1,721,025 research outputs found
Determining the upper thermal tolerance of Athabasca Rainbow Trout (<i>Oncorhynchus mykiss</i>) across naturally varying stream temperatures.
Get PDFStream temperature is a key driver of physiological function in ectothermic fish, and fish have clear upper and lower limits to thermal habitat use. Stream temperature increases from climate change are a major threat to coldwater taxa like Athabasca Rainbow Trout (Oncorhynchus mykiss), listed as Endangered under Canada's Species at Risk Act. To better understand their vulnerability to climate change and prioritize recovery locations, Athabasca Rainbow Trout were collected in August 2021 from three streams in the upper Athabasca River, Alberta, Canada, across a gradient of thermal regimes ranging from cold to warm. Individual thermal tolerance was measured using two physiological metrics: agitation temperature (Tag) and critical thermal maxima (CTmax) using a portable streamside laboratory. Tag is a behavioural indicator of a thermal avoidance threshold, whereas CTmax is a physiological response that can be interpreted as the upper thermal limit where long term survival is reduced. Results provide strong evidence that CTmax is a plastic metric in Athabasca Rainbow Trout; however, Tag is not. This suggests that Athabasca Rainbow Trout demonstrate some thermal plasticity in terms of CTmax, yet the lack of plasticity in Tag indicates potential limitations in their adaptability to warming stream temperatures
Threat-sensitive learning and generalization of predator recognition by aquatic vertebrates
Get PDFMany prey species lack innate recognition of their potential predators. Hence, learning is required for them to recognize and respond to predation threats. When wild-caught, these same species may show amazing sophistication in their responses to predator cues. They are able to adjust the intensity of their antipredator responses to a particular predator according to the degree of threat posed by that predator. This ability is therefore acquired through learning. While many studies have shown that prey can learn to respond to predator cues through different learning modes, little is known about what the prey are actually learning. The results presented in this thesis show that learned predator recognition goes beyond the simple labelling of predators as dangerous. Using fathead minnows (Pimephales promelas), woodfrog (Rana sylvatica) tadpoles and boreal chorus frog (Pseudacris maculata) tadpoles, I demonstrated that a one time learning event, either through pairing with alarm cues or through social learning, was enough for prey to learn the level of threat associated with the novel predator cues. I showed that the level of danger associated with the predator cues was determined by the concentration of alarm cues when learning through pairing of alarm cues, or by the intensity of antipredator response displayed by the tutors and by the tutor-to-observer ratio when learning occurred through cultural transmission. Moreover, when subsequently exposed to predator cues, prey adjusted their antipredator responses according to the change in concentration of predator cues between the learning event and the subsequent exposure. Prey displayed stronger antipredator responses when exposed to higher concentrations of predator cues and vice versa. When minnows were provided with conflicting information about the danger level associated with a predator, they displayed a safety strategy and used the most recent information available to respond to predation threats. On a longer time scale, the data also suggest that woodfrog tadpoles are able to learn to respond to predation threats according to the risk posed by the predator at different times of day. Finally, I showed that prey learn to recognize particular characteristics of predators and can generalize their antipredator responses to novel species sharing those characteristics. However, generalization of predator recognition is dependent on the level of risk associated with the predator. Threat-sensitive learning is an extremely complex process shaped by the millions of years of selection imposed by predators on prey
The Effects of noise of Zebrafish (Danio rerio) memory
Get PDFAbstract
Ever since the start of the industrial revolution anthropogenic disturbances have increased in severity. Anthropogenic noise is one such example, which has deleterious effects on organisms in both terrestrial and aquatic habitats. The range of effects may vary from interruptions in behavioural functions such as communication, feeding, breeding, and prey-predator interactions to physiological alterations in hormones levels or even severe damages to internal organs. In this study, I investigated the effects of white noise on the cognitive performance of zebrafish (Danio rerio) and its possible mechanism of action, focusing on GABA neurotransmitter levels in the brain. To this end, adult zebrafish were exposed to four sound treatments: a medium intensity sound presented in either a regular and irregular pattern, or a high intensity sound presented with either a regular or irregular pattern for 30 min. Subsequently, alterations in cognitive performance were evaluated using a plus maze associative learning paradigm and novel object recognition paradigm. The first experiment results showed a significant drop in the total travelling distance in noise-exposed treatments compared to controls without supplementary noise. Moreover, in the noise treatments, there was a trend towards fewer visits to the target arm of the maze in comparison to the control group. Although the total time spent in the target arm among noise-exposed treatments was significantly different compared to control, only the High-Irregular treatment was significantly different from the Medium-Regular and High-Regular treatments. In the second test, no significant difference was observed in the total travelling distance except for Medium-Irregular and High-Irregular groups that showed reduced movement. Fish in the High-Irregular treatment had the lowest visiting frequency and accumulated time around the novel object, and the highest latency to visit the novel object, which can be an indicator of developing neophobia in this group. Furthermore, the High-Irregular treatment had a significant difference compared to other noise-exposed treatments. The noise intensity and predictability did not reveal a significant difference between treatments. However, slight changes were noticeable in some of the behavioural variables. Our results indicated that noise exposure can affect zebrafish performance, and different patterns of noise may result in different outcomes. However, whether these changes are the results of a direct effect of noise on memory requires more studies
SOUND BITES: THE IMPACT OF BOAT NOISE ON FRESHWATER FISH
Get PDFNoise pollution is rapidly becoming more prevalent on a global scale, yet it is one of the least studied anthropogenic disturbances. Sound has low attenuation in water where it travels five times further than it does in air. Such effects, coupled with the wide spatial and temporal distribution of anthropogenic noise, makes noise pollution a major concern for aquatic species that may lack refuge from this modern-day stressor.
