The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Kenneth J. Lohmann - One of the best experts on this subject based on the ideXlab platform.
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Magnetic orientation by hatchling loggerhead sea turtles (caretta caretta).
The Journal of experimental biology, 1991Co-Authors: Kenneth J. LohmannAbstract:Laboratory experiments were conducted to test the ability of loggerhead sea turtle hatchlings (caretta caretta L.) to orient using the magnetic field of the earth. Hatchlings were tethered to a rotatable lever-arm apparatus which tracked swimming orientation in complete darkness. Hatchlings tested in the earth9s magnetic field were nonrandomly oriented with a mean angle of 42 degrees; those tested under an earth-strength field with a reversed horizontal component were also nonrandomly oriented, but with a mean angle of 196 degrees. The distributions under the two magnetic field conditions were significantly different, indicating that loggerhead sea turtle hatchlings can detect the magnetic field of the earth and use it as a cue in orientation.
Karen A Bjorndal - One of the best experts on this subject based on the ideXlab platform.
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effect of repeated tissue sampling on growth rates of juvenile loggerhead turtles caretta caretta
Diseases of Aquatic Organisms, 2010Co-Authors: Karen A Bjorndal, Kimberly J Reich, Alan B. BoltenAbstract:We evaluated the effect of repeated tissue sampling on growth rates of juvenile loggerhead sea turtles caretta caretta. Samples of blood, skin, and scute (keratinized epidermal layer covering the bony shell) were collected at 3 intervals over a 120 d period from 37 loggerheads; 8 control turtles were not sampled. No infections or scarring occurred at the sampling sites, and growth in mass of experimental and control turtles was not significantly different. The sampling regime did not affect the health or physiological status of the turtles.
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foraging ecology of oceanic stage loggerhead turtles caretta caretta
Endangered Species Research, 2009Co-Authors: Michael G. Frick, Kristina L. Williams, Karen A Bjorndal, Alan B. Bolten, Helen R MartinsAbstract:We examined stomach contents (n = 12) and fecal samples (n = 4) in the first quantita- tive analysis of diet composition of oceanic-stage loggerhead turtles caretta caretta from the North Atlantic Ocean. We found that loggerheads from the Azores are opportunistic carnivores that feed upon a variety of oceanic and pelagic organisms; our results also show that they exploited novel food resources, such as non-indigenous species. The diversity of prey species was positively correlated with loggerhead body size and volume of stomach contents. Because loggerhead body size was also positively correlated with stomach content volume, we were unable to determine whether increased prey diversity was a result of turtle foraging behavior or simply due to a larger sample volume from larger turtles. Ecological associations among prey species increase the diversity, and possibly the nutritional quality, of prey items, and periodic meteorological events can also increase the diversity of prey items available to loggerhead turtles. Aspects of the life history of some of these prey organ- isms, such as continued egg brooding, increase the nutritional value of prey items consumed by juve- nile turtles.
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Polymodal foraging in adult female loggerheads (caretta caretta)
Marine Biology, 2009Co-Authors: Kimberly J Reich, Michael G. Frick, Karen A Bjorndal, Blair E. Witherington, Chris Johnson, Alan B. BoltenAbstract:To determine whether loggerhead turtles (caretta caretta) nesting in southeastern USA exhibit polymorphic foraging strategies, we evaluated skin samples for stable isotopes of carbon (δ13C) and nitrogen (δ15N) from 310 loggerheads from four locations on the east coast of Florida and epibionts from 48 loggerheads. We found a dichotomy between a depleted δ13C cluster and an enriched δ13C cluster. Epibionts from oceanic/pelagic or neritic/benthic habitats were largely consistent with this dichotomy. The bimodal distribution of δ13C could reflect a bimodal foraging strategy or—because of the potential for confounding among four gradients of δ13C in marine environments—a polymodal foraging strategy. We integrate our results with results from other stable isotope studies, satellite telemetry, and flipper tags to evaluate potential foraging strategies. Understanding foraging strategies is essential for development of management plans for this endangered species that has suffered a 43% population decline over the last decade.
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carapace epibionts of loggerhead turtles caretta caretta nesting at canaveral national seashore florida
Journal of Natural History, 2008Co-Authors: Joseph B. Pfaller, Michael G. Frick, Kristina L. Williams, Kimberly J Reich, Karen A BjorndalAbstract:A survey of the epibionts inhabiting the carapace of loggerhead sea turtles caretta caretta (Linnaeus) nesting on Canaveral National Seashore, Florida was conducted from 2003–2004. Epibionts were sampled and identified to the lowest taxonomic level possible. Eleven newly documented epibiont species were observed from 52 individual loggerheads. We present the first records of sea urchins as loggerhead epibionts. Data are presented on the behavioural, physical, and ecological characteristics of some of these newly documented species to understand better the relationship between loggerhead turtles and their epibiota.
Graeme C. Hays - One of the best experts on this subject based on the ideXlab platform.
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Asynchronous emergence by loggerhead turtle ( caretta caretta ) hatchlings
Die Naturwissenschaften, 2001Co-Authors: Jonathan D. R. Houghton, Graeme C. HaysAbstract:For many decades it has been accepted that marine turtle hatchlings from the same nest generally emerge from the sand together. However, for loggerhead turtles (caretta caretta) nesting on the Greek Island of Kefalonia, a more asynchronous pattern of emergence has been documented. By placing temperature loggers at the top and bottom of nests laid on Kefalonia during 1998, we examined whether this asynchronous emergence was related to the thermal conditions within nests. Pronounced thermal variation existed not only between, but also within, individual nests. These within-nest temperature differences were related to the patterns of hatchling emergence, with hatchlings from nests displaying large thermal ranges emerging over a longer time-scale than those characterised by more uniform temperatures.
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Clutch size for Mediterranean loggerhead turtles (caretta caretta)
Journal of Zoology, 1992Co-Authors: Graeme C. Hays, John R. SpeakmanAbstract:We investigated the number of eggs laid and the total clutch volume for loggerhead turtles (caretta caretta L.) nesting on the Greek island of Cephalonia (38° 09′ N, 20° 33′ E) during 1990. Both the number of eggs laid and clutch volume were positively related to female body size, and the mean explained variation for these relationships (36·6% and 37·7%, respectively) were not significantly different. Clutch volume decreased as the season progressed because individuals laid successively smaller clutches. The inter-nesting interval (range 15–19 days) did not significantly influence the number of eggs laid or clutch volume. For individuals seen laying more than once, female size in combination with the number of a clutch in relation to all the clutches observed for that individual, together explained 65·5% of the variation in clutch volume.
U. Schumacher - One of the best experts on this subject based on the ideXlab platform.
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Histochemical characterisation of carbohydrate residues during the morphogenesis of the urogenital system in caretta caretta
Tissue & Cell, 2005Co-Authors: R Sharma, U. SchumacherAbstract:Abstract The distribution of carbohydrates in the urogenital system of caretta caretta during embryogenesis and post-natal development was investigated by classical carbohydrate histochemical techniques and by the use of fluorescein-labelled lectins. PAS positive glycoconjugates were observed in nephrons of the mesonephros at an earlier stage of development than those from the metanephros. The lectin binding pattern of both kidney precursors revealed that the appearance of terminal carbohydrates in various parts of the nephron are dependent on the developmental stage of the animal. Binding sites for Wheat germ agglutinin and Maclura pomifera agglutinin were the most abundant throughout the developing kidney, whereas reactivity for Soy bean agglutinin and phythaemagglutinin was limited to fewer sites. The results indicate that the compartmentalised expression of cell glycoconjugates in the kidneys of juvenile caretta caretta reflects the morphological and functional maturation of the nephron during development. Less pronounced lectin binding pattern of the gonad and genital ducts and the absence of changes during organogenesis indicate that terminal carbohydrates in the genital system of caretta caretta do not play a major role in sexual differentiation.
