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At least 253 records · Page 14Linked to original sources
PubMed1996

Histological and ultrastructural study of the lingual epithelium of the juvenile Pacific ridley turtle, Lepidochelys olivacea (Chelonia, Cheloniidae).

Histological and ultrastructural studies ot the dorsal lingual epithelium of the juvenile Pacific ridley turtle, Lepidochelys olivacea, were performed by light and electron microscopy, and the results were compared to those of freshwater turtles in order to clarify the relationship between the histological and cellular differences of the lingual epithelium and the habitat of the turtles. The tongue of the juvenile Pacific ridley turtle is triangular with a round apex when viewed from above, but it appears flattened in lateral view. Scanning electron microscopy (SEM) revealed no lingual papillae on the dorsal surface of the tongue. Instead, transverse plicae are found on the surface of the body and the radix. The surface of the apex is smooth. Microridge-like structures are present on the surfaces of the cells, and the cell margins are thickened. The mucosal epithelium is keratinized, stratified squamous with a relatively thick layer of desquamating cells. Cells of the basal and deep intermediate layers appear elliptical in shape; and their nuclei are elliptical and centrally located. Numerous desmosomes join the processes of adjacent cells; and hemidesmosomes anchor the basal cells to the basal lamina. The cytoplasm of these cells contains mitochondria, free ribosomes, rough endoplasmic reticulum, vacuoles, and bundles of tonofilaments. Cells and their nuclei in the intermediate layer display gradual flattening. In the shallow intermediate layer, the cells are significantly flattened, with nuclei condensed or absent. The cytoplasm contains many tonofibrils or bundles of tonofilaments, free ribosomes and keratohyalin granules, with numerous ribosomes attached to their surfaces. A few collapsed mitochondria are visible. Cell membranes of the shallow intermediate cells are smooth and attached to those of adjacent cells by desmosomes. The keratinized layer is located on top of the shallow intermediate layer, and consists of significantly flattened cells lacking nuclei and filled with keratin fibers. Very fine cellular processes joined by desmosomes are visible. The desquamating cells located on top of the keratinized layer contain keratin fibers that are somewhat thicker than tonofibrils and tonofilaments, and clearly distinguishable individually. The microridge-like structures visible by SEM could be attributed to the persistence of cells formed in underlying layer. In conclusion, the histology of the lingual epithelium of the juvenile Pacific ridley turtle differs significantly from that of the adult freshwater turtle in spite of the similarity of the gross morphology of their tongues.

Animals↗
PubMed2003

Induction of vitellogenesis by estradiol-17beta and development of enzyme-linked immunosorbant assays to quantify plasma vitellogenin levels in green turtles (Chelonia mydas).

Treatment of juvenile green turtles (Chelonia mydas) with estradiol-17beta resulted in the induction of a 200 kDa plasma protein, consistent with vitellogenin (Vtg). The N-terminal 15 amino acids of the anion exchange purified protein shared sequence homologies with vitellogenins of several vertebrate species. Rabbit antiserum raised against purified Vtg recognized the plasma protein as well as several yolk proteins. Monoclonal antibody (Mab) HL1248, produced by inoculating mice with turtle yolk granules, showed specificity for plasma Vtg as well as a set of yolk proteins 120, 82, 43 and 32 kDa in size. The N-terminal 22 amino acids of the 43 kDa yolk protein was similar to the lipovitellin I subunit of Vtg of several vertebrate species. The peptide mass map of the 82 kDa yolk protein shared enough ions with that of purified plasma Vtg to support the conclusion that this protein was derived from plasma Vtg. Taken together, these results validate the specificity of Mab HL1248 for Vtg. Using purified Vtg concentration standards, competition and antigen capture enzyme-linked immunosorbant assays (ELISAs) were shown to quantitatively detect Vtg in green turtle plasma. Pre-induced plasma of juvenile turtles had Vtg levels of 2-4 micrograms/ml whereas post-estradiol exposure samples had 38-40 mg/ml. The plasma Vtg concentration of a nesting female turtle was 4.6 mg/ml, approximately 20-fold higher than that of a non-nesting adult female. The antigen capture ELISA will be useful in population studies of this endangered species, to detect vitellogenesis in females that will nest in a given year and to detect inappropriate Vtg levels in turtles exposed to xenoestrogens.

Amino Acid Sequence↗
PubMed1985

Effect of cyclic AMP on acidification in the isolated turtle bladder.

Cyclic AMP (10 mM) has been demonstrated to inhibit hydrogen ion secretion in the isolated turtle bladder. These experiments were designed to study the effect of cyclic AMP on hydrogen ion secretion in the isolated turtle bladder using both the pH stat and the reverse short circuit current techniques. Sodium transport was measured as the short circuit current. Studies were carried out at 0% CO2 and 1% CO2 at pH 7.4. Cyclic AMP (10 mM) was added to either the serosal or mucosal solutions, and hydrogen ion secretion was measured from 0 to 120 min. In the presence or absence of carbon dioxide, cyclic AMP and dibutyryl cyclic AMP had no effect on hydrogen ion secretion in fasted turtles. The addition of theophylline (10 mM) to the serosal solution, with or without cyclic AMP had no effect on proton secretion. Sodium transport was unchanged from control following serosal or mucosal addition of 10 mM cyclic AMP in the presence or absence of carbon dioxide. In chronically bicarbonate-loaded turtles proton secretion was the same as control fasted turtles. In these animals, however, serosal administration of 10 mM cyclic AMP significantly stimulated bicarbonate secretion. Stimulation of bicarbonate secretion occurred in the presence of a 20 mM bicarbonate gradient. When there was no bicarbonate gradient, cyclic AMP was without effect; cyclic AMP had no effect on bicarbonate permeability when measured in the presence of acetazolamide. These results indicate that cyclic AMP has no effect on hydrogen ion secretion or sodium transport in the isolated turtle bladder when studied at two different rates of acidification (0 and 1% CO2). Cyclic AMP appears to stimulate active bicarbonate secretion.

Acetazolamide↗
PubMed2001

Ultrastructural changes in granulosa cells and plasma steroid levels after administration of luteinizing hormone-releasing hormone in the Western painted turtle, Chrysemys picta.

In this study we investigated the effects of treatment by luteinizing hormone-releasing hormone (LHRH) on the morphology and steroid release of ovarian tissues in the Western painted turtle, (Chrysemys picta). In Experiment I, four adult female turtles were injected with synthetic mammalian LHRH (i.p., 500 pg/g bodyweight) and four with saline 2-3 weeks prior to ovulation. Granulosa cells from LHRH-treated turtles vs controls contained both preovulatory follicles (16-20 mm in diameter) and small follicles (0.5-1.00mm in diameter) with increased RER, free ribosomes and mitochondria with swollen cristae. An increase in the amount of cytoskeletal material (microfilaments) was observed in granulosa cells of the experimental turtles compared to the controls. Cytoplasmic extensions of the oocyte and granulosa cells were longer in the small follicles of treated animals, accounting for the observed increase in the thickness of the zona pellucida (ZP) over the controls. In Experiment II, administration of LHRH (i.p.) to 10 turtles during the same period triggered a substantial increase in plasma progesterone and estradiol-17beta levels over the 10 saline-injected controls. This supports the idea that in this species, as in mammals, steroidogenic activity in the ovarian follicles are under the control of the hypothalamic-pituitary axis. The ultrastructure and hormonal levels of the experimental animals were typical of untreated turtles just prior to ovulation. In this species the development of follicles and steroidogenesis can be stimulated prematurely by a releasing hormone from a nonreptilian origin.

Animals↗
PubMed1995

Risk assessment, life history strategies, and turtles: could declines be prevented or predicted?

The process of ecological risk assessment should involve the ability to predict adverse outcomes of particular environmental contaminants or human intrusions. Ecological risk assessment generally focuses on populations, communities, and ecosystems, rather than on individual health. We explore the importance of life history strategies of aquatic turtles to their risk from environmental contaminants and other human activities using three examples: the wood turtle Clemmys insculpta, a freshwater species; the diamondback terrapin Malaclemys terrapin, a littoral species; and marine turtles as a group. These turtles are partly herbivorous and are at low or intermediate levels on the food chain, yet are particularly vulnerable due to their life history strategies of being long-lived with relatively low survival of young. They suffer a variety of natural mortality factors that include predation, starvation, and disease, as well as inundation and destruction of nesting beaches and their eggs by storms. Yet they also face a number of anthropogenic hazards, including toxic chemicals and floatables (plastics); capture for food, other products, and pets; incidental mortality in fishing gear; disturbance while nesting or moving on land; injuries or death by collision with boats; and increased predator exposure because of humans. The three turtle species (or groups of species) examined have experienced these natural and anthropogenic pressures differentially, with resultant differences in the rates of population declines. Because they are lower on the food chain than other obligate carnivores, they are less vulnerable to toxics, and to date, toxics seem a relatively inconsequential environmental risk to turtles.

Animals↗
PubMedDate not supplied

Geographic variation of the physiological response to overwintering in the painted turtle (Chrysemys picta).

We compared the physiological responses of latitudinal pairings of painted turtles submerged in normoxic and anoxic water at 3 degrees C: western painted turtles (Chrysemys picta bellii) from Wisconsin (WI) versus southern painted turtles (Chrysemys picta dorsalis) from Louisiana (LA), Arkansas (AR), and Alabama (AL), and eastern painted turtles (Chrysemys picta picta) from Connecticut (CT) versus C. p. picta from Georgia (GA). Turtles in normoxic water accumulated lactate, with C. p. bellii accumulating less than (20 mmol/L) the other groups (44-47 mmol/L), but with relatively minor acid-base and ionic disturbances. Chrysemys picta bellii had the lowest rate of lactate accumulation over the first 50 d in anoxic water (1.8 mmol/d vs. 2.1 for AR C. p. dorsalis, 2.4 mmol/d for GA C. p. picta, and 2.5 mmol/d for CT C. p. picta after 50 d and 2.6 mmol/d for AL C. p. dorsalis after 46 d). Northern turtles in both groups survive longer in anoxia than their southern counterparts. The diminished viability in C. p. dorsalis versus C. p. bellii can be partially explained by an increased rate of lactate accumulation and a decreased buffering capacity, but for the CT and GA C. p. picta comparison, only buffering capacity differences are seen to influence survivability.

Analysis of Variance↗
PubMed2005

Effects of diving and swimming behavior on body temperatures of pacific leatherback turtles in tropical seas.

Mathematical models and recordings of cloacal temperature suggest that leatherback turtles (Dermochelys coriacea) maintain core body temperature higher than ambient water temperature (T(W)) while freely swimming at sea. We investigated the thermoregulatory capabilities of free-ranging leatherbacks and, specifically, the effect that changes in diving patterns and ambient temperatures have on leatherback body temperatures (T(B)). Data loggers were used to record subcarapace and gastrointestinal tract temperatures (T(SC) and T(GT), respectively), T(W), swim speed, dive depth, and dive times of female leatherback turtles during internesting intervals off the coast of Guanacaste, Costa Rica. Mean T(SC) (28.7 degrees -29.0 degrees C) was significantly higher than mean T(W) (25.0 degrees -27.5 degrees C). There was a significant positive relationship between T(SC) and T(W) and a significant negative correlation between T(SC) and dive depth and T(GT) and dive depth. Rapid fluctuations in T(GT) occurred during the first several days of the internesting interval, which suggests that turtles were ingesting prey or water during this time. Turtles spent 79%-91% of the time at sea swimming at speeds greater than 0.2 m s(-1), and the average swim speed was 0.7 +/- 0.2 m s(-1). Results from this study show that alterations in diving behavior and T(W) affect T(B) of leatherback turtles in the tropics. Body temperatures of free-ranging leatherback turtles correspond well with values for T(B) predicted by mathematical models for tropical conditions.

