No description available.

Ecological and physiological comparisons were made mainly between two populations of Primula farinosa Linn, from northern England and some of their closely related arctic-alpine species:- P. frondosa, P. darialica, P. halleri, P. laurentiana, P. modesta, P. scotica, P. scandinavica, and P. stricta, which have contrasting habitats and natural distribution. The germination of primulas showed a negative or neutral response to the density of seeds sown. They also showed intrinsic seed-dormancy which can be overcome by chilling treatment. Most of the species tested had significantly higher percentage germination in a diurnally fluctuating temperature regime than at 15ºC constant temperature. The results from analyses of leaf characteristics showed significant variation between species studied. Significant correlations were found between chromosome numbers of the species studied and some leaf characteristics, e.g. cell size, stomatal index. Plant growth analyses were investigated along an altitudmal gradient in the north of England. Both vegetative and reproductive growth was clearly affected by microclimate. The primulas showed more sensitive responses to drought than frost as regards to their survival. They responded to water stress by accumulating proline as well as increasing their total protein contents. Photosynthesis measurements showed optimum temperature for O(_2) evolution at warm temperatures of 20-25ºC. The difference in physiological performances of the primulas is discussed in relation to their leaf characteristics, ploidy levels and habitats of origin. This study demonstrates clearly that the two populations of P. farinosa differed in a number of morphological and physiological characteristics; some of which could make it possible for the different races to occupy different ecological habitats.

The hypothalamic-pituitary-adrenal (HPA) axis, or stress axis, is a key physiological system that mediates the relationship of the organism with its environment. Because activation of the HPA axis mobilizes energy stores for immediate use, but sustained activation can have deleterious effects on survival, the HPA axis has been implicated in the tradeoff between reproduction and survival. In this thesis, I investigate whether there is an association between one life history trait, reproductive lifespan, and the functioning of the HPA axis as predicted by the “adaptive stress hypothesis”. The adaptive stress hypothesis predicts that species adopting life history strategies characterized by short lifespans and early reproduction should maximize the energy available for reproduction through high levels of circulating glucocorticoids caused by the dysregulation of the HPA axis in the breeding season, whereas those characterized by long lifespans and extended reproduction should maintain a functioning HPA axis with low levels of glucocorticoids throughout life. To test this hypothesis, I studied five species of ground squirrels that vary dramatically in male reproductive lifespan: arctic, Richardson’s, Columbian, thirteen-lined, and Franklin’s ground squirrels (Urocitellus parryii, U. richardsonii, U. columbianus, Ictidomys tridecemlineatus, and Poliocitellus franklinii). I used a stress profile to characterize the HPA axis of male ground squirrels immediately before and immediately after the breeding season. The stress profile included measures of plasma glucocorticoid concentrations, determinants of plasma glucocorticoid concentrations (corticosteroid binding globulin levels, adrenal sensitivity/capacity, negative feedback, and intrinsic restraint), and markers of the biological effects of glucocorticoids (energy mobilization, health, and immune function). Contrary to the adaptive stress hypothesis, I found no relationship between reproductive lifespan and postbreeding glucocorticoid levels. Species also varied significantly and unexpectedly in how determinants of glucocorticoid levels changed over the breeding season, and in how glucocorticoids levels translated into biological effects. I also observed unexpected patterns of individual variation within species. Thus, life history alone did not predict HPA axis functioning. My results suggest that the HPA axis is so flexible in its functioning, that we will need to adopt a much more detailed model of the HPA axis in order to fully understand the relationship between the HPA axis and life history variation.

