks and there were no trade-offs between different cooperative behaviours within individuals. Body mass did not predict cooperative behaviour expression and behavioural phenotypes as well as maximum body mass were continuously distributed, showing no signs of discrete functional or morphological castes. Repeatability of cooperative behaviour was low, suggesting behavioural plasticity similarly to other cooperatively breeding vertebrates. In sum, we found no evidence of a distinct caste system in subordinate naked mole-rats. To investigate the mechanisms responsible for the observed variation in behaviour, future research requires longitudinal data from individuals of known age throughout ontogeny as well as data from free-ranging mole-rats.Master thesis - University of Veterinary Medicine Vienna - 2020In cooperatively breeding vertebrates, non-reproductive group members assist in rearing offspring that is not their own and perform a variety of cooperative tasks such as foraging, nest building, and group defence. Investment in these activities varies between individuals according to state-dependent changes in fitness costs and benefits. The most extreme form of cooperative breeding is found in eusocial insects, where cooperative labour is divided among non-breeders via task specialisation, which leads to the formation of morphologically distinct permanent castes or temporal (age-based) castes. Naked-mole rats (Heterocephalus glaber) were the first mammals to be described as eusocial. Large group size and high reproductive skew make them unique among mammals and may have led to the development of a highly specialised social organisation similar to that of eusocial insects. The aim of the study was to clarify whether non-reproductive colony members of naked mole-rats are organised in a rigid caste system of behavioural specialisation or whether they show social plasticity similar to other cooperatively breeding mammals. We collected observational and body mass data from five naked mole-rat colonies over several months and employed multilevel, multinomial regression models to investigate task specialisation and the distribution of body mass and cooperative behaviour. Non-breeders did not specialise on specific tasks and there were no trade-offs between different cooperative behaviours within individuals. Body mass did not predict cooperative behaviour expression and behavioural phenotypes as well as maximum body mass were continuously distributed, showing no signs of discrete functional or morphological castes. Repeatability of cooperative behaviour was low, suggesting behavioural plasticity similarly to other cooperatively breeding vertebrates. In sum, we found no evidence of a distinct caste system in subordinate naked mole-rats. To investigate the mechanisms responsible for the observed variation in behaviour, future research requires longitudinal data from individuals of known age throughout ontogeny as well as data from free-ranging mole-rats.Masterarbeit - Veterinärmedizinische Universität Wien - 2020Nicht-reproduktive Mitglieder von Gruppen kooperativ brütender Wirbeltiere helfen bei der Aufzucht von Jungen, die nicht ihre eigenen sind, und verrichten eine Reihe an kooperativen Aufgaben wie Futtersuche, Nestbau und Gruppenverteidigung. Das Investment in diese Aktivitäten variiert zwischen den einzelnen Tieren mit vom individuellen Zustand abhängigen Veränderungen in Fitnesskosten und -vorteilen. Die extremste Form des kooperativen Brütens findet man in eusozialen Insekten, in deren Kolonien die kooperative Arbeit mittels Spezialisierung auf bestimmte Aufgaben zwischen den Nicht-Brütern aufgeteilt ist, was zur Bildung von morphologisch abgegrenzten, dauerhaften Kasten oder temporären, altersabhängigen Kasten führt. Der Nacktmull (Heterocephalus glaber) war die erste Säugetierart, die als eusozial beschrieben wurde. Die hohe Anzahl an Gruppenmitgliedern sowie der äußerst ungleiche Reproduktionserfolg in ihren Kolonien (reproductive skew) mögen zur Entwicklung einer hochspezialisierten sozialen Ordnung beigetragen haben, die der von eusozialen Insekten ähnelt. Das Ziel der Studie war es herauszufinden, ob die nicht-reproduktiven Mitglieder von Nacktmullkolonien in einem strikten Kastensystem mit Verhaltensspezialisierung organisiert sind oder ob sie sozial flexibel sind wie andere kooperativ brütende Säugetiere. Wir sammelten Beobachtungs- und Körpergewichtsdaten von fünf Nacktmullkolonien über mehrere Monate und verwendeten multilevel, multinomiale Regressionsmodelle, um Aufgabenspezialisierung und die Verteilungen von Körpergewicht und kooperativem Verhalten zu untersuchen. Nicht-Brüter spezialisierten sich nicht auf bestimmte Aufgaben und es gab keine Trade-offs zwischen verschiedenen kooperativen Verhaltensweisen innerhalb der Individuen. Verhaltensexpression war nicht abhängig vom Körpergewicht und Verhaltensphänotyp sowie maximales Körpergewicht waren stetig verteilt und ließen keine klar abgegrenzten funktionalen oder morphologischen Kasten erkennen. Die Wiederholbarkeit kooperativen Verhaltens war gering, was eine Verhaltensflexibilität ähnlich derer von kooperativ brütenden Vertebraten nahelegt. Zusammenfassend fanden wir keine Anzeichen für die Existenz eines strikten Kastensystems in nicht-reproduktiven Nacktmullen. Um die Mechanismen zu erforschen, die den beobachteten Verhaltensunterschieden zugrunde liegen, bedarf es weiterer Studien mit longitudinalen Daten von Tieren bekannten Alters sowie von freilebenden Nacktmullen
Telomere dynamics in naked mole-rats
No full textMaster thesis - University of Veterinary Medicine Vienna - 2020Masterarbeit - Veterinärmedizinische Universität Wien - 202
Do ultrasonic vocalizations reveal inbreeding depression?