Animals↗
PubMed1988

Purification and characterization of alpha-macroglobulin and ovomacroglobulin of the green turtle (Chelonia mydas japonica).

The plasma alpha-macroglobulin and egg white ovomacroglobulin were purified from the sea turtle, Chelonia mydas japonica, and their structural and functional properties were studied with the aim of clarifying the degree of evolutional divergence of two homologous proteins specific to different tissues of the same animal. The concentration of alpha-macroglobulin in green turtle plasma was about 4 mg/ml. The protein was purified from the plasma by precipitation with polyethylene glycol 6000, followed by zinc chelate chromatography and gel chromatography on Sepharose CL-6B. The concentration of ovomacroglobulin in green turtle egg white was about 0.4 mg/ml. Ovomacroglobulin was purified by gel chromatography on Sepharose CL-6B. The two proteins had similar molecular weights and amino acid compositions, and both inhibited proteinases such as trypsin, chymotrypsin, papain, and thermolysin. The amino terminal sequences of the two proteins were homologous to each other but higher homologies were found between the ovomacroglobulin of turtle and chicken, and between the serum macroglobulins of the same animals. The functional difference between turtle alpha-macroglobulin and ovomacroglobulin became clear when they were treated with methylamine, which is known to destroy the inhibitory activity of human alpha 2-macroglobulin by splitting internal thiolester bonds. The inhibitory activity of the turtle plasma protein was completely destroyed by methylamine but that of ovomacroglobulin was only partially affected. The number of sulfhydryl groups as titrated with 5,5'-dithiobis(2-nitrobenzoate) before and after treatment with proteinases or methylamine was different for the two proteins. The amount of radioactive methylamine that was incorporated was also different between the two proteins. The two proteins purified in this study had no immunological cross-reactivity.

Amino Acid Sequence↗
PubMed2005

First records of dive durations for a hibernating sea turtle.

The first published record, from the early 1970s, of hibernation in sea turtles is based on the reports of the indigenous Indians and fishermen from Mexico, who hunted dormant green turtles (Chelonia mydas) in the Gulf of California. However, there were no successful attempts to investigate the biology of this particular behaviour further. Hence, data such as the exact duration and energetic requirements of dormant winter submergences are lacking. We used new satellite relay data loggers to obtain the first records of up to 7h long dives of a loggerhead turtle (Caretta caretta) overwintering in Greek waters. These represent the longest dives ever reported for a diving marine vertebrate. There is strong evidence that the dives were aerobic, because the turtle surfaced only for short intervals and before the calculated oxygen stores were depleted. This evidence suggests that the common belief that sea turtles hibernate underwater, as some freshwater turtles do, is incorrect.

Animal Migration↗
PubMed1998

The navigational feats of green sea turtles migrating from Ascension Island investigated by satellite telemetry.

Previous tagging studies of the movements of green turtles (Chelonia mydas) nesting at Ascension Island have shown that they shuttle between this remote target in the Atlantic Ocean and their feeding grounds on the Brazilian coast, a distance of 2300 km or more. Since a knowledge of sea turtle migration routes might allow inferences on the still unknown navigational mechanisms of marine animals, we tracked the postnesting migration of six green turtle females from Ascension Island to Brazil. Five of them reached the proximity of the easternmost stretch of the Brazilian coast, covering 1777-2342 km in 33-47 days. Their courses were impressively similar for the first 1000 km, with three turtles tracked over different dates following indistinguishable paths for the first 300 km. Only the sixth turtle made some relatively short trips in different directions around Ascension. The tracks show that turtles (i) are able to maintain straight courses over long distances in the open sea; (ii) may perform exploratory movements in different directions; (iii) appropriately correct their course during the journey according to external information; and (iv) initially keep the same direction as the west-south-westerly flowing current, possibly guided by chemical cues.

