Caretta Research Articles

Plasticity and variation of cirral attributes in Chelonibia spp. barnacles

Prior studies suggest that many species of intertidal Balanomorph barnacles exhibit plastic responses to wave action and variable rates of water flow, with this environmental variability intrinsic to shaping the morphology of feeding cirri. However, this idea has not been quantitatively demonstrated in barnacles of the family Coronulidae, which exhibit obligatory epibiotic life-history patterns as adults. If the recent single-species classification of Chelonibia testudinaria continues to be upheld, the species represents a cosmopolitan and highly diverse life history with settlement on sea turtles, manatees, dugongs, and crustaceans. This species is therefore exposed to a wide variety of environmental conditions, including changes in ecosystems, water flow, pressure, and salinity. While spatial distribution of C. testudinaria on loggerhead turtle (Caretta caretta) carapaces—and therefore areas of variable flow—presents some evidence for potential plasticity in epibiotic cirri, interhost comparisons are lacking. To determine if morphology differs significantly by host, we conducted discriminant function analyses (DFAs) with twelve cirral measurements from barnacle specimens collected from both sea turtle and manatee hosts. Overall, we show greater than 94% discrimination in the classification of original grouped cases and cross-validated grouped cases in generalized and stepwise discriminant models. While plasticity remains evident within the Chelonibia genus, our data provide evidence contradictory to the currently accepted hypothesis that this plasticity is dependent upon, and strongly correlated with, host association. Therefore, we suggest that the single-species designation of the Chelonibia testudinaria complex be reevaluated.

Using ISSR markers to detect genetic variation for marine turtles populations in Egypt loggerhead (Caretta caretta) and green turtles (Chelonia mydas)

In Egypt, along the Mediterranean coast, the loggerhead (Caretta caretta) and green (Chelonia mydas) come during nesting season to lay their eggs or for food with a rare occurrence for the leatherback turtle (Dermochelys coriacea). In the Egyptian Red Sea there are five species that come to visit, the most common to observe are hawksbill (Eretmochelys imbricata) and green (Chelonia mydas). The goal of this study is to conduct some genetic and ecological analyses a) to generate new markers that include other segments of marine turtles’ genome, as a tool to investigate new areas of variation/polymorphism between, among, and within populations and individuals; b) determine genetic diversity between and within the Mediterranean and the Red Sea populations using (individuals from the same and different habitats using ISSR); and c) determine allele frequency. At the ecological level, this study aims to assess sea turtles' habitat and population distribution among different habitats in Egypt. Throughout the duration of this study, it was noted that there was a decrease in nesting areas attributable to the loss and fragmentation of habitats. Although there are some areas with no significant nesting prosperities it considered significant areas for foraging and highly important as migratory corridors, especially in the Mediterranean. The massive urbanization and unplanned touristic developments affect sea turtle habitat over the Egyptian Mediterranean coast. The Mediterranean coast showed demographic changes in the coastal regions. On the other hand, areas could still be valued with significant nesting areas for sea turtles, but an intense and regular monitoring programme should be established. The Red Sea needs a regular monitoring programme for better management conservation measures to be adopted. The polymorphism percentage resulting from ISSR marker was 45 and 36 for both loggerhead and green turtle populations in the Mediterranean, respectively; and 69 for the green turtle populations in the Red Sea.

Loggerhead Sea Turtles Hand-Reared in Captivity: Isotopic Insights into Their Inherent Dietary Variation

Loggerhead Sea Turtles Hand-Reared in Captivity: Isotopic Insights into Their Inherent Dietary Variation

Small differences between primary and breeding sex ratios at the largest loggerhead turtle rookery in the North Pacific

Small differences between primary and breeding sex ratios at the largest loggerhead turtle rookery in the North Pacific

Satellite telemetry reveals high-use internesting areas and international foraging extent for loggerhead turtles tagged in southeast Florida, USA

Satellite telemetry reveals high-use internesting areas and international foraging extent for loggerhead turtles tagged in southeast Florida, USA

Conservation Genetics of the Loggerhead Sea Turtle, Caretta caretta, from the Central Mediterranean: An Insight into the Species' Reproductive Behaviour in Maltese Waters.

