Publications

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depletions in the cervical and thoracolumbar sympathetic system following removal of neural crest from the embryo of chelydra serpentina. 19665969768
primary structure of the cytochrome c from the snapping turtle, chelydra serpentina. 19665968568
food imprinting in the snapping turtle, chelydra serpentina.three groups of hatchling snapping turtles, totaling 20, were fed either meat, fish, or worms. when they were tested for preference after 12 daily feedings, each preferred the diet to which it was accustomed. after 12 more days of eating a different food, each still preferred its original diet. a form of imprinting may be operative in the feeding behavior of this species.19665908961
experimental studies on the columella-capsular interrelationship in the turtle chelydra serpentina. 19655861722
an experimental approach to the development of ear capsule in the turtle, chelydra serpentina. 196514329484
hypoxia: effects on heart rate and respiration in the snapping turtle.in response to atmospheres containing decreasing amounts of oxygen, snapping turtles (chelydra serpentina) maintained a fairly constant oxygen uptake. their heart rate increased and the period of apnea between breathing cycles decreased. small animals had a slightly greater mean uptake per gram than those five to ten times as large.196314014707
analysis of vagal and cholinesterase effects on the heart of chelydra serpentina. 195813606222
circulation and blood pressure in the great vessels and heart of the turtle (chelydra serpentina). 195713458464
the effects of electrolytes and sugars on the erythrocytes of the turtle, chelydra serpentina. 194918108892
on chelydra serpentina. 189317832441
resistance of the shell membrane and mineral layer to diffusion of oxygen and water in flexible-shelled eggs of the snapping turtle (chelydra serpentina).at oviposition, flexible eggshells of many turtles have an outer mineral layer and an inner membrane layer of approximately equal thickness. we measured conductances of both layers to h2o and o2 at various levels of eggshell hydration. both the mineral layer of the eggshell and the shell membrane offer significant resistance to diffusion of water vapor and oxygen in eggshells of the snapping turtle, chelydra serpentina. conductance to water vapor increases in both the membrane and mineral layer ...19826890707
possible adaptive value of water exchanges in flexible-shelled eggs of turtles.use of energy reserves by embryos of common snapping turtles (chelydra serpentina) is related to the hydric conditions to which eggs are exposed during incubation and to the net exchanges of water through the eggshells. embryos developing inside eggs with a relatively favorable water balance use more of their energy reserves metabolically and grow larger before hatching than embryos inside eggs with less favorable water exchanges.198117760193
horizontal cells of the turtle retina. ii. analysis of interconnections between photoreceptor cells and horizontal cells by light microscopy.criteria were established whereby the chief and accessory members of double cones, red-, green-, and blue-sensitive single cones, and rods could be distinguished from one another in 1-micrometer sections through the retinas of pseudemys scripta elegans and chelydra serpentina. criteria included the presence of absence of an oil droplet, the size, color, and radial position of the oil droplet, the size and shape of the inner and outer segments, and the shape orientation of the connection between ...1978730848
chemical and electrical synapses between photoreceptors in the retina of the turtle, chelydra serpentina.electron microscopic observation of the distal retina of the turtle, chelydra serpentina, revealed that photoreceptors contact each other by means of a variety of junctions. the synaptic terminals of the primary and accessory members of a double cone invariably make punctate contact with each other distal to the basal surfaces. this type of contact was only rarely seen between the synaptic terminals of single photoreceptors. photoreceptor telodendria which emanate from the basal surface of the s ...19852468693
electron microscopy of golgi-impregnated photoreceptors reveals connections between red and green cones in the turtle retina.red and green cones of two turtle species (pseudemys scripta elegans and chelydra serpentina) retina have been stained with golgi procedures and examined by light microscopy of whole-mount tissue and by electron microscopy of serial thin sections. by light microscopy, red and green single cones appear indistinguishable, but double cones can be readily identified. all golgi-stained photoreceptors in turtle retina have a spray of telodendria radiating from their synaptic pedicles. the telodendria ...19854031990
control of metabolism and growth in embryonic turtles: a test of the urea hypothesis.we performed two experiments to determine (1) whether the metabolism and growth of embryonic snapping turtles (chelydra serpentina) incubating in wet and dry environments are correlated inversely with the concentration of urea inside their eggs, and (2) whether urea accumulating inside eggs might be the cause of reductions in metabolism and growth by embryos. eggs in the first experiment were incubated in different hydric environments to induce different patterns of net water exchange between th ...19892614338
voltage noise observed in rods of the turtle retina.1. intracellular voltage was recorded from rods in isolated retinae of the snapping turtle, chelydra serpentina. the voltage was observed during darkness or during uniform illumination of a large retinal area. during darkness the voltage fluctuated continuously about a mean level. the spontaneous fluctuation is termed ;noise'. during illumination the amplitude of the noise was reduced.2. the noise observed during darkness could also be reduced by injecting a hyperpolarizing current into the impa ...1977592191
ultrastructural analysis of normal and immunized spleen of the snapping turtle, chelydra serpentina.in the ultrastructural comparison of normal, unimmunized spleens with immunized spleens at key intervals after antigenic stimulation with keyhole limpet hemocyanin (klh), we noted cellular and cytological features which reflect the cellular kinetics of the primary immune response, particularly with respect to plasma cell production. although lymphoblasts and mature plasma cells are present in the white and red pulp, respectively, intermediate stages of the plasma cell line are rarely found in no ...1976945353
