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PubMed2003

Current transport of leatherback sea turtles (Dermochelys coriacea) in the ocean.

While the long-distance movements of pelagic vertebrates are becoming known thanks to satellite telemetry, the factors determining their courses have hardly been investigated. We have analysed the effects of oceanographic factors on the post-nesting movements of three satellite-tracked leatherback turtles (Dermochelys coriacea) moving in the southwest Indian Ocean. By superimposing the turtle tracks on contemporaneous images of sea-surface temperatures and sea height anomalies, we show that currentrelated features dominate the shape of the reconstructed routes. After an initial offshore movement, turtles moved along straight routes when in the core of the current, or executed loops within eddies. Large parts of the routes were strikingly similar to those of surface drifters tracked in the same region. These findings document that long-lasting oceanic movements of marine turtles may be shaped by oceanic currents.

Animal Migration↗
PubMed2006

First gut contents in a Cretaceous sea turtle.

Modern sea turtles utilize a variety of feeding strategies ranging from herbivory to omnivory. In contrast, the diets of fossil sea turtles are poorly known. This study reports the first direct evidence: inoceramid bivalve shell pieces (encased in phosphatic material) preserved within the body cavities of several small protostegid turtles (cf. Notochelone) from the Lower Cretaceous of Australia. The shell fragments are densely packed and approximately 5-20 mm across. Identical shell accumulations have been found within coprolite masses from the same deposits; these are of a correct size to have originated from Notochelone, and indicate that benthic molluscs were regular food items. The thin, flexible inoceramid shells (composed of organic material integrated into a prismatic calcite framework) appear to have been bitten into segments and ingested, presumably in conjunction with visceral/mantle tissues and encrusting organisms. Although protostegids have been elsewhere interpreted as potential molluscivores, their primitive limb morphology is thought to have limited them to surface feeding. However, the evidence here that at least some forms were able to utilize benthic invertebrate prey indicates that, like modern sea turtles, protostegids probably exhibited a much broader range of feeding habits.

Animals↗
PubMed2006

A primitive protostegid from Australia and early sea turtle evolution.

Sea turtles (Chelonioidea) are a prominent group of modern marine reptiles whose early history is poorly understood. Analysis of exceptionally well preserved fossils of Bouliachelys suteri gen. et sp. nov. a large-bodied basal protostegid (primitive chelonioid) from the Early Cretaceous (Albian) of Australia, indicates that early sea turtles were both larger and more diverse than previously thought. The analysis implies at least five distinct sea turtle lineages existed around 100 million years ago. Currently, the postcranially primitive Ctenochelys and Toxochelys are interpreted as crown-group sea turtles closely related to living cheloniids (e.g. Chelonia); in contrast, the new phylogeny suggests that they are transitional (intermediate stem-taxa) between continental testudines and derived, pelagic chelonioids.

Animals↗
PubMed1994

Mitochondrial DNA control region polymorphisms: genetic markers for ecological studies of marine turtles.

We describe a rapid and sensitive method for the detection of population-specific genetic markers in mitochondrial DNA (mtDNA) and the use of such markers to analyse population structure of marine turtles. A series of oligonucleotide primers specific for the amplification of the mtDNA control region in Cheloniid turtles were designed from preliminary sequence data. Using two of these primers, a 384-385-bp sequence was amplified from the 5' portion of the mtDNA control region of 15 green turtles Chelonia mydas from 12 different Indo-Pacific rookeries. Fourteen of the 15 individuals, including some with identical whole-genome restriction fragment patterns, had sequences that differed by one or more base substitutions. Analysis of sequence variation among individuals identified a total of 41 nucleotide substitutions and a 1-bp insertion/deletion. Comparison with evidence from whole-genome restriction enzyme analysis of the same individuals indicated that this portion of the control region is evolving approximately eight times faster than the average rate and that the sequence analysis detected approximately one fifth of the total variation present in the genome. Restriction enzyme analysis of amplified products from an additional 256 individuals revealed significant geographic structuring in the distribution of mtDNA genotypes among five of the 10 rookeries surveyed extensively. Additional geographic structuring of genotypes was identified through denaturing gradient gel electrophoresis (DGGE) of amplified products. Only two of the 10 rookeries surveyed could not be differentiated, indicating that the Indo-Pacific C. mydas include a number of genetically differentiated populations, with minimal female-mediated gene flow among them. Important applications for genetic markers in the conservation and management of marine turtles include the identification of appropriate demographic units for research and management (i.e. genetically discrete populations) and assessment of the composition of feeding and harvested populations.

