The demography and reproductive biology of the gopher tortoise (Gopherus polyphemus) was studied for two years at White Oak Plantation (WOP), located in northeast Florida along the St. Mary’s river. Two sub‐populations were studied in regions I referred to as Site A and Site B. I located 312 burrows and captured 109 different tortoises, either by hand or using bucket traps. Tortoise density was 4.48/ha at Site A and only 1.15/ha at Site B. Juveniles were the most abundant age class overall, while hatchlings were numerous at Site A but virtually absent at Site B. The combined sex ratio for adult tortoises at WOP was 1:1.55 (F:M). Six nests were discovered over the course of the study, all located at Site A. Mean clutch size was 3.8, much lower than other studies conducted in Florida and Georgia, but egg hatching success (87.5%) was comparable to other studies. Growth rates were mostly consistent with other studies for juvenile, sub‐adult and adult age classes, but were unusually high for hatchlings. In light of the fact that habitat fragmentation is currently one of the leading threats to tortoise populations, I propose management recommendations that will merge these two sub‐populations and lead to increased potential and gene flow for their long‐term viability.

Stress has been identified as one of the primary factors influencing the structure of food webs, but few conclusions about the effects of stress on community dynamics have emerged. This study examined generalities that exist between salt stress and insect herbivore responses. Ambient salinity was artificially increased by adding 1.3 kg/m2 of salt to six different plant species: Avicennia germinans, Baccharis halimifolia, Batis maritima, Borrichia frutescens, Iva frutescens, and Spartina alterniflora. By performing a multiple species examination, stress responses were examined to determine if consistencies within and between plant type, ambient salinity conditions, and host plant species (among other criteria) existed, allowing for generalizations to be made about stress and herbivore interactions. Herbivore responses were determined by direct visual counts and indirect visual evidence of insects (e.g. galls, stem boring, and leaf mining). A metaanalysis was then performed on the data to determine the factors that may result in consistent responses to salt stress. No differences were found between insect feeding guilds. Herbivory increased in the presence of that added salt in high ambient salinity conditions, increased on experimental Spartina plants, and decreased on experimental Iva plants. These findings suggest that stress is generally a more important factor for plants in areas of already high ambient salinity. Results have been disparate in various studies, likely due to the difficulty in making comparisons between different field sites and experimental designs. This study addresses these issues, and ultimately finds that consistencies can be found among multiple species within communities.

Basigin gene products are cell adhesion molecules that are expressed by photoreceptor cells, Müller cells and endothelial cells of the mammalian retina. Previous studies have suggested that a lactate shuttle exists between the photoreceptor cells and the Müller cells, with Basigin being an essential component in this shuttle. Deletion of the Basigin gene in mice results in blindness with an eventual retinal degeneration. It was hypothesized that the lactate shuttle between photoreceptors and Müller cells does not form in Basigin null mice and that the blindness is attributed to faulty photoreceptor metabolism. Therefore, the purpose of this study was to determine whether the mitochondria of the Basigin null mice are metabolically active in the absence of the lactate shuttle. Mitochondrial health in the Basigin null mouse retina was assessed by a variety of assays, including ELISA analyses to measure Cytochrome c concentration and expression of autophagy-specific proteins. Mitotracker dyes were used to stain the mitochondria of Basigin null and normal retinas to determine the number of metabolically active mitochondria and the total number of mitochondria. The results showed that apoptosis and autophagy are not occurring in the Basigin null animals at a rate greater than that of the normal animals. The Mitotracker assay showed that there is a ~60% decrease in the total number of mitochondria in the null animals compared to their normal counterparts. A recalculation of the Cytochrome c assay in light of the reduced number of mitochondria in Basigin null mice revealed that apoptosis is likely occurring in these animals prior to the first signs of cytoarchitectural changes in the tissue. These results suggest that in the absence of the lactate shuttle in the Basigin null animals, the photoreceptors are unable to perform oxidative phosphorylation at the necessary rate, thus decreasing the number of mitochondria, which results in limited photoreceptor functionality, hence blindness.

