Baseline plasma corticosterone, haematological and biochemical results in nesting and rehabilitating loggerhead sea turtles (Caretta caretta)

Does seasonal variation in the corticosterone response affect the nutritional ecology of a free-ranging lizard?

Challenging events in the environment that are both predictable (e.g. seasonal patterns in breeding activities) and unpredictable (e.g. predator encounter) are known to induce a glucocorticoid response that facilitates metabolic requirements during the challenge. Given its role in mobilizing energy, glucocorticoid levels can influence the nutritional ecology of an individual by shifting dietary intake or retention patterns, but this relationship has not been tested in free-ranging vertebrates. Using a tropical lizard species (Psammophilus dorsalis) as a model system, we tested whether the elemental composition of dietary intake and excretion (faecal samples) varies with stress-induced corticosterone levels in males and females across different seasons. From free-ranging lizards in the wild, we measured levels of stress-induced corticosterone and glucose in blood and determined diet composition from gut-flushing. Elemental composition of the diet was determined by analysing the carbon and nitrogen content of identified prey Orders caught from the wild. We also collected faecal samples and estimated their elemental composition. We found that stress-induced corticosterone levels varied across seasons, with the lowest levels during the breeding season for both males and females. Despite high variation in corticosterone responsiveness, lizards did not shift the elemental composition of their diets and maintained an intake carbon:nitrogen ratio of 4.56. We did, however, find a negative correlation between stress-induced corticosterone levels and faecal elemental composition, suggesting selective retention of both carbon and nitrogen in individuals that have higher corticosterone responsiveness. This study highlights the interplay between corticosterone responsiveness and nutritional ecology, challenging the existing links in literature and illustrating how free-ranging animals, such as lizards, adjust the elemental composition of excretion and not dietary intakes as a potential strategy to modulate natural physiological and ecological challenges.

Not Just Corticosterone: Further Characterization of the Endocrine Response of Kemp's Ridley Sea Turtles (Lepidochelys kempii) Reveals Elevated Plasma Aldosterone Concentrations During Field Capture Events

To develop safe and effective management policies, it is important to understand the physiologic effects of fishing interactions and scientific research methods on endangered marine species. In the present study, validated assays for plasma corticosterone, free thyroxine (fT4), and aldosterone were used to assess the endocrine status of 61 presumed healthy, wild Kemp's ridley sea turtles (Lepidochelys kempii) that were captured for separate ecological studies using two capture methods (trawl net n = 40; manual capture n = 21). Plasma hormone concentrations were also assessed in relation to eight clinical plasma biochemical analytes. Corticosterone and aldosterone concentrations were moderately high after capture, with significantly higher concentrations in turtles captured by trawl net vs. manual capture. Free thyroxine concentrations were within previously published ranges for healthy individuals of this species. Clinical biochemical data revealed moderately elevated potassium and lactate concentrations in many individuals, with significantly greater lactate concentrations in trawl-captured turtles. Aldosterone concentrations were positively correlated with corticosterone. The results of the present study indicate that Kemp's ridley sea turtles have robust adrenocortical activity immediately after capture, resulting in high plasma concentrations of corticosterone and aldosterone. Researchers who use such methods to access sea turtles can consider these results in planning careful and efficient field studies.

Health assessment of nesting loggerhead sea turtles (Caretta caretta) in one of their largest rookeries (central eastern Florida coast, USA)

Reproduction is a physiologically demanding process for sea turtles. Health indicators, including morphometric indices and blood analytes, provide insight into overall health, physiology and organ function for breeding sea turtles as a way to assess population-level effects. The Archie Carr National Wildlife Refuge (ACNWR) on Florida's central eastern coast is critical nesting habitat for loggerhead sea turtles (Caretta caretta), but health variables from this location have not been documented. Objectives of the study were to (1) assess morphometrics and blood analyte data (including haematology, plasma biochemistry, protein electrophoresis, β-hydroxybutyrate, trace nutrients, vitamins and fatty acid profiles) from loggerheads nesting on or near the beaches of the ACNWR, (2) investigate correlations of body condition index (BCI) with blood analytes and (3) analyse temporal trends in morphometric and blood analyte data throughout the nesting season. Morphometric and/or blood analyte data are reported for 57 nesting loggerheads encountered between 2016 and 2019. Plasma copper and iron positively correlated with BCI. Mass tended to decline across nesting season, whereas BCI did not. Many blood analytes significantly increased or decreased across nesting season, reflecting the catabolic state and haemodynamic variations of nesting turtles. Twenty-three of 34 fatty acids declined across nesting season, which demonstrates the physiological demands of nesting turtles for vitellogenesis and reproductive activities, thus suggesting potential utility of fatty acids for the assessment of foraging status and phases of reproduction. The findings herein are relevant for future spatiotemporal and interspecies comparisons, investigating stressor effects and understanding the physiological demands in nesting sea turtles. This information provides comparative data for individual animals in rescue or managed care settings and for assessment of conservation strategies.

