Loggerhead Marine Turtles Research Articles

Phthalate metabolites in loggerhead marine turtles (Caretta caretta) from the Mediterranean Sea (East Spain region)

The exposure of marine reptiles to phthalates has received considerable attention due to the ubiquitous occurrence of these contaminants in the marine environment. The occurrence of phthalate metabolites is established in human populations and marine mammals, but data is scarce for marine reptiles. In this study, concentrations of 18 phthalate metabolites were determined in liver samples from 79 loggerhead marine turtle (Caretta caretta) samples collected between 2016 and 2021 in the limits of the Valencian Community (East Spain). For this purpose, the phthalate metabolites were purified from the livers by solid phase extraction and were quantified by UPLC-MS/MS. Fifteen phthalate metabolites were detected in the samples. Monoethyl phthalate (mEP), monomethyl phthalate (mMP), mono-n-butyl phthalate (mBP), phthalic acid (PA) and mono-n-hexyl phthalate (mHxP) were the most abundant metabolites, accounting for detection rates >85%. The highest median concentrations were found for PA (24.2 ng/g dry weight, d.w.) and mHxP (20.3 ng/g d.w.) followed by mMP (12.0 ng/g d.w.), mEP (5.76 ng/g d.w.) and mBP (4.26 ng/g d.w.). The sum of the medians of these five phthalate metabolites (Σ5PhMet) indicated that concentrations were higher for turtles during year 2020, while a negative association was found between [Σ5PhMet] and the turtle size. To our knowledge, this is the first study on the biomonitoring of 18 phthalate metabolites in loggerhead marine turtles, and results show that western Mediterranean loggerhead turtles are usually exposed to these contaminants.

Loggerhead marine turtles (Caretta caretta) nesting at smaller sizes than expected in the Gulf of Mexico: Implications for turtle behavior, population dynamics, and conservation

AbstractEstimates of parameters that affect population dynamics, including the size at which individuals reproduce, are crucial for efforts aimed at understanding how imperiled species may recover from the numerous threats they face. In this study, we observed loggerhead marine turtles (Caretta caretta) nesting at three sites in the Gulf of Mexico at sizes assumed nonreproductive in this region (≤87 cm curved carapace length‐notch [CCL‐n]). These smaller individuals ranged from 74.0 to 86.9 cm CCL‐n, and the proportion of smaller nesting loggerheads was 0.13 across three study sites: Gulf Shores, AL; Dry Tortugas National Park, Florida (FL); and Everglades National Park (ENP), FL. The greatest proportion of smaller nesters was observed at ENP at 0.24. Tracking data indicated that the smaller nesters migrated shorter distances and swam in shallower waters compared to the larger nesting loggerheads (>87 cm CCL‐n) in our dataset. These results provide valuable information on two of the smallest subpopulations of NW Atlantic loggerheads and understudied ENP turtles. Our results have potential applications in the classification and interpretation of stranding limits and bycatch estimates, population modeling (e.g., stage durations and fecundity), and understanding threats and subpopulation recovery efforts for multiple subpopulations of this imperiled species.

Habitat models and assessment of habitat partitioning for Kemp’s ridley and loggerhead marine turtles foraging in Chesapeake Bay (USA)

Understanding the spatial distribution of a species is required to enact effective conservation. Complications to effective conservation can arise when the distributions of multiple target species are non-overlapping. Conservation efforts meant to protect one species may shift threats into the distribution of another species. Two species of marine turtle, loggerhead Caretta caretta and Kemp’s ridley Lepidochelys kempii, are common seasonally in Chesapeake Bay, a large estuary on the US east coast. Both species are protected under the US Endangered Species Act and face spatially complex threats in the region. We created habitat suitability models for these 2 species to inform conservation efforts in the region and explore the extent of overlap between their distributions. Argos satellite tags were deployed on 24 Kemp’s ridley and 10 loggerhead turtles to record animal locations within the Bay. Boosted regression tree models were created for each species using presence-only animal locations, predicting suitable habitat within the Bay. Habitat for Kemp’s ridley turtles was predicted in shallow, coastal areas of the southern Bay as well as in brackish areas of rivers. Loggerhead turtle habitat was predicted to extend farther north than Kemp’s ridley habitat and was generally found in deeper areas of the middle Bay. There is some evidence that these 2 species are partitioning habitat. Any conservation measures adopted to conserve marine turtles in the Chesapeake Bay should consider the habitat of both species holistically to avoid shifting impacts from one species to another.

