Marine turtles produce many offspring which offsets the high mortality experienced by turtles during early development. Juvenile mortality might be reduced by evolving effective behavioral as well as morphological anti-predator defenses. Body proportions of three species (Caretta caretta, Chelonia mydas, Dermochelys coriacea) of turtles were measured in the first fourteen weeks of development to examine how growth may mitigate predation by gape-limited predators. Growth was categorized as isometric if shape did not change during development or allometric if body shape did change. All three species showed allometric growth in carapace width; however it was less pronounced in the larger D. coriacea turtles. Allometric growth in carapace width decreased as all three species grew in size. When high predation occurs in early development, many species will favor rapid growth into a size refuge. Juvenile sea turtles may optimize their survival by growing allometrically when predation risk is the greatest. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

The reproductive success of leatherback turtles (Dermochelys coriacea) is typically the lowest of the seven sea turtle species. Why this vital rate is decreased has remained unanswered for nearly a century. Recently, detailed postmortem examination of leatherback hatchlings identified muscular pathologies that suggested possible selenium deficiency. High bodily burdens of mercury compounds are associated with selenium depletion. Selenium is a necessary detoxifying nutrient that itself can be toxic at elevated concentrations. Mercury compounds are toxicants with no known biological function. High bodily concentrations of mercury can be detrimental to marine organismal health, reproduction and survival, both directly and indirectly through inducing selenium depletion. The goals of this dissertation are to evaluate several related hypotheses to explain low leatherback nest success. ... Because leatherbacks take in high volumes of prey, high tissue concentrations of mercury and selenium can result. This study provides the first evidence that chemical contaminants may explain low reproductive success in leatherback sea turtles. / by Justin R. Perrault. / Thesis (Ph.D.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

The dinoflagellate Karenia brevis is one organism responsible for harmful algal blooms (HABs) that severely impact marine life. K. brevis produces a suite of neurotoxins referred to as brevetoxins (PbTx) which bind to voltage-gated sodium channels (VGSCs) in excitable tissues, affecting cellular permeability leading to a suite of symptoms and potentially cell death. Brevetoxicosis is difficult to treat in sea turtles as the physiological impacts have not been investigated and the magnitude and duration of brevetoxin exposure are generally unknown. Due to their threatened and endangered status, experimental exposures cannot be performed to determine the fate of brevetoxin in sea turtle tissues, making it difficult to design appropriate treatments. The freshwater turtle, Trachemys scripta, was utilized as a model for brevetoxin exposure in turtles. Turtles were exposed to intratracheal instillation (10.53μg/kg) or oral dosing (33.48μg/kg) of PbTx-3 3x weekly over a period of 2-4 weeks. Tissues and fluids were collected for ELISA to determine PbTx-3 uptake and distribution, routes of excretion and rates of clearance (1h-1wk post-exposure). Tissues were also preserved for histopathology. Primary turtle neuronal cell cultures were exposed to PbTx-3 in the presence and absence of various agonists and antagonists to determine brevetoxin’s mode of action. PbTx-3 was widely distributed in all tissues and fluids following both intratracheal and oral exposures, but was largely cleared from the system within 24 hours; PbTx-3 moved into the bile and feces over 48h post exposure indicating that this is the main route of excretion. While exposed animals showed clear behavioral symptoms of toxicity including muscle twitching, swimming in circles, and ataxia, there was no evident tissue pathology. Despite the evident behavioral effects, turtle neurons are surprisingly resistant to PbTx-3, with an EC50 significantly higher than is seen in mammalian neurons. While PbTx-3 exposure resulted in significant Ca2+ influx, various antagonists prevented Ca2+ influx when added with PbTx-3 confirming the mechanism of action through VGSCs. Upregulation of Hsp72 in the turtle brain could be enhancing cell survival. Based on results, intralipid treatment post PbTx-3 exposure rapidly decreases symptoms and proves to be a suitable treatment for toxin exposure. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Sea turtle hatchlings emerge from their nest and quickly crawl to the surf. During the crawl, hatchlings may encounter threats, biotic and abiotic, which can affect their ability to successfully reach the surf. The impact of these threats on hatchling survival during that crawl is largely undocumented. Current methods used to estimate cohort recruitment rely heavily on nest inventory data. This method, however, does not account for post-emergent hatchling mortality that occurs during the crawl. During the 2017-2018 nesting seasons, I quantified the fates of 1,379 loggerhead (Caretta caretta) hatchlings from 26 nest emergences during their crawl from the nest to the surf on the east and west coasts of Florida. I documented hatchling fates at 5 Florida nesting beaches: Wabasso, Boca Raton, Keewaydin Island, Naples, and Anna Maria Island. Overall, 6.5% of all emergent hatchlings died during the crawl from the nests to the surf. Ghost crabs, night herons, foxes, and coyotes killed hatchlings and photopollution and barriers on the beach (both abiotic threats) caused hatchling mortality. Anthropogenic (abiotic) threats accounted for more mortality than did predators. In order to assess how beach urbanization impacts hatchling mortality, I categorized each study site as urban (Wabasso and Naples), intermediate (Anna Maria Island and Boca Raton), or natural (Keewaydin Island) based on the relative levels of shoreline development and human activity at each beach. Sites with intermediate levels of urbanization accounted for greater levels of hatchling mortality than at other beaches due to the absolutely larger numbers of hatchlings lost to a disorientation event and to a beach barrier. Given the small numbers of emergences, at all sites, only a small proportion of the hatchlings mortalities (e.g., between 3 and 12 percent), site type could not be rigorously used as a discriminator. My results provide a better understanding of how specific environmental threats contribute to hatchling mortality. While nest-to-surf mortality is relatively low, its cumulative costs add up to several hundreds of thousands of hatchlings. Armed with this information, nesting beach managers can assess risks and focus their efforts to implement the most effective management practices to minimize losses of this imperiled species. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Worldwide, sea turtles are especially vulnerable immediately after emerging from nests. Many monitoring programs measure hatchling production from nest inventories. These inventories rarely account for mortality occurring post-emergence, leaving an incomplete estimate of hatchling production. This study addresses the nest-to-surf data gap for Florida’s east coast nesting assemblages of loggerhead sea turtles (Caretta caretta). Five locations were surveyed during the 2016 nesting season by using infrared time-lapse imagery, night vision optics, and track maps. Over all beaches, 7.6% of the observed hatchlings did not survive to reach the water. Mortality sources varied by location. Observed predators included: foxes, bobcats, yellow-crowned night herons, ghost crabs, and gulls. Hatchling disorientation and misorientation occurred more frequently in urban areas than natural areas. Factors including number of hatchlings emerging, nest-to-surf distance, and urbanization may help managers estimate nest-to-surf mortality. This study will improve life history models that serve as foundations of conservation management. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Two species of sea turtle, loggerheads (Caretta caretta) and leatherbacks (Dermochelys coriacea) are caught frequently as bycatch in longline fisheries. These fisheries use hooks baited with fish or squid. Yet, leatherbacks feed on gelatinous prey while loggerheads are carnivores. I investigated the responses of these two species to bait odors in controlled laboratory experiments to better understand their feeding behavior and why they interact with longlines. Both species initiated feeding behavior in the presence of squid bait odors and just C. caretta showed feeding behavior with sardine odors; neither responded to mackerel odors. The turtles are hooked differently on longlines. Loggerheads are usually hooked in the mouth while leatherbacks are usually hooked in the shoulder or flippers. Comparisons of prey attack behavior and accuracy in apprehending a stimulus in the presence of waterborne food odors identified speciesspecific differences that may predispose the turtles to particular kinds of hooking. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection