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PubMed2000

Comparative molecular phylogeography of North American softshell turtles (Apalone): implications for regional and wide-scale historical evolutionary forces.

We use a comparative analysis of partial cytochrome b sequences to evaluate the evolutionary forces shaping wide-scale phylogeographic patterns of all three North American softshell turtles (Apalone ferox, A. mutica, and A. spinifera). The overall phylogeographic patterns are concordant with results from both extensive regional studies of southeastern species, implicating historical vicariant processes during the Pliocene and Pleistocene, and investigations of more northerly distributed species, indicating a bottleneck effect of recent dispersal into postglacial habitat. We also resolved a novel, shared genetic break between northern-western and southeastern populations within both A. mutica and A. spinifera, demonstrating the value of using widespread taxa to evaluate both regional and wider scale phylogeographic patterns. The extensive phylogenetic structure and sequence divergences within both A. mutica and A. spinifera contrast sharply with most previous studies of turtles and with the hypothesis that turtles in general have slow rates of mtDNA evolution.

Animals↗
PubMed2001

A Paedomorphic parasite associated with a neotenic amphibian host: phylogenetic evidence suggests a revised systematic position for Sphyranuridae within anuran and turtle Polystomatoineans.

The phylogenetic relationships of the families Polystomatidae and Sphyranuridae (subclass Polystomatoinea) within tetrapod monogenean parasites were investigated using partial 18S rDNA sequences. About 600 nucleotides of 11 species were sequenced, including 7 species of the most common subfamilies of Polystomatidae found in anurans and turtles, 1 species of the family Sphyranuridae parasitizing exclusively urodelans, and 3 species of the subclass Oligonchoinea infesting teleostean fishes. The phylogenetic analyses were performed using three reconstruction methods: neighbor-joining, maximum-parsimony, and maximum-likelihood. Polystomatoineans but not polystomatids were shown to be monophyletic. Within the polystomatoineans there are two clades: one includes the amphibian monogeneans (anuran polystomatids and urodelan sphyranurids) and the other includes the turtle polystomatids. Polystomatoineans may have coevolved with amphibian hosts, and an ancestral "polystome" dispersed at least 200 million years ago, either from the basal stem of lissamphibians or from an anuran ancestral stock, to freshwater turtles. Furthermore, the urodelan genus Sphyranura, initially assigned to the family Sphyranuridae on the basis of morphological and ontogenetic evidence, is clearly nested within polystomatids, suggesting that its systematic status must be revised. This supports recent findings which argue that species of the family Sphyranuridae may be paedomorphic parasites exclusively infesting neotenic mudpuppies.

Animals↗
PubMed2002

Molecular phylogenetics of emydine turtles: taxonomic revision and the evolution of shell kinesis.

The 10 extant species of emydine turtles represent an array of morphological and ecological forms recognizable and popular among scientists and hobbyists. Nevertheless, the phylogenetic affinities of most emydines remain contentious. Here, we examine the evolutionary relationships of emydine turtles using 2092 bp of DNA encoding the mitochondrial genes cyt b, ND4, and adjacent tRNAs. These data contain 339 parsimony informative characters that we use to erect hypotheses of relationships for the Emydinae. Both maximum parsimony and maximum likelihood methods yield a monophyletic Emydinae in which all but three nodes are well resolved. Emys orbicularis, Emydoidea blandingii, and Clemmys marmorata form a monophyletic clade, as do the species of Terrapene. Clemmys muhlenbergii and Clemmys insculpta form a third monophyletic group that may be sister to all other emydines. Clemmys guttata is problematic and probably related to Terrapene. Based on this phylogeny, and previous molecular work on the group, we suggest the following taxonomic revisions: (1) Clemmys should be restricted to a single species, C. guttata. (2) Calemys should be resurrected for C. muhlenbergii and C. insculpta. (3) Emys should be expanded to include three species: E. orbicularis, E. blandingii, and E. marmorata. Furthermore, our analyses show that neither kinetic-shelled nor akinetic-shelled emydines form monophyletic groups. Therefore, shell kinesis was either independently gained in Emys and Terrapene or secondarily lost in E. marmorata and C. guttata. Parsimony, paleontological evidence, and the multiple origins of shell kinesis in related turtle lineages (especially geoemydines) support the independent origin of plastral kinesis.

Animals↗
PubMed1995

Three-dimensional reconstruction of the rubrocerebellar premotor network of the turtle.

Neuroanatomical studies have demonstrated that the organization of the reptilian rubrocerebellar limb premotor network is similar to that of mammals. This network is composed of prominent recurrent connections among the red nucleus, lateral cerebellar nucleus and lateral reticular nucleus. In this paper the rubrocerebellar system of the turtle was three-dimensionally reconstructed to permit detailed examination of its anatomical organization. Each nucleus and its major efferent pathway was imaged and reconstructed from separate anatomical cases. Section images were used to draw tissue boundaries, mark cell positions and locate axonal trajectories. For each nucleus, drawings of section images containing labeled cells were stacked in the rostrocaudal direction using anatomical landmarks, and a graphic model of the surface was constructed using the method of triangulation. An ellipsoid of equal concentration was computed for each nucleus to ascertain their three-dimensional boundaries and location within the brainstem. To examine the entire rubrocerebellar network, a template of the turtle brainstem and cerebellum was constructed. The component nuclei of the rubrocerebellar network and their axonal projections were then spatially warped onto the template reconstruction on a section by section basis. The final three-dimensional reconstruction of the turtle rubrocerebellar limb premotor network could be rotated in space, allowing proper visualization of the anatomical details of this system. Furthermore, we were able to mathematically section through the reconstruction to obtain brainstem slices with differing orientations and thickness.

Animals↗
PubMed2001

Quantitative analysis of herpesvirus sequences from normal tissue and fibropapillomas of marine turtles with real-time PCR.

Quantitative real-time PCR has been used to measure fibropapilloma-associated turtle herpesvirus (FPTHV) pol DNA loads in fibropapillomas, fibromas, and uninvolved tissues of green, loggerhead, and olive ridley turtles from Hawaii, Florida, Costa Rica, Australia, Mexico, and the West Indies. The viral DNA loads from tumors obtained from terminal animals were relatively homogeneous (range 2-20 copies/cell), whereas DNA copy numbers from biopsied tumors and skin of otherwise healthy turtles displayed a wide variation (range 0.001-170 copies/cell) and may reflect the stage of tumor development. FPTHV DNA loads in tumors were 2.5-4.5 logs higher than in uninvolved skin from the same animal regardless of geographic location, further implying a role for FPTHV in the etiology of fibropapillomatosis. Although FPTHV pol sequences amplified from tumors are highly related to each other, single signature amino acid substitutions distinguish the Australia/Hawaii, Mexico/Costa Rica, and Florida/Caribbean groups.

Amino Acid Sequence↗
PubMed1994

Distribution of glial fibrillary acidic protein-immunopositive structures in the brain of the red-eared freshwater turtle (Pseudemys scripta elegans).

The distribution of glial fibrillary acidic protein (GFAP)-immunoreactivity is described in serial Vibratome sections of the turtle brain. The results are discussed in relation to our previous studies of rat and chicken brains. In the turtle brain, the distribution of GFAP-positive elements is rather evenly abundant as compared to that observed in the chicken and rat. The GFAP-positive structures are fibers of different length and orientation, but the stellate cells are not GFAP-positive. The basic systems is the radial ependymoglia, directed from the ventricles toward the outer surface of the brain. This system also contains some transverse and randomly oriented fibers. The cell bodies are not usually GFAP-positive. The large brain tracts could be recognized by their weak immunostaining, but gray matter nuclei could not be identified on the basis of immunostaining against GFAP. The layers of the optic tectum could be distinguished, as well as the gray and white matter of brain stem and spinal cord and the molecular and granular layers of the cerebellum. In the cerebellum, a fiber system resembling the Bergmann-fibers, a strong midline raphe and coarse transverse fibers could be observed. These latter fibers have no equivalent in other cerebella. Their perikarya proved also to be GFAP-positive, and seemed to be dividing in the adult turtle brain. We conclude that the appearance of GFAP-positive stellate cells had a great importance in the evolution of avian and mammalian brains strengthening the thicker brain walls and assisting in the formation of local differences of GFAP-immunoreactivity in different brain areas.

Animals↗
PubMed1992

Anoxic survival of the isolated cerebellum of the turtle Pseudemis scripta elegans.

Intact turtle brain provides a useful model for the study of anoxia and potential survival strategies, since this tissue maintains transmembrane ion gradients and ATP levels during prolonged anoxia and recovers functional activity afterwards. Since isolated tissues offer experimental advantages, the present study sought to determine effects of anoxia on the isolated turtle cerebellum and to define relationships between anoxia survival and glucose supply. In normoxia, the extracellular potassium ([K+]o) activity and evoked potentials were maintained with 5 mM glucose, but 20 mM glucose was required to maintain adenosine triphosphate (ATP) levels and prevent significant increases in [K+]o during anoxia. Inhibition of glycolysis by iodoacetic acid (IAA) during anoxia provoked large increases in [K+]o at all glucose levels. These results demonstrate the usefulness of the isolated turtle cerebellum for studies of anoxic survival since this tissue can maintain ATP levels and [K+]o during prolonged anoxia with 20 mM glucose in the artificial cerebrospinal fluid medium. They also suggest the presence of a Pasteur effect at least during the transition to a hypometabolic state.

Adenosine Triphosphate↗
PubMed1985

Renal responses to diuretics in the turtle.

We administered the diuretics furosemide and ethacrynic acid to conscious freshwater turtles to assess changes in renal function and plasma renin activity (PRA) in an animal which lacks a loop of Henle. Furosemide (2 and 5 mg/kg) produced no changes in blood pressure, hematocrit, plasma electrolytes, glomerular filtration rate (GFR), or PRA. Furosemide doubled urine volume while sodium excretion increased 20-fold and chloride and potassium excretion increased 12-fold (P less than 0.05 in each case). Net potassium secretion was observed. Ethacrynic acid (2 and 5 mg/kg) also produced no changes in blood pressure, hematocrit, plasma electrolytes, or PRA. At the lower dose GFR increased by 40% and urine volume nearly doubled (P Less than 0.05 in each case). Sodium, chloride, and potassium excretion increased roughly 10-fold (P less than 0.05 in each case). At the higher dose, GFR increased by 80% and urine volume more than doubled (P Less than 0.05 in each case). Sodium excretion rose 40-fold, chloride excretion rose 25-fold, and potassium excretion rose 10-fold (P less than 0.05 in each case). At both doses net potassium secretion occurred. The results demonstrate that both drugs inhibit tubular reabsorption in the turtle, acting primarily on distal segments of the nephron. The failure of either drug to alter PRA suggests that the turtle lacks a tubular mechanism for altering renin release.

Animals↗
PubMed1995

cAMP-dependent protein kinase and anoxia survival in turtles: purification and properties of liver PKA.

The catalytic subunit of turtle (Trachemys scripta elegans) liver cyclic AMP-dependent protein kinase (PKAc) was purified to homogeneity with a final specific activity of 65,783 pmol phosphate transferred.min-1.mg protein-1. Subunit molecular weight was 42-43 kDa as determined by SDS-PAGE and Sephacryl S-300 chromatography. The isolectric point was pH 6.41 +/- 0.02. Turtle liver PKAc showed highest activity with kemptide as its substrate; activity with other artificial substrates, histone IIA and protamine, was only 21 and 11%, respectively, of the activity with kemptide. Km values were 83 +/- 6.5 microM for Mg.ATP and 11.7 +/- 0.5 microM for kemptide and enzyme activity was strongly reduced by inhibitors of mammalian PKA (H-89, PKA-1) but not by inhibitors of other protein kinases. The enzyme was also inhibited by salts, especially fluoride salts (I50 about 30 mM), and showed a sharp break in the Arrhenius plot (0-45 degrees C) with activation energy increasing by 4-fold from 27.9 +/- 1.85 to 115 +/- 2.5 kJ/mol for temperatures above versus below 15 degrees C. Temperature effects may be important in suppressing PKA function, and therefore PKA-mediated responses, in vivo to enhance anoxic survival time during winter hibernation under water. Analysis of the effects of in vivo anoxia exposure at 7 degrees C on PKA in turtle organs showed a rapid 2.3-fold increase in the amount of active enzyme in liver within 1 h of anoxic submergence accompanied by a 60% increase cAMP levels; with longer anoxia (5 or 20 h) the percentage of active PKA was suppressed to 2.1-3.7% of the total.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Effect of quinidine on Na, H+, and water transport by the turtle and toad bladders.

The effect of quinidine on Na and H+ transport by the turtle bladder and water transport by the toad bladder was examined. Quinidine inhibited the short-circuit current and the potential difference in a dose-dependent fashion. The effect of quinidine on the short-circuit was not dependent on extracellular calcium concentration and was not reversible with removal of the drug. Quinidine inhibited H+ secretion in a dose-dependent fashion. The effect of quinidine on H+ secretion also was not dependent on extracellular calcium concentration and was not reversible, either with removal of the drug or with stimulation of H+ secretion with 5% CO2. The effect of quinidine on Na or H+ transport could not be elicited by an equivalent dose of tetracaine, suggesting that the inhibitory effect of quinidine is not dependent on its anesthetic properties. Quinidine also inhibited vasopressin and cyclic AMP stimulated water flow in the toad bladder. Quinidine did not alter calcium uptake by the turtle bladder but increased calcium efflux by the turtle and toad bladders. These observations suggest that a rise in cytosolic calcium is responsible for the inhibitory effect of quinidine on Na, H+, and water transport.

Animals↗
PubMed1996

Quantitative anatomy, synaptic connectivity and physiology of amacrine cells with glucagon-like immunoreactivity in the turtle retina.

Although a wide variety of neuropeptides have been localized in vertebrate retinas, many questions remain about the function of these peptides and the amacrine cells that contain them. This is because many of these peptidergic amacrine cells have been studied using only immunocylochemical techniques. To address this limitation, the present study used a combination of quantitative anatomy, biochemistry and electrophysiology to examine amacrine cells in the turtle retina that contain the neuropeptide glucagon. In the turtle retina, there is a small population of 2500 glucagonergic amacrine cells, which probably represents < 1% of the total number of amacrine cells. Circular distribution statistics indicated that many of these tristratified amacrine cells had asymmetric dendritic arborizations that were radially oriented toward the retinal periphery. The cells were found to have similar dendritic coverage factors, to be distributed in a non-random arrangement in all regions of the retina, and to peak in density in the visual streak region. Electron microscopic studies indicated that glucagonergic amacrine cells made synaptic contacts primarily with other amacrine cells, and small numbers of bipolar cells. The synaptic inputs and outputs were balanced in the inner strata of the inner plexiform layer, and were biased toward synaptic outputs in the outer strata of the inner plexiform layer. These contacts involved small unlabelled synaptic vesicles, and not the large labelled dense core vesicles also found in these neurons. The biochemical studies indicated that glucagon could be released from the retina in a calcium dependent manner by high potassium stimulation. The electrophysiology found no color opponency, and the glucagonergic amacrine cells gave sustained hyperpolarizing responses to small stimulation spots and had antagonistic surrounds. The results of these studies suggest that there are significant regional specializations of glucagonergic amacrine cells, and that they may provide OFF-modulation in interactions between the ON-and OFF-centre visual pathways in the turtle retina.

Animals↗
PubMed2006

Sex ratio estimations of loggerhead sea turtle hatchlings by histological examination and nest temperatures at Fethiye beach, Turkey.

Hatchling sex ratios in the loggerhead turtle (Caretta caretta) were estimated by placing electronic temperature recorders in 21 nests at Fethiye beach during 2000-2002. Over the seasons, the mean temperature in the middle third of the incubation period ranged from 26.7 to 32.1 degrees C, and incubation periods ranged from 49 to 67 days. Based on the mean temperatures during the middle third of the incubation period, and on histologically sexed dead hatchlings, the sex ratios of hatchlings at Fethiye beach were roughly equal, i.e. 60-65% of the hatchlings were females. This contrasts with the highly female-skewed sex ratios in loggerhead turtles elsewhere; Fethiye has a relatively high proportion of male hatchlings. For endangered sea turtles, the knowledge of hatchling sex ratios at different beaches, coupled with appropriate conservation measures, can make an important contribution to their survival.

