Establishment, characterization, and toxicological application of loggerhead sea turtle (Caretta caretta) primary skin fibroblast cell cultures

Primary Cell Culture as a Model System for Evolutionary Molecular Physiology

Primary cell culture is a powerful model system to address fundamental questions about organismal physiology at the cellular level, especially for species that are difficult, or impossible, to study under natural or semi-natural conditions. Due to their ease of use, primary fibroblast cultures are the dominant model system, but studies using both somatic and germ cells are also common. Using these models, genome evolution and phylogenetic relationships, the molecular and biochemical basis of differential longevities among species, and the physiological consequences of life history evolution have been studied in depth. With the advent of new technologies such as gene editing and the generation of induced pluripotent stem cells (iPSC), the field of molecular evolutionary physiology will continue to expand using both descriptive and experimental approaches.

Establishment and Characterization of a Primary Fibroblast Cell Culture from the Amazonian Manatee (Trichechus inunguis)

The vulnerable status of the Amazon manatee, Trichechus inunguis, indicates the need to seek measures to guarantee its conservation. In this context, the cultivation of cells in vitro is a strategy that should at least guarantee the preservation of their genetic material. Thus, we established for the first time a primary culture of Amazonian manatee fibroblasts (TINsf) from a skin biopsy of a young male. Karyotypic analysis of the 3rd, 7th, and 12th passages confirmed the taxonomic identity of the species T. inunguis (2n = 56/NF = 92) and indicated that this culture presents genomic stability. Gene and protein expression of vimentin at the 13th passage show the predominant presence of fibroblasts in TINsf. To test the cell line's responsiveness to materials and demonstrate a possible application of this culture, it was exposed to andiroba seed oil (ASO), and its viability and proliferative capacity were evaluated. ASO demonstrated toxic effects at the highest concentrations and longest exposure times tested, reproducing results observed in human cultures, indicating the applicability of TINsf in toxicological and biotechnological studies. After cryopreservation, the TINsf line maintained its proliferative potential, indicating the establishment of a new culture available for future studies.

The initial steps toward the formation of somatic tissue banks and cell cultures derived from captive Antillean manatee (Trichechus manatus manatus) skin biopsies

The declining population of the Antillean manatee caused by ecosystem degradation and rising pollution has prompted interest in developing conservation strategies for this species. Given this scenario, somatic tissue banks are important tools for acquiring knowledge about the species, as well as for obtaining somatic cells for biotechnological and ecotoxicological applications. Therefore, we aimed to assess the effects of slow freezing (SF) and solid-surface vitrification (SSV) of the dermis of captive Antillean manatees on the histology and ultrastructure of the tissue and cell viability in culture. While the SSV did not change the dermis thickness, the SF maintained the tissue proliferative potential, assessed by the nucleolar organizer region area, similar to noncryopreserved tissues. Moreover, both techniques reduced the number of fibroblasts and increased the percentage of collagen fibers. Nevertheless, only tissues cryopreserved with SF and noncryopreserved tissues were able to produce cells after in vitro culture. Although SF did not alter cell viability and proliferative activity, cells derived from cryopreserved tissues showed decreased metabolism, altered apoptosis, increased levels of reactive oxygen species, and mitochondrial membrane potential compared to cells from noncryopreserved tissues. In summary, we demonstrated for the first time that Antillean manatee somatic tissues can be cryopreserved by SF, and cells can be obtained after in vitro culture. Improvements in cryopreservation conditions, especially vitrification, of somatic samples are needed to increase the quality of somatic tissue banks in this species.

Assessment of polycyclic aromatic hydrocarbons (PAHs) in mediterranean top marine predators stranded in SE Spain

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants. Although they are not bioaccumulated in vertebrates, chronic exposures might still derive on serious toxic effects. We studied concentrations of 16 reference PAHs on blubber of two dolphin species (striped dolphin, n = 34; and bottlenose dolphin, n = 8) and one marine turtle (loggerhead turtle, n = 23) from the Mediterranean waters of SE Spain, an important or potential breeding area for these and other related species. Σ16 PAHs concentrations were relatively similar between the three species, but they were in the lower range in comparison to worldwide data. Of the six PAHs detected, fluoranthene was the only high molecular weight (HMW) PAH, so low molecular weight (LMW) PAHs predominated. Naphthalene and phenanthrene were invariably those PAHs with higher detection rates as well as those with higher concentrations. In accordance with the literature, sex and length did not have significant influence on PAHs concentrations, probably due to high metabolization rates which prevent for observation of such patterns. Despite LMW PAHs are considered less toxic, we cannot dismiss toxic effects. This is the first work assessing PAHs concentrations in cetaceans and sea turtles from the SE Spain, which could serve as the baseline for future research.