Loggerhead marine turtle (Caretta caretta) ecological facts from a trophic relationship model in a hot spot fishery area: Gulf of Ulloa, Mexico

The oceanographic conditions in the Gulf of Ulloa (GU) region make a distinctive faunal assemblage, allowing the presence of species both ecologically and economically important. Constant interaction of emblematic species with the fishing activity has brought social and conservation problems due to the lack of ecological information and/or management tools. For the loggerhead turtle (Caretta caretta), the GU is an important feeding area, so the interaction with anglers is frequent. In this sense, some events of high loggerhead mortality have resulted in restrictive fishing measures; nevertheless, alternative hypotheses should be explored to explain this fact better. With the purpose of not only knowing the ecosystem ecological attributes but also obtaining specific ecological facts of the loggerhead turtle – as instantaneous total mortality – this study proposes Ecopath with Ecosim (EwE) model by calculating Allen's approximation of production to biomass ratio (P/B). Using the thermoregulation theory of ectotherms and this baseline model, the scenarios were run in Ecosim combining two forcing factors (FF): sea surface temperature (SST) and different fishing effort (F) values. All Ecosim scenarios were run over 30 simulated years taking the (P/B) values of the loggerhead turtle. According to the results in this study, the model allowed us to obtain specific ecological attributes for C. caretta, particularly for the P/B estimates in different simulation scenarios, which showed that colder sea surface temperature increases loggerhead mortality. All the information combined provided a better panorama to understand the role this turtle has within the Biological Action Center of the GU system and its interaction with other activities developed on site, such as fishing.

Notes on amphipods associated with loggerhead marine turtle Caretta caretta (Linnaeus, 1758) in south-eastern Brazil

Abstract The loggerhead marine turtle is an ideal substrate for epibionts and presents the highest diversity of associated fauna among marine turtles. Here we report the occurrence of two amphipod species, Caprella andreae Mayer, 1890 and Podocerus chelonophilus (Chevreux and Guerne, 1888) from the carapace of one stranded Caretta caretta (Linnaeus , 1758) in Ubatuba, Sao Paulo state, Brazil. This is the first record of P. cheloniphilus for Brazil and for the South Atlantic Ocean.

Complete mitochondrial genome of the nesting Colombian Caribbean loggerhead turtle: first approach of tRNAs and phylogenetic analysis

The loggerhead marine turtle, Caretta caretta, is a widely distributed and endangered species that is facing critical population decline, especially in Colombian Caribbean rookeries. Mitochondrial DNA sequence data are of great importance for the description, monitoring, and phylogenetic analyses of migratory turtle populations. In this study, the first full mitochondrial genome of a loggerhead turtle nesting in the Colombian Caribbean was sequenced and analyzed. This mitochondrial genome consists of 16 362 bp with a nucleotide composition of T: 25.7 %, C: 27 %, A: 35 % and G: 12 %. Sequence annotation of the assembled molecule revealed an organization and number of coding and functional units as reported for other vertebrate mitogenomes. This Colombian loggerhead turtle (Cc-AO-C) showed a novel D-Loop haplotype consisting of thirteen new variable sites, sharing 99.2 % sequence identity with the previously reported Caribbean loggerhead CC-A1 D-Loophaplotype. All 13 protein-coding genes in the Cc-AO-C mitogenome were compared and aligned with those from four other loggerhead turtles from different locations (Florida, Greece, Peru, and Hawaii). Eleven of these genes presented moderate genetic diversity levels, and genes COII and ND5 showed the highest diversity, with average numbers of pair-wise differences of 16.6 and 25, respectively. In addition, the first approach related to t-RNAs 2D and 3D structure analysis in this mitogenome was conducted, leading to observed unique features in two tRNAs (tRNATrp and tRNALeu). The marine turtle phylogeny was revisited with the newly generated data. The entire mitogenome provided phylogenetically informative data, as well as individual genes ND5, ND4, and 16S. In conclusion, this study highlights the importance of complete mitogenome data in revealing gene flow processes in natural loggerhead turtle populations, as well as in understanding the evolutionary history of marine turtles.