Cyanobacteria are important components of the aquatic system, valued for their oxygen production, nitrogen fixation, and as the base of many aquatic food webs. This study investigated several aspects of cyanobacteria such as the diversity and response to nutrient enrichments. A survey of Northeast Florida was conducted between the years of 2010 and 2012; a total of 145 taxa were identified in freshwater habitats, such as springs, lakes, rivers, and retention ponds. While surveying the St. Johns River in Jacksonville, Florida, a novel Stigonematalean taxon was isolated and cultured. Subsequent morphological and genetic analyses indicate that this taxon is related to Fischerella, Nostochopsis, and Westelliopsis, though with poor bootstrap support. Thus, a new genus and species (Reptodigitus chapmanii gen. et sp. nov.) is proposed. Cyanobacterial community shifts are increasingly being employed as an indicator of ecosystem health. The last part of this study is an experimental manipulation of nutrients and subsequent community analyses. Chlorophyll a, total number of cells, and Dmax were significantly different between control groups and nutrient enriched groups. Phosphate was not strongly correlated to species richness, chlorophyll a, evenness, total number of cells, species richness, or diversity in either the control or the nutrient enriched groups. Nitrogen displayed similar results, though it was slightly more strongly correlated to evenness and diversity in the nutrient enriched group than the control group. The results of the survey and nutrient enrichment experiment are important parts of the investigation into how cyanobacterial communities respond to changes in nutrient concentrations, which can then be used to devise a standard metric against which water management agencies can compare to determine the health of a given aquatic system.

Seagrass meadows are essential to coastal ecosystems and have experienced declines in abundance due to a series of environmental stressors including elevated salinity and incidence of disease caused by the pathogen Labyrinthula sp. This thesis evaluated the dynamics between T. testudinum and Labyrinthula concerning the impacts of short term elevated salinity stress on the early stages of infection in Thalassia testudinum (Chapter 2) as well as the presence of anti-labyrinthulid secondary metabolites produced by the tropical seagrass (Chapter 3). The results showed that short term exposure to hypersalinity alters some cellular processes but does not necessarily lead to an immediate increase in wasting disease susceptibility. Specifically, the occurrence of disease was significantly lower in the hypersalinity treatments possibly due to a direct osmotic shock to Labyrinthula or indirectly due to the increase in in vivo H2O2 concentrations that may have inhibited Labyrinthula growth. In addition, it was shown that 4 phenolic acids commonly found in turtlegrass leaf tissue were able to inhibit Labyrinthula growth in culture. Using a bioassay-guided fractionation technique, several purified fractions of T. testudinum leaf tissue showed anti-labyrinthulid activity, however the detailed characterization of the unknown compounds was inconclusive. The results presented in this thesis highlight the halotolerant characteristics of the seagrass T. testudinum as well as suggest that T. testudinum has the capability of defending itself against Labyrinthula infection using secondary metabolites.

Hypoxia in coastal estuaries is a topic of increasing concern, as the magnitude and frequency of hypoxic events have increased over the past several decades. These hypoxic events are highly detrimental to the coastal biota, particulary fish. The hypoxia-inducible factor 1α (HIF-1α) protein was used as a candidate biomarker for deciphering exposure of fish to hypoxic events. In chapter one, Spot (Leiostomus xanthurus) were exposed to three treatment groups of DO (means 7.32 ± 0.18, 5.15 ± .37, and 2.57 ± 0.01 mg Lˉ¹ DO) and sampled (n = 5) at time zero, 36 and 72-h for each treatment. The results of the laboratory trials suggested that duration had a significant effect (F = 28.9, p < .001) on concentration of HIF-1α protein, however, the DO treatment group did not have a significant effect (F = .739, p = .546) on the concentration of HIF-1α protein. L. xanthurus were also analyzed for HIF-1α from field sites of varying DO concentrations (7.0, 5.2, 4.8, and 3.3 mg Lˉ¹ DO), with no significant differences (F = 1.621, p = .208) between sample sites, and with a negative relationship between DO and HIF-1α protein (p = .197) from these sites. Leiostomus xanthurus were exposed to either constant or diel-cycling hypoxia, and HIF-1α expression was compared to normoxic control over three days. The results indicated that HIF-1α protein significantly (p = 0.02) increased in muscle tissue after three days exposure to both constant and a simulated diel-cycling hypoxic event in a laboratory setting when compared to normoxic control animals. It was also found that body mass (measured in wet weight, grams) was a significant covariate for the concentration of HIF-1α produced under normoxia (p = 0.04) and constant hypoxia (p = 0.03), but did not affect the diel-cycling (p = 0.83) groups, suggesting that body mass is a confounding factor when measuring HIF-1α. The correlation of HIF-1α with body mass is likely due to the different tolerances to hypoxia between small and large young-of-year L. xanthurus, an effect that was possibly overshadowed by the acclimation response under diel-cycling hypoxia.