Animals↗
PubMed2004

Contaminant residues in snapping turtle (Chelydra s. serpentina) eggs from the Great Lakes-St. Lawrence River basin (1999 to 2000).

To determine temporal and geographic variations of environmentally persistent pollutants, the concentrations of several contaminants were measured in snapping turtle eggs in 1999 and 2000. Contaminants included polychlorinated biphenyls (PCBs), non- ortho PCBs, polychlorinated dibenzodioxins and furans, organochlorine pesticides, and total mercury. Egg collection sites within the St. Lawrence Area of Concern (AOC) and the Territory of Akwesasne included Turtle Creek, Snye Marsh, and Raquette River. Additional contaminated sites were Gray's Creek (within the St. Lawrence AOC boundary), Coote's Paradise (Hamilton Harbour AOC), and the Territory of Walpole Island (St. Clair AOC). Reference sites were Lake Sasajewun, Algonquin Provincial Park in central Ontario, and in close proximity to the St. Lawrence Area AOC, Hoasic Creek and Cooper Marsh. Eggs from clutches collected from Akwesasne contained the highest concentrations of contaminants. Mean total PCB concentrations for Akwesasne clutches ranged from 1,900 to 61,000 ng/g wet weight (w.w.), which was 360 to 3,100 times higher than the mean concentrations at the reference sites. The high levels of contaminants in eggs, from sites within Akwesasne, were consistent with trends reported in the past and reflect the influence of the proximity of heavy industry. Current contaminant concentrations in clutches from Coote's Paradise are comparable with those recorded in 1989 and 1990 but are 200 to 800 times lower than concentrations reported in 1984 and 1988. Eggs from Lake Sasajewun contained relatively low contaminant levels, which is consistent with atmospheric deposition. Our results support that snapping turtles are good indicators of temporal and geographic contaminant trends.

Animals↗
PubMed1998

Trace elements in egg contents and egg shells of slider turtles (Trachemys scripta) from the Savannah River Site.

In this paper we examine the levels of trace elements in the egg contents and egg shells of slider turtles (Trachemys scripta) from the Savannah River Site, near Aiken, South Carolina. Trace elements have seldom been examined in the tissues or eggs of reptiles, although some turtles and large snakes occupy a high trophic level. Lead, mercury, cadmium, selenium, chromium, and manganese levels were examined in one egg and its egg shell collected from each of 16 females that laid in late May and June 1996. We were interested in determining background levels, whether certain metals were sequestered in the egg shells, and whether levels were higher in contents or shells. Concentrations were higher in egg contents than in shells for lead, mercury, and selenium, while chromium was higher in the shell. There were no differences for cadmium and manganese. Compared to eggs from other reptiles, levels in slider turtles were generally similar for cadmium and selenium, lower for chromium and lead, and higher for manganese.

Animals↗
PubMed2002

Oxygen consumption and force development in turtle and trout cardiac muscle during acidosis and high extracellular potassium.

Relative to species such as rainbow trout, freshwater turtle shows a high tolerance to challenges involving acidosis and increases in extracellular K+. Therefore, the effects of acidosis or high K+ on twitch force and oxygen consumption were examined in ventricular ring preparations from these two species. The oxygen consumption associated with force development was estimated by net oxygen consumption (oxygen consumption during twitch force development minus that during rest). For turtle, elevation of CO2 from 2% (pH 7.7) to 12% (pH 6.9) in the gas equilibrating the muscle bath decreased twitch force by 20% without any effects on oxygen consumption. Decreasing pH from 7.7 to 6.9 with 22 mM lactic acid had similar effects. For trout, CO2-induced acidosis decreased twitch force by approximately 60%. Furthermore, force development became energetically less efficient as it fell disproportionately more than net oxygen consumption. This was not observed for lactic acidosis. For trout but not for turtle, acidosis resulted in an increase in oxygen consumption during rest. An increase in extracellular K+ from 2.5 mM to 10 mM depressed force and oxygen consumption proportionately for both species. Adrenaline (10 microM) increased twitch force for both species and oxygen consumption for trout; it attenuated the effects of high extracellular K+. Neither adrenaline nor high K+ influenced the ratio of force to net oxygen consumption. As opposed to high extracellular K+, acidosis appears to increase the energetic cost of contractility, particularly for the trout heart.