Husbandry Protocols for Juvenile Loggerhead Sea Turtles (Caretta caretta) Based on Stress Response to Stocking Density and Dry-Dock Time

When necessary, sea turtles are held captive for veterinarian care and research purposes. Protocols and basic guidelines have been described for husbandry of sea turtles with veterinarian needs but not considering physiological indicators of animal welfare. Because all sea turtle are imperiled species, monitoring their welfare is important. The aim of this study was to standardize husbandry protocols for loggerhead (Caretta caretta) juveniles held under seminatural conditions, based on circulating concentration of plasma corticosterone (Cort) and behavior. Two experiments were performed to analyze physiological and behavioral responses of the animals facing changes in stocking density and different dry-docking times. Cort analyses suggested that the number of animals per tank can be modified occasionally, without affecting their health and welfare. However, dry-docking time should be < 30 min, as indicated by the significant elevation of circulating Cort at ≥ 30 min, rising from 1.51- ng/ml to 5.28-ng/ml. Protocols tested did not affect behavioral responses, except for the breaths per move, which increased while Cort increased, despite differences exhibited by experimental animals in behavioral responses according to daily times (morning vs afternoon) and the sex of the animals.

Loggerhead sea turtle Caretta caretta plasma biochemistry and proteome profile modulation during recovery

The aim of the study was to monitor and analyse injured and diseased loggerhead sea turtles (Caretta caretta) plasma proteome profiles and biochemistry parameters during their recovery period in rescue centre within different age and recovery period groups, and determine the potential biomarkers that can be used in diagnostics. The plasma biochemical parameters of total protein and glucose content, accompanied by aspartate aminotransferase (AST) and N-acetyl-cystein-activated creatinine kinase (CK-NAC) are highlighted as valuable and potential biomarkers of turtle's health status and condition. Using high throughput tandem mass tag (TMT)-based proteomic approach we identified 913 plasma proteins, 12 of which shown to be modulated in loggerheads age groups, and identified as a part of (i) platelet degranulation, (ii) neutrophil degranulation, and (iii) innate immune system pathways. The neurofascin (NFASC) is shown to be differentially abundant among all the age groups, and alpha-1-acid glycoprotein 2-like (ORM2) and alpha-1-antitrypsin-like (SERPINA1) proteins were recognized as members of all three above mentioned REACTOME pathways. Furthermore, 29 of plasma proteins were significantly differentially abundant in loggerheads age and recovery period groups. Out of 15 recognized pathways, those proteins were mostly included in three specific REACTOME pathways: (i) post-translational phosphorylation, (ii) regulation of Insulin-like Growth Factor (IGF) transport and uptake by Insulin-like Growth Factor Binding Proteins (IGFBPs), and (iii) platelet degranulation. The alpha-fetoprotein (AFP) was the only protein which showed statistically significant up-regulation patterns in all loggerhead age groups before release from the rescue centre, and the complement component 3 (C3) protein was the only protein modulated in all recovery period groups. Furthermore, C3 protein takes part in 9; and followed up with apolipoprotein A-I (APOA1) in 7; complement component 4 (C4), complement component 5 (C5) and kininogen-1 (KNG1) in 6 REACTOME pathways. Thereby, those proteins are highlighted and recommended as potential biomarkers of turtle's health status. Data are available via ProteomeXchange with identifier PXD029569. Finally, based on our results, we believe that comprehensive omics approach and routine plasma biochemical analysis, accompanied by proteins of acute phase, acid-base status and immune-response indicator analysis may significantly and reliably improve assessment of captive loggerheads rehabilitation and medication. SIGNIFICANCE: Monitoring and comparison of loggerhead sea turtles (C. caretta) blood plasma biochemistry parameters and plasma proteome profiles in relation to the age, and recovery period pointed out significantly differentially abundant proteins, along with certain biochemical parameter contents as potential biomarkers of turtle's fitness, health status and physiology.