Animals↗
PubMed2001

Trophic status drives interannual variability in nesting numbers of marine turtles.

Large annual fluctuations are seen in breeding numbers in many populations of non-annual breeders. We examined the interannual variation in nesting numbers of populations of green (Chelonia mydas) (n = 16 populations), loggerhead (Caretta caretta) (n = 10 populations), leatherback (Dermochelys coriacea) (n = 9 populations) and hawksbill turtles (Eretmochelys imbricata) (n = 10 populations). Interannual variation was greatest in the green turtle. When comparing green and loggerhead turtles nesting in Cyprus we found that green turtles were more likely to change the interval between laying seasons and showed greater variation in the number of clutches laid in a season. We suggest that these differences are driven by the varying trophic statuses of the different species. Green turtles are herbivorous, feeding on sea grasses and macro-algae, and this primary production will be more tightly coupled with prevailing environmental conditions than the carnivorous diet of the loggerhead turtle.

Animals↗
PubMed1994

Identification of cholecystokinin from frog and turtle. Divergence of cholecystokinin and gastrin occurred before the evolution of amphibia.

Cholecystokinins from brain and small intestine of the bullfrog (Rana catesbeiana) and red-eared slider turtle (Pseudomys scripta) were isolated. The purifications were monitored by an antiserum specific for the common C-terminus of mammalian cholecystokinin and gastrin. The peptide structures were identified by sequence analysis of the intact peptides and proteolytic fragments, mass spectrometry, and amino acid analysis. Brain and small intestine of both species contained cholecystokinin-8 and substantial amounts of cholecystokinin-7. Furthermore, the small intestine of both frog and turtle contained a major fraction of the immunoreactive material as large peptides consisting of 69 residues and 70 residues, respectively. The structure for frog cholecystokinin-69 is ASSSAQLKPFQRIDGTSDQKAVIGAMLAKYLQTRKAGSSTGRYAVLPNRPVIDPTHRINDRDYMGWMDF .NH2 and the structure for turtle cholecystokinin-70 is VPSSAGQLKPIQRLDGNVDQKANIGALLAKYLQQARKGPTGRISMMGNRVQNIDPTHRINDRDYMGWMD F.NH2. All the isolated peptides were tyrosine sulfated at the seventh last residue. The peptides are highly similar to each other and to mammalian cholecystokinins (70% mutual identity and more than 50% identity with human cholecystokinin). Thus, they are clearly related to the known mammalian cholecystokinins. Both peptides include the monobasic and dibasic cleavage sites giving rise to cholecystokinins-33, -39, and -58 in mammals. However, only a small amount of turtle cholecystokinin-40 (corresponding to mammalian cholecystokinin-39) was isolated. This confirms that post-translational processing is highly species dependent. Recently, we isolated peptides from frog and turtle antrum. Following their origin they were named gastrins in spite of their C-terminal cholecystokinin-like structure. Thus, two different cholecystokinin/gastrin peptides exist in frog and turtle justifying the choice of two names. This finding of two members of the cholecystokinin/gastrin family in frog shows that the divergence of cholecystokinin and gastrin occurred simultaneously with or earlier than the appearance of amphibia during phylogenesis. Frog cholecystokinin and gastrin show sufficient similarity along the whole sequence to support the notion of a gene duplication of a common ancestor.

Amino Acid Sequence↗
PubMed2006

Plasmid-mediated high-level gentamicin resistance among enteric bacteria isolated from pet turtles in Louisiana.

