Browsing by Subject "Reproduction"

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Causes and consequences of alterations in stress physiology, immunity and oxygen delivery in a small mammalian hibernator
(2017) Havenstein, Nadine; Fietz, Joanna
The different functions and activities of an organism require substantial amounts of energy and thus compete for the limited available resources. During demanding situations, allocation decisions potentially result in trade-offs between physiological processes that can have consequences on the performance and fitness of an individual. Endocrine mediators, especially glucocorticoid hormones (GCs) build the bridge between environmental stimuli and the responses of an individual via regulating energy allocation and numerous other physiological processes as well as behavior and are therefore of special interest in ecophysiological studies. The immune and the oxygen delivery system represent two vital body functions that are essential for survival and respond sensitively to altered environmental conditions, nutrient deficiencies and stress hormone levels, representing therefore further suitable targets of investigation in ecophysiological studies. Our study species, the edible dormouse (Glis glis) is a small arboreal rodent characterized by an extraordinarily long hibernation period. The aim of this study was to elucidate physiological mechanisms underlying the evolution of life history strategies and variations in fitness parameters associated with stressful and demanding situations like hibernation, reproduction, limited food availability and high population density. To achieve these goals urinary GC levels as well as white and red blood cell (WBC and RBC) parameters were investigated and urine samples were examined for haemoglobinuria of free ranging edible dormice in South Western Germany. Results of this study reveal that the post-hibernation period represents an extremely challenging period for edible dormice as their phagocytic cells, the immunological first line of defense, obviously become depleted during the extended hibernation period and recover only slowly at the beginning of the active season. The need to invest into the restoration of regressed organs and body functions directly after hibernation when high quality food is still limited, may explain the delayed recovery of these innate immune cells. Slightly elevated cortisol levels presumably reflect the mobilization of energy from body stores for these restoration processes. As the phenomenon of low phagocyte counts was even more pronounced at the beginning of a low food year and the few neutrophils present in the blood of dormice were primarily immature, preparatory mechanisms occurring during late arousals of the hibernation period seem to determine the regeneration of phagocytes before hibernation is terminated. This, in turn, indicates that dormice are able to predict upcoming food availability and, consequently, future reproductive effort and accordingly invest into physical-physiological recovery. Apparently edible dormice trade off restoration of regressed organs for immunity. Survival probabilities of edible dormice are lowest at that time of the annual cycle, suggesting that this post-hibernation impairment of the innate immune system may entail detrimental effects for their fitness. Elevated cortisol levels during mating and gestation-lactation, respectively, show that reproduction represents a stressful life history event in both sexes. This event furthermore coincides with drastic increases in the ratio of phagocyte to lymphocyte counts (P/L ratio), a stress response of the immune system, as well as distinct impairments in the oxygen delivery system. The latter seems to be in a large part due to energetic and nutrient deficits and large amounts of senescent RBCs. High frequency of haemoglobinuria in females support the notion of a nutrient-deficient anaemia. When all reproductive effort has ended, cortisol levels decrease whereas the strong increases in the P/L ratio persist until the end of the active season which gives notice of the prolonged immunological effects of chronic stress. As mortality is increased during reproductive years, the high cortisol levels measured during reproduction suggest an allostatic overload that has exceeded adaptive levels and the high P/L ratios might represent a pivotal indicator for the beginning of a stress-induced deprivation of immunity that contribute to reduced survival. Prolonged food limitation does not elevate cortisol levels and P/L ratios, supporting the hypothesis that food availability is predictable for edible dormice and that a restriction therefore does not cause considerable stress. During late summer of a low food year the oxygen delivery capacity is decreased. However, erythrocyte parameters furthermore indicate a senescent RBC pool, suggesting that a reduced erythrocyte production is part of the energy saving strategy. As survival is increased during years of low food availability, these findings indicate that dormice are able to perfectly adapt to prolonged periods of limited food availability.
