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At least 91 records · Page 5Linked to original sources
PubMed1990

Seasonal changes in serum gonadal steroids associated with migration, mating, and nesting in the loggerhead sea turtle (Caretta caretta).

Adult male loggerhead sea turtles, Caretta caretta, exhibited a "prenuptial" spermatogenic cycle that was coincident with increased concentrations of serum testosterone (T). Serum T was high during the months when migration and mating have been recorded for males. In contrast to females, males appear to be annual breeders. Nine reproductively active female C. caretta (as verified through laparoscopy) were tagged with sonic transmitters and were repeatedly bled prior to migration. Four months prior to the nesting season, the ovaries of reproductively active females had hundreds of vitellogenic follicles of approximately 1.5 cm in diameter (i.e., half the size of ovulatory follicles). Approximately 4-6 weeks prior to migration from feeding grounds to mating and nesting areas, serum estradiol-17 beta (E2) concentrations increased significantly and remained high for approximately 4 weeks, suggesting a period of increased vitellogenesis. During a 1- to 2-week period prior to migration, serum E2 decreased significantly, while serum T concentrations increased (at least) until the time of migration. Serum T, E2, and progesterone (PRO) were elevated during nesting if a turtle was going to nest again during that nesting season. During the last nesting of a season, turtles had low serum concentrations of T, E2, and Pro. The prenuptial pattern of gonadal recrudescence and gonadal steroid production in both male and female C. caretta contrasts with those of many temperate freshwater turtles, and this type of reproductive pattern may have been facilitated by adaptation to a tropical marine environment.

Animals↗
PubMed1991

Evolutionary distinctiveness of the endangered Kemp's ridley sea turtle.

The endangered Kemp's ridley sea turtle (Lepidochelys kempi) nests almost exclusively at a single locality in the western Gulf of Mexico, whereas the olive ridley (L. olivacea) nests globally in warm oceans. Morphological similarities between kempi and olivacea, and a geographical distribution that "...makes no sense at all under modern conditions of climate and geography", raise questions about the degree of evolutionary divergence between these taxa. Analysis of mitochondrial (mt) DNA restriction sites shows that Kemp's ridley is distinct from the olive ridley in matriarchal phylogeny, and that the two are sister taxa with respect to other marine turtles. Separation of olive and the Kemp's ridley lineages may date to formation of the Isthmus of Panama, whereas the global spread of the olive ridley lineage occurred recently. In contrast to recent examples in which molecular genetic assessments challenged systematic assignments underlying conservation programmes, our mtDNA data corroborate the taxonomy of an endangered form.

Animals↗
PubMed1995

Reptile heme protein structure: X-ray crystallographic study of the aquo-met and cyano-met derivatives of the loggerhead sea turtle (Caretta caretta) myoglobin at 2.0 A resolution.

The X-ray crystal structures of the aquo-met and cyano-met derivatives of the loggerhead sea turtle (Caretta caretta) myoglobin have been determined at 2.0 A resolution (R = 0.182, and 0.178, respectively). The results here reported, representing the first reptile globin solved by X-ray crystallography, have been analyzed in parallel with data for related monomeric hemoproteins, and indicate a strong overall structural similarity between the loggerhead sea turtle and mammalian myoglobins, reflected by the 63% amino acid identity of their primary structures. The root-mean-square deviation between the entire polypeptide backbones of loggerhead sea turtle and sperm whale myoglobins, after structure superposition, is 0.83 A. Upon cyanide binding to the protein distal site, the iron-bound water molecule present in the aquo-met form is displaced by the incoming ligand. Cyanide is oriented towards the inner part of the heme distal site forming a Fe-C-N angle of 133 degrees.

Animals↗
PubMed2004

Comparison of functional aspects of the coagulation cascade in human and sea turtle plasmas.

Functional hemostatic pathways are critical for the survival of all vertebrates and have been evolving for more than 400 million years. The overwhelming majority of studies of hemostasis in vertebrates have focused on mammals with very sparse attention paid to reptiles. There have been virtually no studies of the coagulation pathway in sea turtles whose ancestors date back to the Jurassic period. Sea turtles are often exposed to rapidly altered environmental conditions during diving periods. This may reduce their blood pH during prolonged hypoxic dives. This report demonstrates that five species of turtles possess only one branch of the mammalian coagulation pathway, the extrinsic pathway. Mixing studies of turtle plasmas with human factor-deficient plasmas indicate that the intrinsic pathway factors VIII and IX are present in turtle plasma. These two factors may play a significant role in supporting the extrinsic pathway by feedback loops. The intrinsic factors, XI and XII are not detected which would account for the inability of reagents to induce coagulation via the intrinsic pathway in vitro. The analysis of two turtle factors, factor II (prothrombin) and factor X, demonstrates that they are antigenically/functionally similar to the corresponding human factors. The turtle coagulation pathway responds differentially to both pH and temperature relative to each turtle species and relative to human samples. The coagulation time (prothrombin time) increases as the temperature decreases between 37 and 15 degrees C. The increased time follows a linear relationship, with similar slopes for loggerhead, Kemps ridley and hawksbill turtles as well as for human samples. Leatherback turtle samples show a dramatic nonlinear increased time below 23 degrees C, and green turtle sample responses were similar but less dramatic. All samples also showed increased prothrombin times as the pH decreased from 7.8 to 6.4, except for three turtle species. The prothrombin times decreased, to varying extents, in a linear fashion relative to reduced pH with the rate of change greatest in leatherbacks>green>>loggerhead turtles. All studies were conducted with reagents developed for human samples which would impact on the quantitative results with the turtle samples, but are not likely to alter the qualitative results. These comparative studies of the coagulation pathway in sea turtles and humans could enhance our knowledge of structure/function relationships and evolution of coagulation factors.

Animals↗
PubMed2005

Saving sea turtles: the evolution of the IUCN Marine Turtle Group.

When Peter Scott became chairman of the Survival Service Commission of the International Union for the Conservation of Nature and Natural Resources (IUCN) in 1963, he invited Archie Carr to chair the Marine Turtle Group (MTG). A leading authority on the ecology and conservation of sea turtles, Carr believed that the MTG could be the first international forum for sea turtle research and conservation. The assembly of data for the IUCN Red Data Book revealed which species of turtles were threatened with extinction and the array of risks that they faced. Although Carr and Scott differed on what courses of action should be taken in light of this, the MTG did emerge as an important international congress that remains an inspiration to current marine protection efforts.

Animals↗
PubMed1991

Magnetic orientation by hatchling loggerhead sea turtles (Caretta caretta).

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 earth's 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.

Animals↗
PubMed1977

Quantitative requirements of the hatchling green sea turtle for lysine, tryptophan, and methionine.

The quantitative requirement for the amino acids lysine, tryptophan, and methionine was determined for the hatchling green sea turtle (Chelonia mydas). Hatchling green sea turtles were fed synthetic diets of purified substances with the composition of the diet varying in the amount of lysine, tryptophan or methionine present. The lysine requirement was found to be 4.8% of the crude protein (N X 6.25) or 1.7% of the dry diet. The tryptophan requirement was found to be 0.63% of the crude protein or 0.22% of the dry diet. The methionine requirement, in the presence of adequate cystine (3.1% of the crude protein), was found to be 1.5% of the crude protein or 0.49% of the dry diet.

Animals↗
PubMed2004

Intestinal candidiasis in a loggerhead sea turtle (Caretta caretta): an immunohistochemical study.

