Organizational Unit:
School of Biological Sciences

Permanent Link
https://hdl.handle.net/1853/70750
Research Organization Registry ID
Description
Previous Names
Parent Organization
Parent Organization
Organizational Unit
Includes Organization(s)
ArchiveSpace Name Record
https://finding-aids.library.gatech.edu/agents/corporate_entities/1131

Filters

2009 - 2009 1 2010 - 2018 9
10
5 4 1
10
10
Reset filters

Settings
search.filters.applied.f.advisor: Goodisman, Michael × End date: 2019 × Start date: 2000 × search.filters.applied.f.isOrgUnitOfPublicationTitle: College of Sciences ×

Publication Search Results

Now showing 1 - 10 of 10
Thumbnail Image
Item

Dominance and exhibit use in captive African elephants (Loxodonta africana)

2018-12-06 , Iacono, Jennifer

The African elephant (Loxodonta africana) is a highly social species that typically lives in large, matrilineal family groups called herds which contain a linear dominance hierarchy between the adult females. Management plans for African elephants in human care try to replicate their natural social structures by creating small herds of females but these individuals typically are unrelated except in the case of mothers and their offspring. Despite low genetic relatedness, these females still create their own dominance hierarchies within the herds. Although elephants in human care have all of their needs provided for, dominance within herds can lead to preferential access to high-value resources such as food, water, and shade structures. The purpose of this study was to observe how the two female African elephants at Zoo Atlanta, Tara and Kelly, interacted with each other in terms of their usage of their current exhibit space. An incident occurred during data collection that led to a week-long physical separation of the elephants and the results of this study were then separated into two data sets. Anecdotal evidence of Kelly being the dominant individual was confirmed by Kelly initiating all 110 observed social interactions throughout the course of the study. Tara typically showed her submissiveness by walking away from the interaction. After the incident there was a higher mean frequency of social interactions between the two elephants per hour. The amount of neutral and agonistic behaviors rose as well. It appeared that Kelly was re-establishing her dominance over Tara after their separation. Both elephants had non-random patterns of exhibit spatial use when they were together and when they were alone in the exhibit, as well as before and after the incident. Before the incident, Kelly dominated use of the two areas that had direct access to the indoor barn when both females were in the exhibit together while Tara used the remaining two areas more often. These elephants have a complex social history, which includes Kelly dominating use of the barn and resources after a change to their social structure. As the dominant individual, Kelly had preferential access to this putative high-value area. Kelly continued to stay in the areas closest to the barn when separated from Tara. The pattern of spatial use in the exhibit displayed by Tara when separated from Kelly was different from her pattern when they were together; Tara used the area closest to the barn when alone. The patterns after the incident were similar to those from the before results except Tara used the furthest area from the barn with a higher frequency when alone in the exhibit in addition to the closest. This change may have been caused by Tara’s restricted mobility after the incident. Before the incident all social interactions between the elephants, including agonism, occurred randomly throughout the outside portion of the exhibit despite both elephants having specific patterns in how they used the exhibit. After the incident there was a non-random pattern in the location of all social interactions. More occurred in the area closest to the barn than would be randomly expected, which matches Kelly’s dominating use of that area. Although the occurrence of agonistic behaviors by area changed after the incident, the pattern was still not statistically significant.

View
Thumbnail Image
Item

Determining how Freshwater Copepods Follow Planar Dextrain Trails

2017-05 , Young, Madison Ruth

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). 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.

View
Thumbnail Image
Item

Use of RNAi in Brachionus manjavacas to Inhibit Cold-Related Genes Implicated in Aging

2015-08-18 , Wilson, Julie

Aging 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.

View
Thumbnail Image
Item

Queen-specific selective pressures and caste dimorphism in the social wasp Vespula maculifrons

2009-08-19 , Kovacs, Jennifer L.

Within social insect colonies, sterile workers are responsible for brood care, while queens are the primary egg-layers. These reproductive caste differences are often accompanied by pronounced morphological distinctions. Queen and worker phenotypic differences are particularly remarkable considering caste is environmentally, rather than genetically, determined. Environmental caste determination can produce intralocus genetic conflict between castes, particularly when homologous traits are highly dimorphic. Therefore, when studying the evolution of social insect caste dimorphism, one must consider the genetic architecture underlying phenotypic expression as well as the selective pressures that have shaped caste morphology. This dissertation presents the results of four studies that investigated factors affecting caste morphology in the social wasp Vespula maculifrons. The first two studies focused on identifying queen morphological traits that were positively associated with queen fitness and would therefore be subject to selection. Queen length, specifically gaster length, was positively associated with overwintering survival and was consistently associated with mating success. Both of these findings suggest that queen gaster length is under selection during two life-history events, mating and overwintering, in which workers do not participate. These findings provide empirical support for the adaptive evolution of a caste dimorphic trait. The third and fourth studies used classical quantitative genetic and morphological analyses to examine the genetic architecture underlying caste dimorphism in V. maculifrons. I determined which traits were under caste-specific selection by analyzing trait allometries and the levels of genetic control, variation, and dimorphism of traits between castes. Little genetic variation for morphological trait size was detected for most worker and queen traits, suggesting a strong influence of environment on phenotypic variation. Additionally, analyses of trait allometries indicated that several queen traits (mass, thorax width and length) were under queen-specific selection. The relationship between thorax length, gaster length, and overall body size is further evidence of selection on length in queens. Overall, these studies provide evidence for the importance of queen-specific selection in the evolution of caste dimorphism. When placed in the broader context of caste evolution, they point to the importance of life-history in shaping the genetic architecture underlying caste dimorphism.

