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Breeding sex ratios of three imperiled marine turtles nesting in southern Florida
Title
Breeding sex ratios of three imperiled marine turtles nesting in southern Florida.
Creator
Lasala, Jacob, Hughes, Colin, Wyneken, Jeanette, Graduate College
Abstract/Description
Sound assessment of the status of a threatened or endangered organism depends on understanding key aspects of behavior throughout its life history. Sometimes organisms can be difficult to observe and key aspects of behavior may not be accessed directly. Alternative assessment techniques include using molecular markers to identify fundamental relationships among males and females. In the context of assessing the status of imperiled populations’ sex ratios, population size and the relatedness...
Show moreSound assessment of the status of a threatened or endangered organism depends on understanding key aspects of behavior throughout its life history. Sometimes organisms can be difficult to observe and key aspects of behavior may not be accessed directly. Alternative assessment techniques include using molecular markers to identify fundamental relationships among males and females. In the context of assessing the status of imperiled populations’ sex ratios, population size and the relatedness of the individuals are important metrics. Environmental sex determination directs developing marine turtle sex so that primary sex ratios depend upon weather and climate; those sex ratios are estimated by proxies. Adult population sizes are inferred from numbers of females nesting on the beach, but numbers of males are unknown. Male breeding population size can be estimated from subtracting maternal genotypes from genotypes of offspring exclusion analyses. The resulting adult sex ratios differ greatly from those estimated for hatchlings. To refine current adult sex ratios in ways that are relevant to production of future generations and add to our understanding of effective population size we compare the breeding sex ratios the number of males and females contributing to a population of three species of sea turtles nesting in southern Florida. We will use the same genetic data to measure relatedness of the female nesters and the male contributors and describe how that relates to genetic flow and population structure.
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00005893
Format
Document (PDF)
Experimental assessment of moisture effects on loggerhead sea turtle sex ratios
Title
Experimental assessment of moisture effects on loggerhead sea turtle sex ratios.
Creator
Lolavar, Alexandra, Wyneken, Jeanette, Graduate College
Abstract/Description
Nest sand temperature strongly influences development of sea turtle embryos and sex differentiation; however in nature eggs experience temperature along with other environmental factors. We tested the hypothesis that moisture effects sea turtle hatchling sex ratios. We studied the relationships among moisture, temperature, and loggerhead Caretta caretta sex ratios in an experimental study. Eggs were incubated in sterile nest sand in the laboratory under different moisture regimes to test the...
Show moreNest sand temperature strongly influences development of sea turtle embryos and sex differentiation; however in nature eggs experience temperature along with other environmental factors. We tested the hypothesis that moisture effects sea turtle hatchling sex ratios. We studied the relationships among moisture, temperature, and loggerhead Caretta caretta sex ratios in an experimental study. Eggs were incubated in sterile nest sand in the laboratory under different moisture regimes to test the role of humidity at a constant incubation temperature. Incubator temperature was set at 29.4 degrees C, a temperature that is slightly above the temperature that should yield a 1:1 sex ratio. Nest moisture was maintained by daily DI water treatments and high relative humidity was maintained with the aid of a mist humidifier throughout incubation. All hatchlings were collected, raised for several months and sexed laparoscopically to establish sex ratios for each treatment. The experimental treatments tested the effects of i very high moisture, ii moisture with potential for evaporative cooling, and iii moisture added at average rain temperatures plus the potential for evaporative cooling. The nests were expected to produce a moderate female bias if moisture played no role. We found 87-96 males across all experimental treatments. Our results support our hypothesis. High moisture conditions can produce shifts in developmental response from that expected based on temperature alone.
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00005897
Format
Document (PDF)
Using an immunohistochemical approach to identify the sex of marine turtles
Title
Using an immunohistochemical approach to identify the sex of marine turtles.
Creator
Tezak, Boris, Wyneken, Jeanette, Graduate College
Abstract/Description
Marine turtles exhibit temperature-dependent sex determination (TSD). During critical periods of embryonic development, the nest’s thermal environment directs whether an embryo will develop as a male or a female. At warmer sand temperatures the nest tends to produce female-biased sex ratios. The rapid increase of global temperature highlights the need for a clear assessment of effects on sea turtle sex ratios. However, identifying hatchling sex ratios at rookeries remain coarse estimates due...
Show moreMarine turtles exhibit temperature-dependent sex determination (TSD). During critical periods of embryonic development, the nest’s thermal environment directs whether an embryo will develop as a male or a female. At warmer sand temperatures the nest tends to produce female-biased sex ratios. The rapid increase of global temperature highlights the need for a clear assessment of effects on sea turtle sex ratios. However, identifying hatchling sex ratios at rookeries remain coarse estimates due to the lack of any external gender markers. We rely mainly upon laparoscopic procedures to verify a hatchling sex; however, in some species, morphological sex can be ambiguous even at the histological level. Recent studies using immunohistochemical techniques identified that red-eared slider (Trachemys scripta) embryos over-expressed a particular cold-induced RNA binding protein in the ovaries in comparison to the testes. This principle allows the distinction between females and males. We developed a variation of this technique and successfully identified the sexes of loggerhead sea turtle (Caretta caretta) hatchlings, as confirmed by standard histological and laparoscopic methods that reliably identifies the sex in this species. Next, we tested a more challenging species, the leatherback turtle (Dermochelys coriacea), which retains many neotenic features. The morphology of leatherback hatchling gonads remains difficult to interpret, particularly when dead-in-nest hatchlings and embryos are the source tissues. In summary, this new and more efficient technique enhances our ability to investigate and identify baseline hatchling sex ratios, a critical progression in assessing global climate change on sea turtle populations.
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00005915
Format
Document (PDF)
How many males are there? An examination of operational sex ratio within marine turtle nesting populations in southern Florida.
Title
How many males are there? An examination of operational sex ratio within marine turtle nesting populations in southern Florida.
Creator
Lasala, Jacob, Wyneken, Jeanette, Graduate College
Abstract/Description
Characterizing a species mating system is integral to understanding its natural history and is critical to the development of effective conservation strategies. A mating system is typically described by examining a single population and subsequently drawing inferences on the whole of the species. Variation among populations and gaps in understanding of a species often are revealed when studies are compared between several locations. The majority of available marine turtle mating system data...
Show moreCharacterizing a species mating system is integral to understanding its natural history and is critical to the development of effective conservation strategies. A mating system is typically described by examining a single population and subsequently drawing inferences on the whole of the species. Variation among populations and gaps in understanding of a species often are revealed when studies are compared between several locations. The majority of available marine turtle mating system data stem from nesting females or hatchlings scurrying off the beach. This practice left glaring holes in the understanding of these imperiled organisms in particular with respect to males. We use exclusion paternity analysis to compare the genotype of a nesting female with genotypes from a subset of her offspring and deduce male genotypes to identify and count the number of males contributing per clutch. Loggerheads Caretta caretta, green turtles Chelonia mydas and tleatherbacks Dermochelys coriacea are protected species with spatially and temporally overlapping nesting beaches. The genotypes of the three species nesting in southern Florida will be compared among clutches to define mating systems. Additionally, we will provide the first measure of operational population size for both males and females in southern Florida. Finally, by comparing results from several beaches, the interconnectedness of rookeries through male-mediated gene flow will be determined as well as the relatedness of males. Our approach to establishing the mating systems of hard-to access-life stages will have strong conservation value in strengthening the demographics that form the core of species assessment and management.
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Date Issued
2014
PURL
http://purl.flvc.org/fau/fd/FA00005155
Format
Document (PDF)