Pharmacokinetics of ketorolac in juvenile loggerhead sea turtles (Caretta caretta) after a single intramuscular injection

Ketorolac is a non-steroidal anti-inflammatory drug administered as an analgesic in humans. It has analgesic effects comparable to opioids but without adverse effects such as respiratory depression or restrictions because of controlled drug status. We designed this study to examine the potential of ketorolac as an analgesic for sea turtle rehabilitative medicine. Our objective was to determine the pharmacokinetics of a single 0.25 mg/kg intramuscular dose of ketorolac in a population of 16 captive-raised juvenile loggerhead sea turtles (Caretta caretta). A sparse sampling protocol was utilized, and blood samples were collected for 12 hours after administration of ketorolac. Samples were analyzed with high-pressure liquid chromatography (HPLC), and a nonlinear mixed effects model (NLME) was used to determine parameters for the population. With these methods, we identified a long elimination half-life (βT_1/2  = 11.867 hr) but a low maximum concentration (C_MAX  = 0.508 µg/mL) and concentrations were below the level proposed to be therapeutic in humans (EC₅₀  = 0.1-0.3 μg/mL) for most of the collection period. We conclude that ketorolac may not be an appropriate long-term analgesic for use in loggerhead sea turtles at this dose; however, it may have some benefit as a short-term analgesic.

Influence of exercise and fasting on blood parameters in juvenile green turtles (Chelonia mydas): implications for health assessments

This study investigated the influence of exercise and fasting state on haematologic and biochemical parameters in juvenile green turtles (Chelonia mydas). Animals were divided into two groups; one group was fasted for 72 h and one group was fed 1 h prior to exercise. Exercise was induced by repeated righting reflexes and blood values were measured prior to and post-exercise. Prior to exercise, fasted animals showed significantly decreased levels of urea, pH, PVCO2 and HCO3- and significant increases in Cl- and PVO2, compared to fed animals and fasted animals had significantly poorer exercise performance. Following exercise both fasted and fed animals had significant increases in Na+, K+, Cl-, PVCO2, PVO2, urea and lactate and significant decreases in pH and HCO3-. The magnitude of increase in lactate levels was significantly less in fasted animals. Prior to exercise, a significant correlation was calculated in fasted animals between pH and HCO3-. Following exercise, significant correlations were calculated in fed animals between pH and HCO3-, PVCO2 and lactate, and between pH and HCO3- in fasted animals. These results show that analytical method, fasting state and the physiologic changes induced during the intense exercise can affect haematologic and biochemical analytes and these factors should be considered when interpreting results from health assessment of wild animals.

Cardioprotective effects of acute sleep deprivation on ischemia/reperfusion injury

OBJECTIVES

Modulation of sympathetic activity during acute sleep deprivation can produce various effects on body functions. We studied the effects of acute sleep deprivation before ischemia/reperfusion on myocardial injury in isolated rat hearts, and the role of sympathetic nervous system that may mediate these sleep deprivation induced effects.

METHODS

The animals were randomized into four groups (n = 11 per group): Ischemia- Reperfusion group (IR), Acute sleep deprivation group (SD), Control group for sleep deprivation (CON-SD) and Sympathectomy + ASD group (SYM-SD). In SD group, sleep deprivation paradigm was used 24 h prior to induction of ischemia/reperfusion. In SYM-SD group, the animals were chemically sympathectomized using 6-hydroxydopamine, 24 h before sleep deprivation. Then, the hearts of animals were perfused using Langendorff setup and were subjected to 30 min regional ischemia followed by 60 min of reperfusion. Throughout the experiment, the hearts were allowed to beat spontaneously and left ventricular developed pressure (LVDP) and rate pressure product (RPP) were recorded. At the end of study, infarct size and percentage of the area at risk were determined.

RESULTS

We found that SD increased LVDP and RPP, while reducing the myocardial infarct size. Moreover, sympathectomy reversed SD induced reduction in infarct size and showed no differences as compared to IR.

CONCLUSION

This study shows cardioprotective effects of acute sleep deprivation, which can be abolished by chemical sympathectomy in isolated hearts of rats.

