Gulf War Illness (GWI) is a multi‐symptom disorder with features characteristic of persistent sickness behavior. Among conditions encountered in the Gulf War (GW) theater were physiological stressors (e.g., heat/cold/physical activity/sleep deprivation), prophylactic treatment with the reversible AChE inhibitor, pyridostigmine bromide (PB), the insect repellent, N,N‐diethyl‐meta‐toluamide (DEET), and potentially the nerve agent, sarin. Prior exposure to the anti‐inflammatory glucocorticoid, corticosterone (CORT), at levels associated with high physiological stress, can paradoxically prime the CNS to produce a robust proinflammatory response to neurotoxicants and systemic inflammation; such neuroinflammatory effects can be associated with sickness behavior. Here, we examined whether CORT primed the CNS to mount neuroinflammatory responses to GW exposures as a potential model of GWI. Male C57BL/6 mice were treated with chronic (14 days) PB/ DEET, subchronic (7–14 days) CORT, and acute exposure (day 15) to diisopropyl fluorophosphate (DFP), a sarin surrogate and irreversible AChE inhibitor. DFP alone caused marked brain‐wide neuroinflammation assessed by qPCR of tumor necrosis factor‐α, IL6, chemokine (C‐C motif) ligand 2, IL‐1β, leukemia inhibitory factor, and oncostatin M. Pre‐treatment with high physiological levels of CORT greatly augmented (up to 300‐fold) the neuroinflammatory responses to DFP. Anti‐inflammatory pre‐treatment with minocycline suppressed many proinflammatory responses to CORT+DFP. Our findings are suggestive of a possible critical, yet unrecognized interaction between the stressor/environment of the GW theater and agent exposure(s) unique to this war. Such exposures may in fact prime the CNS to amplify future neuroinflammatory responses to pathogens, injury, or toxicity. Such occurrences could potentially result in the prolonged episodes of sickness behavior observed in GWI.
The behavior of many wild animals remains a mystery, as it is difficult to quantify behavior of species that cannot be easily followed throughout their daily or seasonal movements. Accelerometers can solve some of these mysteries, as they collect activity data at a high temporal resolution (<1 s), can be relatively small (<1 g) so they minimally disrupt behavior, and are increasingly capable of recording data for long periods. Nonetheless, there is a need for increased validation of methods to classify animal behavior from accelerometers to promote widespread adoption of this technology in ecology. We assessed the accuracy of six different behavioral assignment methods for two species of seabird, thick‐billed murres (Uria lomvia) and black‐legged kittiwakes (Rissa tridactyla). We identified three behaviors using tri‐axial accelerometers: standing, swimming, and flying, after classifying diving using a pressure sensor for murres. We evaluated six classification methods relative to independent classifications from concurrent GPS tracking data. We used four variables for classification: depth, wing beat frequency, pitch, and dynamic acceleration. Average accuracy for all methods was >98% for murres, and 89% and 93% for kittiwakes during incubation and chick rearing, respectively. Variable selection showed that classification accuracy did not improve with more than two (kittiwakes) or three (murres) variables. We conclude that simple methods of behavioral classification can be as accurate for classifying basic behaviors as more complex approaches, and that identifying suitable accelerometer metrics is more important than using a particular classification method when the objective is to develop a daily activity or energy budget. Highly accurate daily activity budgets can be generated from accelerometer data using multiple methods and a small number of accelerometer metrics; therefore, identifying a suitable behavioral classification method should not be a barrier to using accelerometers in studies of seabird behavior and ecology. 相似文献
Variation in somatic growth rates is of great interest to biologists because of the relationship between growth and other fitness‐determining traits, and it results from both genetic and environmentally induced variation (i.e. plasticity). Theoretical predictions suggest that mean somatic growth rates and the shape of the reaction norm for growth can be influenced by variation in predator‐induced mortality rates. Few studies have focused on variation in reaction norms for growth in response to resource availability between high‐predation and low‐predation environments. We used juvenile Brachyrhaphis rhabdophora from high‐predation and low‐predation environments to test for variation in mean growth rates and for variation in reaction norms for growth at two levels of food availability in a common‐environment experiment. To test for variation in growth rates in the field, we compared somatic growth rates in juveniles in high‐predation and low‐predation environments. In the common‐environment experiment, mean growth rates did not differ between fish from differing predation environments, but the interaction between predation environment and food level took the form of a crossing reaction norm for both growth in length and mass. Fish from low‐predation environments exhibited no significant difference in growth rate between high and low food treatments. In contrast, fish from high‐predation environments exhibited variation in growth rates between high and low food treatments, with higher food availability resulting in higher growth rates. In the field, individuals in the high‐predation environment grow at a faster rate than those in low‐predation environments at the smallest sizes (comparable to sizes in the common‐environment experiment). These data provide no evidence for evolved differences in mean growth rates between predation environments. However, fish from high‐predation environments exhibited greater plasticity in growth rates in response to resource availability suggesting that predation environments may exhibit increased variation in food availability for prey fish and consequent selection for plasticity. 相似文献