This thesis explores how boat noise impacts freshwater fish behaviour and is divided between a lab and field experiment. The lab experiment investigated how fathead minnow and brook char’s anti-predator responses to a looming stimulus was influenced by play-back tracks. Tracks were either recordings of boat noise from different distances (100, 250, 500 and 1000 m) or ambient lake recordings for our control. The field experiment looked at how yellow perch’s oxygen consumption, or stress level, was influenced by exposure to boat noise at different distances away from the running motor (same distances as lab experiment) compared to ambient lake noises.
The results from our field experiment showed generally that the closer the boat was to the yellow perch, the more stressed the individual was. Furthermore, the majority of the fish exposed to boat noise at any distance used significantly more DO (dissolved oxygen) compared to individuals that were only exposed to ambient lake noises. In contrast, the lab experiment showed no evidence that boat noise influenced fathead minnow or brook char anti-predator responses; however, use of pre-recorded tracks in the laboratory may minimize effects. Future research needs to continue to understand how to use play-back tracks in a lab setting to create more ecologically relevant conditions. This research adds to the limited literature on how anthropogenic noise is influencing freshwater species
The Effects of noise of Zebrafish (Danio rerio) memory
No full textAbstract
Ever since the start of the industrial revolution anthropogenic disturbances have increased in severity. Anthropogenic noise is one such example, which has deleterious effects on organisms in both terrestrial and aquatic habitats. The range of effects may vary from interruptions in behavioural functions such as communication, feeding, breeding, and prey-predator interactions to physiological alterations in hormones levels or even severe damages to internal organs. In this study, I investigated the effects of white noise on the cognitive performance of zebrafish (Danio rerio) and its possible mechanism of action, focusing on GABA neurotransmitter levels in the brain. To this end, adult zebrafish were exposed to four sound treatments: a medium intensity sound presented in either a regular and irregular pattern, or a high intensity sound presented with either a regular or irregular pattern for 30 min. Subsequently, alterations in cognitive performance were evaluated using a plus maze associative learning paradigm and novel object recognition paradigm. The first experiment results showed a significant drop in the total travelling distance in noise-exposed treatments compared to controls without supplementary noise. Moreover, in the noise treatments, there was a trend towards fewer visits to the target arm of the maze in comparison to the control group. Although the total time spent in the target arm among noise-exposed treatments was significantly different compared to control, only the High-Irregular treatment was significantly different from the Medium-Regular and High-Regular treatments. In the second test, no significant difference was observed in the total travelling distance except for Medium-Irregular and High-Irregular groups that showed reduced movement. Fish in the High-Irregular treatment had the lowest visiting frequency and accumulated time around the novel object, and the highest latency to visit the novel object, which can be an indicator of developing neophobia in this group. Furthermore, the High-Irregular treatment had a significant difference compared to other noise-exposed treatments. The noise intensity and predictability did not reveal a significant difference between treatments. However, slight changes were noticeable in some of the behavioural variables. Our results indicated that noise exposure can affect zebrafish performance, and different patterns of noise may result in different outcomes. However, whether these changes are the results of a direct effect of noise on memory requires more studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Social learning of predation risk and safety: fish behaviour as a model for fear recovery
Get PDFAs animal behaviour theory has developed over the past 70 years, much attention has gone toward social information use. Social cues in a variety of forms can be critically important in finding food and mates, in defending territories, and in avoiding predators. A wide variety of prey species are capable of learning from social information regarding predation threats, but little attention has gone toward factors that influence the acquisition of such information, how it compares to other learning mechanisms, or how prey learn socially about the absence of risk. Herein, I present research with fathead minnows, Pimephales promelas, where I first showed that learned fear responses were similar between social learning and individual learning, but socially-acquired information was more persuasive and had an overriding effect on previously learned safety. Using repeated exposures to general predation cues that lacked specific information about the predator’s identity, I induced uncertainty in naïve individuals (observers) or in knowledgeable individuals (models) within a social pairing. Repeated exposure to risk, regardless of uncertainty, promoted a high-risk phenotype that was characterized by propensity to freeze, stereotypic route-tracing, and neophobia – a phenomenon where animals show generalized fear responses toward novel stimuli. Attempting to weaken this phenotype, I paired high-risk individuals with models that were experienced with an odour as safe, but a single conditioning with one ‘safety model’ had little effect. Instead, interacting with high-risk individuals caused models to indirectly acquire the high-risk phenotype. Hence, this social transfer of information caused models to behave fearfully, making them poor demonstrators of safety. To counteract this, I used groups of calm models, or multiple, individual calm models in succession. Both strategies weakened fear in observers, as well as socially-transferred fear in models, but surprisingly this effect was much stronger among individuals exposed to risk in isolation, despite their tendency for stronger neophobia initially. While our basic knowledge of social systems has grown substantially in recent years, rarely has it been applied to human issues. My work bridges animal behaviour theory and human psychology, arguing that our understanding of predation-related fear and the information transfer in social animals can prove fruitful in understanding post-traumatic stress and behavioural therapy for its recovery
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