Browsing by Subject "Fish"
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Item Behavioral lateralization in zebrafish and four related species of minnows (Osteichthyes: Cyprinidae)(2009-05) Stennett, Curtis R.; Strauss, Richard E.; Schmidt, Kenneth A.; Wilde, Gene R.Lateralization occurs when the left and right sides of some portions of the body differ from each other either in structure or function. It was once believed that humans were the only animals to exhibit lateralization of the brain. However, research throughout the last few decades has clearly shown that lateralization is not unique to humans. In fact, many vertebrates are known to exhibit lateralization of a type that is similar to humans. In a monocular test, the subject is exposed to a stimulus and the eye that it uses to inspect the stimulus is recorded. The binary data obtained from these tests is often pooled among individuals of the same species in order to test hypotheses of species-level behavioral lateralization. Hypotheses of individual level behavioral lateralization are rarely tested. Therefore, I examined nine different statistical tests that are capable of testing binary data, which is commonly recorded in these types of behavioral tests. Using the p-value as an indication of the effectiveness of a test to show departures from randomness when such departures actually exist, and considering the growing necessity for providing confidence intervals associated with a given test, I found the score test to be the most satisfactory. Behavioral lateralization has been observed in many species of fishes during stimulus specific tasks. However, one area that has been overlooked is the study of naïve side bias in motor behavior of fishes in the absence of any direct stimulus. Therefore, I also examined naïve side biases in motor behavior in five species of minnows (Osteichthyes: Cyprinidae). Fifteen individuals of each species were subjected to a ‘T’ shaped test arena, with 40 replicates/individual. This experiment took advantage of rheotaxis by running a slow current of water through each arm of the test apparatus. A total of 55 of 75 individuals tested exhibited a rightward turning preference. The significantly right-biased behavior observed in these fishes in the absence of any systematic stimulus suggests that it is imperative in future studies of laterality in fishes, and presumably in other organisms, that a stimulus-free control condition be included in the experimental design.Item Creating Automated Interactive Video Playback for Studies of Animal Communications(2010-01-16) Butkowski, TrishaVideo playback is a technique used to study the visual communication and behaviors of animals. While video playback is a useful tool, most experiments lack the ability for the visual stimulus to interact with the live animal. The limited number of experiments involving interactive video playback can be attributed partially to the lack of software available to conduct instructive interactive video playback experiments. To facilitate such interactive experiments, I have created a method that combines real-time animations with video tracking software. This method may be used to conduct interactive playback experiments. To demonstrate this method, a prototype was created and used to conduct automated mating choice trials on female swordtail fish. The results of the mating choice trials show that this prototype is able to create effectively interactive visual stimulus automatically. In addition, the results show that the interactive video playback has a measurable effect on the female swordtail fish, Xiphophorus birchmanni.Item Direct measurement of effective medium properties of model fish schools(2014-05) Dolder, Craig Nealon; Wilson, Preston S.The scattering and attenuation caused by fish schools has been extensively studied for applications in fisheries management and naval sonar. The literature contains extensive in situ measurements of scattering by fish schools, however significant uncertainties exist with respect to characterizing the size, quantity, and distribution of fish within the schools, that confounds accurate measurement-model comparison. Hence there is a need for application of measurement techniques that can more precisely characterize the acoustic properties of fish schools and the variations intrinsic to live subjects in continual motion. To begin to address this deficiency, measurements of the sound speed through collections of live fish were conducted in a laboratory setting. The species chosen for measurement were zebrafish (Danio rerio). The sound speed was investigated using a resonator technique which yielded inferences of the phase speed within the fish school though measurements of the resonances of a one-dimensional waveguide. The waveguide was calibrated to compensate for finite wall impedance and for finite reflections from the ends of the waveguide. Fish densities were investigated ranging from 8.6 to 1.7 fish lengths per mean free path. Measurements agree well with a predictive model that is based on shell-free spherical bubbles, which indicates that the phase speed is not significantly affected by the fish flesh or swimbladder morphology for the species studied. The variation in phase speed due to individual fish motion within the model school was measured to be up to ± 5.6 %. This indicates that precise knowledge of the fish position is required to achieve greater model accuracy. To compliment the phase speed measurements, the attenuation through a cloud of encapsulated bubbles was evaluated through insertion loss measurements. Multiple arrangements of balloons of radius 4.68 cm were used to surround a projector. The insertion loss measurements indicated an amplification of around 10 dB at frequencies below the individual balloon resonance frequency and an insertion loss of around 40 dB above the individual balloon resonance frequency. Analytical modeling of the bubble collection predicted both the amplification and loss effect, but failed to accurately predict the level of amplification