Acidosis↗
PubMed2003

Creatine kinase and mitochondrial respiration in hearts of trout, cod and freshwater turtle.

The importance of the creatine kinase system in the cardiac muscle of ectothermic vertebrates is unclear. Mammalian cardiac muscle seems to be structurally organized in a manner that compartmentalizes the intracellular environment as evidenced by the substantially higher mitochondrial apparent Km for ADP in skinned fibres compared to isolated mitochondria. A mitochondrial fraction of creatine kinase is functionally coupled to the mitochondrial respiration, and the transport of phosphocreatine and creatine as energy equivalents of ATP and ADP, respectively, increases the mitochondrial apparent ADP affinity, i.e. lowers the Km. This function of creatine kinase seems to be absent in hearts of frog species. To find out whether this applies to hearts of ectothermic vertebrate species in general, we investigated the effect of creatine on the mitochondrial respiration of saponin-skinned fibres from the ventricle of rainbow trout, Atlantic cod and freshwater turtle. For all three species, the apparent Km for ADP appeared to be substantially higher than for isolated mitochondria. Creatine lowered this Km in trout and turtle, thus indicating a functional coupling between mitochondrial creatine kinase and respiration. However, creatine had no effect on Km in cod ventricle. In conclusion, the creatine kinase-system in trout and turtle hearts seems to fulfil the same functions as in the mammalian heart, i.e. facilitating energy transport and communication between cellular compartments. In cod heart, however, this does not seem to be the case.

Adenosine Diphosphate↗
PubMed2006

The effects of temperature and inter-individual variation on the locomotor performance of juvenile turtles.

The effects of temperature on aquatic and terrestrial locomotor performance, including measures of burst speed, endurance, and righting response, the inter-individual correlation between measures of locomotor performance, and the temporal repeatability of performance were assessed in juvenile western painted turtles, Chrysemys picta bellii. Locomotor performance increased as temperature increased, with Q(10) values ranging from 1.33 to 1.98 for burst speed and 2.28 to 2.76 for endurance measures. Righting response performance also increased with temperature. Aquatic and terrestrial measures of locomotor performance were highly correlated; however, righting response was not correlated with any other measure of performance. Measures of terrestrial locomotor performance were highly repeatable over the entire 30-week study period, whereas aquatic locomotor performance was only repeatable through week 12. The righting response was repeatable over a 6-week study period. Both the interindividual variation and temperature effects on locomotor performance likely influences the survival of turtles, especially juveniles, by affecting the length of time turtles are exposed to potential predators and their ability to escape.

Animals↗
PubMed2001

Pulmonary receptors in reptiles: discharge patterns of receptor populations in snakes versus turtles.

This study examines the effects of lung inflation/deflation with and without CO2 on the entire population of pulmonary receptors in the vagus nerve in two species of snakes and two species of turtles. We asked the question, "how does the response of the entire mixed population of pulmonary stretch receptors (PSR) and intrapulmonary chemoreceptors (IPC) in species possessing both differ from that in species with only PSR"? This was studied under conditions of artificial ventilation with the secondary goal of extending observations on the presence/absence of IPC to a further three species. Our results indirectly illustrate the presence of IPC in the Burmese python and South American rattlesnake but not the side necked turtle, adding support to the hypothesis that IPC first arose in diapsid reptiles. In both species of snake, CO2-sensitive discharge (presumably from IPC) predominated almost to the exclusion of CO2-insensitive discharge (presumably arising from PSR) while the opposite was true for both species of turtle. The data suggest that for animals breathing air under conditions of normal metabolism there is little to distinguish between the discharge profiles of the total population of receptors arising from the lungs in the different groups. Interestingly, however, under conditions of elevated environmental CO2 most volume-related feedback from the lungs is abolished in the two species of snakes, while under conditions of elevated metabolic CO2, it is estimated that volume feedback from the lungs would be enhanced in these same species.

Animals↗