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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Thermoregulatory behavior and habitat use of Liolaemus aparicioi at two different altitudes

Gustafsson, Jannie Frida Linn January 2015 (has links)
The thermoregulation of lizards depends highly on the environment they inhabit. Thermoregulation is crucial for physiological processes and affects therefore the life history of the lizard. High altitudes are characterized by a colder climate than on lower altitudes, and these environmental factors affects the thermoregulation of lizards. Lizards can however adapt to colder climates by adjusting their physiology and/or behavior. In this study two populations of Liolaemus aparicioi, an endemic lizard inhabiting the valleys close to La Paz, were observed at two different altitudes to investigate any differences in behavior or habitat use that could compensate for the high altitude. The behavioral displays associated to thermoregulation and the use of habitat were recorded in order to assess how they allocated their time and how they used the habitat available. The mean values of most parameters measured indicated that the population on the high altitude do compensate for the high altitude by behavior and habitat use.
32

Thermoregulating behavior and habitat use of Liolaemus aparicioi

Gustafsson, Jennie Frida Linn January 2015 (has links)
The thermoregulation of lizards depends highly on the environment they inhabit. Thermoregulation is crucial for physiological processes and affects therefore the life history of the lizard. High altitudes are characterized by a colder climate than on lower altitudes, and these environmental factors affects the thermoregulation of lizards. Lizards can however adapt to colder climates by adjusting their physiology and/or behavior. In this study two populations of Liolaemus aparicioi, an endemic lizard inhabiting the valleys close to La Paz, were observed at two different altitudes to investigate any differences in behavior or habitat use that could compensate for the high altitude. The behavioral displays associated to thermoregulation and the use of habitat were recorded in order to assess how they allocated their time and how they used the habitat available. The mean values of most parameters measured indicated that the population on the high altitude do compensate for the high altitude by behavior and habitat use.
33

Thermoregulation and Resource Management in the Honeybee (Apis mellifera) / Thermoregulation und Ressourcenmanagment bei der Honigbiene (Apis mellifera)

Basile, Rebecca January 2009 (has links) (PDF)
Ein grundlegender Faktor, der für das Überleben einer Kolonie sozialer Insekten ausschlaggebend ist, liegt in der Fähigkeit Nahrung durch sogenannte „Trophallaxis“ auszutauschen. Diese Fütterungskontakte sorgen für die gleichmäßige Verteilung der Nahrung innerhalb der Kolonie und werden als einer der Grundpfeiler der Sozialität der Staatenbildenden Insekten erachtet. Im Fall der Honigbienen finden diese Kontakte in vollkommener Dunkelheit statt. Damit es in dieser Situation überhaupt zum Nahrungsaustausch kommen kann, sind die Antennen von großer Wichtigkeit. Ein erster Schritt in den Verhaltensweisen, die der Rezipient eines trophallaktischen Kontaktes zeigt, ist der Kontakt einer Antennenspitze mit den Mundwerkzeugen des Donoren, da sich dort die regurgitierte Nahrung befindet. Diese Berührung hat aufgrund der gustatorischen Sensibilität der Antenne den Zweck, das angebotene Futter zu „erschmecken“. Die rechte Antenne wird vom Rezipienten eines trophallaktischen Kontakts signifikant häufiger eingesetzt als die linke Antenne. Die Präferenz für die rechte Antenne bleibt dabei auch erhalten, wenn ein Teil der Antennengeisel abgetrennt wurde, also die sensorischen Fähigkeiten der rechten Antenne stark beeinträchtigt wurden. Der Grund für die Präferenz der rechten Antenne könnte ihrer erhöhten Sensibilität gegenüber Zuckerwasser zugrunde liegen, da die rechte Antenne im Laborversuch signifikant stärker auf Stimulationen mit Zuckerwasser verschiedener Konzentrationen reagierte als die linke. Trophallaktische Kontakte sichern Individuen innerhalb einer Kolonie den Zugang zur lebenswichtigen Nahrung. Im Beispiel der Honigbienen ist ständige Zugriff auf Nahrung besonders wichtig, da es sich um ein heterothermes Tier handelt, das die Fähigkeit besitzt, aktiv seine Körpertemperatur zu regulieren. Obgleich jedes Individuum in der Lage ist, seine Körpertemperatur den eigenen Bedürfnissen anzupassen, ist diese Fähigkeit streng durch den in der Nahrung aufgenommenen Zucker reguliert. Im Gegensatz zu den Säugetieren oder Vögeln, die für eine Erhöhung des Blutzuckerspiegels auch auf Fett- oder Eiweißressourcen zurückgreifen können, ist die Honigbiene auf die Glucose aus der aufgenommenen Nahrung angewiesen. Die Ergebnisse dieser Untersuchung zeigen, dass der Zuckergehalt der aufgenommenen Nahrung positiv mit der Thoraxtemperatur der Bienen korreliert. Dieser Zusammenhang tritt auf, selbst wenn keine Wärmeerzeugung für die Brutpflege oder für das Erwärmen der Wintertraube notwendig ist und die Tiere außerhalb des Stockes ohne eigentliche Notwendigkeit für die Wärmeerzeugung in einem Käfig gehalten werden. Die Ergebnisse der Untersuchung zeigen, dass die Rezipienten beim Nahrungsaustausch eine signifikant höhere Thoraxtemperatur haben als die Donoren. Außerdem zeigen die Rezipienten nach der Fütterung signifikant häufiger Brutwärmeverhalten als die Donoren. Letztere haben eine signifikant niedrigere Thoraxtemperatur als die Rezipienten und zeigen eine Verhaltenstendenz, häufig zwischen Brutbereich und Honiglager hin- und her zu pendeln. Dabei nehmen sie im Honiglager Honig in ihren Kropf auf und füttern mit dieser Nahrung danach Bienen im Brutbereich. Außerdem zeigen die Ergebnisse, dass es einen wärmegesteuerten Auslösemechanismus gibt, der den Donoren und Rezipienten des trophallaktischen Kontakts dazu verhilft, trotz der Dunkelheit des Stocks praktisch verzögerungsfreie Nahrungsübertragung am Ort des höchsten Energieverbrauchs zu gewährleisten. Das Hervorwürgen von Nahrung angesichts einer Wärmequelle könnte seinen Ursprung in einer Beschwichtigungsgeste haben. Aggressive Tiere zeigen neben sichtbaren aggressiven Verhalten auch durch ihre erhöhte Körpertemperatur, dass sie bereit sind sich auf einen Kampf einzulassen. Die Temperaturerhöhung eines aggressiven Tieres beruht dabei auf der erhöhten Muskelaktivität, die vor allem bei Insekten dazu nötig ist, einen entsprechende Reaktion im Falle eines Kampfes oder der Flucht zeigen zu können. Wird ein Individuum mit Aggression konfrontiert, so bleibt ihm die Wahl sich auf einen Kampf einzulassen, zu flüchten oder durch eine Beschwichtigungsgeste eine Deeskalation der Situation einzuleiten. Besonders häufig wird für diesen Zweck Nahrung regurgitiert und dem dominanteren Tier angeboten, um einem Konflikt aus dem Weg zu gehen. Die Fähigkeit, Arbeiterinnen mit kleinen Portionen konzentrierter Nahrung zu versorgen trägt zu einer ökonomischen Verteilung der Ressourcen bei, die mit den physiologischen Bedürfnissen der Honigbienen konform geht und die ökologischen Erfordernisse des Stockes