Hormonal and metabolic responses to nesting activities in the green turtle, Chelonia mydas

We examined the association between green turtle nesting activities and plasma profiles of hormones that are widely implicated in aspects of heightened metabolism and energy regulation; epinephrine (EPI), norepinephrine (NE) and corticosterone. In conjunction, we examined plasma profiles of glucose and lactate to infer metabolic processes associated with green turtle nesting behaviour. Finally, because these hormones are also involved in mediating behaviour and physiology associated with stressful situations, we examined the effect of a stressor encountered during nesting, physical disturbance, on hormone levels. Plasma profiles of epinephrine, norepinephrine and corticosterone were not significantly altered across different stages of nesting. Plasma glucose and lactate both exhibited significant increases related to nesting activity; glucose increased dramatically during the emergence stage of nesting before stabilizing, and lactate levels continued to increase throughout the nesting process. There was no significant association between plasma hormones and glucose. For female turtles that abandoned nesting activities due to competition for nest space, there was no significant difference in plasma levels of epinephrine, norepinephrine and corticosterone compared to females that persisted with nesting activities. Overall, while distinct metabolic changes took place in nesting females, there was little association in profiles of hormones typically considered important for regulating heightened metabolism and nesting activity. This disassociation could arise because hormonal action may be altered in breeding female green turtles to facilitate reproductive processes.     

Renal responses to diuretics in the turtle

Summary We administered the diuretics furosemide and ethacrynic acid to conscious freshwater turtles to assess changes in renal function and plasma renin activity (PRA) in an animal which lacks a loop of Henle. Furosemide (2 and 5 mg/kg) produced no changes in blood pressure, hematocrit, plasma electrolytes, glomerular filtration rate (GFR), or PRA. Furosemide doubled urine volume while sodium excretion increased 20-fold and chloride and potassium excretion increased 12-fold (P<0.05 in each case). Net potassium secretion was observed. Ethacrynic acid (2 and 5 mg/kg) also produced no changes in blood pressure, hematocrit, plasma electrolytes, or PRA. At the lower dose GFR increased by 40% and urine volume nearly doubled (P<0.05 in each case). Sodium, chloride, and potassium excretion increased roughly 10-fold (P<0.05 in each case). At the higher dose, GFR increased by 80% and urine volume more than doubled (P<0.05 in each case). Sodium excretion rose 40-fold, chloride excretion rose 25-fold, and potassium excretion rose 10-fold (P<0.05 in each case). At both doses net potassium secretion occurred. The results demonstrate that both drugs inhibit tubular reabsorption in the turtle, acting primarily on distal segments of the nephron. The failure of either drug to alter PRA suggests that the turtle lacks a tubular mechanism for alterig renin release.Abbreviations GFR glomerular filtration rate - PRA plasma renin activitySupported by the University of Delaware Honors Program, American Heart Association of Delaware, NIH Biomedical Support Program, and USPHS #HL2808401     

Species differences in responses to captivity: stress, welfare and the comparative method

Approximately 26 billion animals, spanning over 10 000 species, are kept on farms and in zoos, conservation breeding centers, research laboratories and households. Captive animals are often healthier, longer-lived and more fecund than free-living conspecifics, but for some species the opposite is true. Captivity is a very long way from the ideal 'common garden' often assumed by evolutionary and ecological researchers using data for captive animals. The use of comparative methods to investigate the fundamental biological causes of these species differences would help to improve husbandry and enclosure design, and might even reveal relationships between susceptibilities to poor captive welfare and susceptibilities to anthropogenic threat in the wild. Studies of these species differences could also inspire and facilitate 'evo-mecho' research into the functions of behavioral control mechanisms.     

Spatial distribution of turtle barnacles on the green sea turtle, Chelonia mydas

Distribution patterns of epibiotic barnacles on green sea turtles were investigated in waters neighboring Okinawa, Japan. A number of barnacle species were found to coexist on the turtles and were classified into three genera: Chelonibia, Platylepas and Stomatolepas. Attachment sites on the turtles varied among the barnacle species, suggesting that there is niche partitioning with respect to their microhabitat selection. Turtle bodies offer a “patchy” environment for barnacles, so we also analyzed coexistence patterns in the context of an aggregation model. Within each genus, individual barnacles showed a clumped distribution. The different genera do not have mutually exclusive distribution patterns, but instead occur on the same turtle to various degrees. However, when turtles were divided into two size classes, both the level of aggregation and the degree of interspecific overlap among the barnacles was significantly lower on large turtles. We suggest that obtaining basic information on turtle epibionts will shed light on the biology of wild turtles, which is still largely unknown.     

Hatch rates of green turtle eggs in Sarawak

Hatch rates of green turtle Chelone mydas (L.) eggs in the beach hatchery of the turtle islands of Sarawak varied between 53% and 96% during the period 1970–1990. The hatch rates of natural or in situ nests were 71.8 + 18.4% and 65.3 + 5.9% at Talang-Talang Besar and Talang-Talang Kecil respectively. There was no significant difference between the hatch rates of in situ nests and replanted hatchery nests in both the Talang-Talang islands.     

Physiological responses to supercooling and hypoxia in the hatchling painted turtle, Chrysemys picta

We investigated physiological responses to supercooling in hatchling painted turtles (Chrysemys picta) which remain in their natal nests over winter and therefore may become exposed to subzero temperatures. These turtles are freeze tolerant but also must rely on supercooling to survive exposure to the lower temperatures occurring in nests during winter. We compared whole-body concentrations of lactate, glucose, glycerol, and ATP in turtles chilled at 0 degrees C, -4 degrees C, or -6 degrees C for 5 days, or at 6 degrees C for 19 days. In a companion experiment, we measured metabolite concentrations in turtles exposed to a hypoxic environment for 1 day, 4 days, or 8 days. Supercooling and hypoxia exposure were both associated with an increase in concentrations of lactate and glucose and a decrease in glycerol concentrations (albeit no change in the ATP pool), suggesting that supercooling induces functional hypoxia. We conclude that hypoxia tolerance may be an important pre-adaptation for surviving exposure to subzero temperatures in hatchling C. picta.     

Association of herpesvirus with fibropapillomatosis of the green turtle Chelonia mydas and the loggerhead turtle Caretta caretta in Florida.

Sea turtle fibropapillomatosis (FP) is a disease marked by proliferation of benign but debilitating cutaneous fibropapillomas and occasional visceral fibromas. Transmission experiments have implicated a chloroform-sensitive transforming agent present in filtered cell-free tumor homogenates in the etiology of FP. In this study, consensus primer PCR methodology was used to test the association of a chelonian herpesvirus with fibropapillomatosis. Fibropapilloma and skin samples were obtained from 17 green and 2 loggerhead turtles affected with FP stranded along the Florida coastline. Ninety-three cutaneous and visceral tumors from the 19 turtles, and 33 skin samples from 16 of the turtles, were tested. All turtles affected with FP had herpesvirus associated with their tumors as detected by PCR. Ninety-six percent (89/93) of the tumors, but only 9% (3/33) of the skin samples, from affected turtles contained detectable herpesvirus. The skin samples that contained herpesvirus were all within 2 cm of a fibropapilloma. Also, 1 of 11 scar tissue samples from sites where fibropapillomas had been removed 2 to 51 wk earlier from 5 green turtles contained detectable herpesvirus. None of 18 normal skin samples from 2 green and 2 loggerhead turtles stranded without FP contained herpesvirus. The data indicated that herpesvirus was detectable only within or close to tumors. To determine if the same virus infected both turtle species, partial nucleotide sequences of the herpesvirus DNA polymerase gene were determined from 6 loggerhead and 2 green turtle samples. The sequences predicted that herpesvirus of loggerhead turtles differed from those of green turtles by only 1 of 60 amino acids in the sequence examined, indicating that a chelonian herpesvirus exhibiting minor intratypic variation was the only herpesvirus present in tumors of both green and loggerhead turtles. The FP-associated herpesvirus resisted cultivation on chelonian cell lines which support the replication of other chelonian herpesviruses. These results lead to the conclusion that a chelonian herpesvirus is regularly associated with fibropapillomatosis and is not merely an incidental finding in affected turtles.     

Respiratory responses to short term hypoxia in the snapping turtle, Chelydra serpentina

Among vertebrates, turtles are able to tolerate exceptionally low oxygen tensions. We have investigated the compensatory mechanisms that regulate respiration and blood oxygen transport in snapping turtles during short exposure to hypoxia. Snapping turtles started to hyperventilate when oxygen levels dropped below 10% O(2). Total ventilation increased 1.75-fold, essentially related to an increase in respiration frequency. During normoxia, respiration occurred in bouts of four to five breaths, whereas at 5% O(2), the ventilation pattern was more regular with breathing bouts consisting of a single breath. The increase in the heart rate between breaths during hypoxia suggests that a high pulmonary blood flow may be maintained during non-ventilatory periods to improve arterial blood oxygenation. After 4 days of hypoxia at 5% O(2), hematocrit, hemoglobin concentration and multiplicity and intraerythrocytic organic phosphate concentration remained unaltered. Accordingly, oxygen binding curves at constant P(CO(2)) showed no changes in oxygen affinity and cooperativity. However, blood pH increased significantly from 7.50+/-0.05 under normoxia to 7.72+/-0.03 under hypoxia. The respiratory alkalosis will produce a pronounced in vivo left-shift of the blood oxygen dissociation curve due to the large Bohr effect and this is shown to be critical for arterial oxygen saturation.     

Fine-scale thermal adaptation in a green turtle nesting population

The effect of climate warming on the reproductive success of ectothermic animals is currently a subject of major conservation concern. However, for many threatened species, we still know surprisingly little about the extent of naturally occurring adaptive variation in heat-tolerance. Here, we show that the thermal tolerances of green turtle (Chelonia mydas) embryos in a single, island-breeding population have diverged in response to the contrasting incubation temperatures of nesting beaches just a few kilometres apart. In natural nests and in a common-garden rearing experiment, the offspring of females nesting on a naturally hot (black sand) beach survived better and grew larger at hot incubation temperatures compared with the offspring of females nesting on a cooler (pale sand) beach nearby. These differences were owing to shallower thermal reaction norms in the hot beach population, rather than shifts in thermal optima, and could not be explained by egg-mediated maternal effects. Our results suggest that marine turtle nesting behaviour can drive adaptive differentiation at remarkably fine spatial scales, and have important implications for how we define conservation units for protection. In particular, previous studies may have underestimated the extent of adaptive structuring in marine turtle populations that may significantly affect their capacity to respond to environmental change.     

Thyroid responses to altered photoperiod in the soft-shelled turtle Lissemys punctata punctata bonnoterre

The aim of the current investigation was to investigate the effect of photoperiod on thyroid activity in soft-shelled turtles (Lissemys punctata punctata). Thirty days exposure of short photoperiod with 2L:22D increased relative weight, follicular epithelial height and peroxidase activity of the thyroid gland; whereas exposure of long photoperiod with 22L:2D for 30 days showed reversed changes to those of the short photoperiod in adult female turtles. These findings indicate that short photoperiod stimulates thyroid activity and long photoperiod inhibits its activity in soft-shelled turtles. It is suggested that photoperiod exerts its action on thyroid activity presumably via gonads and/or pineal-gonadal axis in turtles.     

The Green sea turtle (Chelonia mydas): further observations on breeding in captivity

Mating, nesting and hatching of the Green sea turtle on Mariculture Ltd's farm on Grand Cayman Island, BWI in 1973 were recorded in a previous paper. The results described were the first of their kind, so that events in the farm breeding colony in the following year were awaited with much interest, especially as to hatchability of the eggs. The observations made in 1974, which extended and mainly confirmed those made in 1973, are described below.     