The hypothalamic-pituitary-adrenal (HPA) axis, or stress axis, is a key physiological system that mediates the relationship of the organism with its environment. Because activation of the HPA axis mobilizes energy stores for immediate use, but sustained activation can have deleterious effects on survival, the HPA axis has been implicated in the tradeoff between reproduction and survival. In this thesis, I investigate whether there is an association between one life history trait, reproductive lifespan, and the functioning of the HPA axis as predicted by the “adaptive stress hypothesis”. The adaptive stress hypothesis predicts that species adopting life history strategies characterized by short lifespans and early reproduction should maximize the energy available for reproduction through high levels of circulating glucocorticoids caused by the dysregulation of the HPA axis in the breeding season, whereas those characterized by long lifespans and extended reproduction should maintain a functioning HPA axis with low levels of glucocorticoids throughout life. To test this hypothesis, I studied five species of ground squirrels that vary dramatically in male reproductive lifespan: arctic, Richardson’s, Columbian, thirteen-lined, and Franklin’s ground squirrels (Urocitellus parryii, U. richardsonii, U. columbianus, Ictidomys tridecemlineatus, and Poliocitellus franklinii). I used a stress profile to characterize the HPA axis of male ground squirrels immediately before and immediately after the breeding season. The stress profile included measures of plasma glucocorticoid concentrations, determinants of plasma glucocorticoid concentrations (corticosteroid binding globulin levels, adrenal sensitivity/capacity, negative feedback, and intrinsic restraint), and markers of the biological effects of glucocorticoids (energy mobilization, health, and immune function). Contrary to the adaptive stress hypothesis, I found no relationship between reproductive lifespan and postbreeding glucocorticoid levels. Species also varied significantly and unexpectedly in how determinants of glucocorticoid levels changed over the breeding season, and in how glucocorticoids levels translated into biological effects. I also observed unexpected patterns of individual variation within species. Thus, life history alone did not predict HPA axis functioning. My results suggest that the HPA axis is so flexible in its functioning, that we will need to adopt a much more detailed model of the HPA axis in order to fully understand the relationship between the HPA axis and life history variation.