Post mortem examination of a juvenile loggerhead sea turtle (Caretta caretta) stranded in the Canary Islands revealed a fishing-line in the small intestine. Histologically, severe necrotic enteritis, multiple haemorrhages, and marked oedema of the intestinal submucosa were observed. Yeast cells and fungal hyphae were seen in the lamina propria of the intestinal mucosa and in the connective tissue of the submucosa. Because fungal cultures were not taken at the time of necropsy, an immunohistochemical study was performed in order to identify the fungus involved. Specific monoclonal and heterologously absorbed polyclonal antibodies served as the primary reagents for identification of aspergillosis, candidiasis, fusariosis, geotricosis, scedosporiosis, and zygomycosis, using an indirect immunofluorescence staining technique. The fungal elements were strongly stained only by a polyclonal antibody against Candida albicans and a monoclonal antibody against C. albicans. There are no known previous reports of Candida sp. causing skin disease or systemic mycotic infection in sea turtles.

Animals↗
PubMed1994

ACQUISITION OF MAGNETIC DIRECTIONAL PREFERENCE IN HATCHLING LOGGERHEAD SEA TURTLES

During their natal migration, hatchling loggerhead sea turtles (Caretta caretta L.) establish courses towards the open ocean and maintain them after swimming beyond sight of land. Laboratory experiments have demonstrated that swimming hatchlings can orient using the earth's magnetic field. For the magnetic compass to function in guiding the offshore migration, however, hatchlings must inherit or acquire a magnetic directional preference that reliably leads them towards the open sea. On land, hatchlings find the ocean using light cues associated with the seaward horizon. To determine whether turtles might acquire a preference for a specific magnetic direction on the basis of such cues, we studied the magnetic orientation of turtles initially exposed to light from either magnetic east or west. Hatchlings that had been exposed to light in the east subsequently oriented eastward when tested in darkness, whereas those that had been exposed to light in the west swam westward. Reversing the magnetic field resulted in a corresponding shift in orientation, indicating that the turtles were orienting to the ambient magnetic field. These results demonstrate that light cues can set the preferred direction of magnetic orientation by loggerhead hatchlings. We therefore hypothesize that hatchlings initially establish a seaward course using visual cues available on or near land, then maintain the course using magnetic cues as they migrate into the open sea.

Journal Article↗
PubMed1989

Respiratory mechanics of the loggerhead sea turtle, Caretta caretta.

Respiratory mechanics were evaluated in excised lungs and in spontaneously breathing loggerhead sea turtles (Caretta caretta). Respiratory compliance curves reflect the pressure volume characteristics of the body wall. Compliance values are comparable to those of reptiles having simpler lung structure. Maximum flow rates in excised lungs (18-25 ml.sec-1.kg-1) were only slightly below the range reported for marine mammals. During spontaneous tidal breathing expiratory flow rates (11.8 ml.sec-1.kg-1) were lower than maximum values. In the sea turtle, respiratory adaptations including reduced airway resistance and muscular contribution to breathing are similar to marine mammals. These mechanical specializations shorten breathing time, which contributes to diving performance.

Animals↗
PubMedDate not supplied

Effects of organochlorine compounds on cytochrome P450 aromatase activity in an immortal sea turtle cell line.

Many classes of environmental contaminants affect the reproductive function of animals through interactions with the endocrine system. The primary components affected by endocrine active compounds (EACs) are the steroid receptors and the enzymes responsible for steroidogenesis. This study sought to develop an in vitro model for assessing EAC effects in sea turtles by examining their ability to alter cytochrome P450 aromatase (CYP19) activity. Aromatase is the enzyme responsible for the conversion of testosterone to estradiol. This enzyme is critical in the sexual differentiation of reptiles which demonstrate temperature-dependent sex determination. An immortal testis cell line GST-TS from a green sea turtle was grown in culture at 30 degrees C in RPMI 1640 media. The cells were exposed to three known aromatase inducers; dexamethasone (Dex), 8Br-cyclic AMP, or human chronic gonadotropin (HCG) and one aromatase inhibitor 4-androstenol-dione (4-OHA). In addition, the GST-TS cells were exposed to 0.1-30 microM atrazine and 3-100 microM 4,4'-DDE. The inducing compounds that have been shown to increase aromatase activity in other systems failed to induce aromatase activity in the GST-TS cells, yet exposure to the inhibiting compound, 4-OHA, did result in a significant reduction. Atrazine (0.1, 1.0 and 10 microM) significantly induced aromatase activity following a 24 h exposure, and 4,4'-DDE inhibited the activity but only at cytotoxic concentrations (100 microM). Based on these results, this in vitro model can be useful in examining the endocrine effects of EACs in sea turtles.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2006

Inter-seasonal maintenance of individual nest site preferences in hawksbill sea turtles.