and insertion loss. Effective medium models and full scattering models (requiring knowledge of bubble size and position) were evaluated for a model fish school. The two models agree for forward scattering for all frequencies except those immediately around the individual bubble resonance frequency. Back scattered results agree at low frequencies, however as soon as the wavelength becomes smaller than four mean free paths between fish the models diverge. Ramifications of these findings and potential future research directions are discussed.Item The effects of habitat fragmentation on the diversity of nekton inhabiting subtropical seagrass meadows(2011-05) Hensgen, Geoffrey Michael; Holt, G. Joan; Munguia, Pablo; Ojanguren, Alfredo F.; Stunz, Gregory W.Habitat fragmentation is often regarded as a biodiversity threat associated with habitat degradation; however, research has also revealed beneficial effects on biodiversity as well, depending on the ecosystem and species community. This study examined the biodiversity of small nekton residing in seagrass meadows characterized by three levels of habitat fragmentation, and as a habitat gradient comprised of measures such as habitat amount, connectivity, patch shape, and proximity. Landscapes were mapped using recent advances in GPS and GIS technology, and analyzed using established methods from research in terrestrial ecosystems. Species richness was not significantly different as a function of fragmentation regardless of season, suggesting that the amount of habitat and configuration of several patches in fragmented habitats is sufficient to support comparable numbers of species in several patches compared to communities in large, continuous seagrass meadows. Species evenness declined significantly in fragmented habitats versus continuous ones in both seasons. Within fragmented landscapes, evenness progressively declined as habitat amount and connectivity decreased and patch isolation and density increased, suggesting that changes in landscape qualities can differentially impact processes supporting metapopulations such as dispersal and reproduction in certain species, thereby influencing community structure. Analyses that included measures of habitat connectivity, proximity, and patch density in addition to habitat amount accounted for more variability in species evenness than those just containing percent cover, and showed that fragmentation’s impacts can differ geographically. These data suggest that community resilience to fragmentation can differ between similar animal communities residing in separate locations, and that landscape configuration plays an important role in determining how communities respond to fragmentation after a threshold of change in habitat amount has been exceeded.Item Effects of post-settlement habitat use and biotic interactions on survival of the seagrass-associated fish red drum (Sciaenops ocellatus)(2009-12) Fencil, Megan Christine; Holt, J. (Joan); Dunton, Kenneth H.; Montagna, Paul A.; Rocha, Luiz A.; Rooker, Jay R.Due to high mortality encountered by marine fish larvae during their first weeks of life, small changes in the number of individuals surviving through this period can cause large fluctuations in year-class strength. Larval Red Drum (Sciaenops ocellatus) are dependent upon structured estuarine habitat to avoid predation. A study of post-settlement larval Red Drum distribution in a subtropical seagrass meadow in Mission-Aransas Estuary, Texas, USA indicates that larvae settle over approximately two months. Abundance of larger settled larvae was significantly different among sites. The areas of highest larval abundance varied temporally, indicating that the entire extent of the seagrass bed is utilized. Regression analysis of abiotic environmental factors did not explain why larvae were more abundant at particular sites. To characterize the structure and variability of the fish species assemblage that Red Drum encounter upon settlement, larvae and juveniles were captured in the seagrass meadow during weekly collections. Of the 32 fish species collected, seven represented 92% of the assemblage. Multivariate species analysis indicated that collections widely separated in time and space shared the lowest Bray-Curtis similarity. Because Red Drum settle over a relatively long period and co-occur at body sizes known to cause cannibalism under laboratory conditions, I tested combinations of small and large Red Drum larvae at various field-realistic densities and at different levels of seagrass habitat structure to determine potential for cannibalism. Artificial seagrass did not protect small (5 – 6 mm SL) larvae from cannibalism, but natural dense seagrass had a protective effect relative to edge habitat. The final component of this research examined the emergent impacts of a common predator pinfish (Lagodon rhomboides) on mortality and cannibalistic interactions between small and large Red Drum larvae. Both pinfish and large Red Drum larvae alone readily consumed small Red Drum in all seagrass habitat structures tested. However, the combined treatment of pinfish and large Red Drum together led to reduced mortality of small Red Drum. Predation can significantly affect Red Drum survival during the post-settlement period, and multiple predators may have a protective effect on the smallest settlers if predation pressure is re-directed towards a larger size class.Item Increased temperature effects on fish-mediated nutrient cycling in an East Texas stream(2017-11-07) McWilliams, Jessica Lynn; Hargrave, Chad W.The unprecedented rate of global warming is an inevitable outcome of anthropogenic CO2 release into the atmosphere and complex climatic feedbacks. In ectotherms, increasing temperature may increase metabolic rates, which could enhance the energy demands of individuals and should accelerate resource acquisition. Population size and fish biomass were measured seasonally in a small second order stream over a 10-year period to examine seasonal variation in these parameters. I examined effects of increased