View
Thumbnail Image
Item

Population genetics and genomics of eusocial animals

2017-11-09 , Chau, Linh M.

Major evolutionary transitions have been associated with increases in organismal complexity. One of the latest evolutionary transitions is from solitary life to eusociality. This transition led to a reproductive division of labor in which individuals are divided into castes. Reproductive castes are responsible for reproduction, while nonreproductive castes take part in colony maintenance and brood care. This division of labor represents a challenge to selection and has long been of curiosity to researchers. My dissertation research examined the population genetics and genomics of eusociality in a spectrum of eusocial species. First, I examined the population structure and genetic diversity of Vespula pensylvanica, a wasp native to North America that has invaded the Hawaiian archipelago. I found a lack of population structure in V. pensylvanica’s native range and determined how the population structure of invasive social insects can be shaped by geography. I also examined the population genetics of captive naked mole rats, one of the only known eusocial mammals. I sought to understand how captivity can shape the population structure of a eusocial animal. Interestingly, there was evidence that naked mole rat populations are not as inbred as previously theorized and that sex ratios are equal within captive colonies. Finally, I examined how the phenomenon of gene duplication can affect the evolution of castes in eusocial species. I uncovered a relationship between duplication rate and level of sociality across the bees. Also, I saw that duplicates were differently expressed across phenotypes compared to single copy genes. These studies provide insight on an array of population genetic and genomic questions concerning the evolution of eusociality. Therefore, this research furthers our understanding of the rare distribution of this social system across the tree of life.

View
Thumbnail Image
Item

Aggressive Phenotypes in Malawi Cichlids Associated with V1AR Variant

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.

View
Thumbnail Image
Item

A Study of the Relationship Between Bone Morphogenetic Proteins and Craniosynostosis

2015-06-30 , Whitton, Alaina

INTRODUCTION: 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.

View
Thumbnail Image
Item

Determining how Freshwater Copepods Follow Planar Dextran Trails

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.

View
Thumbnail Image
Item

Epigenetics in social insects

2016-01-14 , Glastad, Karl M.

Virtually all multicellular organisms are capable of developing differently in response to environmental variation. At the molecular level, such developmental plasticity requires interpretation and perpetuation of environmental signals without changing the underlying genotype. Such non-genetic, heritable information is known as epigenetic information. This dissertation examines epigenetic information among social insects, and how differences in such information relate to phenotypic caste differences. The studies included herein primarily focus on one form of epigenetic information: DNA methylation. In particular, these studies explore DNA methylation as it relates to and impacts (i) alternative phenotype and particular gene expression differences in two social insect species, (ii) histone modifications, another important form of epigenetic information, in insect genomes, and (iii) molecular evolutionary rate of underlying actively transcribed gene sequences. We find that DNA methylation exhibits marked epigenetic and evolutionary associations, and is associated with alternative phenotype in multiple insect species. Thus, DNA methylation is emerging as one important epigenetic mediator of phenotypic plasticity in social insects.

View
Thumbnail Image
Item

Molecular evolution in the social insects

2011-04-01 , Hunt, Brendan G.

Social insects are ecologically dominant because of their specialized, cooperative castes. Reproductive queens lay eggs, while workers take part in brood rearing, nest defense, and foraging. These cooperative castes are a prime example of phenotypic plasticity, whereby a single genetic code gives rise to variation in form and function based on environmental differences. Thus, social insects are well suited for studying mechanisms which give rise to and maintain phenotypic plasticity. At the molecular level, phenotypic plasticity coincides with the differential expression of genes. This dissertation examines the molecular evolution of genes with differential expression between discrete phenotypic or environmental contexts, represented chiefly by female queen and worker castes in social insects. The studies included herein examine evolution at three important levels of biological information: (i) gene expression, (ii) modifications to DNA in the form of methylation, and (iii) protein-coding sequence. From these analyses, a common theme has emerged: genes with differential expression among castes frequently exhibit signatures of relaxed selective constraint relative to ubiquitously expressed genes. Thus, genes associated with phenotypic plasticity paradoxically exhibit modest importance to overall fitness but exceptional evolutionary potential, as illustrated by the success of the social insects.

View