Within a single population of hawksbill sea turtles (Eretmochelys imbricata), we found a behavioral polymorphism for maternal nest site choice with respect to beach microhabitat characteristics. Some females preferred to nest in littoral forest and in places with overstory vegetation cover, and others preferred to nest in more open, deforested areas. Nest site choice was consistent within and between nesting seasons two years apart. This was not a result of females simply returning to the same location along the shoreline; beach sections used by individual turtles varied between seasons. Nest site choice was not influenced by changes in beach environment (e.g., beach width and foliage cover) or by changes in females' reproductive output (e.g., clutch size), suggesting that fidelity to particular microhabitats is a major determinant of the observed nesting patterns. Because hawksbills exhibit temperature-dependent sex determination, if the behavioral polymorphism in nest site choice has a genetic basis, as is plausible, then this would have implications for sex ratio evolution and offspring survival. By taking an individual-based approach to the study of maternal behavior we reveal previously overlooked individual variation and hope to provide some impetus for more detailed studies of nest site choice.

Animals↗
PubMed1979

Mycotic pneumonia in mariculture-reared green sea turtles.

Microbiologic examination of 29 juvenile green sea turtles with a buoyancy abnormality revealed pulmonary infection with Sporotrichium sp, Cladosporium sp, and Paecilomyces sp. Histologic examination of the lungs revealed granulomatous lesions containing branching septate hyphae. The diagnosis was mycotic pneumonia.

Animals↗
PubMed1989

Increased levels of arginine vasotocin and neurophysin during nesting in sea turtles.

Arginine vasotocin (AVT) and neurophysin (NP) levels were measured by radioimmunoassay in two species of sea turtle, the olive ridley, Lepidochelys olivacea, and the loggerhead, Caretta caretta, during the brief period of nesting and oviposition. In both species, AVT was low in animals which were not reproductively active. AVT was also low at the time animals emerged from the surf to nest, but increased significantly during oviposition and then declined as the animals returned to the water. NP increased in concert with AVT, also reaching highest levels during oviposition. In both species, however, NP levels remained elevated over prenesting levels at the time of return to the water. These findings are consistent with the hypothesis that an AVT-neurophysin complex is released from the neurohypophysis during nesting, and that AVT is a physiological regulator of oviducal contractions in sea turtles.

Animals↗
PubMed2003

Seasonal variation in plasma catecholamines and adipose tissue lipolysis in adult female green sea turtles (Chelonia mydas).

We investigated three aspects of potential interrenal regulation of reproduction in female green sea turtles, Chelonia mydas. First, seasonal trends in plasma catecholamines were examined from female C. mydas at different stages of their reproductive cycles. Second, variation in catecholamine levels during a nesting season were analysed in relation to restraint time, and ecological variables such as nesting habitat, body size, and reproductive investment. Third, catecholamine and corticosterone (CORT) induced lipolysis was investigated with adipose tissue collected from gravid green turtles, using in vitro incubations. Plasma epinephrine (EPI) was lowest in non-vitellogenic (1.55 +/- 0.26 ng/ml) and post-breeding (1.57 +/- 0.22 ng/ml) females, and highest in courting females (2.87 +/- 0.28). Concentrations of norepinephrine (NE) and EPI were relatively constant throughout a nesting season, and not significantly related to restraint time, reproductive investment or nesting habitat. In vitro concentrations of CORT (>3 ng/ml) and NE (2 ng/ml) induced significant release of glycerol after 6h of incubation. Epinephrine tended to induce an antilipolytic affect at low concentrations (0.25 ng/ml) and a net lipolytic response at higher concentrations (>1 ng/ml). Our data suggest that EPI may play a role in regulating body condition during vitellogenesis, and maintaining energy stores during prolonged aphagia during courtship and nesting in female green sea turtles. Furthermore, we provide preliminary evidence that suggests that catecholamine production may be either down regulated or de-sensitised in gravid female C. mydas.