Comprehensive health assessment of green turtles Chelonia mydas nesting in southeastern Florida, USA

Important indicators of population health needed for large-scale sea turtle population recovery efforts include demographics, disease and mortality trends, condition indices, and baseline blood data. With this comprehensive health assessment of adult female green sea turtles Chelonia mydas nesting on Juno Beach, Florida, USA, we (1) established comprehensive baseline health indices; (2) identified individuals with evidence of infection by chelonid alphaherpesviruses 5 and 6 (ChHV5, ChHV6), which are implicated in fibropapillomatosis and respiratory and skin disease, respectively; and (3) compared measured health indices between turtles that did versus those that did not test positive for ChHV5 and/or ChHV6. All 60 turtles included in the study were in good body condition with no external fibropapillomatosis tumors. Hematological and biochemical reference intervals were established. Via quantitative PCR (qPCR), 5/60 turtles (8%) tested positive for ChHV5, and all turtles were negative for ChHV6. Of 41 turtles tested for antibodies to ChHV5 and ChHV6, 29% and 15% tested positive, respectively, and 10% tested positive for antibodies to both viruses. Notably, there were no statistically significant differences between health variables for nesting turtles that tested positive for ChHV5 DNA versus those that tested negative; and also no differences between turtles that tested positive for ChHV5 or ChHV6 antibodies and those that did not. This suggests that these viruses are enzootically stable in Florida’s adult green turtles. This study provides a health profile of nesting green turtles in southeastern Florida applicable to temporal and spatial investigations of this and other populations.

Investigating the relationship between corticosterone and glucose in a reptile

The glucocorticoid hormone corticosterone (CORT) has classically been used in ecophysiological studies as a proxy for stress and energy mobilization, but rarely are CORT and the energy metabolites themselves concurrently measured. To examine CORT's role in mobilizing glucose in a wild reptile, we conducted two studies. The first study measured natural baseline and stress-induced blood-borne CORT and glucose levels in snakes during spring emergence and again when snakes return to the denning sites in autumn. The second study manipulated the hypothalamic-pituitary-adrenal (HPA) axis in male snakes in the autumn by taking a baseline blood sample, then subjecting individuals to one of five treatments (no injection, saline, CORT, adrenocorticotropin hormone and metyrapone). Subsequent samples were taken at 30 and 60 min. In both studies, we found that glucose levels do increase with acute stress, but that the relationship was not directly related to CORT elevation. In the second study, we found that none of the HPA axis manipulations directly affected blood glucose levels, further indicating that CORT may play a complex but not direct role in glucose mobilization in snakes. This study highlights the need for testing mechanisms in wild organisms by combining in situ observations with manipulative studies.

A tale of two islands: evidence for impaired stress response and altered immune functions in an insular pit viper following ecological disturbance

The frequency and intensity of ecological perturbations affecting wild animal populations is expected to increase in the future with animals facing numerous global threats. Seahorse Key is a continental island off mainland Florida that has historically been a major rookery for several species of waterbirds. As a result of an unknown disturbance, the entire rookery abandoned Seahorse Key in April 2015 and shifted nesting activities to nearby Snake Key, resulting in an influx of food resources in the form of fish carrion to resident Florida cottonmouth snakes (Agkistrodon conanti), while snakes on Seahorse Key experienced a drastic reduction in food resources. Our objective was to assess plasma corticosterone concentrations, corticosterone negative feedback using dexamethasone, blood glucose, body condition, packed cell volume, natural antibody agglutination, white blood cell counts and ratios and erythrocyte sedimentation rate to characterize the long-term effects of differential resource availability in these two snake populations 3 years after this major ecological disturbance. We collected blood samples at three time points from cottonmouths on Seahorse Key (n = 6 individuals) and Snake Key (n = 13 individuals) in fall 2018. In due consideration of the small sample size, our study shows evidence that 3 years after the shift in waterbird nesting Seahorse Key cottonmouths exhibit a dampened acute stress response and presumptive impaired innate immune functions relative to cottonmouths on Snake Key. These results highlight the context-dependent nature of biomarkers and implicate the significant decrease in food resources on Seahorse Key in altering hormonal stress responses and innate immune functions, possibly leading to unknown long-term downstream effects. This study assessed the response of a wild population of pit viper to ecological disturbance in situ with the aim to improve our understanding of how animals cope with such perturbations and improve our capacity to make informed decisions for conservation.