Animals↗
PubMed2004

Phylogeography of olive ridley turtles (Lepidochelys olivacea) on the east coast of India: implications for conservation theory.

Orissa, on the east coast of India, is one of the three mass nesting sites in the world for olive ridley turtles (Lepidochelys olivacea). This population is currently under threat as a result of fishery-related mortality; more than 100 000 olive ridleys have been counted dead in the last 10 years in Orissa. In general, the globally distributed olive ridley turtle has received significantly less conservation attention than its congener, the Kemp's ridley turtle (L. kempi), because the latter is recognized as a distinct species consisting of a single endangered population. Our study of mitochondrial DNA haplotypes suggests that the ridley population on the east coast of India is panmictic, but distinct from all other populations including Sri Lanka. About 96% of the Indian population consisted of a distinct 'K' clade with haplotypes not found in any other population. Nested clade analysis and conventional analysis both supported range expansions and/or long-distance colonization from the Indian Ocean clades to other oceanic basins, which suggested that these are the ancestral source for contemporary global populations of olive ridley turtles. These data support the distinctiveness of the Indian Ocean ridleys, suggesting that conservation prioritization should be based on appropriate data and not solely on species designations.

Animals↗
PubMed1992

Identification of cholecystokinin/gastrin peptides in frog and turtle. Evidence that cholecystokinin is phylogenetically older than gastrin.

Peptides homologous to mammalian cholecystokinin (CCK) and gastrin in brain, antrum, and small intestine of an amphibian (the bullfrog, Rana catesbeiana) and a reptile (the turtle, Pseudomys scripta) were characterized. All tissues contained peptides reacting with antisera specific for the carboxyamidated C-terminal tetrapeptide common for CCK and gastrin. Extracts of all tissues, except the turtle antrum, also reacted with an antiserum specific for mammalian sulfated CCK, while no extract contained peptides reacting with an antiserum specific for mammalian gastrin. Both species contained predominantly small acidic forms in the brain and larger less acidic forms in the antrum and intestine. The antral peptides of both species were identified. The largest frog gastrin was a 47-residue peptide: DLLASLTHEQ KQLIMSQLLP ELLSELSNAE DHLHPMRDRD YAGWMDF.NH2. The largest turtle gastrin was a 52-residue peptide: DLLEALSQDQ KLLMAKFLPH IYAELANREG NWHEDAALRP LHDHDYPGWM DF.NH2. They display 51% similarity. Having Tyr in position 7 from the C-terminus, both resemble structurally mammalian CCK rather than gastrin, which suggests that CCK is phylogenetically older than gastrin. The turtle antral peptide contains a Tyr followed by Pro as in chicken gastrin. Thus, apparently at the stage of reptiles, a route different from the mammalian was taken in order to evolve a specific gastrin function.

Amino Acid Sequence↗
PubMed1993

The primary structure of turtle Cu,Zn superoxide dismutase. Structural and functional irrelevance of an insert conferring proteolytic susceptibility.