No full textDiploma thesis - University of Veterinary Medicine Vienna - 2020Adult house mice emit ultrasonic vocalizations enhancing courtship behavior. The aims of my thesis were to show the effect of direct contact, male genetic background and the relatedness to females on males USV emission. The experiment was conducted by recording (USG Electret Ultrasound Microphone, Avisoft Bioacoustics / Knowles FG) breeding pairs (N=38) of F4 offspring of wild-caught house mice (Mus musculus musculus). Four breeding pair groups which differed in genetic background (outbred and inbred) and relatedness to the mating female (familiar litter mates and non related) were recorded during two consecutive encountering phases. First an introduction phase with a perforated, transparent seperation wall restricting physical conctact and second a phase of direct interaction after removing the seperation wall. The analysis of emitted USVs concerning vocal performance (number of USVs), vocal repertoire (types of USVs) and spectrographic features were semiautomatically processed in STx (S_TOOLS-STx Version 4.3.0. (9147) © 1997-2019 Acoustics Research Institute – Austrian Academy of Science). For testing the effect of direct interaction on USV emission the results of phase 1 and 2 were compared. Against my expectation that males would show increased USV emission in phase 2, my results showed that male mice vocalized more for a sister in phase 2. This finding suggests that USV emission might enhance inbreeding avoidance by kinship recognition and further studies are needed addressing this. For testing the effect of male genetic background and kinship to females on USV emission, several variables of all breeding pair groups were compared, seperatelay for phase 1 and 2. Results showed that USV emission has a minor role in revealing inbreeding depression probably due to inbreeding for just one generation, or laboratory conditions might be less comptetitive than in nature or both. Concerning relatedness, the results support the hypothesis that USVs mediate inbreeding avoidance but against my expectation not by vocalizing more for unrelated females but for siblings.Diploma thesis - University of Veterinary Medicine Vienna - 2020Adult house mice emit ultrasonic vocalizations enhancing courtship behavior. The aims of my thesis were to show the effect of direct contact, male genetic background and the relatedness to females on males USV emission. The experiment was conducted by recording (USG Electret Ultrasound Microphone, Avisoft Bioacoustics / Knowles FG) breeding pairs (N=38) of F4 offspring of wild-caught house mice (Mus musculus musculus). Four breeding pair groups which differed in genetic background (outbred and inbred) and relatedness to the mating female (familiar litter mates and non related) were recorded during two consecutive encountering phases. First an introduction phase with a perforated, transparent seperation wall restricting physical conctact and second a phase of direct interaction after removing the seperation wall. The analysis of emitted USVs concerning vocal performance (number of USVs), vocal repertoire (types of USVs) and spectrographic features were semiautomatically processed in STx (S_TOOLS-STx Version 4.3.0. (9147) © 1997-2019 Acoustics Research Institute – Austrian Academy of Science). For testing the effect of direct interaction on USV emission the results of phase 1 and 2 were compared. Against my expectation that males would show increased USV emission in phase 2, my results showed that male mice vocalized more for a sister in phase 2. This finding suggests that USV emission might enhance inbreeding avoidance by kinship recognition and further studies are needed addressing this. For testing the effect of male genetic background and kinship to females on USV emission, several variables of all breeding pair groups were compared, seperatelay for phase 1 and 2. Results showed that USV emission has a minor role in revealing inbreeding depression probably due to inbreeding for just one generation, or laboratory conditions might be less comptetitive than in nature or both. Concerning relatedness, the results support the hypothesis that USVs mediate inbreeding avoidance but against my expectation not by vocalizing more for unrelated females but for siblings.Diplomarbeit - Veterinärmedizinische Universität Wien - 2020Ausgewachsene Hausmäuse erzeugen Vokalisationen im Ultraschallbereich (USVs), um ihre Paarungsbereitschaft zu signalisieren. Das Ziel meiner Arbeit war es, den Einfluss direken Kontaktes, des genetischen Hintergrunds der Männchen und der