As animals age, they are expected to invest successively more energy in reproduction as they have fewer subsequent chances to reproduce (the “restraint” hypothesis). Conversely, the oldest animals may show restraint in reproduction because even a small increase in energy expended during reproduction may lead to death. Alternatively, both young and very old animals may lack the ability to maintain high levels of energy expenditure (the “constraint” hypothesis), leading to reduced reproductive success. Many studies have observed an increase in reproductive success with age followed by a reduction at the end of life, but fewer studies have examined the proximate mechanisms, which provide a context for understanding ultimate causes. I examined over 30 behavioural and physiological metrics of aging in two species of free-living long-lived seabirds (thick-billed murres Uria lomvia and black-legged kittiwakes Rissa tridactyla) and a short-lived passerine (tree swallows Tachycineta bicolor). For all species, reproductive success was high at intermediate ages. In support of the “restraint” hypothesis, when birds were stressed glucocorticoid hormones, which direct energy away from reproduction and towards survival, were higher in young birds (swallows) and both young and very old birds (kittiwakes and murres). When birds were handicapped older birds expended more energy. When challenged exogenously, there was no change in hormone levels with age, implying that they were “choosing” to be restrained. Resting metabolic rate (RMR) declined linearly with age in both seabird species. T3, which I show is indicative of RMR in birds, also declined with age, demonstrating that the reduction in metabolism was strategic and not due to changing body composition. In contrast, daily energy expenditure in both seabird species during breeding was constant with age while antioxidant capacity became elevated during middle age, and further increased with age. Several measures of behavioural performance did not vary with age. I conclude that hormonal cues lead to greater investment in adult’s energy stores over its offspring’s energy reserves (restraint hypothesis) at the start of life. At the end of life, both hypotheses were supported; energy expenditure was constrained by senescence, leading to increased restraint in investing additionally in offspring.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Although malaria remains a major public health concern, especially in sub-Saharan Africa, little information exists on the physiological tolerances of malaria vectors. Here, I aimed to provide a comprehensive set of physiological tolerances for Anopheles arabiensis and An. funestus, by investigating thermal tolerance traits of adults, larvae and pupae; desiccation resistance of adults and development rate-temperature relationships for both vectors. Critical thermal limit (CT) and desiccation data showed significant effects of increasing adult age on reducing tolerance to temperature or dry conditions. Females of both species were more tolerant of high or low temperatures in CT experiments and were more desiccation tolerant than males in desiccation trials. Anopheles funestus was more desiccation tolerant than An. arabiensis, despite the common misconception that An. arabiensis is the more arid-adapted of the two species. Comparisons between thermal tolerance traits of adult laboratory and wild strain progeny of both species indicated a high degree of similarity between critical thermal limits in wild and laboratory strains, suggesting that the use of laboratory populations of both mosquito strains can provide an accurate estimate of wild population responses to thermal change. Lethal temperature estimates for both vectors indicated a higher tolerance to high temperature in An. arabiensis larvae and pupae when compared with An. funestus, and a greater tolerance of high or low temperatures in adult females when compared with adult males. Species differences between the vectors were further highlighted in development rate-temperature experiments. Under fluctuating and constant temperatures, An. arabiensis developed significantly faster than An. funestus and had higher survival to the adult stage. Under fluctuating temperatures, An. arabiensis developed faster or no different to constant temperatures, while survival under fluctuating temperatures was also comparable to constant temperature estimates. This faster development rate of this species is likely a consequence of the puddle-breeding nature of An. arabiensis and the need to develop to adulthood before evaporation of breeding sites. Anopheles funestus on the other hand, showed reduced survival and development under fluctuating temperatures when compared with constant temperatures, probably as a result of the more thermally stable breeding sites usually used by this species. Distribution data of these species, combined with developmental parameters in a process-based distribution model, suggests that both species will show range changes in response to climate change. Areas where these species were previously only present on a seasonal basis might become more suitable for vector population establishment and persistence, while areas on the northern margins of current distributions will become less favourable, leading to an overall southerly shift in habitat suitability for both species. Increases in temperature and changes in rainfall patterns as predicted to occur with climate change are likely to impact the distribution of both malaria vectors. Combining the physiological tolerance data collected in this thesis in a future, planned mechanistic distribution model, will provide an accurate indication of potential range shifts of these vectors and hence, provide an indication of areas that may be at increased risk of malaria. / AFRIKAANSE OPSOMMING: Alhoewel malaria „n groot publieke gesondheidskwelling bly, veral in sub-Sahara Afrika, bestaan min inligting rakende die fisiologiese toleransies van malaria vektore. Hier het ek gepoog om 'n omvattende reeks van fisiologiese toleransies te voorsien vir Anopheles arabiensis en An. funestus, deur termiese verdraagsaamheidseienskappe, uitdrogingsweerstand en ontwikkelingstempo-temperatuur verhoudings vir beide vektore te ondersoek. Kritiese termiese limiet (CT) en uitdroging data het beduidende uitwerkings getoon van toenemende ouderdom op die vermindering van verdraagsaamheid teenoor temperatuur of droë toestande. Wyfies van beide spesies was meer verdraagsaam vir hoë of lae temperature in CT eksperimente en was meer verdraagsaam teenoor uitdroging as mannetjies in die uitdrogingsproewe. Anopheles funestus was meer verdraagsaam teenoor uitdroging as An. arabiensis, ten spyte van die algemene wanopvatting dat An. arabiensis die meer ariede aangepaste van die twee spesies is. Vergelykings tussen termiese verdraagsaamheidseienskappe van laboratorium-en wilde stamlyn nageslagte van beide spesies het 'n hoë mate van ooreenkoms tussen kritieke termiese limiete in wilde en laboratorium stamlyne aangedui, wat voorstel dat die gebruik van laboratorium bevolkings van beide muskiet stamlyne 'n akkurate skatting kan gee van wilde bevolkingsreaksies tot termiese verandering. Fatale temperatuur beramings vir beide vektore het „n hoër toleransie getoon by hoë temperature in An. arabiensis larwes en papies wanneer dit vergelyk word met An. funestus, en 'n groter verdraagsaamheid van hoë of lae temperature in wyfies, wanneer vergelyk word met mannetjies. Spesies verskille tussen die vektore is verder uitgelig in die ontwikkelingstempo-temperatuur eksperimente. Onder wisselende en konstante temperature ontwikkel An. arabiensis aansienlik vinniger as An. funestus en het hoër oorlewing tot die volwasse stadium getoon. Onder wisselende temperature ontwikkel An. arabiensis vinniger of met geen verskil van konstante temperature nie, terwyl oorlewing onder wisselende temperature ook vergelykbaar was met konstante temperatuur beramings. Die vinniger tempo van hierdie spesie is waarskynlik 'n gevolg van die poel-broeiende aard van An. arabiensis en die behoefte om tot volwassenheid te ontwikkel voor die verdamping van broeiplekke. Anopheles funestus aan die ander kant, het verminderde oorlewing en ontwikkeling onder wisselende temperature gewys wanneer dit vergelyk word met konstante temperature, waarskynlik as gevolg van die meer termies stabiele broeiplekke wat gewoonlik gebruik word deur hierdie spesie. Verspreidingsdata van hierdie spesies, gekombineer met ontwikkelings-parameters in 'n proses-gebaseerde verspreidingsmodel, dui daarop dat beide spesies reeks veranderinge sal wys in reaksie tot klimaatsverandering. Gebiede waar hierdie spesies voorheen slegs teenwoordig was op 'n seisoenale basis, mag dalk meer geskik word vir vektor bevolkingsvestiging en volharding, terwyl areas op die noordelike grense van die huidige verspreidings minder gunstig sal word, wat sal lei tot algehele suidelike verskuiwing in die habitat geskiktheid vir beide spesies. Toenames in temperatuur en veranderinge in reënvalpatrone, soos voorspel word om voor te kom met verandering van die klimaat, sal waarskynlik die verspreiding van malaria vektore beïnvloed. Deur die fisiologiese toleransie data, versamel in hierdie tesis, te kombineer met 'n toekoms, beplande meganistiese verspreidingsmodel, sal dit 'n akkurate aanduiding gee van die potensiële verspreidingsverskuiwings van hierdie vektore en dus 'n aanduiding gee van gebiede wat onder verhoogde risiko van malaria sal wees.