A copper,zinc superoxide dismutase, has been isolated from the marine turtle Caretta caretta and the complete amino acid sequence obtained. The sequence was determined by isolation and analysis of peptides obtained after cleavage of the carboxymethylated apoenzyme with trypsin or Staphylococcus aureus protease. Turtle superoxide dismutase consists of 166 amino acid residues, which represents the largest number to date for a cytosolic copper,zinc superoxide dismutase. The comparison of this amino acid sequence with that of bovine superoxide dismutase revealed a one-residue C-terminal extension, two single residue insertions and a 12-residue insertion in the N-terminal region, in turtle superoxide dismutase. The new segment consists of a threefold repeating sequence and was found to be the site for selective proteolytic attack by trypsin under native conditions. The biochemical characteristics, the spectroscopic and catalytic properties as well as the thermal stability and the resistance to irreversible denaturation, were carefully examined and were very similar to those of other superoxide dismutases. These results indicate that the presence of the new polypeptide segment does not affect the main folding of the chain and the quaternary structure, nor the functional parameters of turtle superoxide dismutase. The possibility that the new insert constitutes a loop excluded from the protein scaffold providing the framework of the active site is also discussed.

Amino Acid Sequence↗
PubMed1993

The peripheral-type benzodiazepine receptor ligands [3H]Ro 5-4864 and [3H]PK 11195 bind to the retina of rabbit, but not of turtle.

The binding of [3H]flunitrazepam, [3H]Ro 5-4864, and [3H]PK 11195 to membrane preparations of the retina was studied in the turtle and rabbit. Only a single population of [3H]flunitrazepam binding sites was detected in the turtle, whereas two populations appeared to be present in the rabbit. No specific binding for [3H]Ro 5-4864 and [3H]PK 11195 could be detected in the turtle. In rabbit, both ligands bound with high affinity, revealing a significant population of binding sites (KD values of 24 +/- 2.3 and 2.2 +/- 0.8 nM, and Bmax values of 440 +/- 35 and 1,482 +/- 110 fmol/mg of protein, respectively). The binding was temperature- and protein-dependent. Displacement studies showed a similar rank order of potency of various unlabeled ligands against both [3H]Ro 5-4864 and [3H]PK 11195 (PK 11195 > Ro 5-4864 > flunitrazepam > flumazenil). These results suggest that peripheral-type benzodiazepine receptors are present in the retina of the rabbit, but not of the turtle.

Animals↗
PubMedDate not supplied

Unique features of Myf-5 in turtles: nucleotide deletion, alternative splicing, and unusual expression pattern.

Turtles characteristically possess a bony shell and show an extensive reduction of the trunk muscles. To gain insight into the evolution of this animal group, we focused on the underlying mechanism of the turtle-specific developmental pattern associated with the somitic mesoderm, which differentiates into both skeleton and muscle. We isolated Myf-5, a member of the myogenic-transcription-factor-encoding gene family expressed in the myotome, from the Chinese soft-shelled turtle Pelodiscus sinensis. We detected a deletion of 12 sequential nucleotides in P. sinensis Myf-5 (PsMyf-5), which appears to be shared by the turtle group. The expression pattern of PsMyf-5 in P. sinensis embryos differed from those of its orthologs in other amniotes, especially in the hypaxial region of the flank. We also identified two isoforms of the PsMyf-5 protein, a normal form similar to those of other vertebrates, and a short form produced by a translational frameshift. The short PsMyf-5 showed weaker myogenic activity in cultured cells than that of the normal protein, although the tissue distribution of the two isoforms overlapped perfectly. We propose that the unusual features of PsMyf-5 may be related to the unique developmental patterns of this animal group, and constitute one of the molecular bases for their evolutionary origin.

Alternative Splicing↗
PubMedDate not supplied

Comparative gene expression of steroidogenic factor 1 in Chrysemys picta and Apalone mutica turtles with temperature-dependent and genotypic sex determination.