The sale of small turtles is banned by the Food and Drug Administration from the U.S. market due to concerns about their excretion of Salmonella spp. To produce a safe pet for the export market, the Louisiana pet turtle industry uses gentamicin sulfate baths (1,000 microg/ml) to eradicate Salmonella spp. from turtle eggs. In 1999, we analyzed bacterial samples recovered from turtle farms and found that strains of Salmonella enterica subsp. arizonae and other bacteria, such as Enterobacter cloacae, Citrobacter freundii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia, were resistant to high concentrations of gentamicin (>2,000 microg/ml) and to other aminoglycosides. The goal of this study was to identify the gene(s) which contributes to the high-level gentamicin resistance phenotype observed in bacteria from environmental samples with turtle farming activity, particularly the salmonellae, and to estimate the incidence of such genes in these bacteria. R plasmids from gentamicin-resistant strains were transferred by conjugation and transformation to naive Escherichia coli cells. Cloning and sequencing of the gentamicin resistance determinants on these plasmids revealed the presence of the aminoglycoside acetyltransferase genes aac(3)-IIa and aac(3)-VIa; the latter was present as a gene cassette of a class 1 integron. Multiplex PCR assays showed that every gentamicin-resistant isolate carried one of these acetyltransferase genes. Pulsed-field gel electrophoresis and restriction enzyme digestion analysis of R plasmids carrying these genes revealed different restriction profiles and sizes, indicating a dissemination of the gentamicin resistance genes through mobile molecular elements. The data presented highlight the need to develop an alternate method for the eradication of Salmonella spp. from turtle eggs.

Acetyltransferases↗
PubMed1975

Evaluation of methods for the isolation of Salmonella and Arizona organisms from pet turtles treated with antimicrobial agents.

Turtles infected with and actively excreting Salmonella-Arizona organisms were treated with various concentrations of both Neo-Terramycin (N-Te) and Terramycin (Te) (Pfizer) for various periods of time and then tested for the presence of these pathogens by two methods, excretion and blending. Turtles treated with 200 mug of Te per ml of container water for 9, 12, or 14 weeks, whereas when representative turtles from treatment groups were blended 72 h posttreatment these organisms were isolated from the whole turtle homogenate. Salmonella and Arizona could be recovered from homogenate prepared from turtles treated for 7 and 14 days with 400, 800, or 1,000 mug of Te or N-Te per ml. These findings suggest that the blending methods is more sensistive than the excretion method for the detection of Salmonella-Arizona in the treated turtle.

Animals↗
PubMed2004

Digestive pathology of sea turtles stranded in the Canary Islands between 1993 and 2001.

Digestive lesions were observed in 84 of 136 sea turtles (128 Caretta caretta, four Chelonia mydas and four Dermochelys coriacea) stranded in the Canary Islands between January 1993 and December 2001. In the oral cavity ulcerative and necropurulent stomatitis were the most frequently observed lesions, and in the oesophagus ulcerative and fibrinous oesophagitis, and traumatic oesophageal perforation were most frequently observed; all these lesions were mainly associated with the ingestion of fishing hooks. Different histological types of gastritis were observed in 35 of the turtles; necropurulent and fibrinous gastritis were associated with bacterial infections caused mainly by Proteus species, Vibrio alginolyticus, and Staphylococcus species, and larval nematodes of the genus Anisakis were responsible for a form of parasitic gastritis observed in 16 of the turtles. Different histological types of enteritis, including catarrhal, fibrinous, necropurulent and necrotising enteritis, affected 36 turtles; a wide range of gram-negative and gram-positive bacteria, including Bacillus species, Escherichia coli, Pasteurella species, Proteus species, Staphylococcus species, Streptococcus species and V. alginolyticus, were isolated from these lesions. All the cases of necrotising enteritis were associated with intestinal intussusception caused by the ingestion of monofilament fishing lines. Necrotising and/or multifocal granulomatous hepatitis were the lesions most commonly observed in the liver; they affected 29 of the turtles and were associated with Aeromonas hydrophila, Citrobacter species, E. coli, Proteus species, Staphylococcus species and V. alginolyticus infections. According to the stranding reports and the gross and histological lesions observed, 33 of the turtles had digestive lesions associated with the ingestion of hooks and monofilament lines, and two had lesions associated with the ingestion of crude oil.

Animals↗
PubMed2005

Adenosine and ATP-sensitive potassium channels modulate dopamine release in the anoxic turtle (Trachemys scripta) striatum.

