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PubMed1982

Brain potassium ion homeostasis, anoxia, and metabolic inhibition in turtles and rats.

Microelectrode measurements of tissue oxygen tension (PtO2) and extracellular potassium ion concentration ([K+]o) and dual wavelength spectrophotometric measurements of the reduction/oxidation state of cytochrome aa3 were used to compare the resistance of turtle and rat brain to anoxia in vivo. In both species, respiration with 100% N2 resulted in a decrease of tissue oxygen tension to near 0 mmHg and reduction of cytochrome aa3. However, N2 respiration resulted in only moderate elevation of [K+]o in turtle bran while [K+]o in rat brain was elevated to levels greater than 50 mM. In addition, N2 respiration in turtles had no effect on the rate of recovery of [K+]o, which was elevated by direct electrical stimulation of the brain. Electrocorticographic activity (ECoG) of the turtle brain was only moderately depressed during N2 respiration for up to 4 h whereas the ECoG of rat brain became isoelectric within 1 min. Inhibition of glycolysis with iodoacetate (IAA) resulted in rapid elevation of [K+]o in turtle brain during anoxia, but IAA had little effect on [K+]o during normoxia. These results indicate that the remarkable resistance of the diving turtle to anoxia does not result from continued provision of oxygen to the brain either by redistribution of systemic blood flow or from blood O2 storage. In addition, the turtle brain does not rely on cellular stores of high-energy compounds for maintenance of ionic homeostasis. We conclude that potassium ion homeostasis in the anoxic turtle brain must result from increased glycolytic ATP production and from decreased energy utilization.

Animals↗
PubMed1984

Characterization of the renin-angiotensin system in the turtle Pseudemys scripta.

Studies were conducted in freshwater turtles Pseudemys scripta to define some characteristics of the renin-angiotensin system in this reptile. Dialyzed acid-treated kidney extract (1 g tissue per ml water) produced a prolonged pressor response in unanesthetized turtles, which was eliminated by boiling the extract or by pretreating the turtle with [Sar1, Ile8]angiotensin II. A rat pressor assay was employed because turtle angiotensin (ANG) was bound poorly by the anti-[Asp1, Ile5, His9]ANG I used in our radioimmunoassay. Kidney extract incubated with homologous plasma (pH 5.5 and 25 degrees C) produced a time-dependent pressor response in rats. The pressor activity of the product was eliminated by dialysis or by pretreating the rats with [Sar1, Ile8]ANG II. The pressor response in anesthetized turtles to ANG I was significantly reduced by captopril, whereas the ANG II response remained unchanged, thus demonstrating the presence of ANG-converting enzyme activity in these animals. We determined the velocity of turtle ANG formation at various dilutions of enzyme (kidney extract) or substrate (plasma). Turtle kidney extract incubated with homologous plasma displayed typical Michaelis-Menten kinetics. Finally we conducted experiments to determine whether a portion of turtle plasma renin exists in an inactive form. Trypsinization caused a slight increase in plasma renin activity (PRA), whereas acidification to pH 3.3 yielded a fourfold increase in PRA.

Angiotensin I↗
PubMed1987

Adaptation to metabolic acidosis by turtle urinary bladder.

We utilized the turtle urinary bladder to study the mechanisms responsible for adaptation to metabolic acidosis. Bladders removed from acidotic turtles had a higher rate of H+ secretion in vitro than bladders from control turtles, despite identical extracellular pH. HCO3 secretion, however, was not different between the two groups. The increase in H+ secretion could be mediated by a decrease in intracellular pH and/or by an increase in the number of cells thought to be responsible for H+ secretion. To study this issue, we measured intracellular pH with the fluorescent dye 6-carboxyfluorescein diacetate and quantified the number of cells by fluorescence microscopy utilizing acridine orange, rhodamine 123, and 6-carboxyfluorescein diacetate in turtles receiving different acid loads. Urinary acidification measured in vivo was increased in turtles fed a low-acid load for 48 h and in turtles fed a high-acid load for 24-48 h. Intracellular pH was lower in bladders from turtles fed a high-acid load for 48 h but it was not different from controls in the other groups, indicating that intracellular pH cannot account for the adaptive increase in H+ secretion. Bladders from all groups fed an acid load had a higher number of cells with positive staining for acridine orange compared with controls. Double labeling with acridine orange and the mitochondrial stain rhodamine 123 or 6-carboxyfluorescein showed a significant increase in the number of mitochondria-rich cells between control and bladders from turtles fed an acid load. The increase in the number of rhodamine 123- or 6-carboxyfluorescein-positive cells was lower than the increase in acridine orange-positive cells, suggesting that the apparent increase in the number of acridine orange-positive cells is due to an increase in the number of acidic vesicles in the mitochondria-rich cells and in the granular cells rather than solely to an increase in the number of mitochondria-rich cells. Plasma membrane fraction prepared from control and acidotic bladders failed to disclose an increase in the putative H+-ATPase as assessed by enzymatic activity and transport studies. In conclusion, the present study suggests that the adaptive increase in H+ secretion in metabolic acidosis is associated both with an increase in the number of mitochondria-rich cells as well as with an increase in the number of acidic vesicles in these cells.

Acidosis↗
PubMed2000

Open-sea migration of magnetically disturbed sea turtles.

Green turtles (Chelonia mydas) that shuttle between their Brazilian feeding grounds and nesting beaches at Ascension Island in the middle of the Atlantic Ocean are a paradigmatic case of long-distance oceanic migrants. It has been suggested that they calculate their position and the direction of their target areas by using the inclination and intensity of the earth's magnetic field. To test this hypothesis, we tracked, by satellite, green turtles during their postnesting migration from Ascension Island to the Brazilian coast more than 2000 km away. Seven turtles were each fitted with six powerful static magnets attached in such a way as to produce variable artificial fields around the turtle that made reliance on a geomagnetic map impossible. The reconstructed courses were very similar to those of eight turtles without magnets that were tracked over the same period and in the previous year, and no differences between magnetically disrupted and untreated turtles were found as regards navigational performance and course straightness. These findings show that magnetic cues are not essential to turtles making the return trip to the Brazilian coast. The navigational mechanisms used by these turtles remain enigmatic.

Animals↗
PubMed2001

Comparative kinematics of the forelimb during swimming in red-eared slider (Trachemys scripta) and spiny softshell (Apalone spinifera) turtles.

Softshell turtles (Family Trionychidae) possess extensive webbing between the digits of the manus, suggesting that the forelimb may serve as an effective thrust generator during aquatic locomotion. However, the hindlimb has previously been viewed as the dominant propulsive organ in swimming freshwater turtles. To evaluate the potential role of the forelimb in thrust production during swimming in freshwater turtles, we compared the forelimb morphology and three-dimensional forelimb kinematics of a highly aquatic trionychid turtle, the spiny softshell Apalone spinifera, and a morphologically generalized emydid turtle, the red-eared slider Trachemys scripta. Spiny softshells possess nearly twice as much forelimb surface area as sliders for generating drag-based thrust. In addition, although both species use drag-based propulsion, several aspects of forelimb kinematics differ significantly between these species. During the thrust phase of the forelimb cycle, spiny softshells hold the elbow and wrist joints significantly straighter than sliders, thereby further increasing the surface area of the limb that can move water posteriorly and increasing the velocity of the distal portion of the forelimb. These aspects of swimming kinematics in softshells should increase forelimb thrust production and suggest that the forelimbs make more substantial contributions to forward thrust in softshell turtles than in sliders. Spiny softshells also restrict forelimb movements to a much narrower dorsoventral and anteroposterior range than sliders throughout the stroke, thereby helping to minimize limb movements potentially extraneous to forward thrust production. These comparisons demonstrate considerable diversity in the forelimb kinematics of turtles that swim using rowing motions of the limbs and suggest that the evolution of turtle forelimb mechanics produced a variety of contrasting solutions for aquatic specialization.

Animals↗
PubMed2002

Adrenergic control of the cardiovascular system in the turtle Trachemys scripta.

Freshwater turtles, Trachemys scripta, like all non-crocodilian reptiles, are able to shunt blood between the pulmonary and systemic circulations owing to their undivided ventricle. The prevailing hypothesis is that the ratio of pulmonary and systemic resistances is the primary determinant of cardiac shunting in turtles. In the present study, we have examined the adrenergic influences on vascular resistances in the pulmonary and systemic circulations and the associated effects on cardiac shunts in turtles. To achieve this objective, systemic blood flow and pressures and pulmonary blood flow and pressures were measured simultaneously in anaesthetised turtles during bolus injections of alpha- and beta-adrenergic agonists and antagonists. Total cardiac output, systemic vascular resistance, pulmonary vascular resistance, heart rate and cardiac stroke volume were derived from these measurements. Anaesthetised turtles showed cardiovascular characteristics that were similar to those of non-apnoeic non-anaesthetised turtles, because anaesthesia blocked the cholinergically mediated constriction of the pulmonary artery that is normally associated with apnoea. As a result, the anaesthetised turtles exhibited a large net left-to-right shunt, and the adrenergic responses could be observed without confounding changes resulting from apnoea. Potent alpha-adrenergic vasoconstriction and weaker beta-adrenergic vasodilation were discovered in the systemic circulation. Modest beta-adrenergic vasodilation and possible weak alpha-adrenergic vasodilation were discovered in the pulmonary circulation. This adrenergically mediated vasoactivity produced the largest range of cardiac shunts observed so far in turtles. Regression analysis revealed that 97% of the variability in the cardiac shunts could be accounted for by the ratio of the pulmonary and systemic resistances. Thus, we conclude that, independent of whether the pulmonary vascular resistance is modulated (as during apnoea) or the systemic resistance is modulated with adrenergic mechanisms (as shown here), the consequences on the cardiac shunt patterns are the same because they are determined primarily by the ratios of the pulmonary and systemic resistance.

Adrenergic alpha-Agonists↗
PubMed2003

Plasma concentrations of praziquantel after oral administration of single and multiple doses in loggerhead sea turtles (Caretta caretta).

OBJECTIVE: To determine the pharmacokinetics of praziquantel following single and multiple oral dosing in loggerhead sea turtles. ANIMALS: 12 healthy juvenile loggerhead sea turtles. PROCEDURE: Praziquantel was administered orally as a single dose (25 and 50 mg/kg) to 2 groups of turtles; a multiple-dose study was then performed in which 6 turtles received 3 doses of praziquantel (25 mg/kg, PO) at 3-hour intervals. Blood samples were collected from all turtles before and at intervals after drug administration for assessment of plasma praziquantel concentrations. Pharmacokinetic analyses included maximum observed plasma concentration (Cmax), time to maximum concentration (Tmax), area under the plasma praziquantel concentration-time curve, and mean residence time (MRTt). RESULTS: Large interanimal variability in plasma praziquantel concentrations was observed for all dosages. One turtle that received 50 mg of praziquantel/kg developed skin lesions within 48 hours of administration. After administration of 25 or 50 mg of praziquantel/kg, mean plasma concentrations were below the limit of quantification after 24 hours. In the multiple-dose group of turtles, mean plasma concentration was 90 ng/mL at the last sampling time-point (48 hours after the first of 3 doses). In the single-dose study, mean Cmax and Tmax with dose were not significantly different between doses. After administration of multiple doses of praziquantel, only MRTt was significantly increased, compared with values after administration of a single 25-mg dose. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of 25 mg of praziquantel/kg 3 times at 3-hour intervals may be appropriate for treatment of loggerhead sea turtles with spirorchidiasis.

Administration, Oral↗
PubMed2006

Prevalence of Salmonella spp in cloacal, fecal, and gastrointestinal mucosal samples from wild North American turtles.

OBJECTIVE: To determine prevalence of Salmonella spp in samples collected from wild North American turtles. ANIMALS: 94 wild North American turtles of 6 species in 2 genera. DESIGN: Prospective microbiologic study. PROCEDURES: A convenience sample of wild North Carolina turtles admitted to a veterinary college was evaluated for Salmonella spp by use of standard techniques via microbiologic culture of cloacal swab and fecal samples. Gastrointestinal mucosa samples were also collected at necropsy from turtles that died or were euthanized. Cloacal swab samples were also collected from wild pond turtles for bacteriologic culture. Controls were established by use of wild-type Salmonella Typhimurium LT2. RESULTS: 94 turtles were tested for Salmonella spp; Salmonella spp were not detected in any sample. By use of a pathogen-prevalence and sample-size table, the true prevalence of Salmonella spp was estimated as < 5%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that wild turtles in central North Carolina may not be active shedders or carriers of Salmonella spp. Despite this 0% prevalence of infection, proper hygiene practices should be followed when handling wild turtles.

Animals↗
PubMed2003

Bacteraemia in free-ranging Hawaiian green turtles Chelonia mydas with fibropapillomatosis.

Past studies of free-ranging green turtles Chelonia mydas with fibropapillomatosis (FP) in Hawaii have shown that animals become immunosuppressed with increasing severity of this disease. Additionally, preliminary clinical examination of moribund turtles with FP revealed that some animals were also bacteraemic. We tested the hypothesis that bacteraemia in sea turtles is associated with the severity of FP. We captured free-ranging green turtles from areas in Hawaii where FP is absent, and areas where FP has been endemic since the late 1950s. Each turtle was given an FP severity score ranging from 0 (no tumours) to 3 (severely affected). A fifth category included turtles that were stranded ashore and moribund with FP. We found that the percentage of turtles with bacteraemia increased with the severity of FP, and that the majority of bacteria cultured were Vibrio spp. Turtles with severe FP were more susceptible to bactaeremia, probably in part due to immunosuppression. The pattern of bacteraemia in relation to severity of disease strengthens the hypothesis that immunosuppression is a sequel to FP.

Animals↗
PubMed2001

Major difference in the expression of delta- and mu-opioid receptors between turtle and rat brain.

The reptilian turtle brain has a remarkably higher endurance for anoxia than mammalian brains. Since the response to O(2) deprivation is dependent in a major way on the expression and regulation of membrane proteins, differences in such proteins may play a role in the species-related differences in hypoxic responses. Because opioid system is involved in the regulation of hypoxic responses, we asked whether there are differences between rat and turtle brains in terms of opioid receptor expression. In this work, we compared the expression and distribution of delta-and mu-opioid receptors in the turtle and rat brains. Our results show that (1) the dissociation constant (K(d)) for delta-receptor binding was approximately four times lower and B(max) was more than double in the turtle brain homogenates than in rat ones; (2) the delta-receptor binding density was heterogeneously distributed in the turtle brain, with a higher density in the rostral regions than in the brainstem and spinal cord, and was generally much higher than in rat brains from the cortex to spinal cord; (3) the delta-opioid receptors in the rat brains were mostly located in the cortex, caudate putamen, and amygdala with an extremely low density in most subcortical (e.g., hippocampus and thalamus) and almost all brainstem regions; and (4) in sharp contrast to delta-opioid receptors, mu-opioid receptor density was much lower in all turtle brain regions compared with the rat ones. Our results demonstrate that the turtle brain is actually an organ of delta-opioid receptors, whereas the rat brain has predominantly mu-opioid receptors. Because we have recently found that delta-opioid receptors protect neurons against glutamate and hypoxic stress, we speculate that the unique pattern of delta-receptor receptor expression and distribution plays a critical role in the tolerance of turtle brain to stressful situations characterized by glutamate excitotoxicity.

Analgesics, Opioid↗
PubMed1978

Effect of dry versus wet bowl environment on pet turtles.

Recently hatched, certified Salmonella-free, red-eared slider turtles (Pseudemys scripta elegans) were obtained from a commercial breeder. Half of the turtles were kept in a traditional wet-bowl environment, whereas the other half lived in individual dry-bowl environments, except for 30 minutes each day when they were immersed in water and were fed. Both groups were fed commercial turtle food. During the 26 weeks of the study, individual weight and general observations were recorded for each turtle. Neither Salmonella nor Arizona bacteria were recovered from the turtles, their food, or their bowen environments. Histologic observations were completed on organs of both groups. Turtles maintained in the dry-bowl environment ate poorly, were considerably less active and less developed histologically, and lost significantly more weight than those turtles living in the wet bowl environment. Neither the environment nor the feeding program were found to be satisfactory for prolonged household maintenance of pet turtles.

Animals↗
PubMed1996

Anesthetic and postanesthetic management of sea turtles.

OBJECTIVE: To examine the physiologic effects of inhalation anesthesia in aquatic turtles to improve anesthetic techniques and postanesthetic monitoring. DESIGN: Retrospective case series. ANIMALS: 9 Kemp's ridley sea turtles. PROCEDURE: Isoflurane was used as the general anesthetic during 14 minor surgical procedures. Turtles were orotracheally intubated, and a surgical plane of anesthesia was maintained with 2.7 +/- 0.4% (mean +/- SE) isoflurane. The duration of anesthesia was 131 +/- 12 minutes. Pulse rate, blood pressure, blood gases (PaO2 and PaCO2) and pH, blood lactic acid concentration, and capnography were used to evaluate the physiologic responses of sea turtles to isoflurane. RESULTS: An isoflurane concentration of 3.4 +/- 0.3% provided anesthetic induction in 7 +/- 1 minutes. The mean duration of the recovery phase was 241 +/- 31 minutes. The duration of the recovery phase was not affected by the duration of anesthesia, type of carrier gas, method of ventilatory weaning, or use of selected pharmacologic agents. The recovery phase was characterized by hypoxemia, progressive acidemia, hypercapnia, and lactic acidosis. Awakening in the turtles was preceded by a characteristic tachycardia and tachypnea. All sea turtles recovered from isoflurane anesthesia without apparent adverse effects within 24 hours. CLINICAL IMPLICATIONS: Isoflurane appears to be safe and effective in providing surgical anesthesia in turtles that require a timely return to an aquatic environment. This study should assist veterinarians in predicting the physiologic responses of aquatic turtles to inhalation agents.

Anesthesia, Inhalation↗
PubMedDate not supplied

Anoxia and ischemia tolerance in turtle hearts.

It has been known since ancient times that turtle hearts exhibit extraordinary tolerance to anoxia or ischemia. The mechanisms by which they accomplish this remain obscure. The most important adaptation in anoxic turtles is a rapid and dramatic decrease in metabolic rate. Nuclear magnetic resonance measurements indicate that painted turtle (Chrysemys picta) hearts respond to anoxia with a rapid decrease in phosphocreatine (PCr; to 50% of control) after which PCr remains constant for at least 4 h. ATP is defended and does not decrease while intracellular pH (pHi) decreases by 0.2 pH units early in anoxia and is then maintained constant. Softshelled turtles (Trionyx spinifer) have been demonstrated to be far more sensitive than painted turtles to anoxia in vivo. However, isolated hearts from softshelled turtles appear to be as anoxia tolerant as those of Chrysemys. During ischemia there is also little difference in cardic performance, high energy phosphates, or pHi between these two species. A peculiar feature of turtle hearts is an extremely high concentration of phosphodiesters (PDE). The role of cytosolic PDEs remains controversial but they may function as lysophospholipase inhibitors and thereby limit phospholipid turnover (Burt CT and Ribolow H, Comparative Biochemistry and Physiology, 108B: 11-20, 1994). Whether PDEs promote anoxia/ischemia tolerance is unknown but these stresses can result in membrane lipid dysfunction in mammals. Metabolic control, acid-base, and phospholipid homeostasis all play a role in anoxia and ischemia tolerance in turtle hearts. These physiologic processes are interdependent, and how they interact in these animals is unknown, but they are experimentally accessible by modern analytical methods.

Adenosine Triphosphate↗
PubMed1997

Map turtle winter leech loads.

Adult common map turtles, Graptemys geographica (n = 243), were obtained in November 1995 from a hibernation site in the Lamoille River, Vermont. Of the 208 female turtles examined, 151 (72.6%) had at least 1 leech (Placobdella parasitica) attached and 10 of 35 males (28.6%) were similarly parasitized. Mean abundances were 1.49 (SD = 1.461, n = 208) for female turtles and 0.34 (SD = 0.591, n = 35) for males; the difference was significant (t = 4.558, df = 241, P < 0.001). Leech broods were found on 34 of 208 female turtles (16.3%) and 2 of 35 males (5.7%). One of the leeches was of record size (77.7 mm total length); another specimen measuring 64.4 mm had 153 brood-sized (x = 4.5 mm) young attached to its venter. Because of poor visibility and partial ice cover, only 7 turtles were recovered in March 1996. All of these turtles had attached leeches, and 4 turtles had broods of 9-52 young ranging in length from 4.58 to 5.78 mm. One Placobdella ornata was found in the March sample. Our results suggest that leeches of various size classes remain attached to hibernating adult map turtles throughout the winter.

Animals↗
PubMed1971

Shock-induced threat and biting by the turtle.

Shock-induced biting and threat by the male painted turtle (Chrysemys picta marginata) were studied in three experiments. When restrained facing each other, the turtles threatened and bit other turtles in response to electric shock. Shock alone caused turtles to threaten an unshocked turtle; the movements of a shocked turtle were sufficient to cause an unshocked but restrained turtle to threaten. When the turtles were free to move, they avoided an encounter when shocked, even reversing a strong position preference in order to do so.

Journal Article↗
PubMed2000

Comparison of cortically and subcortically controlled motor systems. II. Distribution of anterogradely labeled terminal boutons on intracellularly filled rubrospinal neurons in rat and turtle.

The present study examined the circuitry of the red nucleus of the Sprague-Dawley rat and the freshwater pond turtle, Chrysemys picta, by using intracellular cell filling combined with anterograde tract tracing. Although both species have a well-developed cerebellorubral system, they differ in that the red nucleus of rats receives direct input from the motor areas of the cerebral cortex, whereas turtles do not. However, a direct descending projection from the hypothalamus to the red nucleus of turtles has been described. The aim of this study was to elucidate the relative functional contributions of the cerebellum and descending inputs to motor signal generation in the red nucleus. The results show that the cellular distribution of cerebellar inputs on rubrospinal neurons is similar between the rat and turtle; these projections are observed on the soma and the proximal and distal dendrites. In contrast, the hypothalamic inputs in turtles occupy mainly the more distally located dendrites, similar to the position of the cortical inputs in rats. These findings suggest that, first, the cerebellar inputs are not spatially segregated from the cortical or hypothalamic inputs in rats or turtles, as far as can be determined by light microscopy. Second, there is specificity of input from the cortex in rats and hypothalamus in turtles onto the distal portions of the dendrites. The similarity in the organizational features of the mammalian and non-mammalian cerebellorubrospinal systems has implications for interpretations of the relative roles of the cerebellum and cerebral cortex in motor control.

Animals↗
PubMed1998

Kinematics of aquatic and terrestrial prey capture in Terrapene carolina, with implications for the evolution of feeding in cryptodire turtles.

