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PubMed1981

Temperature-sensitive periods of sex determination in Emydid turtles.

In many turtles sex differentiation is controlled by the incubation temperature of the embryo, with low temperatures producing males, high temperatures producing females. This study investigates the developmental period of temperature-sensitivity in two species of emydid turtles, using different combinations of incubation at a male-determining temperature (25 degrees C) and at a female-determining temperature (31 degrees C). The sensitive period extends throughout much of the middle third of development. Sex is more readily influenced by 25 degrees than by 31 degrees, however, so that maleness can be determined much earlier in development than can femaleness. Comparison of these results with a previous study of snapping turtles indicates that the sensitive period occupies somewhat the same developmental interval in these different turtles. However, in snapping turtles, the female-determining temperature used (30 degrees) is more influential than the male-determining temperature (26 degrees), in contrast with these results from emydids.

Animals↗
PubMed2002

Staging criteria for embryos of the spiny softshell turtle, Apalone spinifera (Testudines: Trionychidae).

Previous work describing the embryonic stages of turtle development has not included members of the highly derived trionychid turtles. Staging criteria are described for the spiny softshell turtle (Apalone spinifera) to facilitate comparisons between phylogenetically distant taxa of turtles. Embryonic development in A. spinifera is placed in the context of the widely used sequence of Yntema stages. Novel features are included in the descriptions of staging criteria for Stages 13-26. Comparisons of the development of specific features are made between A. spinifera and other taxa of turtles. Data on the duration of developmental stages at different temperatures and embryo dimensions support the conclusion that morphology-based staging criteria are superior to developmental rate temperature coefficients.

Age Factors↗
PubMed1976

The cranial arteries of turtles and their evolutionary significance.

In this paper the cranial arteries, cranial arterial foramina, and bony canals of the Cheloniidae, Chelydridae, Pelomedusidae, and Chelidae are described in detail. From skull studies and published material, the general cranial arterial patterns of all the turtle families can be inferred. Sea turtles, the Cheloniidae and Dermochelyidae, possess both a large stapedial artery and a large artery supplying the orbit, which is possibly similar to the primitive cranial arterial pattern for turtles. From a primitive pattern in which stapedial and palatine arteries supply the orbit, the Chelydridae and Testudinidae retained a large stapedial artery and reduced the palatine artery, while the Kinosternidae and Dermatemydidae developed a large palatine artery and reduced the stapedial artery. The Trionychidae and probably the Carettochelyidae evolved a complex arterial pattern in which the stapedial artery was reduced somewhat and the pseudopalatine artery was substituted for the palatine artery. Pleurodires in general retained a large stapedial artery and reduced or eliminated the palatine artery. The Podocneminae, including the Madagascar species, developed a highly modified carotid canal, which is found in no other turtle group. The facts which have been presented should aid in fossil skull studies and in understanding the evolutionary background of recent turtles.

Animals↗
PubMed1994

Thyroxine-binding protein represents the major vitamin D-binding protein in the plasma of the turtle, Trachemys scripta.