Influence of ambient temperature on the phenology of the greater mouse‐eared bat (Myotis myotis)
(2023) Matthäus, Laura; Kugelschafter, Karl; Fietz, Joanna
In order to assess the consequences of climate change and evaluate its impacts on wildlife, it is essential to do so on a species-specific level. It is assumed that changes in the ambient temperature influence energy consumption as well as food availability and thus foraging behavior, reproduction, survival, and therefore population dynamics in bats. Based on this assumption, the present study aims to gain insights into the roosting and breeding behavior of the greater mouse-eared bat (Myotis myotis) in relation to changes of the ambient temperature. For this purpose, we investigated the effect of ambient temperature on the phenology of the greater mouse-eared bat by using activity data of the bats collected using light barriers at the maternity roosts. The light barrier used in this study is a system that detects the interruption of two light beams, for example, by a flying bat, and displays it as an electrical signal. The investigations have shown that 1. the higher the winter temperatures, the earlier the greater mouse-eared bats returned to the roosts to form the maternity colony; however, this was only true for ambient temperatures below 0.5°C, 2. birth season started earlier at higher spring temperatures, 3. the dissolution of maternity roosts occurred earlier with earlier birth season and at higher ambient temperatures during lactation. The results revealed that ambient temperature has an influence on the phenology of the greater mouse-eared bat. Depending on the respective life history stage, an increase in ambient temperature can have a positive or negative effect on the fitness of the animals. In recent years, mild winters have been recorded more frequently, which can have an influence on the behavior of bats. Warm winters within certain limits seem to lead to an earlier formation of the maternity colony, which can be positive or negative for the bats depending on persistent weather conditions and thus insect availability. In the course of climate change, we can also expect earlier spring events and an increase in spring temperature, as well as hot spells in summer. These warm springs and summers seem to lead to an earlier beginning of births, a faster development of the juveniles and an earlier dissolution of the maternity roost. An advance of reproductive activities can be assumed to increase the chance to survive the following winter in both mothers and their young, as they have more time to build up sufficient energy reserves for hibernation before winter starts. Due to the climatic changes, phenological changes of the bats be expected. This study highlights that in order to understand the impact of climate change on biodiversity, it is necessary to investigate in detail effects on a species-specific level and also to consider direct and indirect effects of ambient temperature on different life history stages.
Saponin fractions from fenugreek (Trigonella foenum-graecum L.)as dietary supplements for Nile tilapia (Oreochromis niloticus L.)and common carp (Cyprinus carpio L.)
(2012) Stadtlander, Timo; Focken, Ulfert
The future role and importance of aquaculture for the world food supply is more and more recognized by the public. High quality feed for semi-intensive and intensive aquaculture operations are necessary to guarantee a future continuous growth of fish production. Nutrient utilization efficiency has in the past been augmented by addition of feed additives, mainly anti-biotics and hormones. That practice is prohibited in the European Union since 1st of January 2006 and the consumer acceptance of products produced in that way is low. Around a decade ago saponins, secondary plant metabolites, have been found to be potential alternatives for aquafeeds. Saponinmixtures derived from the South American soap bark tree Quillaja saponaria, have been found to have beneficial effects on growth, feed and nutrient utilization and on metabolism of common carp Cyprinus carpio and Nile tilapia Oreochromis niloticus. Furthermore, in one of the early experiments a sex ratio in favor of males was observed in saponin fed tilapia compared to control fish not supplemented with saponins. An influence on sex ratio of Nile tilapia would be highly desirable since industrially Nile tilapia production is only financially viable if all male populations are produced since mixed sex tilapia populations tend to reproduce uncontrollable. The production of all male tilapia populations is mainly conducted by feeding the potentially environmentally hazardous and carcinogenic synthetic hormone 17--methyltestosterone to sexually undeveloped tilapia fry. The above mentioned problems led to a joint research project with partners in Israel and Palestine in which this dissertation has been conducted. The aim of the project was the fractionation of crude saponin extract derived from fenugreek Trigonella foenum-graecum and its testing in vitro and in vivo. It was assumed that a higher biological activity could be achieved if saponin fractions instead of crude mixtures would be applied. After in vitro testing, different