Studies of aquatic prey capture in vertebrates have demonstrated remarkable convergence in kinematics between diverse vertebrate taxa. When feeding in water, most vertebrates employ large-amplitude hyoid depression to expand the oral cavity and suck in water along with the prey. In contrast, vertebrates feeding on land exhibit little or no hyoid depression. In this study we compared the kinematics of terrestrial and aquatic prey capture within one species of turtle, Terrapene carolina, in order to determine whether an individual species can modulate the magnitude of hyoid depression between air and water. High-speed video (250 frames per second) showed that hyoid depression was over three times greater in aquatic than in terrestrial feedings, indicating that T. carolina is able to modulate hyoid depression magnitude depending on the medium in which feeding occurs. In addition, we observed medium-dependent modulation of hyoid depression in another turtle, Heosemys grandis, and large-amplitude hyoid depression during aquatic feeding in Kinosternon leucostomum, Platysternon megacephalum, and juvenile Chelydra serpentina. In all of these turtles, hyoid depression produced oral cavity expansion during aquatic feeding, but the earthworm prey were never sucked toward the predators. Prey were captured by neck extension (ram feeding), and we conclude that the function of hyoid depression during aquatic feeding in cryptodire turtles is to prevent the forward motion of the predator from pushing the prey away (compensatory suction). Aquatic feeding is probably the primitive condition for all extant turtles, and thus terrestrial feeding in T. carolina and other turtles is a secondarily derived characteristic. We conclude from this historical pattern that it is not appropriate to use extant turtles in attempts to reconstruct the terrestrial feeding mechanisms of primitive amniotes.

Animals↗
PubMed1996

Ultrastructural study of the dorsal lingual epithelium of the soft-shell turtle, Trionyx cartilagineus (Chelonia, Trionychidae).

BACKGROUND: The soft-shell turtle, Trionyx cartilagineus, is classified phylogenetically to the family Trionychidae, whose members live in small rivers or ponds. The purpose of the present study was to examine the ultrastructure of the dorsal epithelium of the tongue of the soft-shell turtle and to compare the results of the observations with those reported for the tongue of other freshwater turtles. METHODS: Light microscopy, transmission electron microscopy, and scanning electron microscopy were used to examine the dorsal epithelium of the tongue of the soft-shell turtle. RESULTS: The tongue is triangular with a slightly round apex when viewed dorsally but it appears flattened when viewed laterally. Lingual papillae were visible on the dorsal surface of the tongue with some localized variations. Irregular, dome-shaped or ridge-like papillae were observed on the anterior part of the dorsal lingual surface. Large, cylindrical papillae were located along the midline of the posterior part of the tongue. Low, disk-like papillae were located on both sides of the dorsal surface of the posterior part of the tongue. Taste pores were recognizable in the center of the disk-like papillae. At higher magnification, scanning electron microscopy revealed microridges on the surface of cells located on the outermost side of the anterior part of the tongue, and the thickenings of cell margins were clearly seen. Microvilli were distributed compactly over the entire posterior part of the tongue. Light microscopy revealed that the mucosal epithelium of the anterior part of the tongue was of the keratinized, stratified squamous type, while the mucosal epithelium of the posterior part of the tongue was of the nonkeratinized, stratified cuboidal type. In the latero-posterior part of the tongue, taste buds were recognized. Transmission electron microscopy revealed that the epithelium of the anterior part of the tongue was of a typical keratinized type. Small numbers of keratohyalin granules and membrane-coating granules appeared in the cytoplasm of the shallow intermediate layer. On the apical side of the lingual papillae located on the posterior side of the tongue, cells from the intermediate layer to the surface layer of the non-keratinized epithelium contained many fine, discoidal granules. A large part of the epithelium consisted of mucous cells in the concave area on the posterior side. CONCLUSIONS: The dorsal surface and epithelium of the tongue of the soft-shell turtle differed significantly from those of other freshwater turtles, in spite of the similarity in terms of gross morphology among the tongues of such turtles.

Animals↗