Structural homology between the high-affinity thyroxine (T4)-binding protein (TBP) in the plasma of the turtle, Trachemys scripta, and vitamin D-binding proteins (DBP) of mammals prompted an investigation of plasma vitamin D binding in the turtle. Several lines of evidence indicate that the TBP represents the primary binding protein for 25-OH-cholecalciferol (D3) in the turtle plasma. D3-binding protein in whole plasma migrates in the same position as TBP by size-exclusion chromatography and polyacrylamide gel electrophoresis; it is electrophoretically distinct from sex hormone-binding proteins. D3 binding to purified TBP alone is enhanced (up to sevenfold) in the presence of plasma proteins, including albumin; with this correction, the D3-binding activity of plasma corresponds to expected TBP titers. Plasma selectively stripped of TBP by affinity chromatography and purified turtle albumin have only trace D3-binding activity. Variations in physiological state (thyroidal status, age, and sex) previously associated with variable T4 binding (and TBP levels) in T. scripta show correlated variability in plasma D3 binding. D3 binding is also highly correlated with T4 binding (r = 0.81; P < 0.001) for plasma samples taken from 30 adults representing 10 different species of Trachemys. D3 binding in plasma exhibits a high-affinity site (Ka = 2.3 x 10(8) M-1) and a second lower-affinity (Ka = 2 x 10(6) M-1), higher-capacity site; capacities are highly variable. Purified TBP has a comparable high affinity (Ka = 2.8 x 10(8) M-1), with a capacity close to 1 mol/mol. Binding of T4 and D3 are not competitive, indicating separate binding sites for the two ligands; in fact, T4 tends to enhance the affinity and the capacity for D3. A single protein in turtle plasma ("TBP/DBP") functions in the transport of two different hormones normally served by two distinct binding proteins (representing different multigene families) in mammals. These results have implications for the mediation of T4 effects on growth.

Animals↗
PubMed1994

The relation of the dual thyroxine/vitamin D-binding protein (TBP/DBP) of emydid turtles to vitamin D-binding proteins of other vertebrates.

The relation of a dual binding protein, involved in the transport of both thyroxine (T4) and vitamin D3, in the blood of emydid turtles to blood proteins in other vertebrates was examined immunologically. Binding studies with 25-OH-[3H]cholecalciferol (D3) confirmed the presence of a D3-binding protein (DBP) in the plasma of a wide variety of chelonian species representing both major suborders, as well as other species of reptiles, amphibians, birds, and mammals. Analysis by polyacrylamide gel electrophoresis (PAGE) showed that these binding proteins exhibited variable electrophoretic mobilities and in some species multiple DBPs were observed. Western blot analysis of these gels and additional tests with SDS-PAGE showed that an antiserum against the dual T4/D3-binding protein (TBP/DBP) from the turtle Trachemys scripta cross-reacted with the DBPs of diverse turtles, one crocodilian (Alligator), and birds; however, there was little or no cross-reaction with plasma from squamate reptiles (three snakes, four lizards), one crocodilian (Osteolaemus), amphibians (two anurans, one urodele), or mammals (six eutherians, one metatherian). The cross-reacting proteins (DBPs) all exhibit a similar M(r) (approximately 60 K). Adsorption of plasma by TBP/DBP-affinity chromatography confirmed this phylogenetic pattern of cross-reactions between the anti-TBP/DBP serum and functional DBPs in chicken, turtle, and alligator blood (affinity adsorption effectively eliminated D3 binding); there was only weak cross-reaction with DBP in a lizard and the second crocodilian (50% reduction in D3 binding) and none with DBP of snakes or mammals (D3 binding was unaffected). Results suggest that the plasma protein (TBP/DBP) that exhibits dual, high-affinity binding of T4 and D3 in one turtle family evolved from the more "primitive" vitamin D-binding protein of stem reptiles; thus, the high-affinity T4-binding site on this molecule is probably a derived characteristic of DBP in the Emydidae.

Amphibians↗
PubMed1995

Estrogen downregulation of albumin and a 170-kDa serum protein in the turtle, Trachemys scripta.