Excessive dopamine (DA) is known to cause hypoxic/ischemic damage to mammalian brain. The freshwater turtle Trachemys scripta, however, maintains basal striatal DA levels in anoxia. We investigated DA balance during early anoxia when energy status in the turtle brain is compromised. The roles of ATP-sensitive potassium (K(ATP)) channels and adenosine (AD) receptors were investigated as these factors affect DA balance in mammalian neurons. Striatal extracellular DA was determined by microdialysis with HPLC in the presence or absence of the specific DA transport blocker GBR-12909, the K(ATP) blocker 2,3-butanedione monoxime, or the nonspecific AD receptor blocker theophylline. We found that in contrast to long-term anoxia, blocking DA reuptake did not significantly increase extracellular levels in 1-h anoxic turtles. Low DA levels in early anoxia were maintained instead by activation of K(ATP) channels and AD receptors. Blocking K(ATP) resulted in a 227% increase in extracellular DA in 1-h anoxic turtles but had no effect after 4 h of anoxia. Similarly, blocking AD receptors increased DA during the first hour of anoxia but did not change DA levels at 4-h anoxia. Support for the role of K(ATP) channels in DA balance comes from normoxic animals treated with K(ATP) opener; infusing diazoxide but not adenosine into the normoxic turtle striatum resulted in an immediate DA decrease to 14% of basal values within 1.5 h. Alternative strategies to maintain low extracellular levels may prevent catastrophic DA increases when intracellular energy is compromised while permitting the turtle to maintain a functional neuronal network during long-term anoxia.

Adenosine↗
PubMed1985

Renin release in turtles: effects of volume depletion and furosemide administration.

To gain insight into the phylogenetic history of mechanisms controlling renin release, we conducted studies in the freshwater turtle Pseudemys scripta. Maneuvers known to stimulate renin release in mammals were evoked in the turtle, and the response was compared with that in mammals. Cumulative hemorrhage (30% blood vol) in anesthetized turtles failed to increase renin even though arterial pressure was reduced to 50% of control. An even more severe hemorrhage (60% blood loss) or hypotension induced by nitroprusside infusion in unanesthetized turtles also failed to evoke an enhanced level of renin. However, under identical experimental conditions, a 15% blood loss in rats increased renin at least fourfold (P less than 0.01). In other studies 48 h of furosemide administration in awake turtles increased renin more than threefold (P less than 0.05) and were accompanied by concomitant reductions in plasma sodium and potassium (P less than 0.05). The general conclusions drawn from these studies is that renin secretion in this primitive vertebrate is similar to that in mammals with respect to renal tubular and electrolyte mechanisms, but unlike all mammals tested these turtles do not possess an intrarenal baroreceptor component in renin control.

Animals↗
PubMed1986

Effect of relative shell size in turtles on water and electrolyte composition.

Interspecific differences in water, sodium, and potassium concentrations of entire freshwater turtles are related to the relative size of the shell. Species with proportionately smaller shells have higher water and potassium concentrations but lower sodium concentrations (expressed as mumol/g wet mass). These effects are associated with variation in the amount of shell bone, which is lower in water and potassium concentrations than other tissues. Within a single species there are also differences in composition related to total wet mass and relative shell mass. Smaller turtles have a relatively larger overall water concentration, a lower overall sodium concentration (expressed as mumol/g wet mass), and a larger relative wet mass of shell (expressed as % total wet mass). The shell in small turtles is lower in relative dry mass, higher in water concentration, and lower in sodium concentration (expressed as mumol/g wet mass) than in large turtles. There is also a striking inverse size-related difference in the proportion of overall sodium that is exchangeable. This is due to a decrease in the proportion of exchangeable sodium in the shell of larger turtles, perhaps related to progressive calcification. The magnitude of the effects of size and/or age on water and electrolyte composition of turtles has not been previously recognized but must now be taken into account before any interspecific or intraspecific comparisons in body composition are made.

Animals↗