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ItemDetermining how Freshwater Copepods Follow Planar Dextran Trails(Georgia Institute of Technology, 2017-05) Young, Madison R.In this study two species of freshwater copepods, Hesperodiaptomus shoshone (H. shoshone), and Hesperodiaptomus arcticus (H. arcticus) will be used to determine how some species of freshwater copepods interact with planar dextran trails. When a copepod swims through water, hydrodynamic disturbances with a variety of structures are created; some are vortical, planar, or laminar. Initial studies show that these copepods avidly follow laminar trails in an upstream fashion [Pender Healy]. However, when copepods execute turns or fast swimming, vortices are created. When copepods execute slow turns, planar wakes are formed. The direction of flow in the wakes and the location of the wakes provide information on the location of the copepod that is generating that wake. The intent of this research is to determine if the signals in the wakes can lead the following copepod to the source of the disturbance. Hence, all analyses focused on events where a copepod responded to the signal. Responses include reorientation or angle of entrance, time spent in trail, preference for a particular trail width and edge following behavior [Strouhal number]. The goal is to understand more about their how they sense and respond to changes in their environment and it is hypothesized that both species will interact more with the wide trail and that H. arcticus will spend more time in the trail and enter at a greater angle. It is also hypothesized that both species adhere to ideal Strouhal values. To test this, two dextran (a polysaccharide) trails will be simultaneously dropped into a tank containing the copepods. One of the trails will be 2mm and the other will be 4mm. It is expected that the copepod will wobble or traverse the trail to contact the edges; edge following enables the copepod to stay on track. Alternatively, the copepod may follow the center of the trail where the flow is the fastest and therefore is relying on flow speed rather than the shear found in the edge of the trail. Analyses of the location of the follower relative to the edge versus the center of the trail can assess whether the copepod is sensing flow shear versus flow speed. A MatLab script will be used to find more detailed information (Figures 11-22). Both species prefer to follow the wider trail (Figure 5 and 6), and H. arcticus spend more time in the trail than H. shoshone. Hesperodiaptomus shoshone followed the 4mm trail eighteen times for an average of 2.14 seconds and the 2mm trail five times for an average of 1.36 seconds. The number of encounters was also determined, which confirms that the proportion of encounters resulting in follows is much higher for the 4mm trial than the 2mm trial in both species (Table 3). This data illustrates statistically significant results (p<0.05) that H. shoshone prefer to follow the wider trail and follow for longer periods of time compared to the smaller one. These results were compared to the results for H. arcticus, which followed the 4mm trail twelve times for an average of 5.08 seconds (Figure 6). This comparison between both species on the 4mm trail confirmed that H. arctius spend more time in the trail than H. shoshone (p<0.05). The average angles of entrance were 29.16° for H. shoshone on the 4mm trail and 21.08° on the 2mm trail, and 39.69° for H. arcticus on the 4mm trail (Table 2). When compared, the results demonstrated that H. arcticus enters the trail at a greater angle than H. shoshone on both the 2mm and 4mm trails (p<0.05). There was not enough of the wobbling behavior shown to find Strouhal Values at this time.
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ItemDetermining how Freshwater Copepods Follow Planar Dextrain Trails(Georgia Institute of Technology, 2017-05) Young, Madison RuthIn this study two species of freshwater copepods, Hesperodiaptomus shoshone (H. shoshone), and Hesperodiaptomus arcticus (H. arcticus) will be used to determine how some species of freshwater copepods interact with planar dextran trails. When a copepod swims through water, hydrodynamic disturbances with a variety of structures are created; some are vortical, planar, or laminar. Initial studies show that these copepods avidly follow laminar trails in an upstream fashion [Pender Healy]. However, when copepods execute turns or fast swimming, vortices are created. When copepods execute slow turns, planar wakes are formed. The direction of flow in the wakes and the location of the wakes provide information on the location of the copepod that is generating that wake. The intent of this research is to determine if the signals in the wakes can lead the following copepod to the source of the disturbance. Hence, all analyses focused on events where a copepod responded to the signal. Responses include reorientation or angle of entrance, time spent in trail, preference for a particular trail width and edge following behavior [Strouhal number]. The goal is to understand more about their how they sense and respond to changes in their environment and it is hypothesized that both species will interact more with the wide trail and that H. arcticus will spend more time in the trail and enter at a greater angle. It is also hypothesized that both species adhere to ideal Strouhal values. To test this, two dextran (a polysaccharide) trails will be simultaneously dropped into a tank containing the copepods. One of the trails will be 2mm and the other will be 4mm. It is expected that the copepod will wobble or traverse the trail to contact the edges; edge following enables the copepod to stay on track. Alternatively, the copepod may follow the center of the trail where the flow is the fastest and therefore is relying on flow speed rather than the shear found in the edge of the trail. Analyses of the location of the follower relative to the edge versus the center of the trail can assess whether the copepod is sensing flow shear versus flow speed. A MatLab script will be used to find more detailed information (Figures 11-22). Both species prefer to follow the wider trail (Figure 5 and 6), and H. arcticus spend more time in the trail than H. shoshone. Hesperodiaptomus shoshone followed the 4mm trail eighteen times for an average of 2.14 seconds and the 2mm trail five times for an average of 1.36 seconds. The number of encounters was also determined, which confirms that the proportion of encounters resulting in follows is much higher for the 4mm trial than the 2mm trial in both species (Table 3). These data illustrates statistically significant results (p<0.05) that H. shoshone prefer to follow the wider trail and follow for longer periods of time compared to the smaller one. These results were compared to the results for H. arcticus, which followed the 4mm trail twelve times for an average of 5.08 seconds (Figure 6). This comparison between both species on the 4mm trail confirmed that H. arctius spend more time in the trail than H. shoshone (p<0.05). The average angles of entrance were 29.16° for H. shoshone on the 4mm trail and 21.08° on the 2mm trail, and 39.69° for H. arcticus on the 4mm trail (Table 2). When compared, the results demonstrated that H. arcticus enters the trail at a greater angle than H. shoshone on both the 2mm and 4mm trails (p<0.05). There was not enough of the wobbling behavior shown to find Strouhal Values at this time.
