Seasonal changes in hepatic lipid metabolism and apoptosis in Chinese soft-shelled turtle (Pelodiscus sinensis)

Chinese soft-shelled turtle (Pelodiscus sinensis) hibernates without eating and drinking when the ambient temperature is very low. To better understand the characteristics of energy utilization during hibernation, the turtles in the physiological phases of summer active (SA), Pre-Hibernation (Pre-H), Mid-Hibernation (Mid-H) and early arousal (EA) were sampled. The results showed that the levels of serum triglyceride and hepatic lipid droplet were markedly increased in Pre-H and decreased in Mid-H compared with that in SA, indicating that P. sinensis experiences lipid accumulation in Pre-H and lipid is the predominant energy reserve during hibernation. The mRNA expression levels of genes (FABP and CPT-2) involved in lipolysis and lipid oxidation were up-regulated in Mid-H, while the genes related to lipid synthesis (FAS, ACSL-1, ACC, elovl5, and SCD1) were inhibited in Mid-H. Meanwhile, the mRNA expression levels of endoplasmic reticulum stress marker gene Bip and key genes (ATF4, ATF6, and IRE1α) involving the unfolded protein response were significantly increased in Mid-H and EA. Also, the expression levels of genes (ASK1, JNK1, and Bax) associated with cell apoptosis increased in Mid-H and EA, however, the expression of Bcl2 was inhibited in Mid-H. Therefore, hibernation can cause endoplasmic reticulum stress and apoptosis. The findings will provide a theoretical framework for an animal's cold adaptation and offer insights into preventing and managing metabolic syndrome.

Embryonic development and transcriptomic analysis in red-eared slider Trachemys scripta elegans under salinity stress

The elevated salinity in freshwater causes a serious threat to the survival and reproduction of freshwater organisms. The effect of salinity on embryonic development of freshwater turtles is little known. In this study, we investigated the embryonic morphology and underlining mechanism of red-eared slider (Trachemys scripta elegans) in different salinities incubated environment (2.5 ppt and 5 ppt). Results showed that salinity caused various forms of malformed embryos, including brain hypoplasia, eye defects, skeletal dysplasia, deformities of carapace, plastron, limb in the embryo. Severely, salinity could lead to embryos decease. Transcriptome analysis showed that differentially expressed genes induced by salinity primarily enriched in development pathways, metabolism pathways, disease pathways as well as cell processes through KEGG enrichment analysis. In addition, in early and middle embryonic developmental stages, the mRNA expression of apoptotic genes (p38 and bax) significantly increased, whereas anti-apoptotic gene bcl-2 decreased in salinities incubated environment. These findings demonstrated that salinity inhibited the process of embryonic development and damaged organogenesis of turtles through promoting apoptotic pathways.

Isolation, identification and characterization of Aeromonas jandaei from diseased Chinese soft-shell turtles

Aeromonas jandaei is a gram-negative bacterium commonly found in aquatic environments and can induce illnesses in amphibians, reptiles and aquatic animals. In this study, a strain of bacteria was isolated from the diseased Chinese soft-shell turtle (Pelodiscus sinensis), then named strain JDP-FX. This isolate was identified as A. jandaei after analysis of morphological, physiological and biochemical characteristics, as well as 16S rRNA and gyrB gene sequences. Virulence genetic testing further detected temperature-sensitive protease (eprCAI), type III secretion system (TTSS) (ascv), nuclease (nuc), cytotonic enterotoxin (alt) and serine proteinase (ser) in JDP-FX. Compared with healthy Chinese soft-shell turtle, the serum levels of total protein (TP), albumin (ALB) and globulin (GLB) were significantly decreased in the diseased Chinese soft-shell turtle, while, the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were significantly increased. Histopathological observations showed that multiple tissues, including intestinal mucosa, liver and kidney, were severely damaged in the diseased Chinese soft-shell turtle. Moreover, the diseased Chinese soft-shell turtle had significant cell degeneration, necrosis, sloughing and interstitial inflammatory cell infiltration. The pathogenicity of JDP-FX was tested via artificial infection. The median lethal dosage (LD50 ) of the strain was 1.05 × 105 colony forming units (CFU/g) per weight of Chinese soft-shell turtle. Drug susceptibility analysis revealed that JDP-FX was susceptible to ceftazidime, minocycline, cefoperazone, ceftriaxone and piperacillin. In addition, JDP-FX was resistant to doxycycline, florfenicol, sulfonamides, gentamicin, ampicillin and neomycin. Therefore, this study may provide guidance for further research into the diagnosis, prevention and treatment of JDP-FX infection.

PHARMACOKINETICS OF TRAMADOL AND O-DESMETHYLTRAMADOL IN GIANT TORTOISES (CHELONOIDIS VANDENBURGHI, CHELONOIDIS VICINA)

The objective of this study was to determine the pharmacokinetics of two orally administered doses of tramadol (1 mg/kg and 5 mg/kg) and its metabolite, O-desmethyltramadol (M1) in giant tortoises (Chelonoidis vandenburghi, Chelonoidis vicina). Eleven giant tortoises (C. vandenburghi, C. vicina) received two randomly assigned, oral doses of tramadol (either 1 mg/kg or 5 mg/kg), with a washout period of 3 wk between each dose. The half-life (t½) of orally administered tramadol at 1 mg/kg and 5 mg/kg was 11.9 ± 4.6 h and 13.2 ± 6.1 h, respectively. After oral administration of tramadol at 1 mg/kg and 5 mg/kg, the maximum concentration (Cmax) was 125 ± 69 ng/ml and 518 ± 411 ng/ml, respectively. There were not enough data points to determine pharmacokinetic (PK) parameters for the M1 metabolite from either dose. Tramadol administered orally to giant tortoises at both doses provided measurable plasma concentrations of tramadol for approximately 48 h with occasional transient sedation. Oral tramadol at 5 mg/kg, on average, achieves concentrations of >100 ng/ml, the reported human therapeutic threshold, for 24 h. Based on the low levels of M1 seen in this study, M1 may not be a major metabolite in this taxon.

Effects of butyl paraben on behavior and molecular mechanism of Chinese striped-necked turtle (Mauremys sinensis)

Butyl paraben (BuP) is widely used in cosmetics, drugs, and food preservation. Recently it is an identified new pollutant that affects various aspects of reproduction, lipid metabolism, and nervous system. Behavioral activity serves as a pre-warning biomarker for predicting water quality. So, in this study, the changes in some behaviors and its neurotransmitters and cell apoptosis in the brain of Chinese striped-necked turtles (Mauremys sinensis) were studied when the turtles were exposed to BuP concentrations of 0, 5, 50, 500, and 5000 µg/L for 21 weeks. The results showed that, the basking time and altering scores to external stimuli in the groups of 50, 500, and 5000 µg/L were significantly reduced, while the time for body-righting was significantly increased, compared with the control (0 µg/L), indicating that the turtles exhibited depression and inactive behavior. The analysis of neurotransmitter in the brain showed that 5-hydroxytryptamine (5-HT) contents in the groups of 500 and 5000 µg/L were significantly higher than the other groups, which was due to an increase in the mRNA relative expression levels of the 5-HT receptor gene (5-HTR), neurotransmitter transporter genes (Drd4, Slc6a4), and neurotransmitter synthase tryptophan hydroxylase (TPH). Furthermore, GABA transaminase (GABA-T) activity increased in the 500 and 5000 µg/L groups, and tyrosine hydroxylase (TH) activity increased dramatically in the 5000 µg/L group. However, acetyl-CoA (AChE) activity was significantly reduced in these four BuP exposure groups. These changes could be attributed to decreased movement velocity and increased inactivity. Meanwhile, the mRNA expression level of BAX, Bcl-2, caspase-9 and TUNEL assay indicated the occurrence of cell apoptosis in the brains of the higher BuP exposed groups, which may play an important role in neuronal death inducing behavior change. In summary, these findings offer fundamental insights into turtle ecotoxicology and serve as a foundation for a comprehensive assessment of the ecological and health risks associated with BuP.

Effects of Brown Fishmeal on Growth Performance, Digestibility, and Lipid Metabolism of the Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

The aim of this study was to evaluate the effect of brown fishmeal in replacement of white fishmeal in the diet of Chinese soft-shelled turtles and to find the optimal amount of brown fishmeal to add. Five experimental groups were set up and fed to animals, and they were composed by different proportions of white and brown fishmeal: G1 (30% white and 25% brown fishmeal), G2 (25% white and 30% brown fishmeal), G3 (20% white and 35% brown fishmeal), G4 (15% white and 40% brown fishmeal), G5 (10% white and 45% brown fishmeal). G1 is regarded as the control group. Turtles were randomly divided into five experimental groups with four replicates each. The experiment lasted 72 days. The results showed that the WGR, SGR, FCR, and HSI of the G3 group were not significantly different from those of the control group (P > 0.05). In addition, brown fishmeal can increase the crude protein content in the muscles of them. Among the serum biochemical indices, there was no significant difference between the G3 group and the G1 group, except for the level of TG (P > 0.05). Meanwhile, the activities of AST, ALT, and CAT in the liver of the G3 group did not differ significantly from those of the G1 group (P > 0.05). However, the activities of ACP, AKP, and T-AOC were significantly decreased in the G3 group (P < 0.05). In addition, the alteration of fishmeal did not affect the digestive enzyme activities in the stomach, liver, and intestine, and there is no significant difference (P > 0.05). Importantly, with increasing brown fishmeal addition, the expression of Fas, Pparγ, Scd, and Stat3 showed a significant increase, while the expression of Bmp4 decreased significantly (P < 0.05). In this study, the addition of 20% white fishmeal and 35% brown fishmeal to the diet of Chinese soft-shelled turtles did not adversely affect growth performance. Therefore, 20% white fishmeal and 35% brown fishmeal are the most practical feed formulations for Chinese soft-shelled turtles in this study.

Angiotensin-(1-7) plays an important role in regulating spermatogenesis in Trachemys scripta elegans under salinity stress

Elevation in water salinity can threaten the spermatogenesis and fertility of freshwater animals. The role of the renin-angiotensin system (RAS) in regulating spermatogenesis has attracted considerable attention. Our previous study found that red-eared sliders (Trachemys scripta elegans), could survive in 10 PSU water for over 1 year. To understand the chronic impact of salinity on testicular spermatogenesis and underlying mechanisms, male T. s. elegans were subjected to treatment with water of 5 PSU and 10 PSU for a year, and spermatogenesis and regulation of the RAS signal pathway was assessed. Results showed induced inflammation in the testes of T. s. elegans in the 10 PSU group, as evidenced by a decrease in the number of testicular germ cells from 1586 to 943. Compared with the control group, the levels of proinflammatory genes, including TNF-α, IL-12A and IL-6 were elevated 3.1, 0.3, and 1.4 times, respectively, in animals exposed to 10 PSU water. Testicular antiapoptotic processes of T. s. elegans might involve the vasoactive peptide angiotensin-(1-7) in the RAS, as its level was significantly increased from 220.2 ng ml-1 in controls to 419.2 ng ml-1 in the 10 PSU group. As expected, specific inhibitor (A-779) for the Ang-(1-7) acceptor effectively prevented the salinity-induced upregulation of genes encoding anti-inflammatory and antiapoptotic factors (TGF-β1, Bcl-6) in the testis of the 10 PSU animals, whereas it promoted the upregulation of proinflammatory and proapoptotic factors (TNF-α, IL-12A, IL-6, Bax and caspase-3). Our data indicated that Ang-(1-7) attenuates the effect of salinity on inflammation and apoptosis of the testis in T. s. elegans. A new perspective to prevent salinity-induced testis dysfunction is provided.

Comparative genomic survey and functional analysis of DKKL1 during spermatogenesis in the Chinese soft-shelled turtle (Pelodiscus sinensis)

A feature of the Chinese soft-shelled turtle (Pelodiscus sinensis) is seasonal spermatogenesis; however, the underlying molecular mechanism is not well clarified. Here, we firstly cloned and characterized P. sinensis DKKL1, and then performed comparative genomic studies, expression analysis, and functional validation. P. sinensis DKKL1 had 2 putative N-glycosylation sites and 16 phosphorylation sites. DKKL1 also had classic transmembrane structures that were extracellularly localized. DKKL1's genetic distance was close to turtles, followed by amphibians and mammals, but its genetic distance was far from fishes. DKKL1 genes from different species shared distinct genomic characteristics. Meanwhile, they were also relatively conserved among themselves, at least from the perspective of classes. Notably, the transcription factors associated with spermatogenesis were also identified, containing CTCF, EWSR1, and FOXL2. DKKL1 exhibited sexually dimorphic expression only in adult gonads, which was significantly higher than that in other somatic tissues (P < 0.001), and was barely expressed in embryonic gonads. DKKL1 transcripts showed a strong signal in sperm, while faint signals were detected in other male germ cells. DKKL1 in adult testes progressively increased per month (P < 0.05), displaying a seasonal expression trait. DKKL1 was significantly downregulated in testes cells after the sex hormones (17β-estradiol and 17α-methyltestosterone) and Wnt/β-catenin inhibitor treatment (P < 0.05). Likewise, the Wnt/β-catenin inhibitor treatment dramatically repressed CTCF, EWSR1, and FOXL2 expression. Conversely, they were markedly upregulated after the 17β-estradiol and 17α-methyltestosterone treatment, suggesting that the three transcription factors might bind to different promoter regions, thereby negatively regulating DKKL1 transcription in response to the changes in the estrogen and androgen pathways, and positively controlling DKKL1 transcription in answer to the alterations in the Wnt/β-catenin pathway. Knockdown of DKKL1 significantly reduced the relative expression of HMGB2 and SPATS1 (P < 0.01), suggesting that it may be involved in seasonal spermatogenesis of P. sinensis through a positive regulatory interaction with these two genes. Overall, our findings provide novel insights into the genome evolution and potential functions of seasonal spermatogenesis of P. sinensis DKKL1.

In situ hybridization analysis of odorant receptor expression in the olfactory organ of the pig-nosed turtle Carettochelys insculpta

The turtle olfactory organ consists of upper (UCE) and lower (LCE) chamber epithelium, which send axons to the ventral and dorsal portions of the olfactory bulbs, respectively. Generally, the UCE is associated with glands and contains ciliated olfactory receptor neurons (ORNs), while the LCE is devoid of glands and contains microvillous ORNs. However, the olfactory organ of the pig-nosed turtle Carettochelys insculpta appears to be a single olfactory system morphologically: there are no associated glands; ciliated ORNs are distributed throughout the olfactory organ; and the olfactory bulb is not divided into ventral and dorsal portions. In this study, we analyzed the expression of odorant receptors (ORs), the major olfactory receptors in turtles, in the pig-nosed turtle olfactory organ, via in situ hybridization. Of 690 ORs, 375 were classified as class I and 315 as class II. Some class II ORs were expressed predominantly in the posterior dorsomedial walls of the nasal cavity, while other class II ORs and all class I ORs examined were expressed in the remaining region. These results suggest that the pig-nosed turtle olfactory organ can be divided into two regions according to the expression of ORs.

Expression patterns of the transcription factors Fezf1, Fezf2, and Bcl11b in the olfactory organs of turtle embryos

Many tetrapod vertebrates have two distinct olfactory organs, the olfactory epithelium (OE) and vomeronasal organ (VNO). In turtles, the olfactory organ consists of two types of sensory epithelia, the upper chamber epithelium (UCE; corresponding to the OE) and the lower chamber epithelium (LCE; corresponding to the VNO). In many turtle species, the UCE contains ciliated olfactory receptor cells (ORCs) and the LCE contains microvillous ORCs. To date, several transcription factors involved in the development of the OE and VNO have been identified in mammals. Fez family zinc-finger protein 1 and 2 (Fezf1 and 2) are expressed in the OE and VNO, respectively, of mouse embryos, and are involved in the development and maintenance of ORCs. B-cell lymphoma/leukemia 11B (Bcl11b) is expressed in the mouse embryo OE except the dorsomedial parts of the nasal cavity, and regulates the expression of odorant receptors in the ORCs. In this study, we examined the expression of Fezf1, Fezf2, and Bcl11b in the olfactory organs of embryos in three turtle species, Pelodiscus sinensis, Trachemys scripta elegans, and Centrochelys sulcata, to evaluate their involvement in the development of reptile olfactory organs. In all three turtle species, Bcl11b was expressed in the UCE, Fezf2 in the LCE, and Fezf1 in both the UCE and LCE. These results imply that the roles of the transcription factors Fezf1, Fezf2, and Bcl11b in olfactory organ development are conserved among mammals and turtles.

Effects of dietary sodium butyrate on growth performance, immune function, and intestinal microflora of Chinese soft-shelled turtle (Pelodiscus sinensis)

The Chinese soft-shelled turtle (Pelodiscus sinensis) has become increasingly susceptible to frequent diseases with the intensification of farming, which severely impacts the development of the aquaculture industry. Sodium butyrate (SB) is widely used as a feed additive due to its promotion of growth, enhancement of immune function, and antioxidative properties. This study aimed to investigate the effects of dietary SB on the growth performance, immune function, and intestinal microflora of Chinese soft-shelled turtles. A total of 300 Chinese soft-shelled turtles (mean weight: 11.36 ± 0.21g) were randomly divided into four groups with three parallel sets in each group. Each group was fed a diet supplemented with 0%, 0.005%, 0.01%, or 0.02% SB for 60 days. The results demonstrated an upward trend in weight gain rate (WGR) and specific growth rate (SGR) with increasing SB supplementation, and the experimental group fed with 0.02% SB showed a significant increase in WGR and SGR compared to other groups (P< 0.05). These levels of SB also decreased the levels of feed conversion ratio (FCR) and the total cholesterol (TC) content of Chinese soft-shelled turtles, and the 0.02% SB was significantly lower than that of other groups (P< 0.05). The activity of complement protein in vivo increased with increases in SB content, and the activities of complement C3 and C4 reached the highest level with 0.02% SB. The species abundance of the experimental group D fed with 0.02% SB was significantly higher than that of other groups (P< 0.05). Furthermore, the relative abundance of Clostridium sensu stricto 1 was significantly increased with 0.02% SB (P< 0.05). In conclusion, adding 0.02% SB to the diet improves the growth performance, feed digestion ability, and intestinal microbiota of Chinese soft-shelled turtles.

Effects of florfenicol on the antioxidant and immune systems of Chinese soft-shelled turtle (Pelodiscus sinensis)

Florfenicol is a commonly used antibiotic for the treatment of bacterial diseases of the Chinese soft-shelled turtle (Pelodiscus sinensis). The study investigated the effects of florfenicol on the antioxidant and immune system of P. sinensis. Results showed that the total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and catalase (CAT) activities were significantly increased in the 10 mg/kg and 40 mg/kg florfenicol treatment groups compared with the control group. Besides, the malondialdehyde (MDA) content was significantly increased, and the glutathione peroxidase (GSH-Px) activity was significantly decreased with 40 mg/kg florfenicol treatment. In addition, florfenicol has effects on the immune system, 10 mg/kg of florfenicol significantly promoted the activities of acid phosphatase (ACP) and alkaline phosphatase (AKP), whereas 40 mg/kg of florfenicol significantly inhibited their activities. To elucidate the molecular mechanisms, a comparative transcriptome analysis was conducted. A total of 59 differentially expressed genes (DEGs) and 12 significantly enriched KEGG pathways were identified in the 10 mg/kg group; 150 DEGs and 10 significantly enriched KEGG pathways were identified in the 40 mg/kg group. Among them, the complement and coagulation cascade pathways were the most significant which may play an important regulatory role in the immune response. The MADCAM1, STAT3, and IL4I1 genes may be the key genes of florfenicol affecting the immune response. The APOA1, APOA4, SPLA2, FADS1, and FADS2 genes may play a key role in anti-inflammatory and antioxidant effects through redox-related pathways. The study lays the foundation for a deeper understanding of the mechanism of the florfenicol effect on P. sinensis.