Dose metric evaluation of a cell-based bioassay for assessing the toxicity of metals to Dugong dugon: Effect of metal-media interactions on exposure concentrations

Cell-based toxicity testing has emerged as a useful tool in (eco)toxicological research, allowing the ethical assessment of the effects of contaminants such as trace metals on marine megafauna. However, metal interactions with various dissolved ligands in the microplate environment may influence the effective exposure concentrations. Hence, the cells are not exposed to the nominal concentrations within the test system. This study aimed to establish and evaluate the effectiveness of cell-based bioassays for investigating the toxicity of selected metals in dugongs through the following objectives: (1) measure the cytotoxic potential of cadmium (Cd²⁺), and chromium (Cr⁶⁺) to dugong skin cell cultures, (2) investigate the interactions between media constituents and selected trace metals in cell-based bioassays, and (3) evaluate the risk to a free-ranging population of dugong based on effect values. Chromium was the most toxic of the metals tested (EC₅₀ = 1.14 µM), followed by Cd (EC₅₀ = 6.35 µM). Assessment of ultrafiltered (< 3 kDa) exposure media showed that 1% and 92.5% of Cr and Cd were associated with larger organic components of the media. Further, the binding of Cd to media constituents was calculated to underestimate Cd toxicity in cell-based assays by an order of magnitude. This understanding of metal partitioning in cell-based bioassays provides a more accurate method for assessing toxicity in cell-based bioassays. In addition, this study illustrated that dugong cells are more sensitive to Cr and Cd than other marine wildlife species. The chemical risk assessment found the dugong population in Moreton Bay to be at high risk from Cd exposure.

Fibroblasts as an experimental model system for the study of comparative physiology

Mechanistic evaluations of processes that underlie organism-level physiology often require reductionist approaches. Dermal fibroblasts offer one such approach. These cells are easily obtained from minimally invasive skin biopsy, making them appropriate for the study of protected and/or logistically challenging species. Cell culture approaches permit extensive and fine-scale sampling regimes as well as gene manipulation techniques that are not feasible in vivo. Fibroblast isolation and culture protocols are outlined here for primary cells, and the benefits and drawbacks of immortalization are discussed. We show examples of physiological metrics that can be used to characterize primary cells (oxygen consumption, translation, proliferation) and readouts that can be informative in understanding cell-level responses to environmental stress (lactate production, heat shock protein induction). Importantly, fibroblasts may display fidelity to whole animal physiological phenotypes, facilitating their study. Fibroblasts from Antarctic Weddell seals show greater resilience to low temperatures and hypoxia exposure than fibroblasts from humans or rats. Fibroblast oxygen consumption rates are not affected by temperature stress in the heat-tolerant camel, whereas similar temperature exposures depress mitochondrial metabolism in fibroblasts from rhinoceros. Finally, dermal fibroblasts from a hibernator, the meadow jumping mouse, better resist experimental cooling than a fibroblast line from the laboratory mouse, with the hibernator demonstrating a greater maintenance of homeostatic processes such as protein translation. These results exemplify the parallels that can be drawn between fibroblast physiology and expectations in vivo, and provide evidence for the power of fibroblasts as a model system to understand comparative physiology and biomedicine.

An established kidney cell line from humpback grouper (Cromileptes altivelis) and its susceptibility to bacteria and heavy metals

Humpback grouper (Cromileptes altivelis), one kind of commercial fish with considerable economic value, has been recognized as a promising candidate for mariculture. In the wake of the development of aquaculture industry, the breeding density of C. altivelis has increased gradually, which gave rise to the occurrence of various pathogenic diseases. In our research, we established a new kidney cell line (designated as CAK) from humpback grouper and evaluated its susceptibility to bacteria and heavy metals. The results of our study showed that the optimal growth temperature was 26 °C, and optimal medium was L-15 supplemented with 20% fetal bovine serum (FBS). The sequencing of 18S rRNA gene indicated that CAK cell line was derived from C. altivelis. Chromosome analysis showed that the number of chromosome in CAK was 48. After being transfected of pEGFP-N3 plasmid, high transfection efficiency of CAK was observed, suggesting the potential to be used for the study of foreign functional genes. Moreover, the bacterial susceptibility results revealed that CAK cells were sensitive to Vibrio harveyi and Edwardsiella tarda, especially V. harveyi. Meanwhile, three heavy metals (Hg, Cu, and Cd) had toxic effects on the CAK cells with a dose-dependent manner. To sum up, the CAK cell line might be an ideal tool in vitro for analyzing the function of exogenous genes, bacterial susceptibility, and toxicity assay of heavy metals.

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.

Differences in marine megafauna in vitro sensitivity highlights the need for species-specific chemical risk assessments

Sea turtles, dolphins and dugongs can be exposed to large mixtures of contaminants due to the proximity of foraging locations to anthropogenic inputs. Differences in accumulation and effect result in differences of chemical risk to these species. However, little is known about the effect of contaminants in marine wildlife. Cell-based, or in vitro, exposure experiments offer an ethical alternative to investigate the effect of contaminants in wildlife. Data from in vitro studies can then be placed in an environmental context, by using screening risk assessments, comparing effect data with accumulation data from the literature, to identify risk to populations of marine wildlife. Cytotoxicity of Cr⁶⁺, Cd²⁺, Hg²⁺, 4,4'-DDE, and PFNA were investigated in primary skin fibroblasts of green turtles, loggerhead turtles, hawksbill turtles, dugongs, Burrunan dolphins, and common bottlenose dolphins. The general order of toxicity for all species was Hg²⁺> Cr⁶⁺ > Cd²⁺> 4,4'-DDE > PFNA, and significant differences in cytotoxicity were found between species for Cr⁶⁺, Cd²⁺ and PFNA. For Cd²⁺, in particular, cells from turtle species were less sensitive than mammalian species, and dugong cells were by far the most sensitive. The results from the cytotoxicity assay were then used in combination with published data on tissue contaminant concentrations to calculate risk quotients for identifying populations of each species most at risk from these chemicals. Cr, Cd and Hg were identified as posing risk in all six species. Dugongs were particularly at risk from Cd accumulation and dolphin species were particularly at risk from Hg accumulation. These results demonstrate the importance of using species-specific effect and accumulation data for developing chemical risk assessments and can be used to inform managers of priority contaminants, species, or populations. Development of additional in vitro endpoints, and improving links between in vitro and in vivo effects, would further improve this approach to understanding chemical risk in marine megafauna.

Systematic review of reptile reproductive toxicology to inform future research directions on endangered or threatened species, such as sea turtles

Threatened or endangered reptiles, such as sea turtles, are generally understudied within the field of wildlife toxicology, with even fewer studies on how contaminants affect threatened species reproduction. This paper aimed to better inform threatened species conservation by systematically and quantitatively reviewing available research on the reproductive toxicology of all reptiles, threatened and non-threatened. This review found 178 studies that matched our search criteria. These papers were categorized into location conducted, taxa studied, species studied, effects found, and chemicals investigated. The most studied taxa were turtles (n = 87 studies, 49%), alligators/crocodiles (n = 54, 30%), and lizards (n = 37, 21%). Maternal transfer, sex steroid alterations, sex reversal, altered sexual development, developmental abnormalities, and egg contamination were the most common effects found across all reptile taxa, providing guidance for avenues of research into threatened species. Maternal transfer of contaminants was found across all taxa, and taking into account the foraging behavior of sea turtles, could help elucidate differences in maternal transfer seen at nesting beaches. Sex steroid alterations were a common effect found with contaminant exposure, indicating the potential to use sex steroids as biomarkers along with traditional biomarkers such as vitellogenin. Sex reversal through chemical exposure was commonly found among species that exhibit temperature dependent sex determination, indicating the potential for both environmental pollution and climate change to disrupt population dynamics of many reptile species, including sea turtles. Few studies used in vitro, DNA, or molecular methodologies, indicating the need for more research using high-throughput, non-invasive, and cost-effective tools for threatened species research. The prevalence of developmental abnormalities and altered sexual development and function indicates the need to further study how anthropogenic pollutants affect reproductive output in threatened reptiles.

Combining analytical and in vitro techniques for comprehensive assessments of chemical exposure and effect in green sea turtles (Chelonia mydas)

Sea turtle populations foraging in coastal areas adjacent to human activity can be exposed to numerous chemical contaminants for long periods of time. For trace elements, well-developed, sensitive and inexpensive analytical techniques remain the most effective method for assessing exposure in sea turtles. However, there are many thousands more organic contaminants present in sea turtles, often at low levels as complex mixtures. Recently developed species-specific in vitro bioassays provide an effective means to identify the presence, and effect of, organic chemicals in sea turtles. This study used a combination of chemical analysis and effects-based bioassays to provide complementary information on chemical exposure and effects for three green turtle foraging populations (Chelonia mydas) in southern Queensland, Australia. Blood was collected from foraging sub-adult green turtles captured in Moreton Bay, Hervey Bay, and Port Curtis. Twenty-six trace elements were measured in whole blood using ICP-MS. Organic contaminants in turtle blood were extracted via QuEChERS and applied to primary green turtle skin fibroblast cell in vitro assays for two toxicity endpoints; cytotoxicity and oxidative stress. The trace element analysis and bioassay results indicated site-specific differences between foraging populations. In particular, turtles from Moreton Bay, a heavily populated coastal embayment, had pronounced cytotoxicity and oxidative stress from organic blood extracts, and elevated concentrations of Cs, Ag, and Zn relative to the other sites. Incorporating traditional chemical analysis with novel effects-based methods can provide a comprehensive assessment of chemical risk in sea turtle populations, contributing to the conservation and management of these threatened species.

Review of petroleum toxicity in marine reptiles

Worldwide petroleum exploration and transportation continue to impact the health of the marine environment through both catastrophic and chronic spillage. Of the impacted fauna, marine reptiles are often overlooked. While marine reptiles are sensitive to xenobiotics, there is a paucity of petroleum toxicity data for these specialized fauna in peer reviewed literature. Here we review the known impacts of petroleum spillage to marine reptiles, specifically to marine turtles and iguanas with an emphasis on physiology and fitness related toxicological effects. Secondly, we recommend standardized toxicity testing on surrogate species to elucidate the mechanisms by which petroleum related mortalities occur in the field following catastrophic spillage and to better link physiological and fitness related endpoints. Finally, we propose that marine reptiles could serve as sentinel species for marine ecosystem monitoring in the case of petroleum spillage. Comprehensive petroleum toxicity data on marine reptiles is needed in order to serve as a foundation for future research with newer, unconventional crude oils of unknown toxicity such as diluted bitumen.

Transcriptional Analyses of Acute Exposure to Methylmercury on Erythrocytes of Loggerhead Sea Turtle

To understand changes in enzyme activity and gene expression as biomarkers of exposure to methylmercury, we exposed loggerhead turtle erythrocytes (RBCs) to concentrations of 0, 1, and 5 mg L-1 of MeHg and de novo transcriptome were assembled using RNA-seq. The analysis of differentially expressed genes (DEGs) indicated that 79 unique genes were dysregulated (39 upregulated and 44 downregulated genes). The results showed that MeHg altered gene expression patterns as a response to the cellular stress produced, reflected in cell cycle regulation, lysosomal activity, autophagy, calcium regulation, mitochondrial regulation, apoptosis, and regulation of transcription and translation. The analysis of DEGs showed a low response of the antioxidant machinery to MeHg, evidenced by the fact that genes of early response to oxidative stress were not dysregulated. The RBCs maintained a constitutive expression of proteins that represented a good part of the defense against reactive oxygen species (ROS) induced by MeHg.

Development and application of species-specific cell-based bioassays to assess toxicity in green sea turtles

Despite the detection of a wide range of contaminants in the blood of green turtle populations foraging in three locations of northern Queensland - Upstart Bay, Cleveland Bay and the Howick Group of Reefs, little is known about the effects of these contaminants on turtle health. Newly developed cell-based bioassays using green turtle primary cell cultures provide an ethical, reproducible, and high-throughput method for assessing the risk of chemical exposure sea turtles. In this project, the toxicity of six priority metals (Mn, Co, Mo, As, Sb, Cu) and blood extracts from foraging turtles were tested in two bioassays adapted to green turtle primary skin and liver cells. Cytotoxicity of metals and blood extracts was measured in primary skin fibroblast cells using a resazurin assay. Glutathione-S-transferase (GST) activity was measured in primary skin fibroblasts and primary liver epithelial cells following exposure to metals and blood extracts. Arsenic, molybdenum, cobalt and copper were found to be cytotoxic to green turtle skin cells. Only manganese, cobalt and copper were found to alter GST activity, predominantly in skin cells, indicating a higher sensitivity of green turtle skin cells compared to liver cells. Effect concentrations of metals in both bioassays were above concentrations found in turtle blood. Turtle blood extracts from the three foraging grounds showed differences in cytotoxicity and GST activity. In both assays, blood extracts of turtles from Upstart Bay were the most toxic, followed by those from Cleveland Bay, then the Howick Reefs, suggesting turtles from Upstart Bay and Cleveland Bay may be at risk from current concentrations of organic contaminants. This study demonstrates that species-specific cell-based bioassays can be used effectively to assess chemical risk in sea turtles and their foraging grounds, and could be applied to assess chemical risk in other marine wildlife.

Disease risk analysis in sea turtles: A baseline study to inform conservation efforts

The impact of a range of different threats has resulted in the listing of six out of seven sea turtle species on the IUCN Red List of endangered species. Disease risk analysis (DRA) tools are designed to provide objective, repeatable and documented assessment of the disease risks for a population and measures to reduce these risks through management options. To the best of our knowledge, DRAs have not previously been published for sea turtles, although disease is reported to contribute to sea turtle population decline. Here, a comprehensive list of health hazards is provided for all seven species of sea turtles. The possible risk these hazards pose to the health of sea turtles were assessed and "One Health" aspects of interacting with sea turtles were also investigated. The risk assessment was undertaken in collaboration with more than 30 experts in the field including veterinarians, microbiologists, social scientists, epidemiologists and stakeholders, in the form of two international workshops and one local workshop. The general finding of the DRA was the distinct lack of knowledge regarding a link between the presence of pathogens and diseases manifestation in sea turtles. A higher rate of disease in immunocompromised individuals was repeatedly reported and a possible link between immunosuppression and environmental contaminants as a result of anthropogenic influences was suggested. Society based conservation initiatives and as a result the cultural and social aspect of interacting with sea turtles appeared to need more attention and research. A risk management workshop was carried out to acquire the insights of local policy makers about management options for the risks relevant to Queensland and the options were evaluated considering their feasibility and effectiveness. The sea turtle DRA presented here, is a structured guide for future risk assessments to be used in specific scenarios such as translocation and head-starting programs.

Establishment and characterization of a fibroblast cell line from postmortem skin of an adult Chinese muntjac (Muntiacus reevesi)

Isolation and culture of somatic cells from animals especially endangered species have raised great concerns as it is being an effective and convenient way to preserve genetic materials for future studies. As a species native to China, Chinese muntjac (Muntiacus reevesi) is listed as a beneficial species with economic and scientific research values. To our knowledge, however, there have been no published reports on somatic cell preservation of this species to date. To conserve biological resources for sustainability of Chinese muntjacs' genetic diversity, we established a fibroblast cell line from the postmortem ear skin of an adult male Chinese muntjac. The cultured cells were adherent to the plastic and showed an elongated, thin, and spindle-like shape. Moreover, they were FSP1- and VIM-positive characterizing them to be fibroblastic. No microorganisms (bacteria, fungi, or mycoplasmas) were detected throughout the whole study. Cell viability was high although it declined somehow after passaging. The population doubling time was 21.28 h according to the growth curve. Chromosome analysis revealed that the established fibroblast cell line contained 23 pairs of chromosomes, one pair of which was sex chromosomes (XY). Mitochondrial cytochrome C oxidase I gene of cultured cells shared 98.32% identity with those of Muntiacus reevesi registered in GenBank, which verified the cell line was derived from Muntiacus reevesi. In conclusion, we propagated and characterized fibroblast cells from a Chinese muntjac. We believe that this somatic cell line could facilitate animal cloning and breeding studies and become a useful in vitro model to address genetic questions.

Towards the development of standardised sea turtle primary cell cultures for toxicity testing

Chemical contaminants are known to accumulate in marine megafauna globally, but little is known about how this impacts animal health. In vitro assays offer an ethical, reproducible and cost-effective alternative to live animal toxicity testing on large, long-lived or threatened species, such as sea turtles. However, using a cell culture from a single animal raise the question of whether the toxicity observed adequately represents the toxicity in that species. This study examined variation in the cytotoxic response of primary skin fibroblasts established from seven green (Chelonia mydas) and five loggerhead (Caretta caretta) sea turtles. Cell viability using resazurin dye was examined in response to exposure to five contaminants. The variation in cytotoxicity was generally low (within a factor of five) for both independent analyses of the same cell culture, and cell cultures from different individuals. This low within and between cell culture variation indicates that primary sea turtle cell cultures can provide a suitable approach to understanding toxicity in sea turtles. In addition, green and loggerhead turtle cells showed similar toxicity to the compounds tested, indicating that only subtle differences in chemical sensitivity may exist between sea turtle species. This study provides a framework for using species-specific cell cultures in future toxicological studies on sea turtles. Although in vivo studies are the gold standard for toxicological studies and species-specific risk assessments, the development of in vitro tools can provide important information when in vivo studies are not possible or practical. For large, endangered species such as sea turtles that are exposed to, and accumulate, a large number of contaminants, using validated cell cultures may facilitate the rapid assessment of chemical risk to these animals.

Cytotoxicity of organic and inorganic compounds to primary cell cultures established from internal tissues of Chelonia mydas

Chemical contaminants have been found in the tissues of sea turtles from all over the world; however, very little is known about the effects. Recently, in vitro alternatives to live animal testing have been applied to sea turtles due to their ethical and practical benefits. While primary skin fibroblasts have been established for several species of sea turtle, cells from internal organs are lacking, though they may be more relevant due to the well documented accumulation of contaminants within internal tissues. This study established primary cell cultures from the small intestine, heart, liver, ovary and skin of green turtles (Chelonia mydas). Cells were exposed to ten contaminants typically found in sea turtles to examine potential variations in sensitivity among cells established from different organs. Differences between cells established from different animals were also examined, including a comparison of cells established from a turtle with fibropapillomatosis (FP) and healthy turtles. Loggerhead (Caretta caretta) primary skin cells were also included for species comparisons. Significant differences were found between the organ types, with liver and heart being the least sensitive, and skin being the most sensitive. Overall, variation between the organ types was low. Primary skin fibroblasts may be a suitable and representative cell type for in vitro turtle toxicology research, as it is relatively easy to obtain from healthy live animals. Skin cultures provide a more sensitive indication of effect, and could be used as an early warning of the potential effects of chemical contamination. Some species differences were found but no differences were found between cell cultures from an FP turtle and healthy turtles. When EC₅₀ values were compared to accumulation values from the literature, inorganic contaminants, such as Zn, Cd, Cr, Hg, and Cu were identified as posing a potential risk to sea turtle populations around the world.

Gene expression profiles of putative biomarkers in juvenile loggerhead sea turtles (Caretta caretta) exposed to polycyclic aromatic hydrocarbons

There is evidence that polycyclic aromatic hydrocarbons (PAHs) are consistently the predominant organic contaminants in concentration found in loggerhead sea turtles (Caretta caretta) from the North and Central Adriatic Sea. Hence this study investigates the PAH toxicity to loggerheads by using a particular set of genes [i.e. CYP1B, CAT, GPX, GSTT1, SOD3, DNMT1, Epoxide hydrolase 1 (EPHX1), Poly (ADP-ribose) polymerase 1 (PARP1), Lamin-A/C isoform 3 (LMNA), Talin 1 (TLN1), Annexin A1 (ANXA1)] whose altered expression is potentially dependent on and specific for the PAH-related mechanism of action. Twenty healthy juvenile loggerheads were thus divided into high and low exposure groups (mean of ΣPAHs: 80.34 ng mL^-1 vs. 8.84 ng mL^-1, P < 0.0001) according to the median split of ΣPAHs. Interestingly, we found that the whole blood mRNA levels of each gene biomarker tested were significantly increased in high PAH-exposed turtles thus proving to be useful for the biological monitoring of PAH toxicity and hematotoxicity in sea turtles.

Primary green turtle (Chelonia mydas) skin fibroblasts as an in vitro model for assessing genotoxicity and oxidative stress

Little is known about the effects of contaminants that accumulate in sea turtles. When in vivo exposure studies have ethical and logistical barriers, as is the case with sea turtles, in vitro tools can provide important information on the effects of contaminants. Several in vitro studies have assessed cytotoxicity of contaminants to sea turtles cells, however to gain a more refined mechanistic understanding of the effects of contaminants, sub-lethal effects also require investigation. Considering the complex mixture of contaminants that sea turtles are potentially exposed to, high throughput testing methods are necessary so that a large number of contaminants (and mixtures) can be rapidly tested. This study examined oxidative stress (reactive oxygen species production) and genotoxicity (micronucleus formation) in primary green turtle skin fibroblasts in response to 16 organic and inorganic contaminants found in coastal environments. Significant induction of oxidative stress was found with Cu, Co, Cr, and Hg. Significant effects on genotoxicity were found with Cu, Co, Cr, Hg, Pb and metolachlor. Effect concentrations from the bioassays were used in a simple risk assessment of turtles worldwide using accumulation values from the literature to identify populations at risk. Cu, Co, Cr and Hg were identified as posing the biggest threat to sea turtles. This study demonstrated the validity of using primary turtle cell cultures in the assessment of risk associated with a large number of contaminants using a high-throughput toxicity testing format.

Intracellular toxicity exerted by PCBs and role of VBNC bacterial strains in biodegradation

Polychlorinated biphenyls (PCBs) are xenobiotic compounds that persists in the environment for long-term, though its productivity is banned. Abatement of the pollutants have become laborious due to it's recalcitrant nature in the environment leading to toxic effects in humans and other living beings. Biphenyl degrading bacteria co-metabolically degrade low chlorinated PCBs using the active metabolic pathway. bph operon possess different genetic arrangements in gram positive and gram negative bacteria. The binding ability of the genes and the active sites were determined by PCB docking studies. The active site of bphA gene with conserved amino acid residues determines the substrate specificity and biodegradability. Accumulation of toxic intermediates alters cellular behaviour, biomass production and downturn the metabolic activity. Several bacteria in the environment attain unculturable state which is viable and metabolically active but not cultivable (VBNC). Resuscitation-promoting factor (Rpf) and Rpf homologous protein retrieve the culturability of the so far uncultured bacteria. Recovery of this adaptive mechanism against various physical and chemical stressors make a headway in understanding the functionality of both environmental and medically important unculturable bacteria. Thus, this paper review about the general aspects of PCBs, cellular toxicity exerted by PCBs, role of unculturable bacterial strains in biodegradation, genes involved and degradation pathways. It is suggested to extrapolate the research findings on extracellular organic matters produced in culture supernatant of VBNC thus transforming VBNC to culturable state.

Discovery of an Australian Chelonia mydas papillomavirus via green turtle primary cell culture and qPCR

The number of reptilian viruses detected are continuously increasing due to improvements and developments of new diagnostic techniques. In this case we used primary cell culture and qPCR to describe the first Australian Chelonia mydas papillomavirus. Commercial chelonian cell lines are limited to one cell line from a terrestrial turtle (Terrapene Carolina). To establish primary cultures from green turtles (Chelonia mydas), turtle eggs were collected from Heron Island, Queensland, Australia. From day 35 of incubation at 29°, the embryos were harvested to establish primary cultures. The primary cell cultures were grown in Dulbecco's Modified Eagle Medium, 90% and foetal bovine serum, 10%. The cells became uniformly fibroblastic-shaped after 15 passages. The growth rate resembled that of cells originating from other cold-blooded animals and the average doubling time was ∼5 days from the 20th passage. Karyotyping and molecular analysis of mitochondrial DNA D-loop gene were carried out for cell authentication. The primary cell cultures were screened to exclude mycoplasma contamination. Two primary cell lineages were found to be susceptible to Bohle iridovirus. The primary cell cultures were used to screen samples from green turtles foraging along the East Coast of Queensland for the presence of viruses. Homogenates from eight skin tumour samples caused cytopathic effects and were confirmed by qPCR to be infected with papillomavirus.

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).

Reprint of: CYP1A protein expression and catalytic activity in double-crested cormorants experimentally exposed to Deepwater Horizon Mississippi Canyon 252 oil

Double-crested cormorants (Phalacrocorax auritus, DCCO) were orally exposed to Deepwater Horizon Mississippi Canyon 252 (DWH) oil to investigate oil-induced toxicological impacts. Livers were collected for multiple analyses including cytochrome P4501A (CYP1A) enzymatic activity and protein expression. CYP1A enzymatic activity was measured by alkoxyresorufin O-dealkylase (AROD) assays. Activities specific to the O-dealkylation of four resorufin ethers are reported: benzyloxyresorufin O-debenzylase (BROD), ethoxyresorufin O-deethylase (EROD), methoxyresorufin O-demethylase (MROD), and pentoxyresorufin O-depentylase (PROD). CYP1A protein expression was measured by western blot analysis with a CYP1A1 mouse monoclonal antibody. In study 1, hepatic BROD, EROD, and PROD activities were significantly induced in DCCO orally exposed to 20ml/kg body weight (bw) oil as a single dose or daily for 5 days. Western blot analysis revealed hepatic CYP1A protein induction in both treatment groups. In study 2 (5ml/kg bw oil or 10ml/kg bw oil, 21day exposure), all four hepatic ARODs were significantly induced. Western blots showed an increase in hepatic CYP1A expression in both treatment groups with a significant induction in birds exposed to 10ml/kg oil. Significant correlations were detected among all 4 AROD activities in both studies and between CYP1A protein expression and both MROD and PROD activities in study 2. EROD activity was highest for both treatment groups in both studies while BROD activity had the greatest fold-induction. While PROD activity values were consistently low, the fold-induction was high, usually 2nd highest to BROD activity. The observed induced AROD profiles detected in the present studies suggest both CYP1A4/1A5 DCCO isoforms are being induced after MC252 oil ingestion. A review of the literature on avian CYP1A AROD activity levels and protein expression after exposure to CYP1A inducers highlights the need for species-specific studies to accurately evaluate avian exposure to oil.

Toxic elements and associations with hematology, plasma biochemistry, and protein electrophoresis in nesting loggerhead sea turtles (Caretta caretta) from Casey Key, Florida

Toxic elements (arsenic, cadmium, lead, mercury, selenium, thallium) are a group of contaminants that are known to elicit developmental, reproductive, general health, and immune system effects in reptiles, even at low concentrations. Reptiles, including marine turtles, are susceptible to accumulation of toxic elements due to their long life span, low metabolic rate, and highly efficient conversion of prey into biomass. The objectives of this study were to (1) document concentrations of arsenic, cadmium, lead, mercury, selenium, and thallium in whole blood and keratin from nesting loggerhead sea turtles (Caretta caretta) from Casey Key, Florida and document correlations thereof and (2) correlate whole blood toxic element concentrations to various hematological and plasma biochemistry analytes. Baselines for various hematological and plasma analytes and toxic elements in whole blood and keratin (i.e., scute) in nesting loggerheads are documented. Various correlations between the toxic elements and hematological and plasma biochemistry analytes were identified; however, the most intriguing were negative correlations between arsenic, cadmium, lead, and selenium with and α- and γ-globulins. Although various extrinsic and intrinsic variables such as dietary and feeding changes in nesting loggerheads need to be considered, this finding may suggest a link to altered humoral immunity. This study documents a suite of health variables of nesting loggerheads in correlation to contaminants and identifies the potential of toxic elements to impact the overall health of nesting turtles, thus presenting important implications for the conservation and management of this species.

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.

Analysis of sugarcane herbicides in marine turtle nesting areas and assessment of risk using in vitro toxicity assays

Agricultural processes are associated with many different herbicides that can contaminate surrounding environments. In Queensland, Australia, herbicides applied to agricultural crops may pose a threat to valuable coastal habitats including nesting beaches for threatened loggerhead turtles (Caretta caretta). This study 1) measured concentrations of herbicides in the beach sand of Mon Repos, an important marine turtle nesting beach in Australia that is adjacent to significant sugarcane crops, and 2) investigated the toxicity of these herbicides to marine turtles using a cell-based assay. Samples of sand from turtle nest depth and water from surrounding agricultural drains and wetlands were collected during the wet season when herbicide runoff was expected to be the greatest and turtles were nesting. Samples were extracted using solid phase extraction and extracts were analysed using chemical analysis targeting herbicides, as well as bioanalytical techniques (IPAM-assay and loggerhead turtle skin cell cytotoxicity assay). Twenty herbicides were detected in areas between sugarcane crops and the nesting beach, seven of which were also detected in the sand extracts. Herbicides present in the nearby wetland were also detected in the beach sand, indicating potential contamination of the nesting beach via the river outlet as well as ground water. Although herbicides were detected in nesting sand, bioassays using loggerhead turtle skin cells indicated a low risk of acute toxicity at measured environmental concentrations. Further research should investigate potentially more subtle effects, such as endocrine disruption and mixture effects, to better assess the threat that herbicides pose to this population of marine turtles.

CYP1A protein expression and catalytic activity in double-crested cormorants experimentally exposed to deepwater Horizon Mississippi Canyon 252 oil

Double-crested cormorants (Phalacrocorax auritus, DCCO) were orally exposed to Deepwater Horizon Mississippi Canyon 252 (DWH) oil to investigate oil-induced toxicological impacts. Livers were collected for multiple analyses including cytochrome P4501A (CYP1A) enzymatic activity and protein expression. CYP1A enzymatic activity was measured by alkoxyresorufin O-dealkylase (AROD) assays. Activities specific to the O-dealkylation of four resorufin ethers are reported: benzyloxyresorufin O-debenzylase (BROD), ethoxyresorufin O-deethylase (EROD), methoxyresorufin O-demethylase (MROD), and pentoxyresorufin O-depentylase (PROD). CYP1A protein expression was measured by western blot analysis with a CYP1A1 mouse monoclonal antibody. In study 1, hepatic BROD, EROD, and PROD activities were significantly induced in DCCO orally exposed to 20ml/kg body weight (bw) oil as a single dose or daily for 5 days. Western blot analysis revealed hepatic CYP1A protein induction in both treatment groups. In study 2 (5ml/kg bw oil or 10ml/kg bw oil, 21day exposure), all four hepatic ARODs were significantly induced. Western blots showed an increase in hepatic CYP1A expression in both treatment groups with a significant induction in birds exposed to 10ml/kg oil. Significant correlations were detected among all 4 AROD activities in both studies and between CYP1A protein expression and both MROD and PROD activities in study 2. EROD activity was highest for both treatment groups in both studies while BROD activity had the greatest fold-induction. While PROD activity values were consistently low, the fold-induction was high, usually 2nd highest to BROD activity. The observed induced AROD profiles detected in the present studies suggest both CYP1A4/1A5 DCCO isoforms are being induced after MC252 oil ingestion. A review of the literature on avian CYP1A AROD activity levels and protein expression after exposure to CYP1A inducers highlights the need for species-specific studies to accurately evaluate avian exposure to oil.

Reptilian exposure to polycyclic aromatic hydrocarbons and associated effects

Reptiles are an underrepresented taxon in ecotoxicological literature, and the means by which toxicants play a role in population declines are only partially understood. Among the contaminants of interest for reptiles are polycyclic aromatic hydrocarbons (PAHs), a class of organic compounds that is already a concern for numerous other taxa. The objectives of the present review are to summarize the existing literature on reptilian exposure to PAHs and synthesize general conclusions, to identify knowledge gaps within this niche of research, and to suggest future directions for research. Results confirm a relative scarcity of information on reptilian exposure to PAHs, although research continues to grow, particularly after significant contamination events. The orders Testudines and Squamata are better represented than the orders Crocodilia and Rhynchocephalia. For the taxonomic orders with relevant literature (all but Rhynchocephalia), some species are more frequently represented than others. Few studies establish solid cause-effect relationships after reptilian exposure to PAHs, and many more studies are suggestive of effect or increased risk of effect. Despite the scarcity of information in this area, researchers have already employed a wide variety of approaches to address PAH-related questions for reptiles, including molecular techniques, modeling, and field surveys. As more research is completed, a thoughtful interpretation of available and emerging data is necessary to make the most effective use of this information. Environ Toxicol Chem 2017;36:25-35. © 2016 SETAC.

The current state and future directions of marine turtle toxicology research

Chemical contamination of marine turtles has been well documented in the literature, although information on the toxicological effects of these contaminants is poorly understood. This paper systematically and quantitatively presents the available marine turtle toxicological research (excluding oil chemicals and natural toxins) and the related fields of cell line establishment and biomarkers as indicators of exposure. Examination of the published literature identified a total of 49 papers on marine turtle toxicology, which were split into three categories: toxicity studies (n=33, 67%), cell line establishment (n=7, 14%), and publications using biomarkers (n=13, 27%). Toxicity studies were further broken down into four subcategories: those correlating contaminants with toxicological endpoints (n=16, 48%); in vitro exposure experiments (n=11, 33%); in vivo exposure experiments (n=5, 15%); and screening risk assessments using hazard quotients (n=3, 9%). In quantitatively assessing the literature, trends and gaps in this field of research were identified. This paper highlights the need for more marine turtle toxicology research on all species, particularly using high throughput and non-invasive in vitro assays developed for marine turtle cells, including investigations into further toxicological endpoints and mixture effects. This will provide more comprehensive species-specific assessment of the impacts of chemical contaminants on these threatened animals, and improve conservation and management strategies globally.

Establishment and characterization of a cell line from the Chinese soft-shelled turtle Pelodiscus sinensis

The establishment and partial characterization of Pelodiscus sinensis continuous cell line is described here. A novel P. sinensis fibroblast cell line, designated PSF, was established from heart tissue by the semi-digestion explant culture technique. Since its initiation in July 2013, the cell line has been subcultured at 30°C in minimal essential medium (MEM) containing 15% (v/v) fetal bovine serum for more than 50 passages. The growth curve of the cell line revealed the population doubling time was 51.1 h. Karyotyping analysis indicated the modal chromosome number was 66, and no microbial contamination was detected. The PSF cell line produced significant fluorescent signals after transfection with plasmid pEGFP-C3. Analysis of mitochondrial cytochrome D-loop sequences revealed 96% identity among other Chinese turtle subspecies. Several cell line characterizations included morphological analysis and immunocytochemistry, which revealed the origin of the PSF cell line was fibroblast-like cells. Measurement of the isoenzymes lactic dehydrogenase and malic dehydrogenase showed no cross-contamination of this cell line with other species. This newly established cell line will be a valuable tool for transgenic and genetic manipulation studies and will act as an efficient instrument for studies of the viral diseases of the soft-shelled turtle.

Hexavalent chromium is cytotoxic and genotoxic to American alligator cells

Metals are a common pollutant in the aquatic ecosystem. With global climate change, these levels are anticipated to rise as lower pH levels allow sediment bound metals to be released. The American alligator (Alligator mississippiensis) is an apex predator in the aquatic ecosystem and is considered a keystone species; as such it serves as a suitable monitor for localized pollution. One metal of increasing concern is hexavalent chromium (Cr(VI)). It is present in the aquatic environment and is a known human carcinogen and reproductive toxicant. We measured the cytotoxicity and genotoxicity of Cr(VI) in American alligator cells derived from scute tissue. We found that particulate and soluble Cr(VI) are both cytotoxic and genotoxic to alligator cells in a concentration-dependent manner. These data suggest that alligators may be used as a model for assessing the effects of environmental Cr(VI) contamination as well as for other metals of concern.