Loggerhead sea turtle, Caretta caretta (Linnaeus, 1758), nestlings were investigated through specimens found dead either after hatching or unhatched (n = 120) from eight nests around the Maltese islands (Central Mediterranean). Molecular genetics was used to conduct maternity and paternity tests of the collected specimens utilizing expanded mitochondrial DNA sequences from the control region (858 bp) and 25 microsatellite loci (12 dinucleotide loci and 13 tetranucleotide loci). Mitochondrial data produced two haplotypes, CC-A2.1 and CC-A3.1, with the most common haplotype being present in seven nests. Microsatellite data revealed the identity of six different females that were involved in the deposition of the eggs in the eight turtle nests analysed. This confirms that two females laid multiple nests. Additionally, microsatellite data allowed for the determination of multiple paternity, with one clutch being sired by two fathers. These results are useful for monitoring the genetic diversity of loggerhead sea turtle nestlings and of the turtle mothers and fathers contributing to future turtle offspring, which rely on Maltese sandy beaches for their successful start to life. Effective conservation management benefits from merging scientific knowledge with effective measures at potential nesting sites to avoid losses of nestlings caused by human negligence.

Occurrence and pattern of legacy and emerging per- and Poly-FluoroAlkyl substances (PFAS) in eggs of loggerhead turtle Caretta caretta from western Mediterranean

Per-and Poly-FluoroAlkyl Substances (PFAS) are a class of persistent, toxic, and mobile and chemicals both from industrial sources and from the use and disposal of Consumers products containing PFAS, whose concentration in marine food webs could pose a toxicological risk for biota and humans. In 2021, unhatched eggs were sampled from 41 loggerhead turtle Caretta caretta nests from the Italian shores of the Campania Region (Southern Italy). Whole eggs were analysed for the presence of 66 legacy and emerging PFAS with Liquid Chromatography coupled to Hybrid High Resolution Mass Spectrometry. A median Σ66 Per- and Poly-FluoroAlkyl Substances value of 3.34 ng/g egg fresh weight was found; perfluoroctane sulfonate (PFOS) represented the most contributing congener (47%), followed by perfluoro-n-undecanoic acid, perfluoro-n-tridecanoic acid, perfluoro-n-decanoic acid, perfluoro-n-decanoic acid, and perfluoro-n-tetradecanoic acid, respectively. Such compounds showed a log-norm distribution, suggesting found concentrations could represent the baseline levels in the considered sampling area. Emerging ChloroPolyFluoroPolyEthers Carboxylic Acids (ClPFECAs) were found in 20 out of 41 samples in the range 0.01–1.59 ng/g. Four samples had 20–100 fold higher concentration compared to that of other samples, suggesting the presence of hot spot areas possibly related to presence of fluoropolymer-based marine litter turtles may ingest. The analysis of two paired eggs/liver samples recovered from stranded animals revealed PFAS concentration in the same order of magnitude, supporting the role of vitellogenin in their selective transfer to yolk. Significant (P = 0.0155) Kendall negative correlation coefficient of −0.2705 among PFOS content in eggs and the recorded hatching success prompts for further investigation on associated exposure assessment and related eco-toxicity risk. This work reports for the first time PFAS presence in georeferenced loggerhead turtle eggs of the Mediterranean Sea and results represent a starting point to study PFAS time-trends in this vulnerable species.

New nesting site for the expanding green, olive ridley and hawksbill turtle populations in Cabo Verde

Currently, some sea turtle populations are expanding their home range distribution toward higher latitudes at an unprecedented rate. These expansions are associated to factors such as climate change or and increased conservation efforts. Already home to one of the largest loggerhead turtle (Caretta caretta) rookeries in the world, the islands of Cabo Verde Archipelago have recorded sporadic nesting of green (Chelonia mydas), olive ridley (Lepidochelys olivacea) and hawksbill (Eretmochelys imbricata) turtles in recent years. Here, we present the compiled information on these sporadic nesting events that occurred between 2013 and 2022 and discuss possible causes for their occurrence. Throughout the study period, the green turtle was documented on 20 occasions, the olive ridley on 25 occasions and the hawksbill on three occasions. All nesting females were found untagged and were subsequently tagged. Nesting activities occurred on the islands of Santo Antão, Sal, Boa Vista and Maio, most of them within the Sea Turtle Natural Reserve in Boa Vista Island. We suggest introducing new conservation strategies targeting the green, olive ridley, and hawksbill turtles nesting in Cabo Verde. We further suggest the use of genetic studies to determine the population origins of these three species.