characteristics of gonads and oviducts in hatchlings and young of chelydra serpentina resulting from three incubation temperatures.eggs of chelydra serpentina were incubated at 30 degrees c and 26 degrees c. in addition, incubation was done at 20 degree c during the temperature-sensitive period for sex determination. incubation at 20 degrees c and 30 degrees c resulted in females; incubation at 26 degrees c resulted in males in 99% of the cases. the average gonadal length was less in the males. the average length of the 20 degree c ovaries did not vary significantly from that of the 30 degrees c ovaries. the condition of th ...19817241601
current-voltage relations in the rod photoreceptor network of the turtle retina.1. electrical coupling between rod photoreceptors was studied in the eyecup preparation of the snapping turtle, chelydra serpentina, using intracellular micro-electrodes.2. the spatial profiles of rod responses to a long narrow slit of light were determined. the peak response amplitudes were found to decline exponentially as the slit was moved from the most sensitive position in the receptive field of each rod. the mean length constant was 55.7 mum.3. rods were simultaneously impaled in pairs an ...19807230014
ultrastructural morphology of the shell and shell membrane of eggs of common snapping turtles (chelydra serpentina).common snapping turtles (chelydra serpentina) lay nearly spherical, flexible-shelled eggs having an outer mineral layer composed of calcium carbonate in the aragonite form. the mineral layer is arranged into loosely organized groups of nodular shell units, with numerous spaces (or pores) between adjacent shell units. shell units are structurally complex, consisting of an inner tip that is morphologically distinct from the main body of the shell unit. contained within an intact shell unit at the ...19807452729
water relations of pliable-shelled eggs of common snapping turtles (chelydra serpentina). 19807427826
the rate of conversion of [14-(14)c]pregnenolone to [4-(14)c]progesterone by corpora lutea of the snapping turtle, chelydra serpentina. 19807419051
ultrastructural changes in testes of the snapping turtle, chelydra serpentina in relation to plasma testosterone, delta 5-3 beta-hydroxysteroid dehydrogenase, and cholesterol.ultrastructural changes in the testes of the common snapping turtle, chelydra serpentina, were observed throughout the year. plasma testosterone levels were measured and compared with the occurrence of delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta-hsd), cholesterol, and steroidogenic ultrastructural features (smooth endoplasmic reticulum (ser), mitochondria with tubular cristae) in sertoli and leydig cells. the testosterone level is highest in may and october (mating) and relatively low du ...19853857207
aerial and aquatic oxygen uptake by freely-diving snapping turtles (chelydra serpentina).aerial oxygen consumption of unrestrained, freely-diving warm-and cold-acclimated snapping turtles, chelydra serpentina, was measured at 10, 20, and 30°c. also, simultaneous determinations of aerial and aquatic oxygen uptake by voluntarilydiving animals were made at 4 and 20°c. the standard rates of aerial oxygen consumption are equivalent in cold-and warm-acclimated animals in water and in cold-acclimated ones in air; these rates are all lower than those of warm-acclimated animals in air. thus ...198028309683
action of sex steroid hormones on temperature-induced sex determination in the snapping turtle (chelydra serpentina).administration of exogenous estradiol benzoate (eb) or an estrogen agonist, r2858, into eggs of snapping turtles caused all embryos incubated at male-producing temperatures to develop as females, whereas testosterone propionate (tp) caused 42% of the embryos to develop as females. some of the embryos treated with eb, r2858, or tp also had hypertrophied oviducts. neither dihydrotestosterone (dht) nor cholesterol had any apparent effect on the sex determination of embryos incubated at male-produci ...19892599345
factors terminating nonventilatory periods in the turtle, chelydra serpentina.pao2, paco2 and pha were measured via an extracorporeal loop in conscious snapping turtles (chelydra serpentina) breathing air or hypoxic (10, 15% o2), hyperoxic (30% o2), or hypercapnic (2% co2) gases. turtles breathed into an inverted funnel ventilated with the test gas. breathing was recorded with a differential pressure transducer. in all turtles, nonventilatory periods were interrupted by breathing episodes containing multiple breaths. in normoxia, pao2 at the end of nonventilatory periods ...19892506623
changes in spleen histology in response to antigenic stimulation in the snapping turtle, chelydra serpentina.proliferative and migratory changes of lymphoid cells in the spleen were observed in turtles stimulated with klh and maintained at 30 degrees c. small foci of pyroninophilic lymphoblasts were first seen in the white pulp at about day 5. progressive enlargement of these centers continued and peaked by days 8-12. by days 15-20 the white pulp returned to a normal (unimmunized) state, while the number of pyroninophilic cells, primarily plasma cells, increased markedly in the red pulp. at days 22-25, ...1976945352
fine structure of the chromophobe in the pars distalis of the common snapping turtle, chelydra serpentina.chromophobes of the pars distalis in young chelydra serpentina have sparse cytoplasm with no specific granules; however, many cytoplasmic filaments are present. the chromophobes are connected to the other cell types by desmosomes, while different types of junctional specializations occur between adjacent chromophobes. cytoplasmic filaments traverse the cytoplasm in a random manner and terminate on both the junctional complexes and the nuclear envelope. it is proposed that, in addition to providi ...19761248046
development of the ovarian follicles in relation to changes in plasma parameters and 5 delta 3 beta hsd in snapping turtle, chelydra serpentina.follicular development in snapping turtle, chelydra serpentina, was studied in relation to changes in plasma levels of estradiol-17 beta, total protein, calcium, inorganic phosphate and cholesterol. histochemical reaction for 3 beta-hsd in granulosa and theca cells of the follicles is strong during the preovulatory and vitellogenic phases when the follicles attain their maximum size (18-22 mm) and estradiol is at a high level. the reaction for 3 beta-hsd is weal during the postovulatory phase wh ...19852864192