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Histochemical characterization of carbohydrate residues during the morphogenesis of gastrointestinal and respiratory systems of caretta caretta
Acta histochemica, 1992Co-Authors: Ram P. Sharma, U. SchumacherAbstract:Summary The distribution of carbohydrates in the gastrointestinal and respiratory tract of caretta caretta during embryogenesis and postnatal development was investigated by histological and histochemical techniques and using fluorescein-labelled lectins. The results indicate that the compartmentalised expression of glycoconjugates found in the juvenile caretta caretta is acquired during development. The occurence of neutral carbohydrates in cells and extracellular matrix was dependent on the developmental stage of the animal. In general, periodic acid Schiff positive glycocon jugates of the respiratory tract occurred at an earlier stage of development than those from the gastrointestinal system. The lectin binding pattern of both organ systems revealed a more refined pattern of the types of carbohydrates present during development. Wheat germ agglutinin showed the broadest binding pattern, whereas Soy bean agglutinin and phythaemagglutinin were more limited in their binding to tissue structures. The terminal carbohydrates detected in the gastrointestinal and respiratory tract of caretta caretta were similar to those observed in mammals; this finding emphasises the suitability of caretta caretta as a model system for amniote development.
Michael G. Frick - One of the best experts on this subject based on the ideXlab platform.
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foraging ecology of oceanic stage loggerhead turtles caretta caretta
Endangered Species Research, 2009Co-Authors: Michael G. Frick, Kristina L. Williams, Karen A Bjorndal, Alan B. Bolten, Helen R MartinsAbstract:We examined stomach contents (n = 12) and fecal samples (n = 4) in the first quantita- tive analysis of diet composition of oceanic-stage loggerhead turtles caretta caretta from the North Atlantic Ocean. We found that loggerheads from the Azores are opportunistic carnivores that feed upon a variety of oceanic and pelagic organisms; our results also show that they exploited novel food resources, such as non-indigenous species. The diversity of prey species was positively correlated with loggerhead body size and volume of stomach contents. Because loggerhead body size was also positively correlated with stomach content volume, we were unable to determine whether increased prey diversity was a result of turtle foraging behavior or simply due to a larger sample volume from larger turtles. Ecological associations among prey species increase the diversity, and possibly the nutritional quality, of prey items, and periodic meteorological events can also increase the diversity of prey items available to loggerhead turtles. Aspects of the life history of some of these prey organ- isms, such as continued egg brooding, increase the nutritional value of prey items consumed by juve- nile turtles.
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Polymodal foraging in adult female loggerheads (caretta caretta)
Marine Biology, 2009Co-Authors: Kimberly J Reich, Michael G. Frick, Karen A Bjorndal, Blair E. Witherington, Chris Johnson, Alan B. BoltenAbstract:To determine whether loggerhead turtles (caretta caretta) nesting in southeastern USA exhibit polymorphic foraging strategies, we evaluated skin samples for stable isotopes of carbon (δ13C) and nitrogen (δ15N) from 310 loggerheads from four locations on the east coast of Florida and epibionts from 48 loggerheads. We found a dichotomy between a depleted δ13C cluster and an enriched δ13C cluster. Epibionts from oceanic/pelagic or neritic/benthic habitats were largely consistent with this dichotomy. The bimodal distribution of δ13C could reflect a bimodal foraging strategy or—because of the potential for confounding among four gradients of δ13C in marine environments—a polymodal foraging strategy. We integrate our results with results from other stable isotope studies, satellite telemetry, and flipper tags to evaluate potential foraging strategies. Understanding foraging strategies is essential for development of management plans for this endangered species that has suffered a 43% population decline over the last decade.
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carapace epibionts of loggerhead turtles caretta caretta nesting at canaveral national seashore florida
Journal of Natural History, 2008Co-Authors: Joseph B. Pfaller, Michael G. Frick, Kristina L. Williams, Kimberly J Reich, Karen A BjorndalAbstract:A survey of the epibionts inhabiting the carapace of loggerhead sea turtles caretta caretta (Linnaeus) nesting on Canaveral National Seashore, Florida was conducted from 2003–2004. Epibionts were sampled and identified to the lowest taxonomic level possible. Eleven newly documented epibiont species were observed from 52 individual loggerheads. We present the first records of sea urchins as loggerhead epibionts. Data are presented on the behavioural, physical, and ecological characteristics of some of these newly documented species to understand better the relationship between loggerhead turtles and their epibiota.