Assessing microplastics contamination in unviable loggerhead sea turtle eggs

Sea turtles, in comparison with marine mammals, sea birds, and fishes, are the most affected by microplastics in terms of number of individuals impacted and concentration within each organism. The ubiquitous nature and persistence of microplastics in the environment further compromises sea turtles as many species are currently vulnerable, endangered, or critically endangered. The objective of this study was to quantify microplastic contamination in unviable loggerhead sea turtle eggs (Caretta caretta). Eggs were collected from seven locations along the northwest coast of Florida. A total of 70 nests and 350 eggs were examined. Microplastics (n = 510) were found in undeveloped loggerhead sea turtle eggs across all seven sites, suggesting that maternal transference and/or exchange between the internal and external environment were possible. The frequency found was 7.29 ± 1.83 microplastic pieces per nest and 1.46 ± 0.01 per egg. Microplastics were categorized based on color, shape, size, and type of polymer. The predominant color of microplastics were blue/green (n = 236), shape was fibers (n = 369), and length was 10–300 μm (n = 191). Identified fragments, films, beads and one foam (n = 187) had the most common area of 1–10 μm2 (n = 45). Micro-Fourier Transform Infrared (μ-FTIR) spectroscopy analysis demonstrated that polyethylene (11 %) and polystyrene (7 %) were the main polymer types. For the first time microplastics were found in unviable, undeveloped loggerhead sea turtle eggs collected in northwest Florida. This work provides insight into the distribution patterns of microplastic pollutants in loggerhead sea turtle eggs and may extend to other species worldwide.

First Record on Loggerhead Nest in Gökçeada, Türkiye in Northern Aegean

This study presents the first report of a loggerhead turtle nest in the northern latitudes in the Aegean Sea of Türkiye, which was found on the Gökçeada Island of Çanakkale Province, Turkey. The nest contains a total of 129 eggs, 103 of which produced hatchlings and 100 of these hatchlings reached to the sea safely. This sporadic record may be a result of mechanisms developed to overcome the limitations of philopatry and increase their ability to adapt to the predicted global climate change.

At sea mortality estimates of loggerhead turtle (Caretta caretta) in Southwestern Atlantic Ocean

Sea turtles are vulnerable to various threats, with incidental capture in fisheries being a main concern. Limited knowledge exists regarding sea turtle mortality at sea, and stranding events serve as an indicator of such mortality. However, stranding data only represent a fraction of the turtles killed in the ocean. The southern coast of Brazil is an important foraging area for loggerhead turtles. This study aimed to estimate loggerhead turtle mortality at sea in southern Brazil using stranding data. Between 2012 and 2016, a total of 70 incidentally caught and dead turtles in pair trawl fisheries were tagged and released back into the sea, with the recording of date and geographic position. Biweekly beach surveys were conducted in an effort to retrieve these carcasses. Bayesian logistic regression models were employed to assess the influence of meteoceanographic and geographic variables on the stranding probabilities of tagged turtles. Considering the total number of stranded loggerhead turtles in the study area and the predicted stranding probabilities, the annual mortality of the species at sea was estimated. Season, distance from the shore, and currents were identified as variables influencing the stranding probability. The stranding probability was 19.72 % for the warm period and 12.96 % for the cold period. A total of 1897 loggerhead turtles stranded between 2012 and 2016. The estimated mortality during this period was 14,377 loggerhead turtles killed. This high mortality can have a substantial impact on the population, thus conservation measures that effectively protect sea turtles are in urgent need.

Glavonošci kao plijen glavate želve, Caretta caretta (Reptilia: Cheloniidae), iz istočnog Tirenskog mora

This study presents the results of the examination of cephalopod remains extracted from the digestive tract of 40 loggerhead turtles, Caretta caretta, stranded along the Campanian coasts (Southern Italy, eastern Tyrrhenian Sea). We retrieved the remains of 23 cephalopods from 16 turtles (frequency of occurrence = 40%). They belonged to Sepia officinalis (19 specimens) and Octopus vulgaris (2 specimens), both of them benthic neritic species, and Histioteuthis reversa (2 specimens), an oceanic species. Accordingly, loggerheads appear to feed both on the bottom, seemingly in shallow waters, and in the open seawater column; both on muscular items (S. officinalis and O. vulgaris) and ammoniacal ones (H. reversa). This is the first record of H. reversa as a prey of the loggerhead turtle.

Uncovering loggerhead (Caretta caretta) navigation strategy in the open ocean through the consideration of their diving behaviour.

While scientists have been monitoring the movements and diving behaviour of sea turtles using Argos platform terminal transmitters for decades, the precise navigational mechanisms used by these animals remain an open question. Until now, active swimming motion has been derived from total motion by subtracting surface or subsurface modelled ocean currents, following the approximation of a quasi-two-dimensional surface layer migration. This study, based on tracking and diving data collected from 25 late-juvenile loggerhead turtles released from Reunion Island during their pre-reproductive migration, demonstrates the importance of considering the subsurface presence of the animals. Using a piecewise constant heading model, we investigate navigation strategy using daily time-at-depth distributions and three-dimensional currents to calculate swimming velocity. Our results are consistent with a map and compass strategy in which swimming movements follow straight courses at a stable swimming speed (approx. 0.5 m s-1), intermittently segmented by course corrections. This strategy, previously hypothesized for post-nesting green and hawksbill turtles, had never been observed in juvenile loggerheads. These results confirm a common open-ocean navigation mechanism across ages and species and highlight the importance of considering diving behaviour in most studies of sea turtle spatial ecology.