saponin fractions or eluates, have been tested on their effects on growth, feed and nutrient utilization, metabolism, proximate composition, gene expression of GH and IGF-1, sex ratio, reproduction and gonad histology. Most of the feeding experiments were conducted with Nile tilapia but one experiment was also conducted with carp. Three of the feeding experiments have been conducted in a system capable of measuring continuous respiration of the fish. Another experiment has been conducted at a field station at Jericho, Palestine. The experiments conducted to evaluate the influence of saponin fractions on sex ratio of undifferentiated tilapia fry have been conducted primarily in a flow-through system. The tested saponin fractions and a tested sapogenin are not suitable to produce male monosex tilapia populations. The sex ratios after supplementation of diets of mixed sexed tilapia fry did only in one case show a significantly higher proportion of males than the control. In a larger scale repetition of that experiment the previous observations could statistically not be proofed. It must be assumed to be random effects or be the result of initially biased sex ratios after stocking undifferentiated tilapia fry. An experiment in which genetically female tilapias were fed with two fenugreek saponin fractions and positive and negative controls supported that finding. A long term feeding experiment conducted at Jericho revealed no influence of the long and short term supplemented Q. saponaria saponin mixtures on sex ratio and reproduction of genetically female tilapia. A similar laboratory experiment with fenugreek saponin fractions could not be evaluated in that regard. The experiments evaluating the effects of the saponin fractions on growth, feed and nutrient utilization, gene expression of GH and IGF-1 and proximate composition revealed no significant differences. But in all experiments one fraction eluated with 60%/40% (v/v) methanol/water showed numerically improved values compared to control and other fractions. Furthermore one fraction eluated with 40%/60%/ (v/v) methanol/water gave constantly numerically inferior results of tested parameters compared to control. That supports the conclusion that the 40% methanol fraction contains saponins generally referred to as anti-nutrients. In only one experiment, conducted at Jericho, significantly higher growth was observed after long term supplementation with a Q. saponaria saponin mixture containing elevated sapogenin content. The presented data in this thesis is not supporting an application of the tested saponin fractions as environmentally friendly alternative to methyltestosterone to produce all male populations of tilapia or to inhibit uncontrollable reproduction. Additional experiments are needed to evaluate different modes of application like immersion treatments or injections since during the experimental work of this thesis all tested saponins were added to the feed. An application of the tested fenugreek saponin fractions as growth promoters yields a higher potential although the experimental results are based upon low sample sizes due to capacity restrictions of the respirometric system. Therefore a repetition under near commercial or commercial conditions must be considered.
Season and reproductive activity influence cortisol levels in the Malagasy primate Lepilemur edwardsi
(2022) Bethge, Janina; Fietz, Joanna; Razafimampiandra, Jean Claude; Ruthsatz, Katharina; Dausmann, Kathrin H.
Throughout the year, wild animals are exposed to a variety of challenges such as changing environmental conditions and reproductive activity. These challenges may affect their stress hormone levels for varying durations and in varying intensities and impacts. Measurements of the glucocorticoid hormone cortisol in the hair of mammals are considered a good biomarker for measuring physiological stress and are increasingly used to evaluate stress hormone levels of wild animals. Here, we examined the influence of season, reproductive activity, sex, as well as body condition on hair cortisol concentrations (HCC) in Lepilemur edwardsi, a small Malagasy primate species. L. edwardsi lives in the seasonal dry forests of western Madagascar, which are characterized by a strongly changing resource availability throughout the year. We hypothesized that these seasonal changes of resource availability and additionally the reproductive cycle of this species would influence HCC of L. edwardsi. Results revealed that hair cortisol concentration of females did not change seasonally or with the reproductive cycle. However, we found a significant increase of hair cortisol levels in males from the early wet season during the early dry season (mating season). This increase is presumably due to changed behavior during the mating season, as sportive lemurs travel more and show aggressive behavior during this time of the year. This behavior is energy‐costly and stressful, and presumably leads to elevated HCC. As elevated cortisol levels may impair immune function, L. edwardsi males might also be more susceptible to parasites and diseases, which is unfavorable in particular during a period of low resource availability (dry season).