erfüllt. Das daraus resultierende Managementsystem, welches sparsam mit den Ressourcen haushaltet und auf die individuellen Bedürfnisse jeder einzelnen Biene einzugehen vermag, könnte ein Grund für die Fähigkeit der Honigbienen zur Entwicklung mehrjähriger Kolonien sein, die, anders als Hummeln oder Wespen, auch den Winter in gemäßigten Zonen als Gemeinschaft zu überstehen vermögen. / Like many other social insect societies, honeybees collectively share the resources they gather by feeding each other. These feeding contacts, known as trophallaxis, are regarded as the fundamental basis for social behavior in honeybees and other social insects for assuring the survival of the individual and the welfare of the group. In honeybees, where most of the trophallactic contacts are formed in the total darkness of the hive, the antennae play a decisive role in initiation and maintenance of the feeding contact, because they are sensitive to gustatory stimuli. The sequences of behaviors performed by the receiver bees at the beginning of a feeding contact includes the contact of one antenna with the mouthparts of a donor bee where the regurgitated food is located. The antennal motor action is characterized by behavioral asymmetry, which is novel among communicative motor actions in invertebrates. This preference of right over left antenna is without exception even after removal of the antennal flagellum. This case of laterality in basic social interaction might have its reason in the gustatory asymmetry in the antennae, because the right antenna turns out to be significantly more sensitive to stimulation with sugar water of various concentrations than the left one. Trophallactic contacts which guarantee a constant access to food for every individual in the hive are vitally important to the honeybee society, because honeybees are heterothermic insects which actively regulate their thoracic temperature. Even though the individual can regulate its body temperature, its heating performance is strictly limited by the amount of sugar ingested. The reason for this is that honeybees use mostly the glucose in their hemolymph as the energy substrate for muscular activity, and the heat producing flight muscles are among the metabolically most active tissues known. The fuel for their activity is honey; processed nectar with a sugar content of ~80% stored in the honeycomb. The results show that the sugar content of the ingested food correlates positively with the thoracic temperature of the honeybees even if they are caged and show no actual heating-related behavior as in brood warming or heating in the centre of the winter cluster. Honeybees actively regulate their brood temperature by heating to keep the temperature between 33 °C to 36 °C if ambient temperatures are lower. Heating rapidly depletes the worker’s internal energy; therefore the heating performance is limited by the honey that is ingested before the heating process. This study focused on the behavior and the thoracic temperature of the participants in trophallactic food exchanges on the brood comb. The brood area is the centre of heating activity in the hive, and therefore the region of highest energy demand. The results show that the recipients in a trophallactic food exchange have a higher thoracic temperature during feeding contacts than donors, and after the feeding contact the former engage in brood heating more often. The donor bees have lower thoracic temperature and shuttle constantly between honey stores and the brood comb, where they transfer the stored honey to heating bees. In addition, the results show a heat-triggered mechanism that enables donor and recipient to accomplish trophallactic contacts without delay in the total darkness of the hive in the brood area as the most energy consuming part of the hive. Providing heat-emitting workers with small doses of high performance fuel contributes to an economic distribution of resources consistent with the physiological conditions of the bees and the ecological requirements of the hive, resulting in a highly economical resource management system which might be one of the factors favouring the evolution of perennial bee colonies in temperate regions. The conclusion of these findings suggests a resource management strategy that has evolved from submissive placation behavior as it is seen in honeybees, bumblebees and other hymenopterans. The heat-triggered feedback mechanism behind the resource management of the honeybee´s thermoregulatory behavior reveals a new aspect of the division of labor and a new aspect of communication, and sheds new light on sociality in honeybees.
34