Verwandschaft zwischen Männchen und Weibchen auf die Aussendung jener Vokalisationen aufzuzeigen. Für das Experiment wurden Zuchtpaare (N=38) aus F4-Nachkommen, wildgefangener Hausmäuse (Mus musculus musculus), aufgezeichnet (USG Electret Ultraschall-Mikrophon, Avisoft Bioacoustics / Knowles FG) - vier Zuchtpaar-Gruppen, welche sich hinsichtlich des genetischen Hintergrunds (Auszucht und Inzucht) und der Verwandschaft zum Paarungsweibchen (Wurfgeschwister und Unverwandte) unterschieden, wurden innerhalb zwei aufeinanderfolgenden Begegnungsphasen aufgezeichnet. Die Erste, eine Einleitungsphase, in der eine perforierte, transparente Trennwand, den physischen Kontakt einschränkte und die Zweite, eine Phase mit direktem Kontakt, nach Entfernung der Trennwand. Die Analyse, hinsichtlich der Menge, Diversität und spectrographischer Eigenschaften der ausgesendeten USVs, wurde halbautomatisch mit STx (S_TOOLS-STx Version 4.3.0. (9147) © 1997-2019 Acoustics Research Institute – Austrian Academy of Science) durchgeführt. Um den Effekt direkten Kontaktes auf die Aussendung von USVs zu testen, wurden die Phasen mit Hilfe eines Wilcoxon-Vorzeichen-Rang-Tests miteinander verglichen. Hingegen meiner Erwartung, dass alle Männchen mehr in Phase 2 vokalisieren würden, taten dies nur Männchen für ihre Schwestern. Diese Erkenntnis impliziert, dass die Aussendung der Vokalisationen möglicherweise der Vermeidung von Inzucht, durch Geschwistererkennung, dient, weshalb weitere Studien diese Fragestellung untersuchen sollten. Um den Einfluss des genetischen Hintergrunds der Männchen und der Verwandschaft zu den Weibchen auf die Aussendung der Vokalisationen zu testen, wurden verschiedenste Variabeln aller Zuchtpaar-Gruppen mit Hilfe eines Mann-Whitney-U-Tests, jeweils für die erste und die zweite Phase, miteinander verglichen. Die Ergebnisse zeigten, dass die Aussendung von USVs eine eher vernachlässigbare Aussage über Inzuchtdepression lieferte. Dies ist möglicherweise auf den zu geringen Inzuchtkoeffizienten erster Generation, oder auf die zu wenig natürlichen und somit nicht ausreichend kompetitiven Verhältnisse der Labortierhaltung, oder beides zurückzuführen. Bezüglich der Verwandschaft, haben die Ergebnisse die Hypothese, dass USV-Aussendung zur Inzuchtvermeidung vermittelt wird, unterstützt, allerdings, hingegen meiner Annahme, nicht durch vermehrte Vokalisation für unverwandte Weibchen sondern für Wurfgeschwister
Telomere Attrition Due to Infection
No full textBackgroundTelomeres--the terminal caps of chromosomes--become shorter as individuals age, and there is much interest in determining what causes telomere attrition since this process may play a role in biological aging. The leading hypothesis is that telomere attrition is due to inflammation, exposure to infectious agents, and other types of oxidative stress, which damage telomeres and impair their repair mechanisms. Several lines of evidence support this hypothesis, including observational findings that people exposed to infectious diseases have shorter telomeres. Experimental tests are still needed, however, to distinguish whether infectious diseases actually cause telomere attrition or whether telomere attrition increases susceptibility to infection. Experiments are also needed to determine whether telomere erosion reduces longevity.Methodology/principal findingsWe experimentally tested whether repeated exposure to an infectious agent, Salmonella enterica, causes telomere attrition in wild-derived house mice (Mus musculus musculus). We repeatedly infected mice with a genetically diverse cocktail of five different S. enterica strains over seven months, and compared changes in telomere length with sham-infected sibling controls. We measured changes in telomere length of white blood cells (WBC) after five infections using a real-time PCR method. Our results show that repeated Salmonella infections cause telomere attrition in WBCs, and particularly for males, which appeared less disease resistant than females. Interestingly, we also found that individuals having long WBC telomeres at early age were relatively disease resistant during later life. Finally, we found evidence that more rapid telomere attrition increases mortality risk, although this trend was not significant.Conclusions/significanceOur results indicate that infectious diseases can cause telomere attrition, and support the idea that telomere length could provide a molecular biomarker for assessing exposure and ability to cope with infectious diseases
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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