Characterizing the molecular network underlying temperature-dependent (TSD) and genotypic (GSD) sex determination, including patterns across closely related taxa, is crucial to elucidate the still enigmatic evolution of sex determining mechanisms in vertebrates. Here we examined the expression of an important gene for sexual differentiation common to both systems, Sf1, at male- and female-producing temperatures, in TSD (Chrysemys picta) and GSD turtles (Apalone mutica). We tested the hypotheses that Sf1 expression responds to temperature consistently across TSD turtles but is unaffected in GSD turtles, and that this differential expression starts no earlier than the onset of the thermosensitive period (TSP). As expected, Sf1 expression was thermally insensitive in A. mutica (GSD). Although Sf1 exhibited a differential expression by temperature in C. picta, the expression pattern differed from other TSD turtles (Trachemys scripta), perhaps reflecting divergence of the gene regulatory networks underlying sex determination over evolutionary time. Most notably, Sf1 was differentially expressed in C. picta (significantly higher at the male-producing temperature) before the onset of the TSP, implying that in TSD taxa significant thermal effects may occur early in development. This result may reconcile field observations where temperatures experienced prior to the TSP have an effect on sex ratios, thus challenging traditional TSP models. Importantly, the molecular factors that render TSD mechanisms thermosensitive remain unknown, and potential candidates are genes that express differentially before the onset of the TSP (genes shaping or opening the TSP-window rather those acting once the TSP window has opened). Therefore, our findings make Sf1 one such potential candidate.

Amino Acid Sequence↗
PubMed1997

Efficacy of praziquantel in the treatment of green sea turtles with spontaneous infection of cardiovascular flukes.

OBJECTIVE: To assess the efficacy of praziquantel as a treatment for cardiovascular flukes in turtles. PROCEDURE: Six green sea turtles (Chelonia mydas) spontaneously infected with cardiovascular flukes (Digenea: Spirorchiidae) were treated orally with praziquantel, and necropsied 3 or 7 days later to look for flukes in the heart and major blood vessels. Six similar animals were maintained as untreated controls. RESULTS: Absence of flukes in treated, but not control turtles, indicated that a one day course of treatment at a dose rate of 3 x 50 mg/kg body weight is effective. CONCLUSION: This result should be of value for preventing disease in wild caught green turtles introduced into farms or aquaria.

Administration, Oral↗
PubMed1981

Electrophysiological analysis of mitral cells in the isolated turtle olfactory bulb.

1. An in vitro preparation of the turtle olfactory bulb has been developed. Electrophysiological properties of mitral cells in the isolated bulb have been analysed with intracellular recordings. 2. Mitral cells have been driven antidromically from the lateral olfactory tract, or activated directly by current injection. Intracellular injections of horseradish peroxidase (HRP) show that turtle mitral cells have long secondary dendrites that extend up to 1800 micrometer from the cell body and reach around half of the bulbar circumference. There are characteristically two primary dendrites, each supplying separate olfactory glomeruli. 3. Using intracellular current pulses, the whole-neurone resistance was found to range from 33 to 107 M omega. The whole-neurone charging transient had a slow time course. The membrane time constant was estimated to be 24-93 msec by the methods of Rall. The electrotonic length of the mitral cell equivalent cylinder was estimated by Rall's methods to be 0.9-1.9. 4. The spikes generated by turtle mitral cells were only partially blocked by tetrodotoxin (TTX) in the bathing medium. The TTX-resistant spikes were enhanced in the presence of tetraethylammonium (TEA), and blocked completely by cobalt. 5. The implications of the electrical properties for impulse generation in turtle mitral cells are discussed. The mitral cells have dendrodendritic synapses onto granule cells, and the TTX-resistant spikes may therefore play an important role in presynaptic transmitter release at these synapses.

Animals↗
PubMed1989

Serotonin-induced bistability of turtle motoneurones caused by a nifedipine-sensitive calcium plateau potential.

1. The effect of serotonin on the firing properties of motoneurones was studied in transverse sections of the adult turtle spinal cord in vitro with intracellular recording techniques. 2. In normal medium, turtle motoneurones adapt from an initial high frequency to a low steady firing during a depolarizing current pulse. In the presence of serotonin (4-100 microM) motoneurones responded with accelerated firing and a frequency jump during a depolarizing current pulse followed by an after-depolarization outlasting the stimulus. From a depolarized holding potential motoneuronal activity was shifted between two stable states by brief depolarizing and hyperpolarizing current pulses. As an expression of this bistable firing behaviour, the frequency-current relation in response to a triangular current injection was counter-clockwise in serotonin while clockwise in normal medium. 3. The delay to onset of the frequency jump was shortened as the amplitude of the activation pulse was increased. From a positive holding potential the after-depolarization exceeded spike threshold and its duration increased with an increase in steady bias current. The effect of serotonin on turtle motoneurones could be blocked by methysergide (10 microM). 4. When action potentials were depressed by tetrodotoxin, a voltage-dependent, non-inactivating plateau potential, intrinsic to the motoneurone, was revealed. Activation of this voltage plateau provides the motoneurones with two stable states of firing. The apparent input resistance was 2-4-fold lower during the plateau than at rest. 5. The serotonin-induced plateau potential was Ca2+-dependent and was blocked when Ca2+ was replaced by either Co2+ (3 mM) or Mn2+ (3 mM). 6. The Ca2+ plateau was blocked by nifedipine (1-15 microM). 7. Serotonin reduced the slow after-hyperpolarization following action potentials. The change in balance between inward and outward currents seems to be sufficient to reveal the plateau response. 8. Although a small plateau response was induced by Bay K 8644 (1-15 microM), this L-channel agonist could not reproduce the pronounced effect of serotonin. 9. It is concluded that serotonin induces a Ca2+-dependent and nifedipine-sensitive plateau potential in turtle motoneurones primarily by reducing a K+-current responsible for the slow after-hyperpolarization.

Animals↗
PubMed1974

Evaluation of methods for isolating Salmonella and Arizona organisms from pet turtles.

Two methods for isolating Salmonella and Arizona organisms from turtles, blending and excretion, were evaluated, and the percentage of isolates obtained by each method was compared with the percentage of isolates obtained by culture of turtle organs. The blending and excretion methods were equally effective in detecting the overall incidence of Salmonella and Arizona infections in turtles. The percentage of isolates obtained by specific organ culture, however, was less than the percentage obtained by the other two methods. The blending method detected a greater number of turtles with Arizona infections than did the excretion method, but there was no difference in the number of Salmonella infections detected by the two methods. The frequency of isolation of Arizona organisms from organs other than the small intestine and colon was higher than that of Salmonella.

Animals↗
PubMed1975

Treatment of Salmonella-Arizona-infected turtle eggs with terramycin and chloromycetin by the temperature-differential egg dip method.

Attempts to eliminate Salmonella and Arizona infection from newly hatched turtles were made by dipping fresh eggs in cold solutions of Terramycin and Chloromycetin at 1,000, 1,200, 1,500 and 2,000 mug per ml for either 10, 20, or 30 min. Control groups consisted of hatchings produced from nondipped eggs or eggs dipped in chilled water. In two of the four experiments 5 to 10 eggs were blended on days 15, 30, and 45 post antibiotic dip treatment. Twenty-five to 60 hatchlings from each control or experimental dip groups were held in containers and the water was tested (excretion method) for Salmonella and Arizona every 15 or 30 days for 180 to 210 days after hatching. Representative turtles were homogenized (blending method) to determine if systemic infections were present. All specimens tested were enriched in tetrathionate and selenite cystine broth. Nondipped eggs and water-dipped eggs routinely showed Salmonella and Arizona present in egg homogenate and hatchlings emerging from these eggs excreted these pathogens. Terramycin- and Chloromycetin-dipped eggs were uniformly negative for these pathogens, only if fresh eggs were dipped. Bacteriological assay of container water and whole turtle homogenate from hatchlings were negative for Salmonella and Arizona if eggs were dipped in 1,000 mug of Terramycin early in the egg laying season or if eggs were dipped in 1,500 or 2,000 mug of Terramycin per ml late in the egg laying season. The results of temperature-differential egg dip studies suggest that this is a feasible and promising method by which to eradicate Salmonella and Arizona from the turtle.

Animals↗
PubMed1976

Effects of temperature transients on gas exchange and acid-base status of turtles.