the role of arginine vasotocin and prostaglandin f2 alpha on oviposition and luteolysis in the common snapping turtle chelydra serpentina.the administration of arginine vasotocin (avt) to gravid snapping turtles with steroidogenically active corpora lutea and high plasma progesterone concentration (1480 +/- 155 pg/ml) did not trigger oviposition, whereas 12 days after ovulation when luteolysis occurred and plasma progesterone concentration was low (570 +/- 78 pg/ml), treatment with avt caused oviposition. controls with high plasma progesterone concentration (1605 +/- 185 pg/ml) oviposited 15-23 days after ovulation when plasma pro ...19883162890
[the orbitotemporal region in the cranium of chelydra serpentina linnaeus (chelonia) and lacerta sicula rafinesque (lacertilia)].an analysis of the ontogenesis of the chondrocranium gives the following homologies in the skull of lacerta and chelydra: (see article). it is shown that the extracranial position of the cavum epiptericum in lacerta corresponds to the stage of maximal development of the chondrocranium in chelydra. but further development brings about a dermal sidewall in the orbitotemporal region, b,ilt up by descending parietal flanges which incorporate the epipterygoid. this not only allows the pila antotica t ...19761007875
chemical synapses between turtle photoreceptors.rod photoreceptors of the snapping turtle retina wer golgi impregnated and studied in the electron microscope. telodendria arising from the synaptic bases ended at rods and cones as lateral or central elements of the ribbon synaptic complex, thus providing clear evidence of chemical synapses between turtle photoreceptors.19846488024
polychlorinated biphenyl, mercury, and cadmium concentrations in minnesota snapping turtles. 19836404330
the effect of malnutrition on immunocompetence and whole body resistance to infection in chelydra serpentina. 1979437240
seasonal fluctuations in the plasma concentrations of progesterone and oestradiol-17 beta in the female snapping turtle (chelydra serpentina).plasma concentrations of progesterone and oestradiol-17 beta were determined by radioimmunoassay procedures in the sexually mature female snapping turtle at four different stages of the annual ovarian cycle. the highest level of progesterone in the peripheral plasma was detected during the luteal stage (june), whereas the concentration of oestradiol was highest (280 pg/ml) in may, immediately before ovulation.1979429947
blood flukes of asiatic softshell turtles: revision of coeuritrema mehra, 1933 (digenea: schistosomatoidea) and a new species infecting chinese softshell turtles, pelodiscus sinensis (trionychidae), from vietnam.coeuritrema mehra, 1933, previously regarded as a junior subjective synonym of hapalorhynchus stunkard, 1922, herein is revised to include coeuritrema lyssimus mehra, 1933 (type species), coeuritrema rugatus (brooks et sullivan, 1981) comb. n., and coeuritrema platti roberts et bullard sp. n. these genera are morphologically similar by having a ventral sucker, non-fused caeca, two testes, a pre-testicular cirrus sac, an intertesticular ovary, and a common genital pore that opens dorsally and in ...201627827338
acanthostomum macroclemidis n. sp. (digenea: cryptogonimidae: acanthostominae) from the alligator snapping turtle, macroclemys temmincki.acanthostomum macroclemidis n. sp. is described from specimens found in the intestine of an alligator snapping turtle macroclemys temmincki from southern mississippi. the most important diagnostic features of the new species are the general shape and proportions of the body, the position of the pharynx (relative length of the prepharynx and esophagus), the egg size, the relative length and position of the vitelline fields, and the number, shape, and size of the circumoral spines. the new species ...200312659321
beveling of fine micropipette electrodes by a rapid precision method.a technique has been developed for embedding alumina particles 0.05 micrometer in size in the surface of a polyurethane film laid on glass. this abrasive surface is used for rapid, precise, and reliable beveling of pyrex micropipettes with tip diameters at least as small as 0.1 micrometer. in the snapping turtle retina the beveled electrodes give much better cell penetration and intracellular response stability than unbeveled electrodes of considerably higher proach to this problem.19744841617
ranking terrestrial vertebrate species for utility in biomonitoring and vulnerability to environmental contaminants.the measurement of contaminant tissue concentrations or exposure-related effects in biota has been used extensively to monitor pollution and environmental health. terrestrial vertebrates have historically been an important group of species in such evaluations, not only because many are excellent sentinels of environmental contamination, but also because they are valued natural resources in their own right that may be adversely affected by toxicant exposure. selection of appropriate vertebrates f ...200312442504
distribution of creatine, guanidinoacetate and the enzymes for their biosynthesis in the animal kingdom. implications for phylogeny.1. the distribution of creatine and the creatine-synthesizing enzymes in the animal kingdom has been investigated. creatine was found in tissues of all vertebrates examined, and in various invertebrates from phyla annelida, echinodermata, hemichordata and chordata, subphylum cephalochordata. the activities of the creatine-synthesizing enzymes, arginine-glycine transamidinase and guanidinoacetate methylpherase, were not detected in the hagfish or in any of the invertebrates, including those in wh ...19725010856
survival of embryonic limb bud transplants in snapping turtles. 19715132600
use of intravascular carbon dioxide gas to demonstrate interatrial septal defects. 195813606221
hematology and clinical chemistry reference ranges for clinically normal, captive new guinea snapping turtle (elseya novaeguineae) and the effects of temperature, sex, and sample type.median values and confidence intervals for hematology and serum and plasma chemistry parameters were established for 29 male and female healthy new guinea snapping turtles (elseya novaeguineae) held at 24.5 degrees c and 30.0 degrees c. creatine kinase, albumin, potassium, and phosphorus values were significantly higher at 24.5 degrees c than at 30.0 degrees c. glucose, alkaline phosphatase, aspartate transaminase, alanine aminotransferase, total carbon dioxide, and chloride values were signific ...19979523632