Ventilatory responses to temperature variation in the fresh water turtle,Mauremys caspica leprosa

A study of lung gas exchange in the fresh water turtle Mauremys caspica leprosa at normal physiological body temperatures (15, 25 and 35 °C) was extended to extreme temperatures (5 and 40 °C) to determine whether the direct relationship between body temperature and ventilatory response found in many lung-breathing ectotherms including other chelonian species was maintained. From 5 to 35 °C the lung ventilation per unit of O₂ uptake and CO₂ removed declined with temperature. Consequently, lung CO₂ partial pressure increased with temperature. Its value was maintained within narrow limits at each thermal constant, suggesting a suitable control throughout the complete ventilatory cycle. At 40 °C the ventilatory response showed the opposite trend. The ratios of ventilation to lung gas exchange increased compared to their values at 35 °C. The impact of this increased breathing-lowering the estimated mean alveolar CO₂ partial pressure-was nevertheless less than expected due to an increase in calculated physiological dead space. This suggests that the relative hyperventilation in response to hyperthermia found in Mauremys caspica leprosa is related to evaporative heat loss.Abbreviations BTPS body temperature, ambient pressure, saturated with water vapour - CTM critical thermal maximum - F_N2 fractional concentration of nitrogen - PA _CO2or PL _CO2 alveolar or lung CO₂ pressure - PA_O2or PL_O2 alveolar or lung O₂ pressure - PI_O2 inspired O₂ pressure - R respiratory exchange ratio - STPD standard temperature, standard pressure, dry - T _a ambient temperature - T _b body temperature - VA alveolar ventilation - VA/VCO₂ relative alveolar ventilation (alveolar ventilation per unit of CO₂ removed) - VO₂ O₂ uptake - VCO₂ CO₂ output - V _D anatomical dead space volume - V _D physiological dead space volume - VE/VO₂ ventilatory equivalent for O₂ - VE pulmonary ventilation or expiratory minute volume - VE/VCO₂ ventilatory equivalent for CO₂ - V _T tidal volume     

Salt gland blood flow in the hatchling green turtle, Chelonia mydas

Microsphere and morphometric techniques were used to investigate any circulatory changes that accompany secretion by the salt glands of hatchling Chelonia mydas. Salt glands were activated by a salt load of 27.0 mmol NaCl kg body mass (BM)⁻¹, resulting in a mean sodium secretion rate of 4.14 ± 0.11 mmol Na kg BM⁻¹ h⁻¹ for a single gland. Microsphere entrapment was approximately 160–180 times greater in the active salt gland than the inactive gland, inferring a similar change in blood flow through salt gland capillaries. The concentration of microspheres trapped in the salt gland was significantly correlated with the rate of tear production (ml kg BM⁻¹ h⁻¹) and the total rate of sodium secretion (mmol Na kg BM⁻¹ h⁻¹) but not with tear sodium concentration (mmol Na l⁻¹). Adrenaline (500 μg kg BM⁻¹) inhibited tear production within 2 min and reduced microsphere entrapment by approximately 95% compared with active glands. The volume of filled blood vessels increased from 0.03 ± 0.01% of secretory lobe volume in inactive salt gland sections to 0.70 ± 0.11% in active gland sections. The results demonstrate that capillary blood flow in the salt gland of C. mydas can regulate the activity of the gland as a whole. Accepted: 12 July 2000     

Tumorigenicity of green turtle fibropapilloma-derived fibroblast lines in immunodeficient mice