The use of miniaturized video cameras to study the at‐sea behavior of flying seabirds has increased in recent years. These cameras allow researchers to record several behaviors that were not previously possible to observe. However, video recorders produce large amounts of data and videos can often be time‐consuming to analyze. We present a new technique using open‐source software to extract bank angles from bird‐borne video footage. Bank angle is a key facet of dynamic soaring, which allows albatrosses and petrels to efficiently search vast areas of ocean for food. Miniaturized video cameras were deployed on 28 Wandering Albatrosses (Diomedea exulans) on Marion Island (one of the two Prince Edward Islands) from 2016 to 2018. The OpenCV library for the Python programming language was used to extract the angle of the horizon relative to the bird’s body (= bank angle) from footage when the birds were flying using a series of steps focused on edge detection. The extracted angles were not significantly different from angles measured manually by three independent observers, thus being a valid method to measure bank angles. Image quality, high wind speeds, and sunlight all influenced the accuracy of angle estimates, but post‐processing eliminated most of these errors. Birds flew most often with cross‐winds (58%) and tailwinds (39%), resulting in skewed distributions of bank angles when birds turned into the wind more often. Higher wind speeds resulted in extreme bank angles (maximum observed was 94°). We present a novel method for measuring postural data from seabirds that can be used to describe the fine‐scale movements of the dynamic‐soaring cycle. Birds appeared to alter their bank angle in response to varying wind conditions to counter wind drift associated with the prevailing westerly winds in the Southern Ocean. These data, in combination with fine‐scale positional data, may lead to new insights into dynamic‐soaring flight. 相似文献
A partial skeleton of the early Eocene tropicbird Prophaethon shrubsolei (Prophaethontidae) from the London Clay of Walton‐on‐the‐Naze (UK) is described. Most of the bones preserved in this fossil have not been described previously for Prophaethon or prophaethontids in general. The pelvis and leg bones of Prophaethon, including the previously unknown tarsometatarsus, are very different from modern tropicbirds and show a strong similarity to procellariiform birds, especially albatrosses. Rather than employing plunge‐diving like their extant relatives, prophaethontids therefore probably used foraging strategies similar to those of modern albatrosses, which seize food on the sea surface. Prophaethontids also appear to have been less pelagic than extant tropicbirds, and these different life modes, as well as the disappearance of Phaethontiformes from northern latitudes, attest to major changes in Northern Hemispheric marine avifaunas during the Cenozoic, which also affected other pelagic birds. The reasons for the profound changes in the historical biogeography and way of living of tropicbirds are unknown, but ecological competition and predation at breeding sites are likely to have played a role. 相似文献
Understanding how animals utilize their habitat provides insights about their ecological needs and is of importance for both theoretical and applied ecology. As changing seasons impact prey habitat selection and vegetation itself, it is important to understand how seasonality impacts microhabitat choice in optimal foragers and their prey. We followed habituated bat‐eared foxes (Otocyon megalotis) in the Kalahari, South Africa, to study their seasonal habitat selection patterns and relate them to the habitat preferences of their main prey, termites (Hodotermes mossambicus). We used Resource Selection Functions (RSFs) to study bat‐eared foxes’ 3rd‐ and 4th‐order habitat selection by comparing used locations to random ones within their home ranges. Third‐order habitat selection for habitat type and composition was weak and varied little between seasons. We found that patterns of fox habitat selection did not mirror habitat selection of Hodotermes (quantified using RSFs), even when feeding on them (4th‐order). Taken together, these results might indicate that bat‐eared foxes’ food resources are homogenously distributed across habitats and that prey other than Hodotermes play an important role in bat‐eared foxes’ space use. 相似文献
Although Balamuthia mandrillaris was identified more than two decades ago as an agent of fatal granulomatous encephalitis in humans and other animals, little is known about its ecological niche, biological behavior in the environment, food preferences and predators, if any. When infecting humans or other animals, Balamuthia feeds on tissues; and in vitro culture, it feeds on mammalian cells (monkey kidney cells, human lung fibroblasts, and human microvascular endothelial cells). According to recent reports, it is believed that Balamuthia feeds on small amebae, for example, Acanthamoeba that are present in its ecological niche. To test this hypothesis, we associated Balamuthia on a one‐on‐one basis with selected protozoa and algae. We videotaped the behavior of Balamuthia in the presence of a potential prey, its ability to hunt and attack its food, and the time required to eat and cause damage to the target cell by direct contact. We found that B. mandrillaris ingested trophozoites of Naegleria fowleri, Naegleria gruberi, Acanthamoeba spp., Trypanosoma cruzi epimastigotes, Toxoplasma gondii tachyzoites, and Giardia. However, it did not feed on Acanthamoeba cysts or algae. Balamuthia caused cytolysis of T. cruzi epimastigotes and T. gondii tachyzoites by direct contact. Balamuthia trophozoites and cysts were, however, eaten by Paramecium sp. 相似文献
The upstream migration of juvenile amphidromous shrimps has been proposed as a source of marine or estuarine‐derived nutrients into fresh water. Little is known about the size and ecological importance of any such subsidy as there have been few observational or empirical studies on the topic.