We examined changes in serum protein composition after estradiol-17 beta treatment of ovariectomized female Trachemys scripta, with the objective of identifying proteins that are repressed by estrogen. The experimental protocol was validated by measuring serum estradiol-17 beta levels with a specific radioimmunoassay. Control turtle sera contained little or no estradiol-17 beta (mean = 25.8 pg/ml) while estrogen-treated turtle sera had elevated estradiol-17 beta levels (mean = 333.3 pg/ml). Estrogen treatment resulted in a significant increase in serum protein concentration. The increase was due largely to a 213-kDa protein that was abundant in estrogen-treated animal sera but was low or absent in control animal sera. This protein was identified as vitellogenin based on its biochemical characteristics (molecular weight, elution profile from DEAE, precipitation in the presence of Mg2+/EDTA). Several proteins were decreased in the sera of estrogen-treated animals. One of these had a molecular weight of 66 kDa and was determined to be serum albumin. This protein crossreacted in Western blot analyses with polyclonal antisera against chicken and human serum albumins. Also, amino acid sequence analysis revealed substantial homology between the 66-kDa turtle protein and serum albumins from other vertebrate species. Another protein decreased by estrogen treatment had a molecular weight of 170 kDa. Both albumin and the 170-kDa protein were reduced in estrogen-treated turtles to levels about 50% of those present in control turtles. Using [35S]methionine-labeling and denaturing (SDS) polyacrylamide gel electrophoresis, we detected the presence of newly labeled albumin and the 170-kDa protein in T. scripta liver cube cultures, indicating that these proteins are derived from the liver. Data from this study reveal that estrogen downregulates several serum proteins in T. scripta, while upregulating serum vitellogenin. The response to estrogen in this reptile is similar to that in the amphibian Xenopus laevis, suggesting that estrogen downregulation of serum proteins during vitellogenesis may be widespread among oviparous vertebrates.

Amino Acid Sequence↗
PubMed1994

Sequence analysis of the ZFY and Sox genes in the turtle, Chelydra serpentina.

We have sequenced regions of the ZFY and Sox genes in the turtle Chelydra serpentina, a reptile with temperature-dependent sex determination. The ZFY gene in mammals encodes a transcription factor with multiple zinc fingers that may be involved in spermatogenesis as well as other processes. The turtle homologue, Zft, is 92% identical to the ZFY gene at the nucleotide and amino acid levels in the region of zinc fingers 7-12. There are several Sox genes in the turtle that are only 57-70% identical at the nucleotide level and about 55% identical at the amino acid level to the human sex-determining SRY gene. However, the turtle Sox genes, termed TSox, have the conserved motif called the HMG-box (for high mobility group DNA-binding protein) that defines a probable DNA-binding region, and thus are in the same gene family as the Sox genes of other organisms from Drosophila to man. One TSox sequence is identical at the amino acid level to a sequence found in birds, and is 98% identical to a sequence encoded autosomally in mouse and in man. The extent of sequence conservation among the Sox genes suggests that some of their functions may be conserved. Phylogenetic analysis of available Sox sequences including SRY (Sry) sequences suggests that there was a high degree of divergence between any possible immediate common ancestor of the turtle Sox sequences and the SRY (Sry) sequences.

Amino Acid Sequence↗
PubMed1995

Physiologic and clinicopathologic effects of crude oil on loggerhead sea turtles.

The physiologic and clinicopathologic effects of weathered South Louisiana crude oil exposure were studied in the laboratory in juvenile loggerhead sea turtles. Sea turtles ingested oil incidentally, and oil was observed clinging to the nares, eyes, and upper esophagus, and was found in the feces. Oiled turtles had up to a four-fold increase in white blood cell counts, a 50% reduction in red blood cell counts, and red blood cell polychromasia. Most serum blood chemistries (e.g., BUN, protein) were within normal ranges, although glucose returned more slowly to baseline values than in the controls. Gross and histologic changes were present in the skin and mucosal surfaces of oiled turtles, including acute inflammatory cell infiltrates, dysplasia of epidermal epithelium, and a loss of cellular architectural organization of hte skin layers. The cellular changes in the epidermis are of particular concern because they may increase susceptibility to infection. Although many of the observed physiological insults resolved with a 21-day recovery period, the long-term biological effects of oil on sea turtles remain completely unknown.

Animals↗
PubMed1995

The effect of prolonged anoxia at 3 degrees C on tissue high energy phosphates and phosphodiesters in turtles: a 31P-NMR study.