An energy budget for the lizard Pseudocordylus melanotus melanotus, an extreme sit-and-wait forager

McConnachie, Suzanne 27 October 2006 (has links)
Faculty of Science School of Animal ,Plant and Enviromental Sciences 9707660j McConnachie@ukzn.ac.za / Characteristics comprising an energy budget of Pseudocordylus melanotus melanotus were investigated in terms of limiting factors for the lizard’s distribution, and included measures of thermal biology, metabolism and digestive physiology. Pseudocordylus m. melanotus is rupicolous, is limited to the temperate parts of southern Africa and exhibits adaptations to these environments. The distribution of the lizard was modelled using two different climate envelope modelling techniques, which are discussed in terms of the energy budget and factors limiting the distribution of the lizard. Pseudocordylus m. melanotus exhibits wide thermal tolerances. It can withstand body temperatures (Tb) below freezing, but freezing of body water, which occurs at ca. -5 ºC, is lethal. The lower critical minimum temperature was a surprisingly high measure for an apparently cold-adapted lizard. In the laboratory, the selected body temperature (Tsel) was ca. 30 ºC. In the wild, lizards thermoregulate by shuttling between hot and cold microclimates, modifying body postures and regulating activity times, and select Tbs of ca. 29 ºC in summer and ca. 26 ºC in winter. Energy expenditure was measured over a range of temperatures. MR increases significantly with increasing temperature. Body mass and metabolic rate (MR) were significantly related at 30 ºC only. The lack of significance at other temperatures can be ascribed to the small range of body mass over which measures were made. Energy gain in P. m. melanotus was quantified in terms of prey capture rates and by measuring aspects of digestive physiology. Prey capture attempts were 35 % successful and occurred ca. every 2 h 30 min in the field. Lizards consumed a variety of arthropods, but mainly ate beetles. Digestive rate and appetite increased significantly with increasing temperature. Apparent digestive efficiency (ca. 94 %) and apparent assimilation efficiency (ca. 87.2 %) were not affected by temperature. iii Two energy budgets were calculated; one based mainly on laboratory measures and the other based on the thermal profile of lizard body temperature measured in the field. The laboratory energy budget was approximately half that of the field energy budget. The field energy budget, however, provided a more realistic view of energy expenditure since it covered almost the entire thermal range experienced by lizards. Between 592.53 kJ (field energy budget) and 940.06 kJ (laboratory energy budget) per year is required for a standard 30 g P. m. melanotus to remain in energy balance. This means that lizards need to consume between 73.55 and 116.69 g of mealworms per year, which equates to ca. 740 to 1200 average mealworms. Any energy gained over and above these requirements can be allocated to growth, reproduction and storage. In terms of the lizard’s distribution, it will be excluded from areas where the available thermal environment and prey abundance do not allow the lizard to maintain a positive energy balance. The lizard is apparently at the cold limit of its range, so predicted climate change in southern Africa is unlikely to have a significant effect on the distribution of the lizard. Suitable crevices are essential to the lizard’s survival, particularly during periods of extreme cold when lizards may experience Tbs where they are incapacitated, or effectively ‘comatose’, while in retreats.
35

Tolerância ao calor em ovelhas de raças de corte lanadas e deslanadas no sudeste do Brasil / Heat tolerance in hair and wool meat breeds ewes in southeast of Brazil

Veríssimo, Cecília José 14 March 2008 (has links)
O trabalho, composto de quatro experimentos, teve como objetivo geral avaliar a tolerância ao calor em ovinos, sua relação com a coloração do pelame e a presença ou ausência de lã em ovelhas de raças lanadas e deslanadas. Os experimentos foram conduzidos no Instituto de Zootecnia, localizado em Nova Odessa, Estado de São Paulo (22º42\'S e 47º18\'W, 570m de altitude). Nos primeiros três experimentos, avaliaram-se 83 ovelhas, das raças Santa Inês (31), Morada Nova (15), Texel (14), Suffolk (11) e Ile de France (12). O índice de tolerância ao calor (ITC) foi calculado pela fórmula 10 - (TR2 - TR1), através das temperaturas retais registradas às 13h (TR1), após duas horas em descanso na sombra, e às 15h, após uma hora de exposição à radiação solar direta e uma hora de descanso à sombra (TR2). No quarto experimento, 90 ovelhas, 18 de cada raça, foram avaliadas quanto à temperatura retal (TR) e freqüência respiratória (FR) às 8h, 13h (após duas horas em descanso à sombra), 14h (após uma hora de exposição ao sol), e depois a cada 15 minutos, na sombra, até às 15h, originando quatro TR2 para cálculo dos índices. Verificou-se que não houve diferença na tolerância ao calor entre animais da raça Santa Inês de pelagem clara e escura. A raça Texel (lanada) teve menor variação de temperatura entre os dois horários, e obteve melhor índice de tolerância ao calor (P<0,05) do que a raça deslanada Morada Nova. Ovelhas das raças Suffolk e Ile de France tiveram altos índices de tolerância ao calor, independente do fato de estarem ou não tosquiadas. No experimento 4, ovelhas da raça Santa Inês tiveram TR inferiores (P<0,05) à TR de algumas raças lanadas, às 13h, 14h, 14h30min e 14h45min. Em todas as raças, não houve diferença (P>0,05) entre as TR medidas às 8h e 13h, assim como não foram encontradas diferenças (P>0,05) entre elas quanto à TR da manhã e aos 60 min após o estresse (15h). As ovelhas deslanadas tiveram FR inferiores (P<0,05) às lanadas. Não houve diferença (P>0,05) entre o ITC calculado com base na TR2 aos 45 e 60 min pósestresse. Concluiu-se que o tempo de registro da TR2 para a espécie ovina pode ser antecipado de 60 para 45 minutos após o estresse, e que as ovelhas avaliadas estão adaptadas ao clima do Estado de São Paulo. / This study consisted of 4 experiments and had as main goal evaluate the heat tolerance in ewes, and its relation to hair color and presence or absence of wool in wool and hair breeds. The experiments were conducted at the Instituto de Zootecnia, located in Nova Odessa city, São Paulo State, Brazil (22º42\'S e 47º18\'W, 570m altitude). Three experiments evaluated 83 ewes of the following breeds: (31) Santa Inês; (15) Morada Nova; (14) Texel; (11) Suffolk and (12) Ile de France. The heat tolerance index is calculated on the formula 10 - (RT2 - RT1) through data on rectal temperatures (RT) as follows: RT1 at 13:00h, after 2 hours of rest in the shade and RT2 at 15:00h, after na hour of sun exposure and one hour of rest in the shade. The fourth experiment examined a 90 ewe flock, consisted of 18 ewes of each breed, which were evaluated for rectal temperature (RT) and respiratory frequency (RF) as follows: 8:00h, 13:00h (after 2 hour shade rest); 14:00h (after one hour sun exposure) and in the shade, every 15 minutes till the hour; which provided four RT2 for the index. There was no heat tolerance difference between light or dark hair colored Santa Ines. Texel ewes (wool breed) presented the lowest variation of temperature between the two timeframes and had best heat tolerance index (P<0,05) than the hair breed Morada Nova. Suffolk and Ile de France ewes had high heat tolerance index values, irrespective of having been sheared or not. In the fourth experiment, Santa Inês ewes presented lower RT (P<0,05), than some wool breeds at 13:00h, 14:00h, 14:30h and 14:45h. In all breeds, there was no difference (P>0,05) between the RT values taken at 8h and 13h. In addition, no significant differences (P>0,05) were found among the breeds between the RT values recorded in the morning and the RT taken 60min after heat stress (15h). The hair breeds presented lower RF (P<0,05) than the wool breeds. No difference was found amongst the heat tolerance indexes based on RT2 at 45 and 60min after stress. It was concluded that the registering time of RT2 for sheep can be advanced from 60 to 45 min after stress, and that the ewes in the experiment are all adapted to São Paulo State\'s weather.
36