Pulmonary ventilation (VE), O2 consumption (VO2), and CO2 production (VCO2) were measured continuously on each of 10 turtles, Pseudemys scripta elegans, at 20 degrees C, during and for 1 h after heating to 30 degrees C and during and for 1 h after cooling to 20 degrees C. In seven of the animals, arterial blood was sampled at the three temperature plateaus. Ventilatory ratios (VE/VO2 and VE/VCO2) and metabolic rate adjusted promptly to temperature change, stabilizing at values similar to those observed previously in turtles following 1 day or more at each temperature. Likewise, mean blood pH and PCO2 values conformed both in absolute values and in temperature-dependence to data previously obtained from animals exposed to the various temperatures for longer time periods or from turtle blood thermally equilibrated in vitro. Total plasma [CO2] did not change significantly, suggesting that steady-state CO2 exchange prevailed throughout the experiment. In accordance with this, R(VCO2/VO2) did not change significantly during the 20-30 degrees C transition; however, R rose during the 30-20 degrees C transition, suggesting possible hyperventilation at this stage. We conclude that the respiratory control of blood acid-base status adjusts rapidly to temperature change in the turtle and its adjustment minimizes disturbance to CO2 balance.

Acid-Base Equilibrium↗
PubMed2006

Calcium flux in turtle ventricular myocytes.

The relative contribution of the sarcoplasmic reticulum (SR), the L-type Ca(2+) channel and the Na(+)/Ca(2+) exchanger (NCX) were assessed in turtle ventricular myocytes using epifluorescent microscopy and electrophysiology. Confocal microscopy images of turtle myocytes revealed spindle-shaped cells, which lacked T-tubules and had a large surface area-to-volume ratio. Myocytes loaded with the fluorescent Ca(2+)-sensitive dye Fura-2 elicited Ca(2+) transients, which were insensitive to ryanodine and thapsigargin, indicating the SR plays a small role in the regulation of contraction and relaxation in the turtle ventricle. Sarcolemmal Ca(2+) currents were measured using the perforated-patch voltage-clamp technique. Depolarizing voltage steps to 0 mV elicited an inward current that could be blocked by nifedipine, indicating the presence of Ca(2+) currents originating from L-type Ca(2+) channels (I(Ca)). The density of I(Ca) was 3.2 +/- 0.5 pA/pF, which led to an overall total Ca(2+) influx of 64.1 +/- 9.3 microM/l. NCX activity was measured as the Ni(+)-sensitive current at two concentrations of intracellular Na(+) (7 and 14 mM). Total Ca(2+) influx through the NCX during depolarizing voltage steps to 0 mV was 58.5 +/- 7.7 micromol/l and 26.7 +/- 3.2 micromol/l at 14 and 7 mM intracellular Na(+), respectively. In the absence of the SR and L-type Ca(2+) channels, the NCX is able to support myocyte contraction independently. Our results indicate turtle ventricular myocytes are primed for sarcolemmal Ca(2+) transport, and most of the Ca(2+) used for contraction originates from the L-type Ca(2+) channel.

Animals↗
PubMed2002

Mechanisms for maintaining extracellular glutamate levels in the anoxic turtle striatum.

The turtle Trachemys scripta is one of a limited group of vertebrates that can withstand hours to days without oxygen. One facet of anoxic survival is the turtle's ability to maintain basal extracellular glutamate levels, whereas in most vertebrates, anoxia triggers massive excitotoxic glutamate release. We investigated glutamate release and reuptake in the anoxic turtle and the effects of adenosine and ATP-sensitive potassium (K(ATP)) channels on glutamate homeostasis. Striatal extracellular glutamate was measured in anesthetized T. scripta by microdialysis in normoxia and over 2-h anoxia. Glutamate release is decreased by 44% in the early anoxic turtle; this anoxia-induced decrease in glutamate release was prevented when K(ATP) channels and adenosine receptors were blocked simultaneously but not when either mechanism was blocked individually. We hypothesize that the continued release and reuptake of glutamate during anoxia help maintain neuronal tone and aid in the recovery of a functional neuronal network after long periods of anoxia, whereas activation of adenosine and/or K(ATP) conserves energy by reducing glutamate release and lowering transport costs.

Adenosine↗