Successful reproduction of female loggerhead sea turtles with severe limb amputations

AbstractWe evaluate the frequency of flipper amputation and its impact on reproduction in the threatened loggerhead turtle (Caretta caretta) population of the Eastern Atlantic, through a long‐term study on several high‐density nesting beaches of Cabo Verde. 5982 adult females were individually identified, tagged and measured, and the presence of limb amputations was recorded. 918 of them had one or multiple amputations of the rear or front flippers. Most of these turtles (n = 778) had partial rather than complete flipper amputations. However, we found no difference in body condition indices (1.2 vs. 1.1), clutch size (82 vs. 83 eggs), or hatching success (79 vs. 80%) between amputated and non‐amputated females. While amputations may cause individual mortality or reduced fitness, our results indicate that some amputated turtles successfully nest and survive across multiple nesting seasons. Moreover, the amputations do not appear to be impacting the strong recovery of this population. This study provides evidence of the successful reproductive capacity of amputated loggerhead sea turtles and, by extension, the potential reproductive success of amputees released from recovery centers.

Whole mitochondrial genome sequencing provides new insights into the phylogeography of loggerhead turtles (Caretta caretta) in the Mediterranean Sea

Population structure and phylogeography of the loggerhead sea turtle (Caretta caretta) have so far been assessed mainly by mitochondrial DNA (mtDNA) single-gene sequencing studies. However, phylogenetic relationships amongst matrilines, genetic characterisation of rookeries and mixed-stock analyses have suffered from the limited resolution obtained by comparison of relatively short sequences such as from the mtDNA control region. Whole mitogenome sequencing can significantly improve population genetics, particularly in marine organisms showing female natal philopatry. Despite mitogenomics becoming increasingly common in biodiversity monitoring and conservation, only a few complete mitogenomes are available for C. caretta. In this study, we sequenced the complete mtDNA of 61 loggerhead turtles sampled between 2008 and 2021 along the Italian coastline and central Mediterranean Sea. We assigned complete mtDNA haplotypes to dead embryos and bycatch samples, and introduced a first nomenclature for loggerhead mitogenomes. Analysis of mtDNA diversity, Maximum Parsimony and Bayesian phylogenetic reconstruction allowed improved resolution of lineages with respect to studies reporting on partial mtDNA control region sequence comparisons, and we were able to further inform previous analyses on loggerhead ancestry based on control region haplogroups. Overall, whole mitogenome analysis has potential for considerable improvement of evolutionary history and phylogeographic investigations as well as mixed-stock surveys of loggerhead turtles.

Quantifying Abundance and Mapping Distribution of Loggerhead Turtles in the Mediterranean Sea Using Aerial Surveys: Implications for Conservation

In the Mediterranean, incidental captures in fishing gear contribute to the high mortality of loggerhead turtles (Caretta caretta). Understanding the effects of bycatch is complex and requires robust knowledge of baseline population parameters such as abundance and density, as well as an understanding of animals’ distribution in relation to commercial fishing efforts. Based on data collected during multi-species line transect aerial surveys conducted between 2009 and 2017, we present density and abundance estimates, corrected for availability bias, for a large sector of the central Mediterranean, discuss temporal and spatial patterns and provide Potential Biological Removal (PBR) values for the monitored areas. Sightings data were also used to evaluate the spatial and temporal usage areas. Strong latitudinal and longitudinal gradients in density, abundance and area usage emerged from the analysis, with turtles occurring in higher numbers in the deeper pelagic waters of the Tunisian Plateau, the Ionian Sea and the Gulf of Taranto, irrespective of the season. PBR values derived from this study are likely unsustainable. This paper investigates the implications of commercial fisheries for Mediterranean loggerhead turtles across an area rarely included in sea turtle monitoring and has the potential to be relevant towards informed management and conservation of this species and highlights the necessity of international collaborative efforts in the region.

Identifying biomarkers of pollutant exposure in ocean sentinels: Characterisation and optimisation of B-esterases in plasma from loggerhead turtles undergoing rehabilitation

Sea turtles are frequently proposed as indicator species for assessing ocean health. To faciliate the use of these species as bioindicators requires the development of tools for rapidly and effectively assessing individual health. Here, we collected 104 blood samples from 69 loggerhead sea turtles, Caretta caretta, undergoing rehabilitation to determine the connection between health status, the activity of B-esterases, and other biochemical parameters. To determine the optimal assay protocol for B-esterases, we measured the activity and kinetics of cholinesterases-(ChEs) and carboxylesterases (CEs) using 3 and 5 commercial substrates, respectively, at different assay conditions. IC50 values for the activity of B-esterases were calculated within a concentration range for model pesticide inhibitors. Turtles’ health status was determined via routine veterinary procedures. During rehabilitation (which was associated with improving health status), we observed a decrease in the activity of most enzymes (especially in acetylcholinesterase) alongside an increase in CE when using p-nitrophenyl acetate as a substrate. As such, it is possible that the activity rates of plasmatic B-esterases could serve as an indicator of health status. There is also high potential that B-esterases could be specifically sensitive to marine pollutants although to further validate this would require future studies to specifically correlate B-esterarse activities to pollutant concentrations in blood or excreta.

Notable Stingray Spine-Associated Strandings Involving Two Female Bottlenose Dolphins in Florida and Massachusetts, USA, in the Context of Literature and Database Reviews

Trauma from stingray spines (caudal barbs) has been intermittently documented as a cause of mild to fatal illness in odontocetes, particularly bottlenose dolphins (Tursiops truncatus), as well as in pinnipeds, sirenians, the loggerhead sea turtle, great white shark, and cobia. Although stingray spines have been noted to cause serious injury to various organ systems, their potential involvement in cetacean reproductive tract pathology has not been previously described. In North America, published descriptions of wild cetacean strandings associated with stingray spines have all involved bottlenose dolphins in the southeastern United States, plus a bottlenose dolphin and a common dolphin (Delphinus delphis) in Mexico. In 2018, uterine rupture was observed in a gravid bottlenose dolphin found deceased in Florida with stingray spine penetration into the abdominal cavity. Gross necropsy and histopathology findings were compatible with the stingray spine being involved with the rupture. To provide fuller insight into the case, a scientific literature review was conducted, and results of an unpublished 1998 necropsy involving a coastal female bottlenose dolphin that stranded in the northeastern state of Massachusetts with stingray spine presence was reviewed. Additionally, a query of the nationwide U.S. marine mammal stranding database was conducted for stingray spine-associated cetacean strandings from 1995 to 2019. Of 61 cetacean strandings revealed in the query to involve stingray spine presence, 59 were bottlenose dolphins from the southeastern U.S. states, plus Puerto Rico and Virginia; a bottlenose dolphin in southern California and a short-finned pilot whale (Globicephala macrorhynchus) were also noted. Query results did not support a bottlenose dolphin sex predilection for stingray spine-associated strandings; most such strandings involved adults. Behavioral, environmental, anthropogenic, and climatic events may influence marine mammal–stingray interactions. Continued vigilance for stingray spine-associated pathologic changes is warranted during marine mammal stranding investigations at diverse geographic sites.

Cetacean and Sea Turtle Observations in the Remote Mid-Atlantic (NW) Ocean

Due to its remoteness, little is known about the occurrence and abundance of cetaceans and sea turtles in the pelagic mid-Atlantic Ocean. Data on cetacean and sea turtle occurrence and distribution were collected by dedicated biological observers to address U.S. monitoring and mitigation requirements associated with a vessel-based academic geophysical survey in international waters in the northwestern and mid-Atlantic Ocean from 14 June through 16 July 2018. A total of 6,949 km (503 h) of visual observations occurred while surveying north from Bermuda and ending in Woods Hole, Massachusetts. A total of 928 cetaceans representing at least 14 species and 15 sea turtles representing three species were observed. The most frequently observed cetacean species was the Atlantic white-sided dolphin (Lagenorhynchus acutus) (340 individuals; 37%) followed by the short-beaked common dolphin (Delphinus delphis) (286 individuals; 31%) and pilot whales (Globicephala spp.) (95 individuals; 10%). These sighting data also included an extralimital sighting of a sperm whale (Physeter macrocephalus) calf at 43.44° N latitude and 36.85° W longitude, and extralimital sightings of Atlantic white-sided dolphins below 38° N latitude. Loggerhead sea turtles (Caretta caretta) were seen most frequently (6 individuals). This study addresses a data gap in documented occurrence and lack of occurrence of cetaceans and sea turtles over a large pelagic area in the northwestern Atlantic Ocean during summer.

Effects of Emergence on Hatchling Phenotypes in Loggerhead Sea Turtles (Caretta caretta) of the North Pacific

Effects of Emergence on Hatchling Phenotypes in Loggerhead Sea Turtles (Caretta caretta) of the North Pacific