COMPARING DAIRY FARM PERFORMANCE AND HEAT STRESS ABATMENT STRATEGIES IN THE UNITED STATES USING SUMMER TO WINTER RATIOS

Guinn, Jenna M. 01 January 2018 (has links)
Heat stress abatement is a challenge for producers in the United States, especially in the southern states. Dairy producers could benefit by having a simply metric to measure heat stress abatement strategies with the goal of motivating improvement in heat stress management. Managing heat stress is key to ameliorating the effects on dairy cow performance. A study was performed to explore the use of a heat stress metric called the Summer to Winter performance ratio (S:W ratio), to quantify and compare farm performance variables among regions of the United States. Summer to Winter ratios were closest to 1.0 in the northern regions and furthest from 1.0 in the southern regions for all performance variables other than milk fat and protein percentage. This suggests that summer performance varies by region and shown using the S:W ratio. A second study compared S:W ratios among Southeast states and then applied the performance ratio to heat abatement strategies in Southeast states. The S:W ratio varied by performance measure and heat abatement strategies but tended to be best for herds implementing cow cooling strategies. The studies in this thesis demonstrated S:W ratios can identify heat stress differences by region and heat abatement strategies by herds.
37

Nesting behaviour of the paper wasp Polistes dominula - with special focus on thermoregulatory mechanisms / Nistverhalten der Feldwespe Polistes dominula - mit besonderem Augenmerk auf thermoregulatorische Mechanismen