Selected tissues (skeletal muscle, heart ventrical, and liver), sampled from turtles (Chrysemys picta bellii) at 3 degrees C either under normoxic conditions or after 12 weeks of anoxic submergence were quantitatively analysed for intracellular pH and phosphorus metabolites using 31P-NMR. Plasma was tested for osmolality and for the concentrations of lactate, calcium, and magnesium to confirm anoxic stress. We hypothesized that, in the anoxic animals, tissue ATP levels would be maintained and that the increased osmolality of the body fluids of anoxic turtles would be accounted for by a corresponding increase in the concentrations of phosphodiesters. The responses observed differed among the three tissues. In muscle, ATP was unchanged by anoxia but phosphocreatine was reduced by 80%; in heart, both ATP and phosphocreatine fell by 35-40%. The reduction in phosphocreatine in heart tissue at 3 degrees C was similar to that observed in isolated, perfused working hearts from turtles maintained at 20 degrees C but no decrease in ATP occurred in the latter tissues. In liver, although analyses of several specimens were confounded by line-broadening, neither ATP nor phosphocreatine was detectable in anoxic samples. Phosphosdiesters were detected in amounts sufficient to account for 30% of normoxic cell osmotic concentration in heart and 11% and 12% in liver and muscle, respectively. The phosphodiester levels did not change in anoxia. Heart ventricular phosphodiester levels in turtles at 3 degrees C were significantly higher than those determined for whole hearts from turtles at 20 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1991

Genetic damage in a population of slider turtles (Trachemys scripta) inhabiting a radioactive reservoir.

Turtles inhabiting a radioactive reservoir appear to experience genetic damage due to environmental exposure to low concentrations of long-lived radionuclides. Total body burdens for the 50 reservoir turtles examined in the survey ranged from 164.7-4679.3 Bq for cesium-137 and from 462.6-5098.3 Bq for strontium-90. Flow cytometric (FCM) assays of red blood cell nuclei demonstrated significantly greater variation in DNA content for the reservoir turtles than for turtles from a nearby, non-radioactive site. Furthermore, two of the reservoir turtles possessed FCM profiles that are indicative of aneuploid mosaicism. These data strongly suggest that exposure to low-level radiation may involve a sensitive genetic response in a natural population.

Animals↗
PubMed1998

The rate of mitochondrial 12S rRNA gene evolution is similar in freshwater turtles and marsupials.

Assertions that the "conventional" rate of mitochondrial DNA (mtDNA) evolution is reduced in poikilotherms in general and turtles in particular were tested for side-necked turtles (Pleurodira: Chelidae). Homologous data sets of mitochondrial 12S rRNA gene sequences were used to compare the average divergence between the Australian and South American species for two Gondwanan groups: the chelid turtles and the marsupials. The mean nucleotide divergences between continental groups for both the turtles and the marsupials are remarkably similar. These data suggest that the rate of evolution of mitochondrial 12S rRNA gene is not substantially slower in turtles than in the homeothermic marsupials.

Animals↗
PubMed2000

Growth-related changes in heavy metal accumulation in green turtle (Chelonia mydas) from Yaeyama Islands, Okinawa, Japan.

Concentrations of nine heavy metals (Fe, Mn, Zn, Cu, Pb, Ni, Cd, Co, and Hg) were determined in liver, kidney, and muscle of 50 green turtles (Chelonia mydas) collected from Yaeyama Islands, Okinawa, Japan, to elucidate growth-related changes in heavy metal accumulation during different growth stage. Considerably high Cu concentrations were found in the liver of smaller turtles. Mean hepatic concentration of Cu was 50.2 microg/g wet weight which varied widely (4.27-113 microg/g wet weight). Cadmium concentrations decreased with increasing the carapace length. The juvenile green turtles in the pelagic ocean are likely feed on zooplankton, while adult coastal inhabiting green turtles mainly feed on sea grasses and seaweeds. Concentrations of Cd in sea plants are lower than those in zooplankton. The specific accumulation of Cd found in the green turtle seems to be attributable to their feeding habit, which is a shift from carnivore to herbivore at different growth stages.

Aging↗
PubMed2002

Electrophysiological properties of spinal motoneurons in the adult turtle.

The purpose of this study was to develop a scheme for classifying turtle motoneurons, such that their properties could be compared to those of other vertebrate species, including, in particular, the cat. A 130-cell sample of turtle motoneurons was provisionally classified into four groups (1-4) on the basis of a cluster analysis of the cells' intracellularly recorded input resistance, rheobase, and slope of their stimulus current-spike frequency relation. These measurements, using sharp microelectrodes and an in vitro spinal cord slice preparation, were particularly robust. It is argued that the cat counterpart of our turtle type 1, 2, and 3 motoneurons innervate slow-twitch muscle fibers, fast-twitch-oxidative fibers, and fast-twitch-glycolytic fibers, respectively. Our turtle type 4 motoneuron is thought analogous to a particularly high-threshold cat and human cell that innervates highly fatigable fast-twitch muscle fibers in both species. Our turtle type 1 category may include cells that innervate non-twitch muscle fibers, which are found in other non-mammalian vertebrates. To advance comparative spinal cord neurobiology, the present results invite comparison to the motoneurons of other vertebrate species, which have yet to be subjected to similar or other classification procedures.

Action Potentials↗
PubMed2004

Turtles (Chelodina longicollis) regulate muscle metabolic enzyme activity in response to seasonal variation in body temperature.

Fluctuations in the thermal environment may elicit different responses in animals: migration to climatically different areas, regulation of body temperature, modification of biochemical reaction rates, or assuming a state of dormancy. Many ectothermic reptiles are active over a range of body temperatures that vary seasonally. Here we test the hypothesis that metabolic enzyme activity acclimatises seasonally in freshwater turtles (Chelodina longicollis) in addition to, or instead of, behavioural regulation of body temperatures. We measured body temperatures in free-ranging turtles (n = 3) by radiotelemetry, and we assayed phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS) and cytochrome c oxidase (CCO) activities in early autumn (March, n = 10 turtles), late autumn (May, n = 7) and mid-winter (July, n = 7) over a range of assay temperatures (10 degrees C, 15 degrees C, 20 degrees C, 25 degrees C). Body temperatures were either not different from, or higher than expected from a theoretical null-distribution of a randomly moving animal. Field body temperatures at any season were lower, however, than expected from animals that maximised their sun exposure. Turtles maintained constant PFK, LDH and CCO activities in different months, despite body temperature differences of nearly 13.0 degrees C between March (average daily body temperature = 24.4 degrees C) and July (average = 11.4 degrees C). CS activity did not vary between March and May (average daily body temperature = 20.2 degrees C), but it decreased in July. Thus C. longicollis use a combination of behavioural thermoregulation and biochemical acclimatisation in response to seasonally changing thermal conditions. Ectothermic reptiles were often thought not to acclimatise biochemically, and our results show that behavioural attainment of a preferred body temperature is not mandatory for activity or physiological performance in turtles.

Acclimatization↗
PubMed1999

Influence of inorganic phosphate and energy state on force in skinned cardiac muscle from freshwater turtle and rainbow trout.