Adipose Tissue↗
PubMed1982

Effects of pH, CO2 and organic phosphates on oxygen affinity of sea turtle hemoglobins.

The affinities of adult-type hemoglobins of green (Chelonia mydas) and loggerhead (Caretta caretta) sea turtles were determined at 25.7 degrees C as a function of pH, PCO2 and each of the organic phosphates found in erythrocytes of these species (ATP, IHP (substitute for IPP) and DPG). Each species showed a single hemoglobin band in cellulose acetate electrophoresis which isoelectric focusing resolved into one major and three minor components having isoelectric points near pH 7.2. Oxygen binding curves were recorded using a modified 'Hemoscan' (Instrument Division, Travenol Laboratories, Savage, MD). Hemolysates were kept saturated with CO during preparation to prevent methemoglobin formation. CO was driven off immediately before performing each oxygen binding determination, using the photodissociative effect of the Hemoscan light beam. In both species, phosphate-free hemoglobin has higher affinity than whole blood, and had lower pH sensitivity. CO2 (37 Torr) reduces affinity, particularly in the green sea turtle, and eliminates pH sensitivity. Each organic phosphate tested reduces affinity, with IHP being most effective at a given concentration and DPG least effective. Organic phosphates are most effective at low pH, and restore both pH sensitivity and oxygen affinity to whole-blood levels taking into account the difference between plasma and intracellular pH. Reasons are suggested why the organic phosphate effect was not detected in a previous study. Hemolysates of both species are distinctive in giving upward-curving Hill plots, with n = 1 asymptotes at low saturation that are insensitive to pH, CO2 and organic phosphates. The oxygen affinities corresponding to these asymptotes are about 100 Torr in both species. Results are compared to oxygen dissociation curves obtained from whole blood.

Animals↗
PubMed2006

Phenotypically linked dichotomy in sea turtle foraging requires multiple conservation approaches.

Marine turtles undergo dramatic ontogenic changes in body size and behavior, with the loggerhead sea turtle, Caretta caretta, typically switching from an initial oceanic juvenile stage to one in the neritic, where maturation is reached and breeding migrations are subsequently undertaken every 2-3 years. Using satellite tracking, we investigated the migratory movements of adult females from one of the world's largest nesting aggregations at Cape Verde, West Africa. In direct contrast with the accepted life-history model for this species, results reveal two distinct adult foraging strategies that appear to be linked to body size. The larger turtles (n = 3) foraged in coastal waters, whereas smaller individuals (n = 7) foraged oceanically. The conservation implications of these findings are profound, with the population compartmentalized into habitats that may be differentially impacted by fishery threats in what is a global fishing hotspot. Although the protection of discrete areas containing coastal individuals may be attainable, the more numerous pelagic individuals are widely dispersed with individuals roaming over more than half a million square kilometers. Therefore, mitigation of fisheries by-catch for sea turtles in the east Atlantic will likely require complex and regionally tailored actions to account for this dichotomous behavior.

Africa, Western↗
PubMed1997

PCB concentrations of eggs and chorioallantoic membranes of loggerhead sea turtles (Caretta caretta) from the Cape Romain National Wildlife Refuge.

PCBs were found in eggs and chorioallantoic membranes (CAMs) of loggerhead sea turtles (Caretta caretta). Total PCB concentrations in CAMs were larger than concentrations in eggs. Total PCB concentrations in egg and CAM tissues were highly correlated (r2 = 0.782; p = 0.0001). Sums of PCB congeners within homologue groups were also correlated in the two tissues. Data from these turtle eggs indicate 1) PCB concentrations in CAMs represent PCB concentrations in whole eggs and 2) CAMs can be collected in a nonlethal manner to determine PCB concentrations in sea turtle hatchlings.

Allantoin↗