Höcherl, Nicole January 2015 (has links) (PDF)
Wasps of the genus Polistes comprise over 200 species and are nearly cosmopolitan. They show a lack of physiological caste differentiation and are therefore considered as primitively eusocial. Furthermore, paper wasps are placed between the solitary living Eumenidae and the highly social organized Vespinae. Hence, they are often called a “key genus” for understanding the evolution of sociality. Particularly, Polistes dominula, with its small easy manageable nests and its frequent occurrence and wide distribution range is often the subject of studies. In Europe, the invasion of this species into northern regions is on the rise. Since little was known about the nesting behaviour of P. dominula in Central Europe, the basic principles about nesting were investigated in Würzburg, Germany (latitude 49°) by conducting a comprehensive field-study spanning three consecutive years. Furthermore, the thermoregulation of individual wasps in their natural habitat had not yet been investigated in detail. Therefore, their ability to respond to external hazards with elevated thorax temperatures was tested. In addition, different types of nest thermoregulation were investigated using modern methods such as infrared thermography and temperature data logger. In the present work, the investigation of basic nesting principles revealed that foundress groups (1-4 foundresses) and nests are smaller and that the nesting season is shorter in the Würzburg area than in other regions. The mean size of newly founded nests was 83 cells and the average nesting season was around 4.6 months. The queens neither preferred single (54%) nor multiple founding (46%) in this study. The major benefit of multiple founding is an increased rate of survival. During the three years of observation, only 47% of single-foundress colonies survived, whereas 100% of colonies that were built by more than two queens, survived. However, an influence of the number of foundresses on the productivity of colonies in terms of number of cells and pupae per nest has not shown up. However, the length of the nesting season as well as the nest sizes varied strongly depending on the climatic conditions of the preceding winter during the three consecutive years. In order to investigate the thermoregulatory mechanisms of individual adult P. dominula wasps, I presented artificial threats by applying smoke or carbon dioxide simulating fire and predator attacks, respectively, and monitored the thorax temperature of wasps on the nest using infrared thermography. The results clearly revealed that P. dominula workers recognized smoke and CO2 and reacted almost instantaneously and simultaneously with an increase of their thorax temperature. The maximal thorax temperature was reached about 65 s after the application of both stressors, but subsequently the wasps showed a different behaviour pattern. They responded to a longer application of smoke with moving to the exit and fled, whereas in case of CO2 the wasps started flying and circling the nest without trying to escape. No rise of the thorax temperature was detectable after an air blast was applied or in wasps resting on the nest. Additionally, the thorax temperatures of queens were investigated during dominance battles. I found that the thorax temperature of the dominant queens rose up to 5°C compared to that of subordinate queens that attacked the former. The study of active mechanisms for nest thermoregulation revealed no brood incubation or clustering behaviour of P. dominula. Furthermore, I found out that wing fanning for cooling the nest was almost undetectable (4 documented cases). However, I could convincingly record that water evaporation is most effective for nest cooling. By the direct comparison of active (with brood and adults) and non-active (without brood and adults) nests, the start of cooling by water evaporation was detected above maximum outside temperatures of 25°C or at nest temperatures above 35°C. The powerful role of water in nest cooling was manifested by an average decrease of temperature of a single cell of about 8°C and a mean duration of 7 min until the cell reached again its initial temperature. The investigation of passive thermoregulatory mechanisms revealed that the nest site choice as well as nest orientation appears to be essential for P. dominula wasps. Furthermore, I was able to show that the architecture of the nests plays an important role. Based on the presented results, it can be assumed that the vertical orientation of cells helps maintaining the warmth of nests during the night, whereas the pedicel assists in cooling the nest during the day. / Die Wespen-Gattung Polistes ist mit über 200 Arten nahezu auf der ganzen Welt vertreten. Da physiologische Unterschiede zwischen den Kasten fehlen, werden sie als primitiv eusozial eingestuft. Des Weiteren werden sie zwischen