Assessment of hematologic and corticosterone response in free-living eastern box turtles (Terrapene carolina carolina) at capture and after handling

Hematology is a common tool for wildlife health assessments. Manual leukocyte counts are required in reptiles, however, disagreement between quantification methods has been observed in some chelonians. This study determined agreement between two methods of leukocyte quantification, eosinophilic leukopet, and blood film white blood cell (WBC) estimates, in free-living eastern box turtles (Terrapene carolina carolina). Simultaneously, we assessed the impact of handling duration on both leukocyte quantity and corticosterone levels. We collected blood at capture (<2 min from disturbance) and again before release 30-150 min later from 92 box turtles at six sites in Illinois and Tennessee. Constant and proportional error was present in the leukopet results for WBC, lymphocytes, and basophils compared to the estimate method. Both methods were in agreement for heterophils, monocytes, and eosinophils. Agreement between the methods was significantly more likely at WBC counts below 23,241/µl. All hematologic parameters were significantly higher at the final blood draw compared to the initial blood draw using both WBC determination methods, except relative eosinophil and basophil counts. Corticosterone levels varied with time, with maximum concentrations reached at 54 min postcapture, followed by a rapid return to baseline levels. Corticosterone level was not significantly associated with any hematologic parameter or sex. This study provides a framework for understanding the effects of animal handling methodology and diagnostic modality when evaluating hematologic health in box turtles.

Investigating the potential impact of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) on gene biomarker expression and global DNA methylation in loggerhead sea turtles (Caretta caretta) from the Adriatic Sea

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are priority contaminants that bioaccumulate through the food webs and affect the biology of a variety of resident and migratory species, including sea turtles. Few studies have evaluated toxicological biomarkers of exposure to PAHs and PCBs in these animals. The present paper reports the results of an initial field study to quantify the association between plasma concentrations of PAHs/PCBs and whole blood cell expression of gene biomarkers in juvenile loggerhead sea turtles (Caretta caretta) rescued along the Italian coasts of the northern and central areas of the Adriatic Sea. While detectable levels of PAHs were found in all plasma samples examined, only three PCB congeners (PCB52, PCB95, and PCB149) were noted, with detection percentages ranging between 48% and 57%. A significant correlation was found between 3 of the 6 gene biomarkers assessed (HSP60, CYP1A and ERα) and plasma levels of some PAH congeners. In contrast, no significant association between PCB burden and gene expression was observed. The global DNA methylation levels were significantly and positively correlated with the concentrations of most of the PAHs and only one of the PCB congeners (PCB52). The relation between PAH concentration and gene expression in whole blood cells suggests that these genes may respond to environmental contaminant exposure and are promising candidates for the development of biomarkers for monitoring sea turtle exposure to persistent organic pollutants (POPs).

Effects of endocrine disrupting chemicals on estrogen receptor alpha and heat shock protein 60 gene expression in primary cultures of loggerhead sea turtle (Caretta caretta) erythrocytes

The loggerhead turtle (Caretta caretta) can be considered a good indicator species for studying the ecological impact of endocrine disrupting chemicals (EDCs) on wildlife. However, the effect of these environmental pollutants on nuclear steroid hormone signaling has not yet been addressed in sea turtles mainly due to the legal constraints of their endangered status. Here we describe the use of primary erythrocyte cell cultures as in vitro models for evaluating the effects of different EDCs on the expression of estrogen receptor α (ERα). In addition, we evaluated erythrocyte toxicity caused by EDCs using Alamar Blue assay and heat shock proteins 60 (HSP60) expression. Primary cultures of erythrocytes were exposed to increasing concentrations of 4-nonylphenol (4NP), Diisodecyl phthalate (DiDP), Tri-m-cresyl phosphate (TMCP) and Tributyltin (TBT) for 48h. Alamar Blue demonstrated that exposure of erythrocytes to each contaminant for up to 48h led to a significant impairment of cellular metabolic activity at 100μM, with the exception of TBT. Moreover, our data indicate that loggerhead erythrocytes constitutively express ERα and HSP60 at the transcript level and respond to EDCs by up-regulating their expression. In this regard, ERα was up-regulated in a dose-dependent manner after 48h exposure to both 4NP and TMCP. Interestingly, the dosage-dependent effects of DiDP on ERα expression were opposite in comparison to that obtained following exposure to the other tested compounds. This work provides the first indication regarding the potential of primary erythrocytes as study models for evaluating the effects of EDCs on sea turtles.