Molecular evolution of fibropapilloma-associated herpesviruses infecting juvenile green and loggerhead sea turtles

Chelonid Alphaherpesvirus 5 (ChHV5) has long been associated with fibropapillomatosis (FP) tumor disease in marine turtles. Presenting primarily in juvenile animals, FP results in fibromas of the skin, connective tissue, and internal organs, which may indirectly affect fitness by obstructing normal turtle processes. ChHV5 is near-universally present in tumorous tissues taken from affected animals, often at very high concentrations. However, there is also considerable asymptomatic carriage amongst healthy marine turtles, suggesting that asymptomatic hosts play an important role in disease ecology. Currently, there is a paucity of studies investigating variation in viral genetics between diseased and asymptomatic hosts, which could potentially explain why only some ChHV5 infections lead to tumor formation. Here, we generated a database containing DNA from over 400 tissue samples taken from green and loggerhead marine turtles, including multiple tissue types, a twenty year time span, and both diseased and asymptomatic animals. We used two molecular detection techniques, quantitative (q)PCR and nested PCR, to characterize the presence and genetic lineage of ChHV5 in each sample. We found that nested PCR across multiple loci out-performed qPCR and is a more powerful technique for determining infection status. Phylogenetic reconstruction of three viral loci from all ChHV5-positive samples indicated widespread panmixia of viral lineages, with samples taken across decades, species, disease states, and tissues all falling within the same evolutionary lineages. Haplotype networks produced similar results in that viral haplotypes were shared across species, tissue types and disease states with no evidence that viral lineages associated significantly with disease dynamics. Additionally, tests of selection on viral gene trees indicated signals of selection dividing major clades, though this selection did not divide sample categories. Based on these data, neither the presence of ChHV5 infection nor neutral genetic divergence between viral lineages infecting a juvenile marine turtle is sufficient to explain the development of FP within an individual.

Embryonic Growth Rate Thermal Reaction Norm of Mediterranean Caretta caretta Embryos from Two Different Thermal Habitats, Turkey and Libya

Abstract Ectothermic species are strongly affected by thermal changes. To assess the viability of these species under climate change constraints, we need to quantify the sensitivity of their life history traits to temperature. The loggerhead marine turtle (Caretta caretta) nests regularly in the Oriental Basin of the Mediterranean Sea. The different populations are separated because of time (< 12,000 yrs) and very different thermal habitats; it is hotter on the southern coast (Libya) than on the northern ones (Cyprus, Greece, and Turkey). Patterns of embryo growth response to incubation temperatures have been searched for these 2 populations. We found that both populations have similar thermal reaction norms for embryonic growth rate. This highlights that 12,000 yrs is not enough time for this species to adapt to specific thermal habitats and raises the question of the persistence of these populations in the context of rapid climate change.

Epibiont communities of loggerhead marine turtles (Caretta caretta) in the western Mediterranean: influence of geographic and ecological factors

This study reports for the first time on the whole epibiont fauna of loggerhead marine turtles,Caretta caretta, in the western Mediterranean, analysing the factors that account for the predictability and composition of the assemblage. A total of 104 loggerhead turtles stranded along the coasts of eastern Spain during 1995–2006 were surveyed for epibionts. A total of 39 epibiont taxa were identified, three of them being new records for loggerhead turtles:Bittiumsp.,Idotea metallicaandJassasp. The assemblage was composed of a group of 27 facultative taxa that use turtles as any inanimate buoyant substrate, and 12 taxa that have developed more specific associations to marine turtles, including six species that occur in marine turtles exclusively, two that dwell also on other hosts, and four that can also survive as free-living forms but have developed a strong association with marine turtles. Hierarchical clustering and Similarity Profile Analysis based on the occurrence of 166 epibiont taxa from nine available surveys indicated that the epibiont assemblages from loggerhead turtles in the western Mediterranean (WM) are similar to those from Central Mediterranean (CM), but significantly different from turtles surveyed in the eastern Mediterranean and the Atlantic. The subset of epibionts occurring on WM and CM turtles is defined by a combination of geographic factors (exclusive Mediterranean epibiont taxa) and ecological factors (relative absence of littoral-benthic taxa). Loggerhead turtles from WM and CM apparently exploit both pelagic and benthic habitats in similar fashion, representing a homogeneous unit for epibiont recruitment.

Sex ratio estimations of loggerhead marine turtle hatchlings by incubation duration and nest temperature at Sirte beaches (Libya)

SUMMARY: Hatchling sex ratios in loggerhead marine turtles (Caretta caretta) were estimated on the beaches near Sirte (Libya), using two methods: incubation duration and nest mean temperature during the middle third of the incubation period. Electronic temperature/humidity loggers were deployed at a total of 13 selected nests at Al-Ghbeba, Al-Thalateen, west of Al- Thalateen, Shash and Al-Arbaeen. The incubation period ranged from 47 to 58 days and average temperature ranged from 29°C to 31.8°C. The maximum temperature during this period increased to between 0.6°C and 3.5°C, while the mean temperature also increased during the middle third of the incubation period compared with the first third and continued to increase during the last third. As expected, this study showed that the temperature in the nest decreased with increasing depth of the nest. The results showed a female-dominated sex ratio at 85.4% on the basis of incubation duration and 70.4% on the basis of mean temperature. These findings support the reported highly female-skewed sex ratios in the Mediterranean and elsewhere.

Testing Supremacy or Inferiority of Multinomial Cell Probabilities with Application to Biting Preferences of Loggerhead Marine Turtles

We propose exact tests for uniform superiority or uniform inferiority of a multinomial cell probability. We extend the approach to testing supremacy or inferiority in multivariate settings. We also show how to perform superiority or inferiority tests in presence of covariates, and discuss the different interpretations of the proposed tests. The tests are illustrated on an original data set on biting behavior of loggerhead marine turtles.

Out-foxing the red fox: how best to protect the nests of the Endangered loggerhead marine turtleCaretta carettafrom mammalian predation?

AbstractRecovery plans for the Endangered loggerhead marine turtleCaretta carettacite mammalian predation as a major threat, and recommend nest protection efforts, already present at many rookery beaches, to protect eggs and hatchlings. Nest protection techniques vary but wire box cages and plastic mesh screens are two common tools used to deter predation by a host of beach-foraging, opportunistic mammalian predators. We empirically tested the efficacy of wire cages and plastic mesh screens in preventing red foxVulpes vulpespredation on artificial nests. Both techniques averted fox predation (0%), whereas unprotected control nests suffered 33% predation under conditions of normal predator motivation, or a level of motivation stimulated by loggerhead turtle egg scent. However, in side-by-side comparisons under conditions of presumed high predator motivation, 25% of mesh screens were breached whereas no cage-protected nests were successfully predated. In addition to effectiveness at preventing predation, factors such as cost, ease of use, deployment time, and magnetic disturbance were evaluated. Our study suggests that the efficacy of plastic screens and the potential disadvantages associated with galvanized wire should influence selection of mechanical barriers on beaches where fox predation threatens loggerhead nests.

Post-nesting movements and submergence patterns of loggerhead marine turtles in the Mediterranean assessed by satellite tracking

Two female loggerhead turtles ( Caretta caretta) were tracked, following nesting at Alagadi Beach (35°33′N, 33°47′E), Northern Cyprus, eastern Mediterranean for 60 and 82 days, respectively. The two individuals showed marked differences in their behaviour. Individual A was tracked to Syrian coastal waters, whereas individual B travelled around the coast of Northern Cyprus to a foraging site in the waters off the east coast of Northern Cyprus. Submergence durations varied markedly during different phases of the migration, suggesting coastal foraging/resting at certain stages en route with sustained directed travelling movements during initial coastal movements and open ocean crossing . Both turtles showed fidelity to foraging grounds for the duration of transmissions (Turtle A: 36 days; Turtle B: 58 days). In both cases, locations were centred in inshore waters although the two individuals exhibited quite different submergence patterns. Individual A carried out very short dives of typical duration <10 min, whereas Individual B carried out longer dives with typical duration >20 min. Diel differences in submergence duration at the foraging grounds suggested longer dives at night/early morning for both turtles. For Turtle A, there was a general reduction in submergence duration as the period of residence increased; a pattern that may have been related to increasing temperature experienced. The total distance travelled by the two turtles (320 and 227 km) was relatively short when compared to satellite tracking studies of conspecifics following nesting in South Africa and USA and tagging studies of nesting loggerhead turtles in Greece and Australia. It is hypothesized that short migratory distance may be correlated with both the small body size and the relatively high frequency of remigration in this population.