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ItemAggressive Phenotypes in Malawi Cichlids Associated with V1AR Variant(Georgia Institute of Technology, 2016-12) Schappaugh, Nicholas A.The cichlid model provides a great opportunity to explore diversity in behavioral phenotypes. Different groups of Malawi cichlids exhibit distinct patterns of behavior for a variety of scenarios, including aggressive encounters. These cichlids, characterized by the rocky or sandy habitats they occupy, exhibit strong genetic divergence, possessing large numbers of alternatively fixed variants between them. One such variant exists in the gene avpr1a, also known as V1aR, a major receptor for vasopressin in humans. This gene has been linked to behavioral effects across a variety of animal species, with this specific variant likely to have significant structural implications for the receptor product. Here we investigate the aggressive behaviors of a set of rock and sand hybrid fish for their association with the variant observed in V1aR. While specific metrics of aggression showed similar trends in these hybrids compared to those observed in the parental rock and sand species, ultimately these trends were not significant and were inconclusive. However, these results serve as a preliminary investigation of this gene’s involvement in cichlid aggressive behavior. In future work, further examination of the locus will be conducted utilizing more precise and powerful methods in order to draw stronger conclusions.
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ItemUse of RNAi in Brachionus manjavacas to Inhibit Cold-Related Genes Implicated in Aging(Georgia Institute of Technology, 2015-08-18) Wilson, JulieAging can be affected by a number of factors, including temperature; for example, organisms tend to live significantly longer when exposed to colder temperatures. Previous studies suggest that this change in life expectancy due to temperature change has a genetic component. Through the use of RNA interference, we have found that aging genes can be knocked-down in our model animal, Brachionus manjavacas (Rotifera). Using RNAi, we examined the effect of genetic knock-down on genes related to life extension at lower temperatures (16oC) compared to standard culture temperatures (22oC). This study has provided evidence that temperature-dependent changes in longevity may be largely due to changes in expression levels in select genes: Forkhead Box C (FhBC), TRP7, and S6P. Future research may show that the life extending effects of certain living conditions may be obtainable through genetic treatment.
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ItemA Study of the Relationship Between Bone Morphogenetic Proteins and Craniosynostosis(Georgia Institute of Technology, 2015-06-30) Whitton, AlainaINTRODUCTION: The high prevalence for craniosynostosis (1) indicates the need for genetic understanding and identification of molecular pathways involved in the premature fusion of the skull sutures. Due to the existing knowledge about bone morphogenetic proteins (BMPs) on ectopic bone formation (2), the role of the BMP family in multiple types of craniosynostosis has long been hypothesized as a key player in the early onset of suture fusion. Based on this hypothesis, the genetic expression of six bone morphogenetic proteins were examined in the four types of synostosis. METHODS: Bone collected from patients undergoing corrective craniotomies at Children’s Healthcare of Atlanta were received and cells were grown from the bone fragments. From those cells, Real-time PCR was performed to determine the mRNA levels of the predetermined genes. RESULTS: Patients expressed individual results based on several factors including suture placement, age at surgery, sex, and predisposition to syndromes known to occur in conjunction with craniosynostosis. The BMPs that were involved in extraneous bone formation and osteoblast hyperactivity were found in high levels in the fused suture bone, while the mRNA levels of the inhibitors of bone formation such as NOG were decreased in fused sutures and exhibited high levels in the patent sutures. CONCLUSION: The study further elucidates the role of BMPs in the onset of craniosynostosis and offers insight to the molecular pathways involved.