lipid provisioning of turtle eggs and hatchlings: total lipid, phospholipid, triacylglycerol and triacylglycerol fatty acids.lipid composition of eggs and hatchlings was studied in painted, snapping and blanding's turtles from western nebraska. the average total lipid proportions of the egg yolk, post-embryonic yolk and hatchling soma dry masses were high in painted turtles (29.80%, 42.16% and 14.18%, respectively) relative to snapping and blanding's turtles (egg yolk < 14%, postembryonic yolk < 17%, hatchling soma < 2%). the proportion of total egg yolk lipid used during development varied among species (painted turt ...19957584861
a phylogenetic and biogeographic analysis of the genera of spirorchinae (digenea: spirorchidae) parasitic in freshwater turtles.cladistic analysis of the freshwater genera of spirorchinae (schistosomatoidea: spirorchidae sensu yamaguti, 1971) plus haematotrema stunkard, 1923, and aphanospirorchis platt, 1990, was completed. the spirorchinae were considered monophyletic based on synapomorphies of the esophagus. three lineages, spirhapalum (europe/asia), plasmiorchis+hemiorchis (india), and spirorchis + henotosoma + haematotrema + aphanospirorchis (north america), were identified. nelsen consensus analysis was used as the ...19921635020
sensitive periods during embryogeny for hormonally induced sex determination in turtles.administration of exogenous estradiol between embryonic stages 10 and 19 inclusive caused embryos of snapping turtles (a species which exhibits temperature-dependent sex determination) to develop ovaries rather than testes, while administration of hormone either prior to stage 10 or after stage 22 did not affect the predicted sex ratio of offspring. thus the sensitive period for hormonal effects on gonadal development apparently coincides with the period of normal gonadal differentiation. in lig ...19883203874
spatial spread of adaptation within the cone network of turtle retina.1. the spatial characteristics of adaptation were studied in the red-sensitive cones of the snapping turtle retina using intracellular microelectrodes. light responses elicited with slit-shaped test and adapting stimuli revealed that test response amplitudes and adaptation decline similarly with distance from the impaled cone. the spatial spread of adaptation and the light response cannot be accounted for by scattered light and must therefore result from electrical coupling between cones. 2. the ...19873446810
disposition of toxic pcb congeners in snapping turtle eggs: expressed as toxic equivalents of tcdd. 19873120832
disposition of low and high environmental concentrations of pcbs in snapping turtle tissues. 19873107636
steroid hormones reverse sex in turtles.injection of estradiol benzoate into eggs of snapping turtles and painted turtles caused all embryos to develop as females. a similar but less consistent female-determining effect was associated with injection of testosterone proprionate. both species of turtles have temperature-dependent sex determination in nature, whereby embryos incubated at cool temperatures (25 degrees) develop as males and embryos incubated at warm temperatures (31 degrees) develop as females. exogenous estrogens have bee ...19863803892
species specific differences in the in vitro metabolism of the flame retardant mixture, firemaster® bz-54.firemaster(®) bz-54 is a flame retardant additive and consists of a brominated benzoate (2-ethylhexyl 2,3,4,5-tetrabromobenzoate; tbb) and a brominated phthalate (bis (2-ethylhexyl) 2,3,4,5-tetrabromophthalate; tbph). previous research has shown that fathead minnows exposed in vivo to firemaster(®) bz-54 accumulate tbb and tbph. this study examined the in vitro biotransformation potential of tbb and tbph in hepatic subcellular fractions (i.e., s9, microsomes and cytosol) in the fathead minnow, c ...201222889877
functional characteristics of lateral interactions between rods in the retina of the snapping turtle.1. intracellular recordings were made of the slow hyperpolarizing light responses of single rods in the retina of the snapping turtle. physiological criteria used to identify rods were verified by intracellular injections of procion yellow. 2. the amplitudes of the responses elicited by fixed intensity flashes increased as the stimulus was enlarged to a diameter of 300 mum. scattered light was found incapable of accounting for this effect, which must result from summative interaction of rods wit ...1976986460
taxonomic assessment of alligator snapping turtles (chelydridae: macrochelys), with the description of two new species from the southeastern united states.the alligator snapping turtle, macrochelys temminckii, is a large, aquatic turtle limited to river systems that drain into the gulf of mexico. previous molecular analyses using both mitochondrial and nuclear dna suggested that macrochelys exhibits significant genetic variation across its range that includes three distinct genetic assemblages (western, central, and eastern = suwannee). however, no taxonomic revision or morphological analyses have been conducted previously. in this study, we test ...201424869532
evolutionary clock: nonconstancy of rate in different species.by using various methods for comparing polypeptide sequences we find that the evolutionary divergence of rattlesnake cytochrome c from cytochromes c of species in other classes has been more rapid than that of cytochrome c of another reptile, the snapping turtle. this suggests that the evolutionary rate of change of cytochromes c is species-dependent as well as time-dependent.19725065730
an unusual mortality event in johnstone river snapping turtles elseya irwini (johnstone) in far north queensland, australia.an unusual mortality event in johnstone river snapping turtles (elseya irwini) in far north queensland, australia, occurred during the summer months of december 2014 and january 2015. we report the data collected during the mortality event, including counts of sick and dead animals, clinical appearance and one necropsy.201728948624