Inorganic phosphate, which increases in the hypoxic cardiac cell, depresses force development. The cardiac muscle of freshwater turtle maintains a remarkably high contractility during hypoxia; this may involve a low sensitivity to phosphate. Therefore, freshwater turtle and rainbow trout were compared with regard to Ca(2+)-activated force in skinned atrial trabeculae in a bath containing 3 mM ATP buffered by 15 mM creatine phosphate in the presence of creatine kinase. For turtle, an increase in phosphate from 0 mM to either 6 mM or 12 mM reduced maximal force by 50% and 80% respectively, whereas the Ca2+ activity eliciting half maximal force (Ca0.5) was increased by 70% in 6 mM and could not be reliably recorded in 12 mM. For trout, the effects of phosphate were less pronounced. An increase from 0 mM to 12 mM did not affect maximal force significantly, but elevated Ca0.5 by 70%. Hypoxia increases ADP as creatine phosphate is shifted to creatine, therefore, creatine phosphate was changed from 15 mM to 3 mM and creatine from 0 mM to 12 mM. After these changes, the elevation of phosphate from 0 mM to 12 mM had no significant effects for either turtle or trout. In conclusion, the high performance of turtle cardiac muscle during hypoxia does not involve a low sensitivity of the contractile system to phosphate. In addition, the effect of increased phosphate seems to be offset by a concomitant increase in ADP.

Adenosine Diphosphate↗
PubMed2006

Heavy metal accumulation in four species of sea turtles from the Baja California peninsula, Mexico.

Heavy metals were assessed in four species of sea turtles from the Baja California Peninsula, Mexico, representing the first report of heavy metal concentrations in tissues of post-yearling sea turtles from the Eastern Pacific. Concentrations of Cd measured in C. mydas kidney (653 microg/g dry wt) were the highest ever reported for any sea turtle species. Cd accumulated preferentially in kidney and the ratios of kidney to liver Cd in Baja California turtles were among the highest reported for sea turtles globally. Zn, Ni, and Mn concentrations were also significantly higher in kidney than other tissues, while Cu and Fe were greatest in liver, and all metals were lowest in muscle. With the exception of one value (69.9 microg/g in kidney of C. caretta), Pb was low in all tissues from Baja California. In comparisons across species, kidney of C. mydas had greater Zn and Ni concentrations as compared to other species, although there was no difference in liver metal levels among the species. Positive correlations were detected in the concentrations of Cd, Cu and Ni with the straight carapace length of C. caretta.

Animals↗
PubMed1991

Turtle cortical neurons survive glutamate exposures that are lethal to mammalian neurons.

Glutamate is an excitatory neurotransmitter in turtle and mammalian cortex. In high concentrations it is toxic to mammalian neurons and is an important mediator in the pathway that leads to neuronal death from anoxia. Turtle neurons are remarkably resistant to anoxic injury and we sought to determine whether part of this resistance could be attributed to the sensitivity of turtle neurons to glutamate toxicity. Embryonic turtle cortical neurons were grown for 25 days in dissociated cell culture using a modification of a method developed for murine cortical cell culture. Turtle neurons in dissociated culture were found to express glutamate receptors which include both N-methyl-D-aspartate (NMDA) and non-NMDA receptor types. Remarkably, these neurons survive 5 minute exposures to glutamate in concentrations up to 3 mM, doses 30 times the LD50 and 6 times the LD100 for mouse cortical neurons. Elucidating the mechanism for this resistance may suggest new strategies for brain protection.

Animals↗
PubMed1984

The effects of estrogen on skeletal calcium metabolism and on plasma parameters of vitellogenesis in the male, three-toed box turtle (Terrapene carolina triunguis).

The box turtle (Terrapene carolina triunguis) does not appear to have evolved a mechanism for secondary bone formation similar to Aves inasmuch as several parameters of bone calcium metabolism were unaffected by estrogen treatment. This suggests that reproduction does not constitute a substantial stress to the calcium stores of the female, even though the box turtle is a terrestrial species for which a supply of calcium may be limited. However, the dermal bone of the shell of the box turtle appears to take up calcium at a rate equivalent to that of endoskeletal bones, suggesting that it participates in mineral homeostasis at least to the extent of other osseous elements. Calcium metabolism in the turtle may be unique among vertebrates in this respect. Estrogen treatment of male box turtles results in the appearance of a specific plasma protein in parallel with pronounced changes in plasma calcium and magnesium, suggesting the induction of vitellogenin. The magnitude of the vitellogenic response may have a seasonal component.

Animals↗