A gopher tortoise population on the campus of University of North Florida is part of an ongoing study initiated during the early 1990s, and this project presents data on this population collected during the 2009-2011 field seasons. The project has three major objectives: 1) measure population demographics including density and structure to assess long-term viability and recruitment, 2) evaluate decadal growth rates of individuals by comparing measurements of tortoises captured and marked in the 1990-1994 study done at the same site with those tortoises recaptured during the current study, and 3) assess the effect of prescribed burning on vegetation. In total, 141 individuals were caught from 2009-2011: 32 adult females, 28 adult males and 17 young adults, 43 juveniles and 21 hatchlings. Of these, 39 are recaptures from the research performed in the early 1990s. Adult burrow aprons were probed using a wire survey flag in an attempt to locate nests. In 2010 we found two intact nests with this technique and recorded two other depredated nests that were unassociated with any burrow. In 2011 we found one nest and a clutch that was laid on the ground’s surface. Four 100m transects were established before prescribed burning began. Vegetation analyses were done bi-monthly and all plants were recorded as well as their percent of each plot. The most abundant plant was milkpea. Preliminary analysis of postburn response has indicated increased groundcover in all burned transects.

Understanding the life history of marine wildlife is essential for the management of both commercial and recreational fisheries. Bonnetheads (Sphyrna tiburo) are a component of the small coastal shark (SCS) fishery complex, and are caught regularly in both types of fisheries. Despite being well studied in the Gulf of Mexico, little is known about bonnetheads from the U.S. Atlantic coast. The goal of the first component of this study was to provide new, key information on their life history to improve management of U.S. Atlantic populations, particularly by identifying reproductive seasonality, periodicity and fecundity. This was accomplished by examining sexually mature male and female bonnetheads, collected monthly (2012-2014) from South Carolina, Georgia, and Florida waters, and monitoring changes in reproductive tract morphology. Changes reflected a seasonal reproductive cycle with an annual breeding periodicity. Histology was used to confirm events and identify other important periods in the reproductive cycle, such as sperm storage in females. Overall, Atlantic coast bonnetheads were found to exhibit reproductive patterns similar to those reported in the Gulf with slight temporal shifts in the time of mating and ovulation and slightly lower fecundity ranging between 1 and 12 with an average (±SE) of 7±3.8. Additionally, the second component of this study aimed to understand gonadal sex hormone regulation in S. tiburo reproduction with a particular focus on female sperm storage. Circulating plasma sex hormones increased in association with specific reproductive events. Plasma 17β-estradiol and testosterone concentrations increased during sperm storage, whereas progesterone levels increased near the end of this stage. Immunocytochemical analysis of androgen, estrogen, and progesterone receptors in the oviducal viii gland, the organ that stores sperm in female bonnetheads, demonstrated that epithelial cells of sperm storage tubules and spermatozoa itself are direct targets for these hormones, playing a role in regulating this poorly understood process.

No description available.

Sharks often bioaccumulate mercury (Hg) concentrations in their muscle to levels that threaten the health of human consumers. However, few published studies have examined if the high Hg levels seen in shark muscle also occur in the shark brain, or if Hg accumulation affects shark neurophysiology. Therefore, this study examined if shark brains accumulate significant levels of Hg, if Hg accumulation occurs in certain subcomponents of the brain, and if Hg accumulation is associated with oxidative stress effects on the shark central nervous system, with special focus on the Atlantic sharpnose shark (Rhizoprionodon terraenovae). Sharks were collected along the U.S. Southeastern coast throughout most of the shark’s geographical range. Known biomarkers of Hg-induced neurological effects (markers of glial cell damage, S100b, and markers of oxidative stress) in the shark cerebrospinal fluid were examined. Brain Hg levels were correlated with muscle Hg levels, but were significantly lower and did not exceed most known thresholds for neurological effects, suggesting limited potential for such responses. Data on known biomarkers of Hg-induced neurological effects support this premise, because they were not correlated with brain Hg levels. Organic methylmercury did not compose of a high percentage of the total mercury in the brain, indicating demethylation of Hg is occurring in the brain. Higher Hg levels were measured in the forebrain of the shark in comparison with the midbrain and hindbrain, but levels in both were below threshold levels for effects. This study is the first to demonstrate the correlation and significant difference of Hg in the brain and muscle of sharks, and it identifies significantly higher Hg levels in the forebrain; making this study one of the most extensive analysis of Hg in a single shark species.