determination of linear and cyclic volatile methylsiloxanes in blood of turtles, cormorants, and seals from canada.we measured the concentrations of linear and cyclic volatile methylsiloxanes (vms) concentrations in the blood plasma of turtles, cormorants, and seals collected from canadian freshwater and marine ecosystems. a modified quick, easy, cheap, effective, rugged, and safe (quechers) method was developed to quantify the levels of linear and cyclic vms in the plasma samples. the cyclic vms of hexamethylcyclotrisiloxane (d3), octamethylcyclotetrasiloxane (d4), decamethylcyclopentasiloxane (d5), and dod ...201727663360
a new haemogregarina species of the alligator snapping turtle, macrochelys temminckii (testudines: chelydridae), in georgia and florida that produces macromeronts in circulating erythrocytes.haemogregarina macrochelysi n. sp. (apicomplexa: haemogregarinidae) of the alligator snapping turtle, macrochelys temminckii, is characterized by slender, recurved gamonts 29-35 x 3-4.5 microm, in which the anterior limb comprises 48-54% of the total length. the gamont nucleus, 5-7.5 x 2-5 microm, is situated at approximately midbody of the gamont. meronts typical of haemogregarina occupying erythrocytes have 3-8 small, compact nuclei and are 13-17 x 4.5-9 microm. erythrocytic meronts that conta ...200919245282
comparative analysis of glucagonergic cells, glia, and the circumferential marginal zone in the reptilian retina.retinal progenitors in the circumferential marginal zone (cmz) and müller glia-derived progenitors have been well described for the eyes of fish, amphibians, and birds. however, there is no information regarding a cmz and the nature of retinal glia in species phylogenetically bridging amphibians and birds. the purpose of this study was to examine the retinal glia and investigate whether a cmz is present in the eyes of reptilian species. we used immunohistochemical analyses to study retinal glia, ...201626053997
metabolic rates are elevated and influenced by maternal identity during the early, yolk-dependent, post-hatching period in an estuarine turtle, the diamondback terrapin (malaclemys terrapin).non-genetic maternal effects, operating through a female's physiology or behavior, can influence offspring traits and performance. here we examined potential maternal influences on metabolic rates (mr) of offspring in an estuarine turtle, the diamondback terrapin (malaclemys terrapin). females and their eggs were collected from the field and the eggs incubated in the laboratory for subsequent measurement of mr of females, late-stage embryos, newly-hatched individuals that were nutritionally depe ...201727894885
dynamics of yolk steroid hormones during development in a reptile with temperature-dependent sex determination.many oviparous reptiles exhibit temperature-dependent sex determination (tsd); i.e., the temperature at which the egg is incubated determines the sex of the offspring. in tsd reptiles, yolk steroids not only may influence sex determination, but also may mediate hormonal effects on subsequent growth and behavior, as in some avian species. we investigated changes in the levels of estradiol (e(2)) and testosterone (t) during development in yolks of snapping turtle eggs, examined how incubation temp ...200212161199
kinetics of synaptic transmission from photoreceptors to horizontal and bipolar cells in turtle retina.the kinetics of synaptic transfer from photoreceptors to second order neurons have been determined in the retina of the snapping turtle. analysis of the fluctuations resulting from the random release of cone transmitter molecules reveals that the action on postsynaptic channels of the depolarizing bipolar cells is prolonged by approximately 10 times compared to the action on the hyperpolarizing bipolar cells. determination of the cone and rod to horizontal cell impulse response shows that the ki ...19836308900
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 dev ...19817338727
mixed rod-cone responses in horizontal cells of snapping turtle retina. 1979473609
morbidity and mortality of wild turtles at a north carolina wildlife clinic: a 10-year retrospective.the medical records from 1,847 wild turtle patients seen between 2005 and 2014 by the turtle rescue team at the north carolina state university college of veterinary medicine were analyzed. eastern box turtles (terrapene carolina carolina; n = 947), yellow-bellied sliders (trachemys scripta scripta; n = 301), cooters ( pseudemys spp.; n = 235), common snapping turtles (chelydra serpentina; n = 165), and eastern painted turtles (chrysemys picta; n = 93) made up 94.3% of all patients. patient admi ...201728920820
wait and snap: eastern snapping turtles (chelydra serpentina) prey on migratory fish at road-stream crossing culverts.there is growing evidence that culverts at road-stream crossings can increase fish density by reducing stream width and fish movement rates, making these passageways ideal predator ambush locations. in this study, we used a combination of videography and δ13c stable isotope analyses to investigate predator-prey interactions at a road-stream crossing culvert. eastern snapping turtles (chelydra serpentina) were found to regularly reside within the culvert to ambush migratory river herring (alosa s ...202032961086
morphometric data for five freshwater turtles in south, central, and west texas.from 2008 to 2013, we sampled freshwater turtle populations at 66 sites in south, central, and west texas, usa. sampling sites included ponds, lakes, resacas (oxbow lakes), canals, and rivers. we sampled turtle populations using baited hoop nets (66 sites) and basking traps (3 sites), and captured turtles by hand opportunistically in terrestrial habitat. we measured carapace length and width, plastron length and width, body depth, and weight of captured turtles. excluding recaptures, we measured ...202032195296
health assessment of free-ranging alligator snapping turtles (macrochelys temminckii) in georgia and florida.the alligator snapping turtle (macrochelys temminckii) is a large freshwater turtle endemic to river systems that drain into the gulf of mexico. turtle populations were sharply reduced by commercial harvest in the 1970s and 1980s; however, the species has yet to be protected under the endangered species act. while anthropogenic stressors such as habitat fragmentation and degradation and illegal capture continue to threaten populations, the degree to which disease may be contributing to any decli ...200818689653