<p>Laser deterrents have been used as a method of deterring birds from problem areas such as fisheries, agricultural fields and airports. This method is considered a nonlethal means of control although lasers are known to cause visual lesions and loss of visual acuity in humans and other animals. Birds have a complex visual system which is necessary for behaviors critical to their survival, such as hunting and foraging, and predator vigilance. The purpose of this study is to determine the safety of laser deterrents for avian eyes using two species of birds: house sparrows (<i>Passer domesticus</i>) and European Starlings (<i>Sturnus vulgaris</i>). We found evidence that laser exposure can cause corneal edema, cataracts, retinal atrophy, displacement of the photoreceptor nuclei, and degeneration of the scleral cartilage. The laser exposure time was an important factor in the likelihood of developing corneal edema and retinal atrophy in starlings. Our findings suggest that lasers may not be completely safe for use as bird deterrents, but further research should be done to find possible solutions to improve laser safety from the avian viewpoint. </p>

<p> The net photosynthetic and dark respiration response to moisture, light level and temperature is discussed with reference to the unique Cladonia rangiferina (L.) Wigg.-Shrub association in Cladonia stellaris (Opiz.) Pouz. Spruce Woodland at Hawley Lake, Ontario. Field measurements provide a description of the summer and winter environmental complex. Winter data shows an exceptional thermal insulation afforded by snow cover, protecting lichen thalli from extreme air temperatures. Summer environmental data highlights the need to dissociate periods of thallus hydration (metabolic activity), and thallus dehydration in order that meaningful comparisons may be made with experimentally derived levels of metabolic activity. Experimentally derived physiology of the hydrated thallus showed a broad amplitude of tolerance to light level and temperature correlating with the wide range of temperature and light level experienced during a single thallus drying cycle in the field. Heat stress experiments illustrate this is indeed, a sensitive species restricted to the more ameliorated temperature regime of mature Spruce-Lichen Woodland. Heat sensitivity may also act to restrict C. rangiferina to the cooler micro-site afforded by the elevated shrub-hummocks.</p> <p> A spring to summer series of collections of a Muskoka population of C. rangiferina were coursed through heat stress experiments. Significant heat tolerance acclimation emerged as an essential response to withstand the high summer temperature regime.</p> / Thesis / Master of Science (MSc)

No description available.

Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye.