Global ETD Search

1	Orientation and survival of hatchlings and reproductive ecology of the common snapping turtle (Chelydra serpentina) in southern Quebec Robinson, Candace January 1989 (has links) The orientation and survival of neonate snapping turtles (Chelydra serpentina) were studied in 1986 and 1987. Orientation mechanisms were tested in an outdoor parabolic arena. These experiments suggested that positive geotaxis was a dominant cue directing neonate snapping turtles to water. / Hatchling survival and movement from nest to water were studied in Calumet, Quebec using isotope tagging. / A highly significant number of hatchlings (95%) released on sloped nest sites were positively geotactic. Hatchlings released on level ground moved in random directions. / Eighty-two percent of hatchlings from nests within 18 m of the shoreline were successful in reaching water. Incidence of mortality was greatest for hatchlings from nests between 121 and 165 m from water. Mortality resulted from vehicles and predation by bullfrogs (Rana catesbieana) and meadow voles (Microtus pennsylvanicus). / Female carapace length was positively correlated with clutch size and mean egg diameter. Egg diameters were positively correlated with hatchling weights. Clutch sizes of nests more than 100 m from water were larger than those closer to water. Chelydra serpentina -- Reproduction. Turtles -- Québec (Province)
2	Orientation and survival of hatchlings and reproductive ecology of the common snapping turtle (Chelydra serpentina) in southern Quebec Robinson, Candace January 1989 (has links) No description available. Turtles -- Québec (Province) Chelydra serpentina -- Reproduction.
3	Conservation Genetics of Freshwater Turtles Davy, Christina M. 19 March 2013 (has links) Turtles have long life spans, overlapping generations and promiscuous mating systems. Thus, they are an ideal system with which to investigate the application of conservation genetics methods and assumptions to long-lived organisms. Turtles are also one of the most threatened groups of vertebrates and conservation genetics studies are essential to effective recovery of turtle species. This thesis has two main objectives: 1) to evaluate some common population genetics assumptions with respect to turtles and other long-lived organisms, and 2) to collect important information on the population genetics of threatened turtles in Ontario, which can be used to inform species recovery. In Chapters Two and Three, I describe the development of novel microsatellite markers for the snapping turtle and spiny softshell. In Chapter Four I demonstrate significant genetic structure in populations of the endangered spotted turtle in Ontario, and find that “bottleneck tests” may fail to detect recent population declines in small turtle populations. I also show that spotted turtles do not show the typical correlation between population size and genetic diversity. In Chapter Five I use microsatellite markers developed in Chapter Two and document population structure in the widespread snapping turtle for the first time. I compare these results with results from Chapter Four to test the traditionally accepted hypothesis that genetic diversity is reduced in small, isolated populations compared to large, connected populations. As in Chapter Four, my results suggest that the usual patterns of genetic structure and loss of diversity may not apply to turtles. In Chapter Six I conduct a conservation genetics study of the endangered Blanding’s turtle. Finally, in Chapter Seven I combine results from spotted, snapping and Blanding’s turtles to test whether vagility predicts population structure, genetic diversity and significant barriers to gene flow in three species sampled across a single landscape. Analyses reveal minimal congruence in barriers to gene flow and the three species show unexpected and contrasting patterns of diversity across the landscape. Discordant patterns among species highlight areas for further research and shed light on possible cryptic behaviour, and I discuss potential further directions for research in the Summary. microsatellite spatial genetics Emys blandingii Chelydra serpentina Clemmys guttata Apalone spinifera 0478 0472 0369
4	Conservation Genetics of Freshwater Turtles Davy, Christina M. 19 March 2013 (has links) Turtles have long life spans, overlapping generations and promiscuous mating systems. Thus, they are an ideal system with which to investigate the application of conservation genetics methods and assumptions to long-lived organisms. Turtles are also one of the most threatened groups of vertebrates and conservation genetics studies are essential to effective recovery of turtle species. This thesis has two main objectives: 1) to evaluate some common population genetics assumptions with respect to turtles and other long-lived organisms, and 2) to collect important information on the population genetics of threatened turtles in Ontario, which can be used to inform species recovery. In Chapters Two and Three, I describe the development of novel microsatellite markers for the snapping turtle and spiny softshell. In Chapter Four I demonstrate significant genetic structure in populations of the endangered spotted turtle in Ontario, and find that “bottleneck tests” may fail to detect recent population declines in small turtle populations. I also show that spotted turtles do not show the typical correlation between population size and genetic diversity. In Chapter Five I use microsatellite markers developed in Chapter Two and document population structure in the widespread snapping turtle for the first time. I compare these results with results from Chapter Four to test the traditionally accepted hypothesis that genetic diversity is reduced in small, isolated populations compared to large, connected populations. As in Chapter Four, my results suggest that the usual patterns of genetic structure and loss of diversity may not apply to turtles. In Chapter Six I conduct a conservation genetics study of the endangered Blanding’s turtle. Finally, in Chapter Seven I combine results from spotted, snapping and Blanding’s turtles to test whether vagility predicts population structure, genetic diversity and significant barriers to gene flow in three species sampled across a single landscape. Analyses reveal minimal congruence in barriers to gene flow and the three species show unexpected and contrasting patterns of diversity across the landscape. Discordant patterns among species highlight areas for further research and shed light on possible cryptic behaviour, and I discuss potential further directions for research in the Summary. microsatellite spatial genetics Emys blandingii Chelydra serpentina Clemmys guttata Apalone spinifera 0478 0472 0369
5	Spontaneous directional preferences in taxonomically and ecologically distinct organisms: examining cues and underlying mechanisms Landler, Lukas 05 May 2015 (has links) The focus of this research was the spontaneous magnetic alignment responses of animals. We show that snapping turtles (Chelydra serpentina) and crayfish (Cambarus sciotensis) spontaneously align their body axes relative to the magnetic field. In snapping turtles, this response is sensitive to low-level radio frequency fields, consistent with a mechanism involving a light-dependent radical pair mechanism. Findings from the turtle experiments also suggest that the Earth's magnetic field plays an important role in encoding spatial information in novel surroundings, and may help to organize multiple locales into a 'mental map' of familiar space. Given the importance of magnetic input in many aspects of spatial behavior, another important finding was that magnetic alignment of yearling turtles was disrupted by high levels of maternally transferred mercury, an industrial waste product found at high levels in some fresh water ecosystems. In crayfish, we investigated the effects of ectosymbionts (Annelida: Branchiobdellida) on magnetic alignment responses. Interestingly, the response of crayfish to magnetic cues parallels the complex symbiotic interaction between crayfish and their ectosymbiotic worms, which changes from mutualistic to parasitic with increasing worm density. Our working hypothesis was that these changes in spatial behavior may increase or decrease contact to other crayfish, and therefore increase or decrease transmission rates. Next, to address the ontogeny of the SMA, we attempted to replicate an earlier study showing a possible magnetic alignment response in chicken embryos. Although chicken embryos did show non-random alignment, we were not able to find a magnetic effect. Alignment is also an important feature of animal constructions and is very likely to have fitness consequences, which we explored in woodpecker cavity alignments in a meta-analysis of available global data. The latitudinal and continental pattern in 23 species of woodpeckers suggests that an alignment response can have the proximate function to regulate microclimate in the cavity and therefore, presumably, optimize incubation temperatures and increase hatching success. Overall, the presented findings show how experimental and observational studies of spontaneous alignment behavior can provide insight into the ecology and sensory biology of a wide range of animals. / Ph. D. Snapping turtles Chelydra serpentina Cambarus sciotensis Gallus domesticus chicken embryos woodpecker spontaneous magnetic alignment radio frequency radical pair mechanism magnetoreception magnetic orientation cavity alignment
6	Assessment of Cranial Morphology and Function Underlying Dietary Diversity inCryptodires Croghan, Jasmine A. January 2022 (has links) No description available. Anatomy and Physiology Animals Biology Biomechanics Comparative Evolution and Development Ecology Morphology Organismal Biology testudines turtle feeding morphology cryptodire functional morphology feeding morphology diet auto3DGM diceCT geometric morphometrics bite force PCSA specific tension dimorphism sexual dimorphism Malaclemys terrapin Trachemys scripta Chelydra serpentina turtle feeding jaw muscle testudine feeding turtle morphology, turtle diet

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