incubation temperature and satiety influence general locomotor and exploratory behaviors in the common snapping turtle (chelydra serpentina).temperature during embryogenesis determines sex and has been shown to influence other physiological traits in reptiles. the common snapping turtle (chelydra serpentina) is an ideal model for testing how temperature impacts behavior in species that display temperature-dependent sex determination. behavioral assays are crucial to understanding how a changing climate may affect whole organism function in the snapping turtle. currently, there are few behavioral assays for semi-aquatic vertebrates li ...202032194070
high prevalence of subclinical frog virus 3 infection in freshwater turtles of ontario, canada.ranaviruses have been associated with chelonian mortality. in canada, the first two cases of ranavirus were detected in turtles in 2018 in ontario, although a subsequent survey of its prevalence failed to detect additional positive cases. to confirm the prevalence of ranavirus in turtles in ontario, we used a more sensitive method to investigate if lower level persistent infection was present in the population. here we report results via a combination of qpcr, pcr, sanger sequencing and genome s ...202032174301
detecting trends in body size: empirical and statistical requirements for intraspecific analyses.attributing biological explanations to observed ecogeographical and ecological patterns require eliminating potential statistical and sampling artifacts as alternative explanations of the observed patterns. here, we assess the role of sample size, statistical power, and geographic inclusivity on the general validity and statistical significance of relationships between body size and latitude for 3 well-studied species of turtles. we extend those analyses to emphasize the importance of using stat ...201931616479
regulation of blood flow in the pulmonary and systemic circuits during submerged swimming in common snapping turtle (chelydra serpentina).blood flow patterns and heart rate have rarely been investigated in freely swimming turtles and their regulation during swimming is unknown. in this study, we investigated the blood flow patterns and heart rate in surfacing and during graded, submerged swimming activity in common snapping turtles. we further investigated the effects of beta-adrenergic and cholinergic receptor blockade on blood flow and heart rate during these activities. our findings illustrate that surfacing is accompanied by a ...201931331940
correction: different mechanisms of serum complement activation in the plasma of common (chelydra serpentina) and alligator (macrochelys temminckii) snapping turtles.[this corrects the article doi: 10.1371/journal.pone.0217626.].201931291346
developmental plasticity of cardiac anoxia-tolerance in juvenile common snapping turtles ( chelydra serpentina).for some species of ectothermic vertebrates, early exposure to hypoxia during embryonic development improves hypoxia-tolerance later in life. however, the cellular mechanisms underlying this phenomenon are largely unknown. given that hypoxic survival is critically dependent on the maintenance of cardiac function, we tested the hypothesis that developmental hypoxia alters cardiomyocyte physiology in a manner that protects the heart from hypoxic stress. to test this hypothesis, we studied the comm ...201931238852
first report of ranavirus mortality in a common snapping turtle chelydra serpentina.an adult male snapping turtle with marked palpebral edema and multifocal skin ulceration was found alive in a marsh in southern ontario in summer 2017. the turtle was transported to a rehabilitation facility and died 4 d after arrival. the carcass was submitted to the canadian wildlife health cooperative for post-mortem examination. gross lesions included ulcerative conjunctivitis, necrotizing stomatitis, and splenomegaly. microscopically, this corresponded to multisystemic fibrinonecrotizing va ...201931188138
different mechanisms of serum complement activation in the plasma of common (chelydra serpentina) and alligator (macrochelys temminckii) snapping turtles.reptiles are declining worldwide yet our understanding of their immune function lags far behind other taxa. the innate immune system is the primary mode of defense in reptiles, and the serum complement cascade is its major component. we assessed serum complement activity of plasma in two closely related aquatic turtle species, the common snapping turtle (cst; chelydra serpentina) and alligator snapping turtle (ast; macrochelys temminckii). we used a sheep red blood cell (srbc) hemolysis assay to ...201931170203
blood flow distribution in embryonic common snapping turtles chelydra serpentina (reptilia; chelonia) during acute hypoxia and α-adrenergic regulation.embryonic turtles have four distinct vascular beds that separately perfuse the developing embryo's body and the extra-embryonic yolk sac, amnion and chorioallantoic membrane (cam). the mechanisms enabling differential regulation of blood flow through these separate beds, in order to meet the varying demands of the embryo during development, is of current interest. the present investigation followed the changes in blood flow distribution during an acute exposure to hypoxia and after α-adrenergic ...201931505219
effects of life-history requirements on the distribution of a threatened reptile.survival and reproduction are the two primary life-history traits essential for species' persistence; however, the environmental conditions that support each of these traits may not be the same. despite this, reproductive requirements are seldom considered when estimating species' potential distributions. we sought to examine potentially limiting environmental factors influencing the distribution of an oviparous reptile of conservation concern with respect to the species' survival and reproducti ...201727488734
traumatic amputation of finger from an alligator snapping turtle bite.legend states that the alligator snapping turtle (macrochelys temminckii) should be handled with extreme caution as it has jaw strength powerful enough to bite a wooden broomstick in half. tales of bite injuries from what is the largest freshwater turtle in north america exist anecdotally, yet there are few descriptions of medical encounters for such. the risk of infection from reptilian bites to the hand in an aquatic environment warrants thorough antibiotic treatment in conjunction with hand s ...201627116923
surgical anatomy of celiotomy approaches to the stomach in the common snapping turtle (chelydra serpentina).entanglement in or ingestion of fishing gear is a common cause of morbidity and mortality in chelonians. commercial and recreational fishing activities exert bycatch pressures sufficient to cause population declines in the common snapping turtle (chelydra serpentina) and the alligator snapping turtle (macrochelys spp.). gastrotomy for the removal of fish hook foreign bodies from the stomach of freshwater turtles typically requires a plastron osteotomy but in sea turtles has been successfully acc ...201931120665
role for androgens in determination of ovarian fate in the common snapping turtle, chelydra serpentina.sex steroids are involved in sex determination in almost all vertebrates, including species with temperature-dependent sex determination (tsd). it is well established that aromatase and estrogens are involved in ovary determination in tsd species. in contrast, the role of non-aromatizable androgens in tsd is less clear. in this study, we used dihydrotestosterone (dht) and an antagonist of the mammalian androgen receptor (flutamide) to examine the impact of androgens on sex determination in the s ...201931059691
positive or negative? the shell alters the relationship among behavioral defense strategy, energy metabolic levels and antioxidant capacity in freshwater turtles.the relationships among energy metabolic levels, behavioral and other physiological traits help to determine the trade-off of energy allocation between different traits and the evolution of life-history driven by natural selection. however, these relationships may be distinctive in selected animal taxa because of their unique traits. in the present study, the relationships among energy metabolic levels, behavioral defense strategies, and antioxidant capacity were explored in three freshwater tur ...201930809267
comparison of alligator snapping turtle ( macrochelys temminckii) plasma biochemical profiles from two clinical analyzers.the interpretation of plasma biochemical profiles can be confounded by the methodologies by which samples are analyzed. the goal of this study was to compare agreement between two biochemical analyzers for plasma samples from alligator snapping turtles ( macrochelys temminckii). blood was obtained from the dorsal coccygeal vein of captive-reared, juvenile turtles ( n = 34), stored in lithium heparin tubes, and centrifuged to separate plasma from whole blood. plasma samples were stored at 5°c pri ...201830592915
draft genome of the common snapping turtle, chelydra serpentina, a model for phenotypic plasticity in reptiles.turtles are iconic reptiles that inhabit a range of ecosystems from oceans to deserts and climates from the tropics to northern temperate regions. yet, we have little understanding of the genetic adaptations that allow turtles to survive and reproduce in such diverse environments. common snapping turtles, chelydra serpentina, are an ideal model species for studying adaptation to climate because they are widely distributed from tropical to northern temperate zones in north america. they are also ...202032998935
comparative cranial morphology of the late cretaceous protostegid sea turtle desmatochelys lowii.the phylogenetic placement of cretaceous marine turtles, especially protostegidae, is still under debate among paleontologists. whereas protostegids were traditionally thought to be situated within the clade of recent marine turtles (chelonioidea), some recent morphological and molecular studies suggest placement along the stem of cryptodira. the main reason why the evolution of marine turtles is still poorly understood, is in part due to a lack of insights into the cranial anatomy of protostegi ...201830568851
purification of thyrotropin from the pituitaries of two turtles: the green sea turtle and the snapping turtle. 19817286628
measurement and modelling of primary sex ratios for species with temperature-dependent sex determination.for many oviparous animals, incubation temperature influences sex through temperature-dependent sex determination (tsd). although climate change may skew sex ratios in species with tsd, few available methods predict sex under natural conditions, fewer still are based on mechanistic hypotheses of development, and field tests of existing methods are rare. we propose a new approach that calculates the probability of masculinization (pm) in natural nests. this approach subsumes the mechanistic hypot ...201930352829
antibacterial activities of plasma from the common (chelydra serpentina) and alligator snapping turtle (macrochelys temminckii).innate immunity provides a fast-acting and nonspecific defense against microbial infection, and appears to have particular importance in the immune response of ectothermic vertebrates. chelonians are a globally distributed and diverse group, yet little is known about their basic immune function. the chelonian family chelydridae is made up of two genera (chelydra and macrochelys), represented in our study by the widespread common snapping turtle ( chelydra serpentina; cst) and the southeast usa e ...201930273972
phylogenetic origins for severe acetaminophen toxicity in snake species compared to other vertebrate taxa.while it has been known for a while that some snake species are extremely sensitive to acetaminophen, the underlying mechanism for this toxicity has not been reported. to investigate if essential detoxification enzymes are missing in snake species that are responsible for biotransformation of acetaminophen in other vertebrate species, livers were collected from a variety of snake species, together with samples from alligator, snapping turtle, cat, rat, and cattle. subcellular fractions were anal ...201930268769
health assessment of free-ranging chelonians in an urban section of the bronx river, new york, usa.the bronx river in bronx, new york, us spans an area of significant human development and has been subject to historic and ongoing industrial contamination. we evaluated the health of freeranging native common snapping turtles ( chelydra serpentina) and nonnative invasive red-eared sliders ( trachemys scripta) in a segment of the bronx river between may and july 2012. in 18 snapping turtles and nine sliders, complete physical examinations were performed, ectoparasites collected, and blood was an ...201930226800
colonization and usage of an artificial urban wetland complex by freshwater turtles.conservation authorities invest heavily in the restoration and/or creation of wetlands to counteract the destruction of habitat caused by urbanization. monitoring the colonization of these new wetlands is critical to an adaptive management process. we conducted a turtle mark-recapture survey in a 250 ha artificially created wetland complex in a large north american city (toronto, ontario). we found that two of ontario's eight native turtle species (snapping turtle (sn), chelydra serpentina, and ...201830123718
using non-destructive techniques to measure mercury (hg) concentrations in gravid blanding's turtles (emydoidea blandingii) in northeastern illinois.aquatic turtles are suitable biomonitors of wetland ecosystem health because they are long-lived and occupy elevated trophic positions in wetland food webs. this study aimed to determine hg exposure in adult blanding's turtles (emydoidea blandingii), an imperiled prairie-wetland species endemic to the northern u.s. and southern canada. claw samples were collected from gravid females from four wetland sites in northeast illinois. claw hg concentrations ranged from 654 to 3132 ng/g and we found no ...201830073403
convective oxygen transport during development in embryos of the snapping turtle chelydra serpentina.this study investigated the maturation of convective oxygen transport in embryos of the snapping turtle (chelydra serpentina). measurements included: mass, oxygen consumption (v̇o2 ), heart rate, blood oxygen content and affinity and blood flow distribution at 50%, 70% and 90% of the incubation period. body mass increased exponentially, paralleled by increased cardiac mass and metabolic rate. heart rate was constant from 50% to 70% incubation but was significantly reduced at 90% incubation. hema ...201830065037
a new method of estimating thermal performance of embryonic development rate yields accurate prediction of embryonic age in wild reptile nests.temperature has a strong effect on ectotherm development rate. it is therefore possible to construct predictive models of development that rely solely on temperature, which have applications in a range of biological fields. here, we leverage a reference series of development stages for embryos of the turtle chelydra serpentina, which was described at a constant temperature of 20 °c. the reference series acts to map each distinct developmental stage onto embryonic age (in days) at 20 °c. by exten ...201829801626
assessment of blood lead, zinc, and mercury concentrations and cholinesterase activity in captive-reared alligator snapping turtles ( macrochelys temminckii) in louisiana, usa.the alligator snapping turtle ( macrochelys temminckii) is a freshwater apex predator that has experienced severe population declines throughout its range due to historical overharvesting and habitat degradation. because of its long lifespan, high trophic level, and limited home range, it is a suitable sentinel species for monitoring environmental contaminants. in louisiana, us a pilot program aims to augment free-ranging populations by releasing captive-reared individuals. baseline values of po ...201829697311
repeatability and sources of variation of the bacteria-killing assay in the common snapping turtle.research on reptile ecoimmunology lags behind that on other vertebrates, despite the importance of such studies for conservation and evolution. because the innate immune system is highly conserved across vertebrate lineages, assessments of its performance may be particularly useful in reptiles. the bacteria-killing assay requires a single, small blood sample and quantifies an individual's ability to kill microorganisms. the assay's construct validity and interpretability make it an attractive me ...201729356460
pulmonary anatomy and a case of unilateral aplasia in a common snapping turtle (chelydra serpentina): developmental perspectives on cryptodiran lungs.the common snapping turtle (chelydra serpentina) is a well studied and broadly distributed member of testudines; however, very little is known concerning developmental anomalies and soft tissue pathologies of turtles and other reptiles. here, we present an unusual case of unilateral pulmonary aplasia, asymmetrical carapacial kyphosis, and mild scoliosis in a live adult c. serpentina. the detailed three-dimensional (3d) anatomy of the respiratory system in both the pathological and normal adult c ...201729063595
characterization of the foxl2 proximal promoter and coding sequence from the common snapping turtle (chelydra serpentina).sex is determined by temperature during embryogenesis in snapping turtles, chelydra serpentina. previous studies in this species show that dihydrotestosterone (dht) induces ovarian development at temperatures that normally produce males or mixed sex ratios. the feminizing effect of dht is associated with increased expression of foxl2, suggesting that androgens regulate transcription of foxl2. to test this hypothesis, we cloned the proximal promoter (1.6kb) and coding sequence for snapping turtle ...201728711355
high levels of maternally transferred mercury disrupt magnetic responses of snapping turtle hatchlings (chelydra serpentina).the earth's magnetic field is involved in spatial behaviours ranging from long-distance migration to non-goal directed behaviours, such as spontaneous magnetic alignment (sma). mercury is a harmful pollutant most often generated from anthropogenic sources that can bio-accumulate in animal tissue over a lifetime. we compared sma of hatchling snapping turtles from mothers captured at reference (i.e., low mercury) and mercury contaminated sites. reference turtles showed radio frequency-dependent sm ...201728501632
embryonic hypoxia programmes postprandial cardiovascular function in adult common snapping turtles (chelydra serpentina).reduced oxygen availability (hypoxia) is a potent stressor during embryonic development, altering the trajectory of trait maturation and organismal phenotype. we previously documented that chronic embryonic hypoxia has a lasting impact on the metabolic response to feeding in juvenile snapping turtles (chelydra serpentina). turtles exposed to hypoxia as embryos [10% o2 (h10)] exhibited an earlier and increased peak postprandial oxygen consumption rate, compared with control turtles [21% o2 (n21)] ...201728495871
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