We investigated the upstream migration of the amphidromous shrimp, Macrobrachium spinipes (Palaemonidae) in the Daly River, of tropical northern Australia, to determine migration phenology, estimate migration biomass and determine whether migrating shrimps transport marine‐derived energy and nutrients upstream.
Field observations over 2 years revealed that juvenile M. spinipes migrate upstream en masse during extended periods of declining discharge over a period of 4–6 weeks during the wet season (March–May). In addition, juvenile atyid shrimps from the genus Caridina were also observed migrating upstream during the same period.
Fine‐scale sampling using fyke nets over 2 years (2013 and 2014) consistently found discharge to be the strongest predictor of M. spinipes and Caridina spp. biomass, while moon illumination and cloud cover were also important predictors. An estimated 10–20 million shrimps migrated upstream during each wet season, transporting c. 100 kg of carbon and c. 28 kg of nitrogen per year.
Muscle sulphur stable isotopes (δ34S) and exoskeleton strontium isotope ratios (87Sr/86Sr) were used to establish if marine carbon was transported upstream by the juvenile M. spinipes. Isotope data from migratory M. spinipes were compared to the non‐migratory freshwater Macrobrachium bullatum. No evidence of a marine signature in body tissue or exoskeleton was found using either technique, suggesting very rapid turnover of body tissues
This study provides key insights into the migration phenology of amphidromous shrimps and, importantly, suggests that migrating M. spinipes do not transport significant amounts of marine‐derived energy and nutrients across the marine/freshwater ecotone.
Intraspecific variation is central to our understanding of evolution and population ecology, yet its consequences for community ecology are poorly understood. Animal personality – consistent individual differences in suites of behaviours – may be particularly important for trophic dynamics, where predator personality can determine activity rates and patterns of attack. We used mesocosms with aquatic food webs in which the top predator (dragonfly nymphs) varied in activity and subsequent attack rates on zooplankton, and tested the effects of predator personality. We found support for four hypotheses: (1) active predators disproportionately reduce the abundance of prey, (2) active predators select for predator‐resistant prey species, (3) active predators strengthen trophic cascades (increase phytoplankton abundance) and (4) active predators are more likely to cannibalise one another, weakening all other trends when at high densities. These results suggest that intraspecific variation in predator personality is an important determinant of prey abundance, community composition and trophic cascades. 相似文献
Humic lakes with a high external supply of DOC and low input of nutrients can often support a high biomass of metazoan zooplankton. In such lakes, autotrophic algae compete with bacteria for inorganic nutrients, but bacteria support mixotrophic growth. Consequently, planktonic communities are often dominated by mixotrophic flagellates, while obligate autotrophic phytoplankton occurs in low numbers for extended periods.
To test the importance of autotrophic phytoplankton and mixotrophic flagellates as food resources for metazoan grazers and, in turn, the feedback effects of grazers on basal food‐web interactions, we conducted a long‐term experiment where we simulated abiotic resource relationships of humic lakes (high DOC [glucose] and low P input). We examined the population dynamics of Daphnia galeata when inoculated in systems with autotrophic algae only, mixotrophic algae only and a mixture of autotrophic and mixotrophic algae, and how the systems changed after the inoculation of Daphnia. All combinations were run at high‐ and low‐light conditions to analyse the effects of light on food quantity and quality.
Daphnia grew to high densities only when mixotrophs were present at high‐light conditions and showed no or only weak growth at low‐light conditions or with autotrophs as the only food source.
Autotrophic algae and bacteria showed a strong competition for nutrients. Autotrophic algae were released from competition for nutrients after Daphnia grazed on bacteria, which led to a probable change of the bacteria community to less edible but less competitive taxa. As a consequence, there was a mutualistic interaction between autotrophs and mixotrophs before Daphnia were introduced which turned into competition after Daphnia inoculation.
We suggest that mixotrophic flagellates can be a critical resource for cladocerans and thereby also have a cascading effect on higher trophic levels, and cladocerans, in turn, have important indirect effects on basal planktonic food webs; hence, both might affect whole lake ecosystems.
Geographical variation in two related seabird species, the razorbill (Alca torda) and common guillemot (Uria aalge), was investigated using sequence analysis of mitochondrial DNA (mtDNA) control regions. We determined the nucleotide sequence of the variable 5' segment of the control region in razorbills and common guillemots from breeding colonies across the Atlantic Ocean. The ecology and life history characteristics of razorbill and common guillemot are in many respects similar. They are both considered highly philopatric and have largely overlapping distributions in temperate and subarctic regions of the North Atlantic, yet the species were found to differ widely in the extent and spatial distribution of mtDNA variation. Moreover, the differences in genetic differentiation and diversity were in the opposite direction to that expected from a consideration of traditional classifications and current population sizes. Indices of genetic diversity were highest in razorbill and varied among colonies, as did genotype frequencies, suggestive of restrictions to gene flow. The distribution of genetic variation suggests that razorbills originated from a refugial population in the south-western Atlantic Ocean through sequential founder events and subsequent expansion in the east and north. In common guillemots, genetic diversity was low and there was a lack of geographical structure, consistent with a recent population bottleneck, expansion and gene flow. We suggest that the reduced level of genetic diversity and differentiation in the common guillemot is caused by an inherent propensity for repeated population bottlenecks and concomitantly unstable population structure related to their specialized feeding ecology. 相似文献
Nutrient enrichment is a key stressor of lakes and streams globally, affecting the relative availability of important basal resources such as algae and detritus. These effects are controlled by responses of autotrophic and heterotrophic microorganisms that subsequently affect primary consumers and higher level predators. Despite the potential for propagation of these bottom‐up effects, few studies have examined how nutrients affect “green” (autotrophic) versus “brown” (heterotrophic) energy pathways to predators via changes in the quantity or type of prey consumed.
We studied the pathways by which nutrient enrichment affected two predatory salamander species (Desmognathus quadramaculatus and Eurycea wilderae) using detailed diet analyses before and during 2‐year nutrient additions to five headwater forest streams. The streams were continuously enriched with different concentrations of dissolved nitrogen (N) and phosphorus (P), creating relatively greater N or P concentrations and distinct N:P ratios (2:1, 8:1, 16:1, 32:1 and 128:1) in each stream.
Nutrient addition resulted in greater prey number, size and biomass consumed by D. quadramaculatus, an effect driven more by P than by N additions. Some of these effects were greater in the second year of enrichment and were greater for larger individuals. Shifts in the prey composition of D. quadramaculatus included increases in algivores and decreases in detritivores, tracking observed treatment effects on basal resource quantity (e.g. algivore abundance in guts was related to algal biomass, which increased with enrichment, and detritivore abundance in guts was related to detrital standing stocks, which declined with enrichment). For E. wilderae diets, there was limited evidence for increased prey size and number, or for alteration of prey composition with enrichment despite evidence of increased larval growth. We hypothesise that body size differences between the two salamander species partially explain their different dietary responses to enrichment.
Our results show that nutrient addition, primarily of P, affected the quantity and composition of predator diets in our nutrient‐poor streams. These effects on diet were consistent with concurrent studies showing that P enrichment resulted in faster growth of salamanders and occurred partly via effects on algal biofilm or “green” food‐web pathways, despite the dominance of detrital or “brown” resources in our heavily shaded forest stream sites. Thus, nutrient enrichment can promote algae‐ versus detritus‐based energy‐flow pathways in nominally light‐limited stream ecosystems, with associated changes in food‐web characteristics and function.
To evaluate mannan oligosaccharide (MOS) and threonine effects on performance, small intestine morphology and Salmonella spp. counts in Salmonella Enteritidis‐challenged birds.
Methods and Results
One‐day‐old chicks (1d) were distributed into five treatments: nonchallenged animals fed basal diet (RB‐0), animals fed basal diet and infected with Salmonella Enteritidis (RB‐I), animals fed high level of threonine and infected (HT‐I), birds fed basal diet with MOS and infected (MOS‐I), birds fed high level of threonine and MOS and infected (HT+MOS‐I). Birds were inoculated at 2d with Salmonella Enteritidis, except RB‐0 birds. Chicks fed higher dietary threonine and MOS showed performance similar to RB‐0 and intestinal morphology recovery at 8 dpi. Salmonella counts and the number of Salmonella‐positive animals were lower in HT+MOS‐I compared with other challenged groups.
Conclusion
Mannan oligosaccharides and threonine act synergistically, resulting in improved intestinal environment and recovery after Salmonella inoculation.
Significance and Impact of the Study
Nutritional approaches may be useful to prevent Salmonella infection in the first week and putative carcass contamination at slaughter. This is the first report on the possible synergistic effect of mannan oligosaccharides and threonine, and further studies should be performed including performance, microbiota evaluation, composition of intestinal mucins and immune assessment. 相似文献
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