den solitär lebenden Eumenidae und den hoch eusozialen Vespinae eingeordnet. Sie werden daher oft als „Schlüssel-Gattung“ für das Verständnis der Evolution von Sozialität bezeichnet. Insbesondere Polistes dominula (Haus-Feldwespe) wird aufgrund der kleinen einfach zu handhabenden Nester, dem häufigen Vorkommen und der weiten Verbreitung vielfach für Studien genutzt. In Europa ist diese Wespenart auf dem Vormarsch in nördlichere Regionen. Bisher war kaum etwas über das Nistverhalten von P. dominula in Zentraleuropa bekannt. Daher wurde eine umfassende, drei aufeinanderfolgende Jahre andauernde Freilandstudie zu den Grundlagen des Nistverhaltens in Würzburg (Deutschland, Breitengrad 49°) durchgeführt. Auch die Thermoregulation der Einzeltiere wurde noch nie im Detail erforscht. Daher wurde ein Experiment durchgeführt, das aufzeigen sollte, ob diese Tiere die Fähigkeit besitzen, mit erhöhten Thoraxtemperaturen auf Gefahr zu reagieren. Zusätzlich kamen neuere Methoden wie die Infrarot-Thermographie und Temperaturdatenlogger zum Einsatz, um die verschiedenen Arten der Nestthermoregulation zu untersuchen. In der vorliegenden Arbeit über die Grundlagen des Nistverhaltens zeigte sich, dass im Vergleich zu anderen Regionen in Würzburg sowohl die Gruppengröße der Nestgründerinnen (1-4 Gründerinnen) als auch die Nester an sich kleiner sind (≈ 83 Zellen) und die Nestsaison kürzer (≈ 4,6 Monate). Die Königinnen bevorzugten weder die Gründung des Nestes allein (54%) noch zusammen mit mehreren Königinnen (46%). Der größte Vorteil einer Gründung der Nester durch mehrere Königinnen liegt in einer erhöhten Überlebensrate der Nester. In der drei Jahre andauernden Studie überlebten nur 47% der Nester, die von einer Königin gegründet wurden, während 100% der Völker, die von mehr als zwei Königinnen gegründet wurden, überlebten. Es konnte jedoch kein Einfluss der Anzahl an Gründerinnen auf die Produktivität (bezüglich der Anzahl von Zellen und Puppen) der Völker festgestellt werden. Allerdings variierten Saisonlängen und Nestgrößen stark in Abhängigkeit der klimatischen Bedingungen des vorangegangenen Winters in den drei aufeinanderfolgenden Jahren. Zur Untersuchung der thermoregulatorischen Mechanismen der adulten Tiere setzte ich künstliche Bedrohungen in Form von Rauch und Kohlendioxid ein, um entweder ein Feuer oder einen Raubtierangriff zu simulieren. Die Thoraxtemperaturen der auf dem Nest sitzenden Feldwespen wurde zeitgleich mit einer Thermokamera überwacht. Die Ergebnisse belegen eindeutig, dass P. dominula-Arbeiterinnen Rauch und CO2 wahrnehmen und beinahe unverzüglich und zeitgleich mit einer Erhöhung der Thoraxtemperatur reagieren. Nach der Applikation der beiden Stressoren war die maximale Temperatur nach durchschnittlich 65 s erreicht, allerdings zeigten die Wespen unterschiedliche Verhaltensmuster. Auf eine längere Rauchapplikation reagierten sie mit Flucht, während sie im Fall von CO2 fliegend das Nest umkreisten, ohne zu fliehen. Nach der Gabe eines Luftstoßes oder bei ruhenden Wespen war kein Anstieg der Thoraxtemperatur nachweisbar. Zusätzlich wurden die Thoraxtemperaturen von Königinnen bei Dominanzkämpfen untersucht. Ich verzeichnete einen Anstieg der Thoraxtemperatur der dominanten Königin um bis zu 5°C im Vergleich zu der Temperatur der untergeordneten Königin, die die dominante angriff. Die Studie der aktiven Mechanismen der Nestthermoregulation belegte, dass bei P. dominula kein Heizen der Brut oder „Clustern“ stattfindet. Des Weiteren war Fächeln zur Kühlung des Nestes so gut wie nicht feststellbar (4 dokumentierte Fälle). Allerdings war ich in der Lage nachzuweisen, dass die Verdunstung von Wasser für die Kühlung des Nestes sehr effektiv ist. Durch den direkten Vergleich von aktiven (mit Brut und adulten Tieren) und nicht-aktiven (ohne Brut und adulten Tieren) Nestern konnte der Beginn des Kühlens bei einer maximalen Außentemperatur von über 25°C oder einer Nesttemperatur von über 35°C ermittelt werden. Die wichtige Rolle, die Wasser für die Nestkühlung spielt, zeigte sich zum Einen durch die mittlere Abkühlung einer einzelnen Zelle von ca. 8°C und zum Anderen durch eine durchschnittliche Dauer von 7 min, bis die Zelle wieder ihre Ausgangstemperatur erreichte. Die Untersuchung der passiven Mechanismen zur Nestthermoregulation zeigte, dass sowohl die Wahl des Nistplatzes als auch die Orientierung des Nestes für die Haus-Feldwespe essentiell ist. Darüber hinaus war ich in der Lage nachzuweisen, dass die Architektur des Nestes eine entscheidende Rolle spielt. Auf der Grundlage der vorgestellten Ergebnisse kann angenommen werden, dass die nach unten ausgerichteten Zellen helfen, das Nest nachts zu wärmen, während der Stiel des Nestes hilft, das Nest tagsüber zu kühlen.
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The Influence of Osmoreceptors and Baroreceptors on Heat Loss Responses during a Whole-body Passive Heat Stress