temperature on nitrogen and phosphorus excretion in the four most abundant fish in this stream system. These fishes represent three functional feeding guilds common to many temperate stream ecosystems and comprise approximately 80-90% of the fish community. I developed temperature dependent nitrogen and phosphorus excretion models for fishes and applied these models to daily average temperatures in the stream. I then simulated climate warming (+2, +4, & +6°C) to examine the potential effects of increased temperature on fish-mediated nutrient dynamics in a southern temperate stream ecosystem. I found that increased temperature does increase nutrient cycling and nutrient flux within aquatic ecosystems; however, these effects appear to be tied to population size, biomass in addition to seasonal temperature. With increased temperature effects in spring and autumn having the greatest effect, when temperatures are cool and fish abundance and biomass is also greatest.Item The role of docosahexaenoic acid in mediating mitochondrial membrane lipid peroxidation and apoptosis in colonocytes.(Texas A&M University, 2005-11-01) Ng, Yee VoonColon cancer is the second leading cause of cancer death in the United States. Epidemiological data indicate that the consumption of dietary fiber and fish/marine products favorably modulate colon tumorigenesis. Docosahexaenoic acid (DHA, 22:6n-3) from fish oil, and butyrate, a fiber fermentation product generated in colon, protect against colon tumorigenesis in part by inducing apoptosis. We have shown that DHA is incorporated into mitochondrial membrane phospholipids, which enhances oxidative stress and mitochondrial membrane potential (MP) dissipation. To elucidate the subcellular origin of oxidation induced by DHA and butyrate exposure, young adult mouse colonocytes (YAMC) were treated with 0200 ??M DHA, linoleic acid (LA, 18:2n-6) or no fatty acid (control) for 72 h with or without 5 mM butyrate for the final 6-24 h. Real time analysis of cellular membrane lipid oxidation, as indicated by oxidation of a lipophilic vital dye, mitochondrial permeability transition (MPT), as characterized by MP dissipation, and cytosolic ROS production, as depicted by hydrophilic ROS reactive fluorophore accumulation, were measured by living cell fluorescence microscopy. After 24 h of butyrate treatment, DHA primed cells showed a 29% increase in lipid oxidation (p<0.01), compared to no butyrate treatment, which could be blocked by a mitochondria targeted antioxidant, MitoQ (p <0.05), whereas LA treatment did not show an effect. In the absence of butyrate, DHA treatment, compared to LA, increased resting MP by 14% (p <0.01). In addition, butyrate-induced MP dissipation was greater (20%) in DHA primed cells as compared to LA (10%). This effect was blocked by pre-incubation with MPT inhibitors, cyclosporin A or bongkrekic acid at 1 ??M. These data suggest an increase in mitochondrial lipid oxidation and the resultant change in MP may contribute to the induction of apoptosis by DHA with butyrate as shown previously.Item Using Advanced Imaging to Study Fish(2013-05-31) Browning, Zoe SwezyAlthough mammals are the most commonly utilized laboratory animal, laboratory animal medicine continually seeks to replace them with animals of lower phylogenic classification. Fish are becoming increasingly important as investigators seek alternative animal models for research. Fish can provide an economical and feasible alternative to typical mammalian models; moreover, many fish, which have comparatively short life spans, can easily reproduce in the laboratory. One key area of animal health research in which fish have been underutilized is the field of advanced imaging. Although many images of fish have been captured through the use of computed tomography (CT), radiography, and ultrasonography, these images have been primarily utilized for anatomical study. In addition, fish have never before been studied with positron emission tomography/ computed tomography (PET/CT). My objectives were to determine if these imaging techniques can be used to obtain physiological information from fish, therefore making it more likely that fish can be utilized as replacement animals using these new imaging techniques (CT, PET/CT). I performed two different types of studies to assess the potential application of advanced imaging techniques to fish. In the first experiment, microCT was used to characterize otolith deformity in vitamin C deficient captive-raised red drum and relate the deformity to behavioral and physiological changes. I found that the normal and abnormal fish had statistically significant differences in behavior, cortisol levels, and otolith volume and density. MicroCT assessment of abnormal fish revealed operculum abnormalities, malocclusions, and several types of otolith malformations. Therefore, the affected fish had not only an abnormal skeletal appearance but also significantly abnormal behavior and cortisol responses. In the second experiment, fluorodeoxyglucose-positron emission tomography/ computed tomography (FDG-PET/CT) was used to quantify glucose uptake in select organs prior to carcinogenesis studies in fish. The quantified glucose uptake was compared to published data on humans, mice, and dogs. Rapid, quantifiable glucose uptake was demonstrated, particularly in brain, kidneys, and liver in all imaged fish species. Glucose uptake in the major organ systems of fish was closer to that in humans than uptake in mice or dogs, indicating that fish may serve as an effective alternative animal model for tumor studies using this technology. Other applications for this technique in fish may include metabolism studies and screening for environmental carcinogenesis. I found that both microCT and PET/CT imaging provided useful and meaningful results. In addition, the use of non-invasive scanning allows for re-use of fish, thus reducing the number of animal models used in experiments. These experiments suggest that fish will be good replacement models for mammals using these advanced imaging techniques.