Fibroblast lines derived from normal skin and spontaneous or experimentally induced fibropapillomas of green turtles (Chelonia mydas) were established and propagated in medium composed of a combination of Dulbecco's minimal essential with F12 medium plus 10% fetal bovine serum at 30 degrees C. Fibropapilloma-derived fibroblasts were indistinguishable from normal skin fibroblasts in vitro. Tumor lines did not exhibit loss of contact inhibition, anchorage independence, or reduced serum requirements. Inoculation of primary and early-passage tumor cells into the medial margin of the pinna of C57BL/6J-nu/nu, C.B17-scid/scid, or NOD-scid/scid mice, however, resulted in fibroma formation, whereas inoculation of normal skin fibroblasts did not. Tumor-derived cells inoculated into the flanks of mice did not form tumors. The turtle origin of fibroblasts in tumors from mouse ears was confirmed by immunohistochemical and karyotype analysis. Fibroblast lines that were established from mouse ear fibromas had the normal karyotype (modal 2N = 55) of C. mydas. The cooler anatomic sites (ears) of immunodeficient mice are useful for confirming the tumorigenic (transformed) phenotype of green turtle fibropapillomatosis-derived fibroblasts. This mouse ear tumorigenicity test should facilitate studies of mechanisms of cellular transformation in green turtle fibropapillomatosis and other neoplastic diseases of poikilothermic vertebrates.     

Nocturnal activity in the green sea turtle alters daily profiles of melatonin and corticosterone

In nature, green turtles (Chelonia mydas) can exhibit nocturnal activity in addition to their typically diurnal activity cycle. We examined whether nocturnal activity in captive and free-living green turtles altered daily plasma profiles of melatonin (MEL) and corticosterone (CORT). In captivity, diurnally active green turtles expressed distinct diel cycles in MEL and CORT; a nocturnal rise was observed in MEL and a diurnal rise was observed in CORT. However, when induced to perform both low- and high-intensity nocturnal activity, captive green turtles exhibited a significant decrease in MEL, compared to inactive controls. In contrast, plasma CORT increased significantly with nocturnal activity, and further, the relative increase in CORT was correlated with the intensity of the nocturnal behavior. In free-living green turtles that performed nocturnal activity including: nesting, mate searching, and feeding/swimming behaviors, plasma profiles in MEL and CORT exhibited relatively little, or no, daily fluctuation. Our findings demonstrate that nocturnal activity in green turtles is often associated with MEL and CORT profiles that resemble those measured during the day. We speculate that these conspicuous changes in MEL and CORT during nocturnal activity could either support or promote behaviors that enable acquisition of transient resources important to the survival and reproductive success of green turtles.     

Cutaneous fibropapillomas and renal myxofibroma in a green turtle, Chelonia mydas

A debilitated 7 kg juvenile green turtle (Chelonia mydas mydas) with multiple ulcerated and infected cutaneous fibropapillomas was clinically evaluated and found to have a nonregenerative anemia, hypoproteinemia, hypoalbuminemia and several electrolyte abnormalities. Surgery was performed to remove the larger tumors. The turtle did not eat postsurgically, and an attempt was made to place a pharyngostomy tube utilizing endoscopy. Edematous esophageal papillae, the angulation of the gastroesophageal junction, and a S-shaped configuration of the esophagous prevented successful placement of the tube. The animal was found dead the next day and necropsied. Multiple large white firm nodules were seen bulging from both kidneys. Microscopic examination of the nodules resulted in a diagnosis of renal myxofibroma.     

Bile salts of the green turtle Chelonia mydas (L.)

1. Bile salts of the green turtle Chelonia mydas (L.) were analysed as completely as possible. 2. They consist of taurine conjugates of 3 alpha, 7 alpha, 12 alpha, 22 xi-tetrahydroxy-5 beta-cholestan-26-oic acid (tetrahydroxysterocholanic acid) and 3 alpha 12 alpha, 22 xi-trihydroxy-5 beta-cholestan-26-oic acid, with minor amounts of 3 alpha, 7 alpha, 12 alpha-trihydroxy-5beta-cholan-24-oic acid (cholic acid), 3alpha, 12 alpha-dihydroxy-5beta-cholan-24-oic acid (deoxycholic acid) and possibly other bile acids. 3. Cholic acid and deoxycholic acid represent the first known examples of bile acids common to chelonians and other animal forms: they may indicate independent evolution in chelonians to C24 bile acids. 4. The discovery of a 7-deoxy C27 bile acid is the first evidence that C27 bile acids or their conjugates have an enterohepatic circulation.