Lynn, Aaron 08 November 2011 (has links)
Exercise and/or heat-induced dehydration is associated with decreases in plasma volume (hypovolemia) and increases in plasma osmolality (hyperosmolality), which are thought to stimulate peripheral baroreceptors and central osmoreceptors respectively. Independently, plasma hyperosmolality and baroreceptor unloading have been shown to attenuate sweating and cutaneous vasodilation during heat stress, and therefore, negatively impact body temperature regulation. However, to date little is known regarding the combined influence of plasma hyperosmolality and baroreceptor unloading on thermoefferent activity. Therefore, we evaluated the separate and combined effects of baroreceptor unloading (via lower body negative pressure, LBNP) and plasma hyperosmolality (via infusion of 3% NaCl saline) on heat loss responses of sweating and cutaneous vascular conductance (CVC) during progressive whole-body heating. We show that the combined nonthermal influences of plasma hyperosmolality and baroreceptor unloading additively delay the onset threshold for CVC, relative to their independent effects. In contrast, baroreceptor unloading has no influence on the sweating response regardless of osmotic state. These divergent roles of plasma hyperosmolality and the baroreflex on heat loss responses might serve to enhance blood pressure and body core temperature regulation during dehydration and heat stress.
39

Body Heat Storage, Sweating and Skin Blood Flow Responses Following Cold and Warm Water Ingestion during Exercise

Bain, Anthony R 18 January 2012 (has links)
Ingestion of cold (<10°C) compared to warm (>37°C) fluid has been suggested to attenuate heat storage levels during exercise. However, modulations in sweat output may yield differences in evaporative heat loss that are greater than differences in heat transfer with the ingested fluid. The purpose of the thesis was to evaluate thermoregulatory control and human heat balance, and compare thermometrically derived values of heat storage with those derived from partitional calorimetry following water ingestion of varying temperature during exercise. We found that water ingestion of 50°C compared to 1.5°C decreases heat storage in thermoneutral environments, and further exacerbates the error of thermometric heat storage estimations. Differences in heat storage were attributed exclusively to disproportionate reductions in whole-body and local sweat output and thus evaporative heat loss potential. Ingested fluid temperature only minimally altered skin blood flow and did not influence dry heat exchange with the ambient environment.
40

The Influence of Osmoreceptors and Baroreceptors on Heat Loss Responses during a Whole-body Passive Heat Stress

Lynn, Aaron 08 November 2011 (has links)
Exercise and/or heat-induced dehydration is associated with decreases in plasma volume (hypovolemia) and increases in plasma osmolality (hyperosmolality), which are thought to stimulate peripheral baroreceptors and central osmoreceptors respectively. Independently, plasma hyperosmolality and baroreceptor unloading have been shown to attenuate sweating and cutaneous vasodilation during heat stress, and therefore, negatively impact body temperature regulation. However, to date little is known regarding the combined influence of plasma hyperosmolality and baroreceptor unloading on thermoefferent activity. Therefore, we evaluated the separate and combined effects of baroreceptor unloading (via lower body negative pressure, LBNP) and plasma hyperosmolality (via infusion of 3% NaCl saline) on heat loss responses of sweating and cutaneous vascular conductance (CVC) during progressive whole-body heating. We show that the combined nonthermal influences of plasma hyperosmolality and baroreceptor unloading additively delay the onset threshold for CVC, relative to their independent effects. In contrast, baroreceptor unloading has no influence on the sweating response regardless of osmotic state. These divergent roles of plasma hyperosmolality and the baroreflex on heat loss responses might serve to enhance blood pressure and body core temperature regulation during dehydration and heat stress.

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