Inter- and intraspecific blood-related biomarkers and chemical exposure in confined and free-living sea turtles.

The relevance of recovery centers and head-starting programs for rescue, rehabilitation, rearing, and conservation of sea turtles is recognized worldwide. In addition, these centers contribute to generating biochemical and physiological data needed to identify health markers and provide baseline values. Because of the marine ecosystems' deterioration, biomarker identification is a global priority for sea turtle conservation; nevertheless, information on specific endpoints, such as neurotoxicity and mutagenesis, is still limited in sea turtles. This study aimed to contrast a set of non-invasive blood biomarkers with ecotoxicological and clinical applications in confined green sea turtles (Chelonia mydas) compared with free-living ones from the Mexican Caribbean. Additionally, interspecific (green, hawksbill (Eretmochelys imbricata), loggerhead (Caretta caretta) turtles) differences were also evaluated. Plasmatic organochlorine pesticides (OCs) and polychlorinated biphenyl (PCBs) were also determined. The concentration ranges of uric acid, total proteins, lipids (cholesterol and triglycerides), and thyroxine of both confined and free-living green turtles fell outside the reference intervals for the species. Additionally, confined green turtles had the highest number of erythrocytic nuclear abnormalities (ENA) and elevated levels of hemoglobin, lipid peroxidation, and activity of glutathione S-transferase, glutathione peroxidase, and carboxylesterase (CE). Contrasts among confined species identified hawksbill turtles with the lowest glutathione reductase activity, green turtles with the lowest ENA frequency and CE activity, and loggerhead turtles with the highest plasmatic concentrations of PCBs and OCs. The information here provided can be used as information in health monitoring programs and for conservation and management policies at regional, national, and international level.

Supplemental description of Benedenia seriolae (Yamaguti, 1934) Meserve, 1938 (Monogenoidea: Capsalidae) and first record of the parasite infecting a wild greater amberjack, Seriola dumerili (Risso, 1810) Hureau and Tortonese, 1973 (Carangiformes: Carangidae) from the northern Gulf of Mexico.

We herein provide a supplemental description of Benedenia seriolae (Yamaguti, 1934) Meserve, 1938 (Monogenoidea: Capsalidae Baird, 1853) based on specimens we collected from the skin of wild-caught greater amberjack (Seriola dumerili) in the northern Gulf of Mexico (GOM). Our specimens of B. seriolae from the GOM resemble those of Benedenia humboldti Baeza, Sepúlveda, and González, 2019 (from yellowtail amberjack, Seriola lalandi Valenciennes, 1833 [Carangidae] off Chile) by having a large body (>7000 µm in total length), non-overlapping anterior and posterior hamuli, an entirely sinistral and convoluted vas deferens, and a common genital pore as well as by lacking glands of Goto. It differs from B. humboldti by the shape of the penis tip. The 28S rRNA gene sequence differed from that of B. seriolae (from Japan) by 8 bp (1.1 %) and B. humboldti by 13 bp (2.8 %-1.7 %). The phylogenetic analysis recovered our sequences of B. seriolae sister to conspecific sequences from Japan, with that clade sister to B. humboldti from Chile. Benedenia was paraphyletic, suggesting some systematic revision to the genus could be warranted. Of 25 Benedenia spp., only Benedenia hendorffii (von Linstow, 1889) Odhner, 1905 had been reported previously from the GOM. Benedenia seriolae had previously not been reported from wild greater amberjack (previous records from greater amberjack were from sea cages only). This is also the first record of B. seriolae from the Northwestern Atlantic Ocean (GOM).

Reassessing leatherback turtle lineages and unveiling the first evidence of nuclear mitochondrial DNA in sea turtles.

A recent study proposed a new genetic lineage of leatherback turtles (Dermochelys coriacea) based on genetic analysis, environmental history, and local ecological knowledge (LEK), suggesting the existence of two possible species or subspecies on the beaches of Oaxaca, diverging ~ 13.5 Mya. However, this hypothesis may be influenced by nuclear mitochondrial DNA segments (NUMTs), which could have been misamplified as true mtDNA. NUMTs are sequences that have migrated from the mitochondrial genome to the nuclear genome and can co-amplify with mtDNA, potentially leading to erroneous phylogenetic interpretations. We re-examined the evidence for this proposed lineage by reviewing taxonomic literature and additional genetic data. Our analysis indicates that the divergent sequences, previously associated with a new lineage of D. coriacea, are NUMTs rather than true mitochondrial sequences. This is the first evidence of NUMTs in sea turtles. We also proposed a more specific primer for the mitochondrial control region (D-loop) for leatherback turtles to avoid amplifying nuclear copies. Our findings highlight the importance of rigorous genetic validation in conservation genetics, where misinterpretations can significantly impact species management. Finally, we developed a general protocol for detecting NUMTs applicable to any species.

Unraveling migratory corridors of loggerhead and green turtles from the Yucatán Peninsula and its overlap with bycatch zones of the Northwest Atlantic.

Bycatch represents a conservation problem when endangered species are affected. Sea turtles are highly vulnerable to this threat as their critical habitats overlap with fishing zones in all regions of the world. We used sequences of the mitochondrial DNA control region obtained from loggerhead (Caretta caretta) and green (Chelonia mydas) turtles to determine the migratory routes between nesting habitats in the Yucatán Peninsula and their critical marine habitats in the Northwest Atlantic. Mixed Stock Analysis revealed that loggerheads from Quintana Roo migrated to foraging areas in the northwestern Atlantic. Migratory routes used by green turtles are determined by their natal nesting colony: (1) green turtles from the Gulf of Mexico migrate to foraging aggregations in Texas and the northern Gulf of Mexico, (2) Mexican Caribbean turtles travel to foraging grounds in Florida, and (3) a smaller proportion of individuals born in the Yucatán Peninsula display a local connectivity pattern. Our results suggest that the migratory corridors used by Mexican loggerheads overlap with longline fisheries in the mid-Atlantic where sea turtle bycatch is comprised predominantly of immature individuals. Green turtles from the Yucatán Peninsula migrate to critical habitats that overlap with shrimp trawl fisheries within the Gulf of Mexico. Bycatch data and the identification of migratory corridors used by loggerheads and green turtles suggests that shrimp trawl fisheries on the east coast of the U.S. and the Gulf of Mexico pose a serious threat to the conservation and recovery of Mexican sea turtle populations.

Pulmonary aspergillosis in green sea turtles (Chelonia mydas): A case series.

We report a series of invasive pulmonary aspergillosis in green turtles (Chelonia mydas) on the southern coast of Brazil. During 13-month period, seven animals were recovered on the coastal beach and sent to a rehabilitation center, dying after a period of captivity up to 27 days. Granulomatous nodules in the lung, with the presence of hyaline and septate hyphae, were found in all. Invasive aspergillosis was confirmed by real-time Polymerase Chain Reaction (PCR). Our study is the first to describe Aspergillus sp. infection in green turtles. Prospective studies are necessary to evaluate the impact of such severe fungal diseases on sea turtles.

This is the first report of a series of invasive pulmonary aspergillosis infections in green sea turtles on the southern coast of Brazil. Future prospective studies are necessary in southern Brazil and other regions to evaluate the impact of such severe fungal diseases on sea turtles.

Citizen science enhances understanding of sea turtle distribution in the Gulf of California.

Citizen science is a valuable tool for addressing spatial distribution gaps in endangered species, especially in data-limited regions. Given the logistical and financial challenges of studying migratory species, this cost-effective approach contributes to strategic conservation planning. The Bay of La Paz, located in Baja California Sur, México, is considered an ecologically important region within the larger Gulf of California. Due to its rich biodiversity and abundant natural resources, the region serves as a hub for ecotourism and fishing, affording diverse opportunities for community-based scientific initiatives. This paper examines the value of citizen science contributions from three diverse community groups (i.e., coastal residents, SCUBA divers, and artisanal fishers) to help scientists obtain information on sea turtle distribution in the Bay of La Paz. Our findings represent the first records of loggerhead turtles (Caretta caretta) in the bay based on ten citizen science reports that include live and dead turtles (either observed swimming, as bycatch, or stranded), providing new information on an endangered pelagic species identified in a coastal bay. Although the sample size is small, our diversity of sources and sighting types highlight the value of collaborative citizen science initiatives in complementing traditional research methods.

Hematological profile and erythrocyte osmotic fragility of free-living yellow-footed tortoise Chelonoidis denticulatus (Linnaeus, 1766).

The yellow-footed tortoise (Chelonoidis denticulatus, Linnaeus, 1766) is among the most consumed chelonian species in the Amazon region, raising concerns about its conservation status. Furthermore, few studies have been carried out on the parameters of physiological normality of this species in free-living conditions, making it difficult to assess the impact of environmental changes on the physiology of the group. The erythrocyte osmotic fragility (EOF) test is a biomarker of environmental changes that cause membrane damage, decreasing erythrocyte resistance to osmotic stress. However, the physiology of the species is still poorly understood, and the reference ranges for hematological parameters and EOF is unknown for most species in natural conditions. Understanding the reference intervals of the physiological parameters of these animals have fundamental importance to assess when a population is under the effect of environmental stressors, such as xenobiotics, as well as to provide comparative parameters in clinical analyzes for the species. The lack of information on normal EOF values ​​makes it difficult to assess the effects of environmental and clinical changes on the physiology of the species. This study aimed to establish reference intervals for hematological parameters and EOF analysis for C. denticulatus, using thirty tortoises (n = 15 males and n = 15 females). The t-test and Mann-Whitney test were used to compare the hematological parameters between sexes, while the Kruskal-Wallis test was used in the EOF analysis, and the reference range was calculated for males and females together. No statistical differences were found in hematological values between sexes, nor in the hemolysis profile in the EOF analysis, demonstrating that in this population, these parameters of C. denticulatus are similar between sexes during the sampling period. According to the results of this study, we can consider the erythrocytes of these animals osmotically resistant, reflecting the stability of the cell membrane. This study reports for the first time hematological values and EOF analysis for the species C. denticulatus in the wild in a region of the far western Brazilian Amazon.

Discovery of the first sea turtle adenovirus and turtle associated circoviruses.

Turtles are an evolutionarily unique and morphologically distinctive order of reptiles, and many species are globally endangered. Although a high diversity of adenoviruses in scaled reptiles is well-documented, turtle adenoviruses remain largely understudied. To investigate their molecular diversity, we focused on the identification and characterisation of adenoviruses in turtle-derived organ, swab and egg samples. Since reptile circoviruses have been scarcely reported and no turtle circoviruses have been documented to date, we also screened our samples for circoviruses. Host-virus coevolution is a common feature of these viral families, so we aimed to investigate possible signs of this as well. Two screening projects were conducted: one on Brazilian samples collected from animals in their natural habitat, and the other on Hungarian pet shop samples. Nested PCR systems were used for the detection of adeno- and circoviruses and purified PCR products were Sanger sequenced. Phylogenetic trees for the viruses were reconstructed based on the adenoviral DNA polymerase and hexon genes, circoviral Rep genes, and for the turtle hosts based on mitochondrial cytochrome b amino acid sequences. During the screening, testadeno-, siadeno-, and circovirus strains were detected. The circovirus strains were classified into the genus Circovirus, exhibiting significant evolutionary divergence but forming a monophyletic clade within a group of fish circoviruses. The phylogenetic tree of turtles reflected their taxonomic relationships, showing a deep bifurcation between suborders and distinct monophyletic clades corresponding to families. A similar clustering pattern was observed among the testadenovirus strains in their phylogenetic tree. As a result, this screening of turtle samples revealed at least three new testadenoviruses, including the first sea turtle adenovirus, evidence of coevolution between testadenoviruses and their hosts, and the first turtle associated circoviruses. These findings underscore the need for further research on viruses in turtles, and more broadly in reptiles, to better understand their viral diversity and the evolutionary processes shaping host-virus interactions.

Extensive sampling and citizen science expand the distribution of the threatened freshwater turtle Ranacephala hogei (Mertens, 1967).

Ranacephala hogei is a South American freshwater turtle considered one of the 25 most endangered chelonian species in the world. Endemic to the Atlantic Forest hotspot of southeastern Brazil, the conservation status of R. hogei is subject to continuous assessment at various levels. However, the scarcity of data regarding this species, particularly its geographic range, challenges these evaluations. In an effort to address these gaps, we conducted a comprehensive long-term inventory using different methods to study this species. Our efforts resulted in a 144% increase in documented occurrence points, including a new hydrographic basin and protected areas. By combining historical and current records, we have observed the persistence of R. hogei in rural areas, even in locations where its extinction was previously predicted. Consequently, our data significantly contribute to supporting future conservation assessments.

A systematic review of the impact of chemical pollution on sea turtles: Insights from biomarkers of aquatic contamination.

Chemical anthropogenic contaminants in the marine environment pose a substantial threat to sea turtles. The current systematic review quantified the published literature on biomarkers of aquatic contamination in sea turtles. It examined the exposure and potential impacts of pollution at biochemical, molecular, and cellular levels, as indicated by these biomarkers. Eighty-seven primary peer-reviewed papers were included, most of which were published from 2013 onwards. Most studies focused on the species Chelonia mydas (n = 43 papers) and Caretta caretta (n = 36) and used blood samples for biomarker (n = 54) and chemical (n = 38) analyses. Chemical analyses were assessed alongside biomarker analyses in most studies (n = 71). Some studies indicated possible damage to the DNA, cells, oxidative balance, and reproduction of sea turtles associated with chemical contaminants as metals, emerging, and mixtures of organic pollutants. Research gaps and recommendations for future studies were addressed to help understand the toxicity of chemical pollutants in sea turtles. The purpose of this review is to contribute for supporting actions to mitigate the threats posed by pollution to these protected species, as well as to plan new studies in this research field for both conservation and biomonitoring purposes.

Lung mechanics in juvenile and adult Chelonoidis carbonarius.

Testudines possess a rigid shell that influences the mechanics of the respiratory system. We studied respiratory mechanics in the terrestrial red-footed tortoise Chelonoidis carbonarius (Cryptodira), comparing juvenile individuals with a less ossified and more flexible carapace with adults with a well-ossified rigid shell. Combined with these ontogenetic differences, we analyzed respiratory system mechanics with animals in a supine and a prone position, as well as in the isolated lungs, to evaluate the impact of the viscera on breathing mechanics. To do so, we used established protocols to measure pulmonary volume (i.e. resting, VLr; and maximum, VLm), static (Cstat) and dynamic (Cdyn) compliance, and the work of breathing (W). We observed that isolated lungs displayed increased VLr, VLm, Cstat and Cdyn and decreased W. Additionally, pulmonary volume, compliance and W were affected by evaluated position, such as a smaller VLr in a supine position. Cdyn and W showed a volume dependency while frequency had less influence on these variables. At similar levels of ventilation, juveniles showed a lower W than adults when standardized by body mass, but similar W when standardized by VLr. Clear ontogenetic changes could be observed in breathing mechanics between juvenile and adult C. carbonarius. While these differences might largely be explained by variation in shell ossification, other explanations such as differences in visceral proportions or developmental degree of the post-pulmonary septum should also be taken into account.

Detection of parasitic forms in feces of Chelonoidis carbonarius (Linnaeus, 1766) from Brazilian Cerrado.

Chelonoidis carbonarius is host to a great diversity of endoparasites. This research aimed to identify and taxonomically classify the parasitic forms of endoparasites found in the feces of C. carbonarius using coproparasitological methods. In total, 38 fecal samples were collected from animals captured in the municipalities of Cuiabá (n = 23) and Jataí (n = 15) in the Brazilian Ceraado. Fecal samples were submitted to at least one of the following techniques: Willis-Mollay flotation technique, zinc sulfate centrifugal flotation technique, and spontaneous sedimentation of Hoffman, and Pons, and Janer. Overall, 86.85% (33/38) of animals were positive in at least one of the diagnostic techniques. Of the 38 samples used, 50% of the animals were captive and 50% of the animals were free-living. Cysts, oocysts, and parasitic eggs were identified, as follows: Chapiniella spp. (65.78%; n = 24), Sauricola spp. (31.57%; n = 12), Ascaroidea (15.78%; n = 6), Oxyuridae (2.63%; n = 1), Trematoda (2.63%; n = 1), Acanthocephala (2.63%; n = 1), Balantidium spp. (39.47%; n = 15), Eimeria spp. (21.05%; n = 8), and Nyctotherus spp. (2.63%; n = 1). The study showed that both captive and free-living C. carbonarius are often parasitized by different endoparasite species, with nematode eggs being the most common.

Comparison of four different protocols using levobupivacaine for spinal anaesthesia in red-footed tortoises (Chelonoidis carbonarius).

Background: The popularity of tortoises kept in captivity is increasing and has caused concern regarding the necessity to establish safe and straightforward anaesthesia for those reptiles. Aim: This study aimed to compare four protocols using levobupivacaine in spinal anaesthesia for the blockade of the caudal neuraxis of red-footed tortoises (Chelonoidis carbonarius). Methods: Twenty-four tortoises were randomly assigned into four groups: G1, levobupivacaine 0.75% (1.15 mg kg-1); G2, levobupivacaine 0.37% (1.15 mg kg-1); G3, levobupivacaine 0.75% (2.3 mg kg-1); and G4, levobupivacaine 0.75% (0.1 ml 5 cm-1 of straight carapace length). Tortoises were evaluated for respiratory rate, muscle relaxation, response to hindlimb or tail pinch, and cloacal reflex. Results: A 1.15 mg kg-1 dose of levobupivacaine 0.37% appears adequate for shorter procedures, whereas a 1.15 mg kg-1 dose of levobupivacaine 0.75% should be appropriate for longer procedures in red-footed tortoises. Conclusion: Our results are the first to show the effects of levobupivacaine on spinal anaesthesia in reptiles. Weight-based doses presented more intense and more homogeneous effects than carapace length-based doses in red-footed tortoises. Spinal anaesthesia of red-footed tortoises was safe and effective with any of the weight-based protocols.

The fungus Aphanoascella galapagosensis affects bacterial diversity of Galapagos giant tortoise carapaces.

AIMS: This study aimed to describe the bacterial microbiome associated with the carapace of three species of Galapagos giant tortoises (Chelonoidis porteri, Chelonoidis donfaustoi, and Chelonoidis vandenburghi) and determine the potential effect of the whitish lesions caused by the fungus Aphanoascella galapagosensis. METHODS AND RESULTS: We used Oxford Nanopore's MinION to evaluate the external bacterial microbiome associated with the carapaces from the aforementioned species. Taxonomic assignment was carried out by Bugseq and the bacterial communities were compared between carapaces with and without lesions using a NMDS with Bray-Curtis as the dissimilarity index. We found four genera of bacteria that were ubiquitous throughout all individuals, suggesting the presence of shared taxa. The results also displayed a significant difference in the microbiome between carapaces with and without lesions, and for species-carapace interaction, but not among species. CONCLUSIONS: This study establishes a baseline of the bacterial diversity of the carapace within three Galapagos giant tortoise species, showcasing the presence of a distinctive microbial community. Furthermore, our findings suggest a significant influence of the fungus Aphanoascella galapagosensis on the bacterial populations inhabiting the carapace of these reptiles.

Lessons learned during a 12-year monitoring project with the endangered Magdalena River turtle (Podocnemis lewyana): hunting pressure, habitat degradation, and methodological considerations.

Turtle species in the Family Podocnemididae, including the Colombian endemic and critically endangered Magdalena River Turtle Podocnemis lewyana, characteristically present low recapture rates that preclude estimation of population parameters using maximum likelihood modeling. In our 12-year monitoring project with this species, we evaluated changes in relative abundances, proportions of sex/size classes, and individual body sizes and body conditions in a population in four channels in the middle Magdalena River drainage. We also inspected for associations between trends in changes in these variables and differences in hunting pressure and habitat degradation. To inspect for temporal and spatial demographic dynamics, we estimated variation in relative abundances using the Catch Per Unit Effort index, the total number of turtles captured over an entire 5-day sampling period using ten baited funnel traps. Relative abundances and the proportions of sex/size classes were different between sites and years. We found a significant decline in the proportion of females and juveniles over time, along with evidence that the females still present were smaller in body size. Our results support the hypothesis that hunting eliminates adult females from these sites, perhaps also translating into a reduction in recruitment. The lack of evidence of generalized declines in body condition of all size classes suggests that habitat degradation might contribute less to the population declines in this region. Our results also illustrate that even when recapture rates are low, monitoring turtles via standardized trapping may yield insights into the population's conservation status that other relative abundance indices cannot.

A novel approach to urban turtle sampling: Assessing Hookless Fishing with clip and two conventional methods.

To address urban turtle sampling challenges, we presented Hookless fishing with clip, a cost-effective method for sampling this important group. Effectiveness, biases and potential advantages were analysed in comparison to two commonly used methods (funnel trap and hand capture). Fieldwork was conducted between August and November/2021 in four areas in Brazil, using the three methods simultaneously. A total of 195 turtles from four species (Phrynops geoffroanus, Hydromedusa tectifera, Trachemys dorbigni and T. scripta elegans) were captured. Funnel trap demonstrate a significantly higher capture than hand capture, while Hookless fishing showed no significant difference in captures compared to funnel trap. The highest catch per unit effort values were observed for the new method (0.37) and the funnel trap (0.34). Despite being widely used, funnel traps were the only method to exhibit male bias. Our findings revealed that Hookless fishing with clip exhibited remarkable capture efficiency, cost-effectiveness, and ease of transport and utilization; however, it requires operator presence. Nevertheless, the proposed method, both as the primary or auxiliary approach, appears efficient in enhancing captures and reducing costs and risks. This innovative method has the potential to assist researchers studying omnivorous and carnivores freshwater turtles in environments worldwide, especially in human settlements.

Morphological comparison of the larynx and trachea of Chelonia mydas (Linnaeus, 1758), Caiman yacare (Daudin, 1802) and Caiman latirostris (Daudin, 1802).

The larynx is in the lower respiratory tract and has the function of protecting the airways, controlling, and modulating breathing, assisting the circulatory system, and vocalizing. This study aims to describe the anatomy and histology of the skeleton of the larynx and trachea of the species Chelonia mydas, Caiman yacare and Caiman latirostris. The study was conducted at the Federal University of Espírito Santo (UFES), using nine specimens of Ch. mydas, 20 of Ca. yacare and four of Ca. latirostris. Samples of the larynx and trachea were collected, fixed, and sent for dissection of the structures and subsequent macroscopic analysis. For histology, samples were processed by the routine paraffin embedding method and stained with hematoxylin-eosin and Verhoeff. For the three species, two arytenoid cartilages, a cricoid cartilage, a hyoid apparatus composed of a base and two horns were found. In Ch. mydas, two structures called thyroid wings were observed, not found in crocodilians. The trachea of crocodilians presented incomplete tracheal rings and musculature, while the trachea of Ch. mydas presented complete tracheal rings. Histologically, the entire cartilaginous skeleton of the larynx of the three species, as well as the tracheal rings, are constituted by hyaline cartilage.

Unoculubranchiobdella sp. (Hirudinea: Ozobranchidae) as a vector for Haemogregarina spp. in freshwater turtles from Brazil.

Species of Haemogregarina are blood parasites known to parasitise vertebrate hosts, including fishes (Haemogregarina sensu lato) and freshwater turtles (Haemogregarina sensu stricto). Their vectors, include gnathiid isopods and leeches, respectively. In turtles, Haemogregarina balli has the best-characterized life cycle in the genus. However, no studies in Brazil have suggested a possible vector for any species of Haemogregarina from freshwater turtles. Therefore, in the present study, we provide insights into a leech vector based on specimens found feeding on two species of freshwater turtles, Podocnemis unifilis and Podocnemis expansa, using morphological and molecular data. In 2017 and 2019, freshwater turtles were collected in Goiás State, Brazil. Hosts were inspected for ectoparasites and leeches were collected from two specimens of P. expansa and nine specimens of P. unifilis. Leeches were subsequently identified as members of the genus Unoculubranchiobdella. Leech histological slides revealed haemogregarine-like structures, similar to post-sporogonic merogony, found near the gills and within the posterior sucker. Molecular analysis of the haemeogregarines resulted in the identification of three species of Haemogregarina: Haemogregarina embaubali, Haemogregarina goianensis, and Haemogregarina brasiliana. Therefore, our findings, based on morphology and DNA data suggest leeches of the genus Unoculubranchiondella as vectors for at least three species of Haemogregarina from Brazilian turtles.

Body size predicts ontogenetic nitrogen stable-isotope (δ15N) variation, but has little relationship with trophic level in ectotherm vertebrate predators.

Large predators have disproportionate effects on their underlying food webs. Thus, appropriately assigning trophic positions has important conservation implications both for the predators themselves and for their prey. Large-bodied predators are often referred to as apex predators, implying that they are many trophic levels above primary producers. However, theoretical considerations predict both higher and lower trophic position with increasing body size. Nitrogen stable isotope values (δ15N) are increasingly replacing stomach contents or behavioral observations to assess trophic position and it is often assumed that ontogenetic dietary shifts result in higher trophic positions. Intraspecific studies based on δ15N values found a positive relationship between size and inferred trophic position. Here, we use datasets of predatory vertebrate ectotherms (crocodilians, turtles, lizards and fishes) to show that, although there are positive intraspecific relationships between size and δ15N values, relationships between stomach-content-based trophic level (TPdiet) and size are undetectable or negative. As there is usually no single value for 15N trophic discrimination factor (TDF) applicable to a predator species or its prey, estimates of trophic position based on δ15N in ectotherm vertebrates with large size ranges, may be inaccurate and biased. We urge a reconsideration of the sole use of δ15N values to assess trophic position and encourage the combined use of isotopes and stomach contents to assess diet and trophic level.

Evidence of oxidative stress responses of green turtles (Chelonia mydas) to differential habitat conditions in the Mexican Caribbean.

Important foraging and nesting habitats for Caribbean green sea turtles (Chelonia mydas) exist within the Mesoamerican Reef System in the Mexican Caribbean. During the last 25 years, urban development and touristic activities have drastically increased in Quintana Roo, Mexico. Moreover, in the last decade, massive pelagic sargasso blooms have also afflicted this region; however, information about the biochemical responses of Caribbean green turtles to these inputs is absent. This study aimed to assess if the oxidative stress indicators in the red blood cells of green turtles are valuable biomarkers of the extent of the anthropic impact in this region. Persistent organic pollutants (POPs) were also measured in the plasma of free-living green turtles during 2015-2018 to characterize these habitats further. As biochemical biomarkers, the production rate of superoxide radical (O2•-), carbonylated protein content, and lipid peroxidation (TBARS) levels, and the activities of superoxide dismutase, glutathione S-transferase (GST), catalase, glutathione peroxidase were measured in erythrocytes. A 15 % occurrence of fibropapillomatosis (FP) was revealed, with tumor size being positively correlated with CAT activity in the affected individuals. A multivariate analysis embracing all oxidative stress markers discriminated green turtles between years of capture (p < 0.001), with those sampled during 2015 presenting the highest production of O2•- (p = 0.001), activities of GST (p < 0.001), levels of TBARS (p < 0.001) and carbonylated proteins (p = 0.02). These local and temporal biochemical responses coincided with the first massive Sargassum spp. bloom reported in the region. The results of this study corroborate the utility of the oxidative stress indicators as biomarkers of environmental conditions (sargasso blooms and POPs) in the green turtle as sentinel species.