Influence of chemical dose and exposure duration on protein synthesis in green sea turtle primary cells

Understanding the impacts of chemical exposure in marine wildlife is challenging, due to practical and ethical constraints that preclude traditional toxicology research on these animals. This study addressed some of these limitations by presenting an ethical and high throughput cell-based approach to elucidate molecular-level effects of contaminants on sea turtles. The experimental design addressed basic questions of cell-based toxicology, including chemical dose and exposure time. Primary green turtle skin cells were exposed to polychlorinated biphenyl (PCB) 153 and perfluorononanoic acid (PFNA) for 24 and 48 h, at three sub-lethal, environmentally relevant concentrations (1, 10 and 100 μg/L). Sequential window acquisition of all theoretical mass spectra (SWATH-MS) identified over 1000 differentially abundant proteins within the 1% false discovery rate (FDR) threshold. The 24 h exposure resulted in a greater number of differentially abundant proteins, compared to 48 h exposure, for both contaminants. However, there were no statistically significant dose-response relationships for the number of differentially synthesised proteins, nor differences in the proportion of increased vs decreased proteins between or within exposure times. Known in vivo markers of contaminant exposure, superoxide dismutase and glutathione S-transferase, were differentially abundant following exposure to PCB153 and PFNA. SIGNIFICANCE: Cell-based (in vitro) proteomics provides an ethical and high throughput approach to understanding the impacts of chemical contamination on sea turtles. Through investigating effects of chemical dose and exposure duration on unique protein abundance in vitro, this study provides an optimised framework for conducting cell-based studies in wildlife proteomics, and highlights that proteins detected in vitro could act as biomarkers of chemical exposure and effect in vivo.

Study of trace elements in stranded green turtles (Chelonia mydas), hawksbill turtles (Eretmochelys imbricata), and olive ridley turtles (Lepidochelys olivacea) in Gulf of Thailand and Andaman Sea

The purpose of this study was to survey and compare the amounts of elements in the serum of stranded sea turtles from the Gulf of Thailand and the Andaman Sea. The sea turtles from the Gulf of Thailand had Ca, Mg, P, S, Se, and Si concentrations significantly higher than those in sea turtles from the Andaman Sea. The Ni and Pb concentrations of sea turtles from the Gulf of Thailand was higher, but not significantly so, than in sea turtles from the Andaman Sea. Rb was detected only in sea turtles from the Gulf of Thailand. This may have been related to the industrial activities in Eastern Thailand. The concentration of Br in the sea turtles from the Andaman Sea were significantly higher than those in sea turtles from the Gulf of Thailand. The higher serum concentration of Cu in hawksbill (H) and olive ridley turtles (O) than in green turtles may be due to hemocyanin, as an important component in the blood of crustaceans. The higher Fe concentration in the serum from green turtles than for H and O may be due to chlorophyll, which is an important component of chloroplasts in eel grass. Co was not found in the serum of green turtles but was found in the serum of H and O. The monitoring of important elements in sea turtles may be used as a tool to assess the levels of pollution in marine ecosystems.

Low production of mitochondrial reactive oxygen species after anoxia and reoxygenation in turtle hearts

Extremely anoxia-tolerant animals, such as freshwater turtles, survive anoxia and reoxygenation without sustaining tissue damage to their hearts. In contrast, for mammals, the ischemia-reperfusion (IR) injury that leads to tissue damage during a heart attack is initiated by a burst of superoxide (O2·-) production from the mitochondrial respiratory chain upon reperfusion of ischemic tissue. Whether turtles avoid oxidative tissue damage because of an absence of mitochondrial superoxide production upon reoxygenation, or because the turtle heart is particularly protected against this damage, is unclear. Here, we investigated whether there was an increase in mitochondrial O2·- production upon the reoxygenation of anoxic red-eared slider turtle hearts in vivo and in vitro. This was done by measuring the production of H2O2, the dismutation product of O2·-, using the mitochondria-targeted mass-spectrometric probe in vivo MitoB, while in parallel assessing changes in the metabolites driving mitochondrial O2·- production, succinate, ATP and ADP levels during anoxia, and H2O2 consumption and production rates of isolated heart mitochondria. We found that there was no excess production of in vivo H2O2 during 1 h of reoxygenation in turtles after 3 h anoxia at room temperature, suggesting that turtle hearts most likely do not suffer oxidative injury after anoxia because their mitochondria produce no excess O2·- upon reoxygenation. Instead, our data support the conclusion that both the low levels of succinate accumulation and the maintenance of ADP levels in the anoxic turtle heart are key factors in preventing the surge of O2·- production upon reoxygenation.

Divergent responses in the gut microbiome and liver metabolome to ammonia stress in three freshwater turtles

Ammonia is a common pollutant in aquaculture system, and toxic to all aquatic animals. However, different aquatic animals exhibit diverse physiological responses to high-level ammonia exposure, potentially indicating their divergent resistance to ammonia stress. In this study, juveniles of three freshwater turtles (Mauremys reevesii, Pseudemys nelsoni and Trachemys scripta elegans) were exposed to different concentrations of ammonia (0, 0.3 and 3.0 mg/L) for 30 days, and their swimming, growth performance, gut microbiota, and hepatic metabolites were measured to evaluate the interspecific difference in physiological responses to ammonia stress. Despite no differences in swimming ability, growth rate, and gut microbial diversity, observable changes in microbial community composition and hepatic metabolite profiles were shown in ammonia-exposed turtles. A relatively higher abundance of potentially pathogenic bacteria was found in M. reevesii than in the other two species. Moreover, microbial compositions and metabolic responses differed significantly among the three species. M. reevesii was, out of the three tested species, the one in which exposure to ammonia had the greatest effect on changes in bacterial genera and hepatic metabolites. Conversely, only a few metabolites were significantly changed in T. scripta elegans. Integrating these findings, we speculated that native M. reevesii should be more vulnerable to ammonia stress compared to the invasive turtle species. Our results plausibly reflected divergent potential resistance to ammonia among these turtles, in view of differential physiological responses to ammonia exposure at environmentally relevant concentrations.

Non-targeted proteomics reveals altered immune response in geographically distinct populations of green sea turtles (Chelonia mydas)

All seven species of sea turtle are facing increasing pressures from human activities that are impacting their health. Changes in circulating blood proteins of an individual, or all members of a population, can provide an early indicator of adverse health outcomes. Non-targeted measurement of all detectable proteins in a blood sample can indicate physiological changes. In the context of wildlife toxicology, this technique can provide a powerful tool for discovering biomarkers of chemical exposure and effect. This study presents a non-targeted examination of the protein abundance in sea turtle plasma obtained from three geographically distinct foraging populations of green turtles (Chelonia mydas) on the Queensland coast. Relative changes in protein expression between sites were compared, and potential markers of contaminant exposure were investigated. Blood plasma protein profiles were distinct between populations, with 85 out of the 116 identified proteins differentially expressed (p < 0.001). The most strongly dysregulated proteins were predominantly acute phase proteins, suggestive of differing immune status between the populations. The highest upregulation of known markers of immunotoxicity, such as pentraxin fusion and complement factor h, was observed in the Moreton Bay turtles. Forty-five different organohalogens were also measured in green turtle plasma samples as exposure to some organohalogens (e.g., polychlorinated biphenyls) has previously been identified as a cause for immune dysregulation in marine animals. The few detected organohalogens were at very low (pg/mL) concentrations in turtles from all sites, and are unlikely to be the cause of the proteome differences observed. However, the changes in protein expression may be indicative of exposure to other chemicals or environmental stressors. The results of this study provide important information about differences in protein expression between different populations of turtles, and guide future toxicological and health studies on east-Australian green sea turtles.

Effect of ammonia stress on AMPK regulating-carbohydrate and lipid metabolism in Chinese striped-neck turtle (Mauremys sinensis)

In aquatic organisms, ammonia is one of the major factors that affect energy levels when it exceeds its optimal concentration. Numerous studies have examined the effects of ammonia on aquatic animals, but its effect on metabolism is still unknown. The effect of ammonia on carbohydrates and lipid metabolism in the Chinese striped neck turtle (Mauremys sinensis) was investigated in this study by exposing the turtle to two different ammonia concentrations (A100: 1.53 mg L^-1) and (A200: 2.98 mg L^-1) for 24 and 48 h, respectively. Our results showed that the mRNA expression of adenosine monophosphate-activated protein kinase α1 (AMPKα1) significantly increased only in A100 at 24 h, whereas its activity increased in both ammonia-exposed groups. The two AMPK-regulated transcription factors responsible for carbohydrate metabolism also exhibited changes in ammonia-treated groups, as hepatocyte nuclear factor-4-alpha (HNF4α) increased and forkhead box protein O1 (FoxO1) decreased. The expression of phosphofructokinase (PFK) and glucose-6-phosphatase (G-6-PAS) was subsequently downregulated. In addition, transcription factors, carbohydrate-responsive element-binding protein (ChREBP), and sterol regulatory element-binding protein 1c (SREBP-1c), which are known to be involved in lipogenesis, were suppressed. These downstream genes include fatty acid synthase, stearoyl CoA desaturase, and acetyl-CoA carboxylase (FAS, SCD-1 and ACC). Moreover, the glucose content decreased, whereas the triglyceride content increased significantly in A200 at 24 h. We concluded that AMPK signaling inhibits gluconeogenesis and lipogenesis, and promotes glycolysis to meet energy demand under stressful conditions in M. sinensis.

Role of Clostridium butyricum, Bacillus subtilis, and algae-sourced β-1,3 glucan on health in grass turtle

This study investigated the effects of two probiotics namely Clostridium butyricum and Bacillus subtilis, and one prebiotic known as algae-sourced β-1,3 glucan, on the overall performances of grass turtles (Chinemys reevesii) juveniles. Growth performance, immune responses, enzymatic antioxidant activities, intestinal histomorphology, and disease resistance against the challenge with Aeromonas veronii were assessed. Two hundred and sixteen (216) juvenile turtles with an average initial weight of 106.35 ± 0.03 g were divided into four groups, each containing three replicates with 18 turtles per each replicate, which were fed a basic diet (control group, GD) and a basal diet supplemented with C. butyricum 1.0 × 10⁸ CFU per kg (GA group), or with B. subtilis 1.0 × 10⁸ CFU per kg (GB group) and with algal-sourced β-1,3-glucan 50 mg per kg (GC group), respectively. After the turtles had been fed for 60 d, 90 d, and 120 d of the experimental period, the growth performance and survival rate (SR), intestinal digestive enzyme, hepatic and intestinal antioxidant capacity, serum biochemical indexes, and immune performance were measured. The results showed that the weight gain rate and SR were significantly enhanced (P < 0.05) after fed probiotics and algae-sourced β-1,3-glucan in all test times;The pepsin, amylase, acid phosphatase, total antioxidant capacity, triglyceride, alkaline phosphatase, urea nitrogen, cholesterol, total protein, IgA, IgG, IgM at 120 d were significantly enhanced (P<0.05) after fed C. butyricum. The intestinal villi heights, widths, and the thickness of the muscle layer were significantly higher in groups GA, GB, and GC than those reared within the GD control group (P < 0.05). After injecting the challenge by A. veronii the survival rate of grass turtles in the GA group (75%) was significantly higher than the other three groups (P<0.05), while there was no significant difference between the GB and GC groups compared with the control GD group, respectively (P>0.05). Overall, these results indicated that dietary supplementation with probiotics or algae-sourced β-1,3 glucan, exhibited positive effects on C. reevesii. In particular, C. butyricum, showed the greatest improvements relating to growth, immune response, antioxidant activity, intestinal health, and disease resistance.

Life after death? Exploring biochemical and molecular changes following organismal death in green turtles, Chelonia mydas (Linnaeus, 1758)

Green turtles, Chelonia mydas, have been included in biomonitoring efforts given its status as an endangered species. Many studies, however, rely on samples from stranded animals, raising the question of how death affects important biochemical and molecular biomarkers. The goal of this study was to investigate post mortem fluctuations in the antioxidant response and metabolism of carbohydrates in the liver of C. mydas. Liver samples were obtained from six green turtles which were submitted to rehabilitation and euthanized due to the impossibility of recovery. Samples were collected immediately after death (t = 0) and at various time intervals (1, 2, 3, 4, 5, 6, 12, 18 and 24 h post mortem), frozen in liquid nitrogen and stored at -80 °C. The activities of catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PDH) were analyzed, as were the levels of lipid peroxidation, glycogen concentration, RNA integrity (RNA IQ) and transcript levels of carbonic anhydrase and pyruvate carboxylase genes. Comparison between post mortem intervals showed a temporal stability for all the biomarkers evaluated, suggesting that changes in biochemical and molecular parameters following green turtle death are not immediate, and metabolism may remain somewhat unaltered up to 24 h after death. Such stability may be associated with the overall lower metabolism of turtles, especially under an oxygen deprivation scenario such as organismal death. Overall, this study supports the use of biomarkers in sea turtles sampled within a period of 24 h post mortem for biomonitoring purposes, though it is recommended that post mortem fluctuations of particular biomarkers be evaluated prior to their application, given that proteins may show varying degrees of susceptibility to proteolysis.

Perturbation of the gut microbiome in wild-caught freshwater turtles (Emydura macquarii macquarii) exposed to elevated PFAS levels

Per- and polyfluoroalkyl substances (PFAS) are environmentally persistent and pervasive. Understanding the toxicity of PFAS to wildlife is difficult, both due to the complexity of biotic and abiotic perturbations in the taxa under study and the practical and ethical problems associated with studying the impacts of environmental pollutants on free living wildlife. One avenue of inquiry into the effects of environmental pollutants, such as PFAS, is assessing the impact on the host gut microbiome. Here we show the microbial composition and biochemical functional outputs from the gut microbiome of sampled faeces from euthanised and necropsied wild-caught freshwater turtles (Emydura macquarii macquarii) exposed to elevated PFAS levels. The microbial community composition was profiled by 16S rRNA gene sequencing using a Nanopore MinION and the biochemical functional outputs of the gut microbiome were profiled using a combination of targeted central carbon metabolism metabolomics using liquid chromatography coupled to a triple quadrupole mass spectrometer (LC-QqQ-MS) and untargeted metabolomics using liquid chromatography coupled to a quadrupole time of flight mass spectrometer (LC-QToF-MS). Total PFAS was measured in the turtle serum using standard methods. These preliminary data demonstrated a 60-fold PFAS increase in impacted turtles compared to the sampled aquatic environment. The microbiome community was also impacted in the PFAS exposed turtles, with the ratio of Firmicutes-to-Bacteroidetes rising from 1.4 at the reference site to 5.5 at the PFAS impacted site. This ratio increase is indicative of host stress and dysfunction of the gut microbiome that was correlated with the biochemical metabolic function data, metabolites observed that are indications of stress and inflammation in the gut microbiome. Utilising the gut microbiome of sampled faeces collected from freshwater turtles provides a non-destructive avenue for investigating the impacts of PFAS in native wildlife, and provides an avenue to explore other contaminants in higher-order taxa within the environment.

Gene synteny, evolution and antiviral activity of type I IFNs in a reptile species, the Chinese soft-shelled turtle Pelodiscus sinensis

Type I interferons (IFNs) are critical cytokines for the establishment of antiviral status in fish, amphibian, avian and mammal, but the knowledge on type I IFNs is rather limited in reptile. In this study, seven type I IFN genes, designed as IFN1 to IFN7, were identified from a reptile species, the Chinese soft-shelled turtle (Pelodiscus sinensis). These identified type I IFNs have relatively low protein identity, when compared with those in human and chicken; but they possess conserved cysteines, predicted multi-helix structure and N-terminal signal peptide. The Chinese soft-shelled turtle IFN1 to IFN5 have two exons and one intron, but IFN6 and IFN7 are the single-exon genes. Chinese soft-shelled turtle type I IFNs are located respectively on the two conserved reptile-bird loci, named as Locus a and Locus c, and are clustered into the four of the five reptile-bird groups (named as Groups I-V) based on phylogenetic evidence, due to the lack of IFNK in the turtle. Moreover, the Chinese soft-shelled turtle type I IFNs can be induced by soft-shelled turtle iridovirus (STIV) infection and show antiviral activity in soft-shelled turtle artery (STA) cells, except IFN6. In addition, due to the difference in genome organizations, such as the number of exons and introns of type I IFN genes from fish to mammal, the definition and evolution of 'intronless' type I IFN genes were discussed in lineages of vertebrates. Thus, the finding of type I IFNs on two different loci in P. sinensis sheds light on the evolution of type I IFN genes in vertebrates.

Molecular characterization and functional analysis of Esr1 and Esr2 in gonads of Chinese soft-shelled turtle (Pelodiscus sinensis)

Estrogens and their receptors play crucial roles in regulating the gonadal development of vertebrates. To clarify the roles of estrogen receptors in the gonadal development of turtles, estrogen receptors (Esr1 and Esr2) in Chinese soft-shelled turtle (Pelodiscus sinensis) were identified and characterized, and their function in gonads was investigated by intraperitoneal injection of agonist propylpyrazoletriol (PPT) and diarylpropionitrile (DPN), and antagonist ICI 182,780 (ICI). Ps-Esr1 encoded a 588 amino acid protein and Ps-Esr2 encoded a 556 amino acid protein. The two receptors contained classic domains, including the DNA-binding domain and ligand-binding domain, and amino acid sequences showed high homology with other turtles. Ps-Esr1 showed the highest expression in the testis, followed by the ovary and liver. However, Ps-Esr2 showed the highest expression in the ovary, followed by the brain and testis. Ps-Esr1 expression showed an up-regulation trend in gonadal differentiation. Histomorphometric analysis showed that the number of follicles increased in female juvenile turtles treated with DPN or PPT. In addition, Tsc2, GnRH, and Fshβ were up-regulated in ovaries of turtles treated with agonists, while Sycp3 and Picalm were up-regulated in testes of turtles treated with agonists. Treatment with the antagonist decreased the number of sperm in matured turtles. Stra8, Scyp3, Dmc1, Picalm, Evl, Boule, and Cdk1 were up-regulated in testis after antagonist treatment. The results indicated that Esr1 might play an important role in gonadal differentiation, and the two estrogen receptors might be involved in the spermatogenesis of the turtle. These results could provide a reference for further research on the function of the estrogen signal in male vertebrates.

Transfer and accumulation of trace elements in seawater, sediments, green turtle forage, and eggshells in the Xisha Islands, South China Sea

Chemical pollutants present a substantial threat to the survival of the green turtle (Chelonia mydas). In this study, the concentrations of 12 trace elements (TEs) in seawater, sediments, and green turtle forage and eggshells from the Xisha Islands in the South China Sea, along with their patterns of transfer and accumulation, were identified. The results revealed that the median TE concentrations in seawater and sediments were lower than the first-grade limit values of the national standard in China, indicating a low ecological risk. The concentrations (μg·g-1) of TEs in forage ranged from 0.05-0.69, 3.43-14.4, 157-2391, 27.9-124, 2.05-9.39, 0.30-9.78, 2.01-80.50, 0.18-5.76, 0.06-0.98, 2.00-18.4, 0.02-0.24, and 0.01-0.09 for Cr, Mn, Sr, Fe, Ni, Cu, Zn, Se, Cd, As, Pb, and Hg, respectively. Seawater, sediments, turtle forage, and eggshells exhibited different TE profiles, which were driven by Hg, Sr, Cr, and Pb in seawater and sediments; Fe and Ni in sediments; Cd and As in forage; and Zn, Se, and Cu in eggshells. The contents of Cu, Zn, and Se increased slightly with trophic level, indicating that they were transferred through dietary pathways. Although Cd and As appeared to bioaccumulate in green turtle forage, it was not transferred to their eggshells, which may be related to the excretion and metabolism process in the mother's body. Thus, eggshells may be a poor bioindicator for the exposure of female green turtles to these toxic elements.

Coastal degradation impacts on green turtle's (Chelonia mydas) diet in southeastern Brazil: Nutritional richness and health

This study evaluated the influence of environmental degradation on the nutritional value of the main marine macrophytes consumed by green sea turtles (Chelonia mydas) in areas with different degrees of urbanization. Macrophyte assemblages in the highly urbanized area (HUa) showed lower richness compared to the lightly urbanized area (LUa) (Mann-Whitney U test: 10.0 ± 3.6 SD genera and 11.9 ± 4.2 taxa per transect vs. 20.1 ± 7.0 genera and 23.5 ± 9.2 taxa per transect) respectively. Also, diet was poorer with 4.0 ± 1.6 genera per turtle (vs. 8.5 ± 4.0 in HUa) and less diverse with Shannon index of diversity = 0.45 ± 0.29 (vs. 0.64 ± 0.46 in LUa). Body condition was similar in both areas. About half of individuals were classified as having normal body condition, 14-15% as underweight and 23-34% as being emaciated. Fibropapillomatosis prevalence (χ² = 8.720; n = 222; df = 1; p = 0.003) was higher in the HUa but, in affected animals, severity was marginally non-significant (χ² = 5.721; n = 82; df = 2; p = 0.057). Significant differences in energy content (kcal) were detected between areas in both summer (S) and winter (W). All ANOVAs on total lipids (F = 22.15 [S] and 30.39 [W]), total water-soluble proteins (F = 327.65 [S] and 64.42 [W]) and total carbohydrates (F = 70.90 [S] and 27.62 [W]) showed high significance (p < 0.001). Carotenoids concentration yielded significant results for Halodule in summer and Hypnea in winter (ANOVAs, F = 39.42 and 13.07, respectively). For both, tests revealed that concentration was higher in LUa than HUa. High levels of phycobiliproteins and proteins in this area probably reflect nitrogen accumulation. Frequency and severity of fibropapillomatosis suggest that urbanization-caused alterations in species diversity and in chemical composition of marine plants affect green turtles' health. LIGHT ABSTRACT: The use of coastal areas by humanity is widespread and increasing. The impacts caused to the coastal environment, be it terrestrial, estuarine or marine, are important and affect numerous species. Our study evaluated the influence of environmental degradation on the nutritional value of the main algae eaten by the green turtle, one of the very few marine megaherbivores (those herbivores with body mass above 10 kg). Diet in the highly urbanized area was richer in proteins, lipids and carbohydrates (sugars) and lower in carotenoids (photosynthetic and photoprotectant pigments in algae and plants; precursors of vitamin A involved in oxygen transport in animals-animals do not synthetize such molecules). High levels in phycobiliproteins (photosynthetic pigments present in some algae) and proteins in the highly urbanized area probably result from organic pollution and nitrogen accumulation in coastal waters. Nitrogen compounds dissolved in water are a threat to vertebrates due to its toxicity and negative effects on the immune system. Our results suggest that algae chemical composition and severity of fibropapillomatosis (tumors caused by a herpesvirus in green sea turtles) are directly related through environmental alterations caused by urbanization.

Health condition of Chelonia mydas from a foraging area affected by the tailings of a collapsed dam in southeast Brazil

In 2015, the failure of the Fundão dam caused the release of 43 million m³ of tailings into the Doce River Basin, in southeast Brazil. It was considered the largest environmental disaster of the world mining industry. The tailings, composed mostly of heavy metals, caused massive destruction of the Doce River ecosystem endangering the organisms that live in the coastal zone where the mud reached the ocean. Among the exposed species are the sea turtles that use the region for food. The aim of this study was to evaluate the effect of contaminants on the health status of juvenile green sea turtles that feed in a coastal area exposed to ore mud (Santa Cruz) and to compare them with animals from an area not directly affected (Coroa Vermelha). A physical examination was performed to determine the health status. Blood samples were analyzed for hematological and biochemical parameters, and metal concentrations (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb, and Zn). Santa Cruz sea turtles had more ectoparasites and a higher incidence of fibropapillomatosis. Statistically significant differences between sites were found for levels of calcium, phosphorus, glucose, protein, albumin, globulin, cholesterol, triglycerides, urea, CPK, ALT, and AST. The count of leukocytes, thrombocytes, and heterophils, as well as the concentrations of As and Cu were higher in Santa Cruz turtles. Together the results show a worse nutritional status and a greater degree of liver and kidney damage in animals affected by the tailings. The health status may indicate a physiological deficit that can affect their immune system and behavior, which is supported by the higher fibropapillomatosis tumor score and ectoparasite load in these animals. These results support the need for long-term monitoring of the exposed area to quantify the direct and indirect influence of the heavy metals levels on sea turtles and how this reflects the environmental health.

A Novel Ex Vivo Approach Based on Proteomics and Biomarkers to Evaluate the Effects of Chrysene, MEHP, and PBDE-47 on Loggerhead Sea Turtles (Caretta caretta)

The principal aim of the present study was to develop and apply novel ex vivo tests as an alternative to cell cultures able to evaluate the possible effects of emerging and legacy contaminants in Caretta caretta. To this end, we performed ex vivo experiments on non-invasively collected whole-blood and skin-biopsy slices treated with chrysene, MEHP, or PBDE-47. Blood samples were tested by oxidative stress (TAS), immune system (respiratory burst, lysozyme, and complement system), and genotoxicity (ENA assay) biomarkers, and genotoxic and immune system effects were observed. Skin slices were analyzed by applying a 2D-PAGE/MS proteomic approach, and specific contaminant signatures were delineated on the skin proteomic profile. These reflect biochemical effects induced by each treatment and allowed to identify glutathione S-transferase P, peptidyl-prolyl cis-trans isomerase A, mimecan, and protein S100-A6 as potential biomarkers of the health-threatening impact the texted toxicants have on C. caretta. Obtained results confirm the suitability of the ex vivo system and indicate the potential risk the loggerhead sea turtle is undergoing in the natural environment. In conclusion, this work proved the relevance that the applied ex vivo models may have in testing the toxicity of other compounds and mixtures and in biomarker discovery.

Characterization of prolactin (PRL) and PRL receptor (PRLR) in Chinese soft-shelled turtle: Molecular identification, ligand-receptor interaction and tissue distribution

Prolactin (PRL) plays crucial roles in many physiological and pathological processes through activating its specific membrane-anchored receptor (PRLR). Although this ligand-receptor pair has been extensively studied in mammals, birds and fishes, researches examining their significance is rather scarce in reptiles. Additionally, the interaction mechanism of PRL-PRLR has abortively understood across vertebrates, since two tandem repeated ligand-binding domains of PRLR have been identified in birds and few reptiles. To lay the foundation to clarify their roles and ligand-receptor interaction in reptiles, using Chinese soft-shelled turtle as model, the cDNAs containing open reading frame of PRL and PRLR were cloned. The cloned PRL consisted of 710 bp and encoded a precursor of 228 amino acid (-aa), while PRLR was 2658 bp in length and predicted to generate a 828-aa precursor. Furthermore, the recombinant PRL protein with high-purity was prepared from Escherichia coli (E. coli) strain Rosetta gamiB (DE3) by using cobalt resin. Using the 5 × STAT5-Luciferase reporter system, we found PRLR and PRLR-M2 (the PRLR-mutant lacking membrane-distal ligand-binding domain) could be dose-dependently activated by recombinant PRL, thereby triggering the intracellular JAK2-STAT5 signaling cascade, suggesting PRL-PRLR is functional in Chinese soft-shelled turtle, and the membrane-proximal ligand-binding domain of PRLR is the critical domain involving in PRL-binding. Quantitative real-time PCR revealed that PRL was predominantly and abundantly expressed in pituitary, while PRLR exhibited ubiquitous expression in all of the tissues examined. Collectively, our data indicate the PRL-PRLR pair may function in reptiles including Chinese soft-shelled turtle, in a way similar to that in birds.

Stress response markers in the blood of São Tomé green sea turtles (Chelonia mydas) and their relation with accumulated metal levels

Metals are persistent worldwide being harmful for diverse organisms and having complex and combined effects with other contaminants in the environment. Sea turtles accumulate these contaminants being considered good bioindicator species for marine pollution. However, very little is known on how this is affecting these charismatic animals. São Tomé and Príncipe archipelago harbours important green sea turtle (Chelonia mydas) nesting and feeding grounds. The main goal of this study was to determine metal and metalloid accumulation in the blood of females C. mydas nesting in São Tomé Island, and evaluate the possible impacts of this contamination by addressing molecular stress responses. Gene expression analysis was performed in blood targeting genes involved in detoxification/sequestration and metal transport (mt, mtf and fer), and in antioxidant and oxidative stress responses (cat, sod, gr, tdx, txrd, selp and gclc). Micronuclei analysis in blood was also addressed as a biomarker of genotoxicity. Present results showed significant correlations between different gene expressions with the metals evaluated. The best GLM models and significant relationships were found for mt expression, for which 78% of the variability was attributed to metal levels (Al, Cu, Fe, Hg, Pb and Zn), followed by micronuclei count (65% - Cr, Cu, Fe, Hg, Mn and Zn), tdx expression (52% - Cd, Fe, Mn, Pb and Se), and cat expression (52% - As, Fe, Se and Cd x Hg). Overall, this study demonstrates that these green sea turtles are trying to adapt to the oxidative stress and damage produced by metals through the increased expression of antioxidants and other protectors, which raises concerns about the impacts on these endangered organisms' fitness. Furthermore, promising biomarker candidates associated to metal stress were identified in this species that may be used in future biomonitoring studies using C. mydas' blood, allowing for a temporal follow-up of the organisms.

Enhanced resistance to Ca2+-induced mitochondrial permeability transition in the long-lived red-footed tortoise Chelonoidis carbonaria

The interaction between supraphysiological cytosolic Ca2+ levels and mitochondrial redox imbalance mediates the mitochondrial permeability transition (MPT). The MPT is involved in cell death, diseases and aging. This study compared the liver mitochondrial Ca2+ retention capacity and oxygen consumption in the long-lived red-footed tortoise (Chelonoidis carbonaria) with those in the rat as a reference standard. Mitochondrial Ca2+ retention capacity, a quantitative measure of MPT sensitivity, was remarkably higher in tortoises than in rats. This difference was minimized in the presence of the MPT inhibitors ADP and cyclosporine A. However, the Ca2+ retention capacities of tortoise and rat liver mitochondria were similar when both MPT inhibitors were present simultaneously. NADH-linked phosphorylating respiration rates of tortoise liver mitochondria represented only 30% of the maximal electron transport system capacity, indicating a limitation imposed by the phosphorylation system. These results suggested underlying differences in putative MPT structural components [e.g. ATP synthase, adenine nucleotide translocase (ANT) and cyclophilin D] between tortoises and rats. Indeed, in tortoise mitochondria, titrations of inhibitors of the oxidative phosphorylation components revealed a higher limitation of ANT. Furthermore, cyclophilin D activity was approximately 70% lower in tortoises than in rats. Investigation of critical properties of mitochondrial redox control that affect MPT demonstrated that tortoise and rat liver mitochondria exhibited similar rates of H2O2 release and glutathione redox status. Overall, our findings suggest that constraints imposed by ANT and cyclophilin D, putative components or regulators of the MPT pore, are associated with the enhanced resistance to Ca2+-induced MPT in tortoises.

Evaluation of dietary zinc on antioxidant-related gene expression, antioxidant capability and immunity of soft-shelled turtles Pelodiscussinensis

Zinc (Zn) plays a role in the antioxidant capacity and immunity of aquatic animals. A twelve-week feeding experiment was performed to estimate the impact of dietary zinc on antioxidant enzyme-related gene expression, antioxidant enzyme activity and non-specific immune functions of soft-shelled turtles, Pelodiscus sinensis. Six fishmeal-based experimental diets with 32.45% protein were formulated, which contained 35.43, 46.23, 55.38, 66.74, 75.06 and 85.24 mg/kg Zn, respectively. Catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) levels improved with an elevation in dietary Zn from 35.43 to 55.38 mg/kg and then reduced when dietary Zn was further elevated. The expression levels of Nrf2 and antioxidant-related genes CuZnSOD, MnSOD, CAT, GPX1, GPX2, GPX3 and GPX4 escalated with elevating Zn concentration up to 55.38 mg/kg in diets and then reduced as dietary Zn elevated. The expression levels of Kelch-like ECH-associating protein 1 (keap1) showed a reverse trend with that of Nrf2. The contents of malondialdehyde (MDA) in the 55.38 and 66.74 mg/kg Zn diet-fed groups were the lowest. Alkaline phosphatase activity (AKP), superoxide anion (O₂^-), lysozyme activity and total antioxidant capacity (T-AOC) improved with an escalation in dietary Zn concentration up to 66.74 mg/kg. Optimal dietary Zn improved antioxidant capability, immunity, and antioxidant enzyme-related gene expression. The dietary Zn demand for soft-shelled turtles were 60.93 and 61.63 mg/kg, based on second regression analysis of SOD and T-AOC activity, respectively.

New Insights to Regulation of Fructose-1,6-bisphosphatase during Anoxia in Red-Eared Slider, Trachemys scripta elegans

The red-eared slider (Trachemys scripta elegans) undergoes numerous changes to its physiological and metabolic processes to survive without oxygen. During anoxic conditions, its metabolic rate drops drastically to minimize energy requirements. The alterations in the central metabolic pathways are often accomplished by the regulation of key enzymes. The regulation of one such enzyme, fructose-1,6-bisphosphatase (FBPase; EC 3.1.3.11), was characterized in the present study during anoxia in liver. FBPase is a crucial enzyme of gluconeogenesis. The FBPase was purified from liver tissue in both control and anoxic conditions and subsequently assayed to determine the kinetic parameters of the enzyme. The study revealed the relative degree of post-translational modifications in the FBPase from control and anoxic turtles. Further, this study demonstrated a significant decrease in the maximal activity in anoxic FBPase and decreased sensitivity to its substrate Fructose-1,6-bisphosphate (FBP) when compared to the control. Immunoblotting demonstrated increased threonine phosphorylation (~1.4-fold) in the anoxic FBPase. Taken together, these results suggest that the phosphorylation of liver FBPase is an important step in suppressing FBPase activity, ultimately leading to the inhibition of gluconeogenesis in the liver of the red-eared slider during anaerobic conditions.

Characterization of the Pelodiscus sinensis polymeric immunoglobulin receptor (P. sinensis pIgR) and its response to LPS and Aeromonas sobria

The polymeric immunoglobulin receptor (pIgR) is one of the most vital components of mucosal immunity that plays a pivotal role in mediating transcytosis of polymeric immunoglobulin (pIg) on epithelial surfaces for protection against invading pathogens. Herein, we cloned the full-length cDNA of Pelodiscus sinensis pIgR, designated as P. sinensis pIgR, made of an open reading frame (ORF) of 1848 bp, molecular weight of 68.2 kDa and estimated isoelectric point of 7.00. The deduced P. sinensis pIgR sequence had a leader peptide, extracellular region containing four immunoglobulin-like domains (Ig like domains), transmembrane and intracellular regions comparable with other vertebrates. P. sinensis pIgR contained four Ig like domains that corresponded with mammalian D1, D3, D4 and D5 similar with reptile and avian Ig like domains. It had 40 potential phosphorylation sites, four putative N-glycosylation sites and several motifs resembling mammalian pIgR motifs. Phylogenetic analysis showed a close relationship between P. sinensis pIgR with avian and reptile pIgRs. P. sinensis pIgR basal levels were higher in the esophagus, small intestine and intestinnum crissum than in other organs of health turtles. Intragastric delivery of LPS and Aeromonassobria led to significant upregulation of P. sinensis pIgR in tissues of the gastrointestinal tract. A polyclonal anti- P. sinensis pIgR antibody produced in rabbit reacted with the recombinant P. sinensis pIgR protein expressed in Escherichia coli in Western blot. These studies demonstrate the existence and immune response of P. sinensis pIgR to stimulation in mucosal organs in Chinese soft-shelled turtles.

Sensitivity of turtles to anticoagulant rodenticides: Risk assessment for green sea turtles (Chelonia mydas) in the Ogasawara Islands and comparison of warfarin sensitivity among turtle species

Although anticoagulant rodenticides (ARs) are effectively used for the control of invasive rodents, nontarget species are also frequently exposed to ARs and secondary poisonings occur widely. However, little data is available on the effects of ARs, especially on marine organisms. To evaluate the effects of ARs on marine wildlife, we chose green sea turtles (Chelonia mydas), which are one of the most common marine organisms around the Ogasawara islands, as our primary study species. The sensitivity of these turtles to ARs was assessed using both in vivo and in vitro approaches. We administered 4 mg/kg of warfarin sodium either orally or intravenously to juvenile green sea turtles. The turtles exhibited slow pharmacokinetics, and prolongation of prothrombin time (PT) was observed only with intravenous warfarin administration. We also conducted an in vitro investigation using liver microsomes from green sea turtles, and two other turtle species (softshell turtle and red-eared slider) and rats. The cytochrome P450 metabolic activity in the liver of green sea turtles was lower than in rats. Additionally, vitamin K epoxide reductase (VKOR), which is the target enzyme of ARs, was inhibited by warfarin in the turtles at lower concentration levels than in rats. These data indicate that turtles may be more sensitive to ARs than rats. We expect that these findings will be helpful for sea turtle conservation following accidental AR-broadcast incidents.

Molecular and functional identification of a short-type peptidoglycan recognition protein, PGRP-S, in the Chinese soft-shelled turtle Pelodiscus sinensis

Peptidoglycan recognition proteins (PGRPs), which are discovered in invertebrates and vertebrates, play an important role in antibacterial immunity. However, the function of PGRPs is largely uninvestigated in reptiles. In the present study, a short-type PGRP gene, designed as C-turtle-PGRP-S, was identified in the Chinese soft-shelled turtle, Pelodiscus sinensis. The C-turtle-PGRP-S contains a highly conserved PGRP domain and has close relationship with PGRP-S orthologues in other species according to sequence and phylogenetic analyses. C-turtle-PGRP-S gene was constitutively expressed in all detected tissues and was induced by Edwardsiella tarda. Additionally, recombinant C-turtle-PGRP-S showed PGN binding activity and antibacterial function against E. tarda. Therefore, it is suggested that the function of PGRP-S is likely to be conserved in reptile vertebrates, as observed in other vertebrates, shedding light on the evolutionary conservation of PGRPs.

Investigation of Proteus vulgaris and Elizabethkingia meningoseptica invasion on muscle oxidative stress and autophagy in Chinese soft-shelled turtle (Pelodiscus sinensis)

Muscle is an important structural tissue in aquatic animals and it is susceptible to bacterial and fungal infection, which could affect flesh quality and health. In this study, Chinese soft-shelled turtles were artificially infected with two pathogens, Proteus vulgaris and Elizabethkingia meningoseptica and the effects on muscle nutritional characteristics, oxidative stress and autophagy were assayed. Upon infection, the muscle nutritional composition and muscle fiber structure were notably influenced. Meanwhile, the mRNA expression of Nrf2 was down-regulated and Keap1 up-regulated, thus resulting in a decrease in antioxidant capacity and oxidative stress. However, with N-acetylcysteine treatment, the level of oxidative stress was decreased, accompanied by significant increases in antioxidant enzyme activities and the mRNA levels of SOD, CAT, GSTCD, and GSTO1. Interestingly, there was a significant increase in autophagy in the muscle tissue after the pathogen infection, but this increase could be reduced by N-acetylcysteine treatment. Our findings suggest that muscle nutritional characteristics were dramatically changed after pathogen infection, and oxidative stress and autophagy were induced by pathogen infection. However, N-acetylcysteine treatment could compromise the process perhaps by decreasing the ROS level and regulating Nrf2-antioxidant signaling pathways.

Lipid peroxidation of kidney of the turtle Mauremys reevesii caused by cadmium

This research was designed to investigate lipid peroxidation of the kidney of turtle (Mauremys reevesii) caused by cadmium. Turtles were injected intraperitoneally with cadmium at the concentration of 0 (control), 7.5, 15, and 30 mg/kg, and 5 turtles were taken from each group after exposure for 1 week (1 w), 2 weeks (2 w), and 3 weeks (3 w). Superoxide dismutase (SOD) and catalase (CAT) activities as well as glutathione (GSH) and malonyldialdehyde (MDA) contents in the homogenate of kidney tissue were analyzed. The results demonstrated that a short time of low dose of cadmium could stimulate the increase of SOD activity in the kidney of turtles, but a long time of high dose of cadmium could induce the decrease of SOD activity in the kidney of turtles. Cadmium could decrease CAT activity and GSH content in turtle kidney, but increased MDA content in turtle kidney. There were some other effects on the turtles, such as depression and diarrhea. The experimental results indicate that cadmium causes temporary oxidative stress on the kidney of turtles.

Accumulation of trace metals in eggs and hatchlings of Chelonia mydas

BACKGROUND

The objective of this study was to verify the accumulation of trace metals in eggs and hatchlings of Chelonia mydas, evaluating if metal accumulation is originated from maternal transfer and/or from the incubation environment. Other assessments were also performed, as metal distribution in different tissues (blood, kidney, liver, muscle, and turtle shells) of newly hatched turtles, and genotoxic analysis, to verify possible damages caused by the presence of metals.

METHODS

The assessments were carried out by quantifying Cd, Ni, Pb, Mn and Fe in egg sample collected during laying time (eggshells (ELT) and egg content (EC)), eggshells from newly hatched turtles (ENH), hatchlings tissues (H - blood, kidney, liver, muscle, and shell)) (n = 18 for each biological sample - 3 of each nest) and nest sediments (n = 6, one of each nest). Comparative analysis were made between ELT and ENH, as well as between egg content (EC) and the sum of tissue samples from hatchlings, using Mann-Whitney hypothesis test (p < 0,05). The amount of metals in different hatchling was quantified and followed by the Dunn post-test. A principal component analysis (PCA) was also employed.

RESULTS

Metals studied were found in all investigated samples. The concentration of a great amount of investigated metals was significantly higher (P=<0.001) in eggshells from ENH than in ELT. An increase in Cd (2.16-fold), Pb (3.47-fold), Fe (6.83-fold) and Mn (195.57-fold) concentration was noticed in ENH. We also observed an increase in Fe (1.59-fold), Mn (1.74-fold) and Ni (1.59-fold) concentration in hatchling, when compared with EC, due to transfer from nest sediments. In relation to the hatchling's tissues, blood was shown to accumulate higher concentrations of Ni and Pb, while shells accumulated more Cd and Fe, and Mn is more associated with liver and kidney. Fe was the highest accumulated metal in both tissues, and muscles presented discrete concentrations of Ni, Mn, and Pb. A mean concentration of 1.25‰ MN was obtained in C. mydas hatchlings, indicating that the accumulation of metals in hatchlings didn't cause toxicology effects.

CONCLUSION

Hatchlings accumulate metals through the maternal and sediment transfer, although the levels of metal accumulation were not enough to cause genotoxic damage.

N-phenyl-1-naphthylamine (PNA) Accumulates in Snapping Turtle (Chelydra serpentina) Liver Activating the Detoxification Pathway

Substituted phenylamine antioxidants (SPAs) are used in Canadian industrial processes. SPAs, specifically N-phenyl-1-naphthylamine (PNA), have received very little attention despite their current use in Canada and their expected aquatic and environmental releases. There is a research gap regarding the effects of PNA in wildlife; therefore, Chelydra serpentina (common snapping turtle) was studied due to its importance as an environmental indicator species. A chronic experiment was performed using PNA spiked food (0 to 3446 ng/g) to determine its toxicity to juvenile C. serpentina. A significant increase in cyp1a mRNA level was observed in the liver of turtles exposed to 3446 ng/g PNA, suggesting that phase I detoxification is activated in the exposed animals. Additionally, a significant decrease in cyp2b transcript level was observed at the two lowest PNA doses, likely indicating another metabolic alteration for PNA. This study helped determine the molecular effects associated with a PNA exposure in reptiles.

Temperature affects the host hematological and cytokine response following experimental ranavirus infection in red-eared sliders (Trachemys scripta elegans)

Pathogen-host interactions are important components of epidemiological research, but are scarcely investigated in chelonians. Red-eared sliders (Trachemys scripta elegans), are recognized as a model for frog virus-3 infection (FV3), a ranavirus in the family Iridoviridae that infects multiple classes of ectothermic vertebrates. Previous challenge studies observed differences in disease outcome based on environmental temperature in this species, but the host response was minimally evaluated. We challenged red-eared sliders with an FV3-like ranavirus at both 28°C and 22°C. We monitored several host response variables for 30 days, including: survival (binary outcome and duration), clinical signs, total and differential leukocytes, and select cytokine transcription in the buffy coat (IL-1β, TNFα, IFYg, IL-10). After 30 days, 17% of challenged turtles survived at 28°C (Median survival time [MST]: 15 days, range: 10–30 days) and 50% survived (MST: 28.5 days, range: 23–30 days) at 22°C (range 23–30 days). The most common clinical signs were injection site swelling, palpebral swelling, and lethargy. The heterophil/lymphocyte ratio at 22°C and interleukin-1 beta (IL1β) transcription at both 22°C and 28°C were significantly greater on days 9, 16, and 23 in FV3 challenged groups. Tumor necrosis factor alpha and interleukin-10 were transcribed at detectable levels, but did not display significant differences in mean relative transcription quantity over time. Overall, evidence indicates an over-robust immune response leading to death in the challenged turtles. FV3 remains a risk for captive and free-ranging chelonian populations, and insight to host/pathogen interaction through this model helps to elucidate the timing and intensity of the host response that contribute to mortality.

Endothelium modulates electrical field stimulation-induced contractions of Chelonoidis carbonaria aortic rings

The role of endothelium in the electrical-field stimulation (EFS)-induced contractions of Chelonoidis carbonaria aorta was investigated. Contractions were evaluated in the presence and absence of L-NAME (100 μM), tetrodotoxin (1 μM), phentolamine (10 and 100 μM), phenoxybenzamine (1 and 10 μM), prazosin (100 μM), idazoxan (100 μM), atropine (10 μM), D-tubocurarine (10 μM) or indomethacin (10 μM). EFS-induced contraction was also carried out in endothelium-denuded rings. EFS-induced contraction was investigated by the sandwich assay. Concentration curves to endothelin-1 (0.1-100 nM) and U46619 (0.001-100 μM) were also constructed to calculate both Emax and EC₅₀. EFS at 16 Hz contracted Chelonoidis aorta, which was almost abolished by the endothelium removal. The addition of L-NAME increased the EFS response (2.0 ± 0.4 and 8.3 ± 1.9 mN). In L-NAME treated aortic rings, tetrodotoxin did not change the EFS-response (5.1 ± 1.8 and 4.9 ± 1.7 mN). Indomethacin, atropine and d-tubucurarine also did not affect the EFS-response. Phentolamine at 10 μM did not change the EFS-induced contraction; however, at 100 μM, reduced it (3.9 ± 1 and 1.9 ± 0.3 mN). Prazosin and idazoxan did not change EFS-induced contractions. Phenoxybenzamine at 1 μM reduced by 76% (9.6 ± 3.4 and 2.3 ± 0.8 mN) and at 10 μM by 90% the EFS response. Immunohistochemistry identified tyrosine hydroxylase in the endothelium and brain, whereas S100 protein was found only in brain. In conclusion, endothelium modulates EFS-induced contractions in Chelonoidis aortic rings and this modulation may be due to endothelium-derived catecholamines, possibly dopamine.

Interaction of Epididymal Epithelia and their Secretions with Spermatozoa Supports Functional and Morphological Changes During Long-Term Storage in the Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

Post-testicular maturation of spermatozoa is crucial for attaining the morphological and functional capabilities needed for successful fertilization. Epididymal epithelia offer a favorable environment for spermatozoa that are stored long term in the turtle epididymis; however, sperm-epithelial interactions during storage, which are enormously important for sperm functional and morphological maturation, are still largely unknown in turtles. The present study examined the epididymis during the sperm-storage period (November-April) in the Chinese soft-shelled turtle (Pelodiscus sinensis). Light and transmission electron microscopy were used to determine the cellular features of each epididymal segment (caput, corpus, and cauda) and their epithelial interactions with the spermatozoa. Spermatozoa were mainly located in the lumena of caput, corpus, and cauda epididymides. Numerous spermatozoa were bound to apical surfaces of the epithelia, and several were even embedded in the epithelial cytoplasm of the caput and corpus epididymides. No embedded spermatozoa were found in the cauda epididymis. In all epididymal segments, principal and clear cells showed the synthetic activity, evidenced by a well-developed endoplasmic reticulum network and high and low electron-dense secretory materials, respectively. Principal and clear cells in the caput and corpus segments showed embedded spermatozoa in electron-dense secretions and in the lipid droplets within the cytoplasm. No lysosomes were observed around the embedded spermatozoa. The lumena of the caput and corpus segments showed few apocrine and low electron density secretions. In the lumen of the cauda epididymidis, different secretions, such as holocrine with low and high electron density and their fragmentation, apocrine, and dictyosome, were found and are summarized. Altogether, sperm physical interactions with secretions either in the cytoplasm of epithelium or in the lumen may support the viability, morphological maintenance, and transfer of various proteins involved in long-term sperm storage in the turtle. This interaction could help us to understand the mechanisms of long-term sperm storage and provide more insights into the reproductive strategies of turtle sperm preservation.

Non-essential toxic element (Cd, As, Hg and Pb) levels in muscle, liver and kidney of loggerhead sea turtles (Caretta caretta) stranded along the southwestern coasts of Tyrrhenian sea

Non-essential toxic metals are environmental pollutants that contaminate the marine ecosystem due to their extensive use and long-range transport (by rivers and air). Their presence into the environment is often linked to the human activity, with an expected bioaccumulation in the food chain. Within the marine animals, sea turtles may be considered as potential sentinel species for environmental assessment because of their long lifetime, habitat use and migratory nature. In this study, non-essential toxic metals in the coastal of Tyrrhenian Sea were monitored, during the 2017-2018 period, using the Mediterranean loggerhead sea turtle (Caretta caretta) as indicator species. The levels of Cadmium (Cd), Arsenic (As), Mercury (Hg) and Lead, (Pb) were determined in 30 turtles stranded in different locations along the coasts of Campania region of Southern Italy. After morphometric analysis, the non- essential toxic metal accumulation in loggerhead sea turtle muscle and organs have been measured analysing the total concentrations of metals in samples of liver, kidney, and muscle by Atomic Absorption Spectrophotometry (AAS) after microwave assisted digestion with nitric acid and hydrogen peroxide. The pattern of contaminants revealed a similar distribution for Pb and total mercury, that were not significantly high in all the analysed matrices. On the contrary, elevated concentrations of total As were found out in all matrices, mainly in muscle (25.7 mg/kg w.w.), and of Cd in liver (1.23 mg/kg w.w.) and kidney (6.82 mg/kg w.w.). These studies allow us to estimate the exposure degree to which these species are subjected.

Persistent organic pollutants in green sea turtles (Chelonia mydas) inhabiting two urbanized Southern California habitats

Within Southern California, east Pacific green sea turtles (Chelonia mydas) forage year-round, taking advantage of diverse food resources, including seagrass, marine algae, and invertebrates. Assessing persistent organic pollutants (POP) in green turtle aggregations in the Seal Beach National Wildlife Refuge (SBNWR, n = 17) and San Diego Bay (SDB, n = 25) can help quantify contamination risks for these populations. Blood plasma was analyzed for polychlorinated biphenyls (PCBs), organochlorinated pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs). PCBs and body size explained much of the separation of turtles by foraging aggregation in a principal component analysis. Turtles from SDB had significantly (p < 0.001) higher total PCBs than SBNWR turtles. Most PCBs detected in turtles were non-dioxin-like PCB congeners (153, 138, 99) that are associated with neurotoxicity. Recaptured turtles' POP levels changed significantly over time indicating significant variation in POP levels through time and space, even among adjacent foraging locations.

Accumulation of trace elements in leatherback turtle (Dermochelys coriacea) eggs from the south-western Caribbean indicates potential health risks to consumers

Trace metal and metalloid levels were measured in eggs of the NW Atlantic leatherback turtle (Dermochelys coriacea) from nesting grounds in the Bocas del Toro province, Panama, to infer exposure and associated risks to local communities. Samples were analyzed for a set of 26 essential and non-essential elements using inductively coupled plasma techniques. Median concentrations of Fe, Zn, As, Se and Sr in D. coriacea eggs were higher than previously reported for this species, which likely reflects differential contamination levels of specimens during foraging. The evaluation of non-carcinogenic human health risks from ingesting leatherback eggs has revealed potential deleterious effects due to high concentrations of As, Se and Sr for all examined age and gender groups, while Hg and Zn levels were above international standards for children. Hazard index (HI) values exceeded unity in all cases indicating serious health impacts related to possible additive effects of multiple metals co-occurring in the eggs. Our findings suggest that exposure to high (inorganic) As and Cr(VI) levels is associated with an increased carcinogenic risk, significantly exceeding the acceptable lifetime risk of 10^-6 for both adults and children. Despite some limitations, such as unclear As and Cr speciation, our results demonstrated that the ingestion of D. coriacea eggs poses considerable health risks to local communities, and their consumption should not exceed 3.4 × 10^-4 g (5.0 × 10^-6 eggs) kg BW d^-1. Resource managers and conservationists should focus their attention to human health effects as an alternative tool to address egg poaching and consumption.

Effects of cadmium on the gene transcription of the liver in the freshwater turtle (Chinemys reevesii)

This study investigated the related gene transcription of liver in freshwater turtle Chinemys reevesii exposed to cadmium (Cd). After acclimation, healthy turtles were selected for experiments. They were randomly divided into four experimental groups and each group had 5 animals. The turtles were treated with 0 mg/kg, 7.5 mg/kg, 15 mg/kg, and 30 mg/kg Cd chloride separately by intraperitoneal injection. Liver samples were collected for examination of the transcription of related genes at 2 weeks after Cd exposure. The transcription of mRNA of MT, SOD, CAT, PNKP, and GPX4 genes in turtle liver cells were analyzed. Results showed that Cd promoted MT mRNA transcription in turtle's liver at low dose (7.5 mg/kg) and inhibited MT mRNA transcription in turtle's liver at middle dose (15 mg/kg) and high dose (30 mg/kg). Cd inhibited the transcription of SOD, CAT, and PNKP mRNA in turtle's liver, and the inhibition was obvious at high dose (30 mg/kg). Cd promoted GPX4 mRNA transcription in turtle's liver, especially at low dose (7.5 mg/kg). In conclusion, Cd had different effects on the mRNA transcription of liver cells in the freshwater turtle Chinemys reevesii exposed to Cd.

Maternal Transfer of Persistent Organic Pollutants to Sea Turtle Eggs: A Meta-Analysis Addressing Knowledge and Data Gaps Toward an Improved Synthesis of Research Outputs

Maternal transfer of persistent organic pollutants (POPs) confronts developing embryos with a pollution legacy and poses conservation concerns due to its potential impacts unto subsequent generations. We conducted a systematic review focusing on: 1) processes of POP maternal transfer, 2) challenges and opportunities to synthesizing current knowledge on POP concentrations in eggs, and 3) a meta-analysis of patterns in current egg pollution data. Results suggest selective maternal transfer of individual compounds. These relate to biological factors such as the foraging and remigration behavior, and to the selective mobilization of POPs during vitellogenesis, such as increased diffusion limitation for lipophilic POPs and slower release and higher reabsorption of apolar POPs. A key gap relates to knowledge of further selective toxicokinetics during embryonic development, as research to date has mainly focused on initial uptake into eggs. Challenges in the synthesis of current data on egg contamination profiles relate to methodological differences, varying analytical approaches, restricted data access, and reporting transparency among studies. To increase opportunities in the use of current data, we propose best practice guidelines, and synthesize a database on POP concentrations within sea turtle eggs. The meta-analysis revealed a geographical and taxonomic bias on the West Atlantic Ocean, including the Gulf of Mexico and Caribbean Sea, with most studies conducted on green turtles. Concentrations of POPs show temporal patterns related to trends in usage, production, release, and persistence in the environment, often with regional patterns. The trophic level has the potential to influence POP patterns with higher concentrations in loggerheads compared to other species, but this is confounded by temporal and geographic trends. We argue for more mechanistically process-focused and methodologically comparable research. Environ Toxicol Chem 2019;39:9-29. © 2019 SETAC.

Role for androgens in determination of ovarian fate in the common snapping turtle, Chelydra serpentina

Sex steroids are involved in sex determination in almost all vertebrates, including species with temperature-dependent sex determination (TSD). It is well established that aromatase and estrogens are involved in ovary determination in TSD species. In contrast, the role of non-aromatizable androgens in TSD is less clear. In this study, we used dihydrotestosterone (DHT) and an antagonist of the mammalian androgen receptor (flutamide) to examine the impact of androgens on sex determination in the snapping turtle. We incubated eggs at a male-producing temperature and treated embryos with drug delivery vehicle (5 L ethanol), DHT in vehicle, or flutamide in vehicle during the sex-determining period. We then measured expression of markers for ovarian and testicular development and genes involved in steroidogenesis. A subset of embryos and hatchlings were collected for histological analysis of gonad differentiation and sex determination. DHT and flutamide both induced ovarian development: 100% of vehicle-treated hatchlings had testes, while 60% of DHT-treated and 32% flutamide-treated hatchlings had ovaries. DHT and flutamide treatments also had feminizing effects on gene expression patterns and the structure of embryonic gonads. DHT treatment increased expression of FoxL2, androgen receptor, aromatase and several steroidogenic genes. Flutamide produced a similar, but weaker, pattern of gene expression. Genes involved in testis development (Sox9 and Amh) were influenced by flutamide treatment. Our findings support the hypothesis that androgens and the androgen receptor are involved in ovary determination in the common snapping turtle.

Polycyclic aromatic hydrocarbons (PAHs) and some biomarkers in the green sea turtles (Chelonia mydas)

Selected blood biochemical parameters (Glutathione S transferase: GST; Alanine aminotransferase: ALT; Aspartate aminotransferase: AST; Lactate dehydrogenase: LD and glucose) and polycyclic aromatic hydrocarbons (PAHs) were measured in blood samples from 18 green sea turtles (Chelonia mydas) from the Iranian coastline on the northern shore of the Sea of Oman. Mean total PAH concentration in the blood samples was 17.802 ± 1.006 ng/gdw. The study found no significant correlation between blood biochemical parameters and PAHs (p > 0.01), however significant correlations were found between total PAHs and GST activity (p < 0.01). The GST activity measured in this study was useful as a first investigation into the biological effects of PAH pollution as well as in determining the bioavailability of pollution. The results suggest that PAHs might be a factor influencing a reduction in green sea turtle egg fertilization and hatching success. Further study is needed concerning the effects of PAHs and other pollutants on green sea turtles, and specifically on the potential impact on the fetal development of green sea turtles.

Tools for non-invasive sampling of metal accumulation and its effects in Mediterranean pond turtle populations inhabiting mining areas

Among reptiles, freshwater turtle species have high potential for metal accumulation because of their long lifespan or their aquatic and terrestrial habits. In order to monitor metal bioaccumulation, determine potential toxic effects, and investigate tools for non-invasive metal sampling in reptiles, we studied lead (Pb) and mercury (Hg) accumulation in Mediterranean pond turtles (Mauremys leprosa) inhabiting two former mining areas, one of them with high environmental concentrations of Pb (Sierra Madrona-Alcudia Valley district) and the other one with high environmental concentrations of Hg (Almadén district). Individuals from the Pb mining area showed mean blood concentrations (i.e. 5.59 μg Pb/g dry weight, d.w.) that were higher than those measured in other populations. Blood Hg concentrations were highest (8.83 μg Hg/g d.w.) in the site close to the former Hg mines, whereas blood Hg concentrations in terrapins from another site of Almadén district, located ∼28 km downstream, were not different from locations at the non-mining area. Animals from the Pb-contaminated site showed evidence of oxidative stress, whereas those from the Hg-contaminated site showed increased activity of the antioxidant enzyme glutathione peroxidase, as well as reduced circulating levels of the main endogenous antioxidant peptide, glutathione. Concentrations measured in feces and carapace scutes were useful indicators to monitor blood concentrations of Pb, but not of Hg. Our results provide evidence of the usefulness of freshwater turtles as sentinels of chronic metal pollution, and validate non-invasive tools to advance Pb monitoring in reptiles.