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Cyanobacteria are known for forming associations with various animals, including sea turtles, yet our understanding of cyanobacteria associated with sea turtles remains limited. This study aims to address this knowledge gap by investigating the diversity of cyanobacteria in biofilm samples from loggerhead sea turtle carapaces, utilizing a 16S rRNA gene amplicon sequencing approach. The predominant cyanobacterial order identified was Nodosilineales, with the genus Rhodoploca having the highest relative abundance. Our results suggest that cyanobacterial communities become more diverse as sea turtles age, as we observed a positive correlation between community diversity and the length of a sea turtle's carapace. Since larger and older turtles predominantly utilize neritic habitats, the shift to a more diverse cyanobacterial community aligned with a change in loggerhead habitat. Our research provides detailed insights into the cyanobacterial communities associated with loggerhead sea turtles, establishing a foundation for future studies delving into this fascinating ecological relationship and its potential implications for sea turtle conservation. [ABSTRACT FROM AUTHOR]

Simple Summary: Loggerhead sea turtles have a flexible distribution from oceanic-pelagic to neritic-benthic areas. Their dietary preferences are expected to change from pelagic prey to benthic prey along with habitat use while they increase in size. This study evaluated the gastrointestinal contents of 150 loggerhead sea turtles stranded and/or bycaught along the Italian coasts of the central Adriatic Sea and central Tyrrhenian sea to assess the most common prey phyla. Information on the ingestion of litter has been collected for each carcass as well. This work highlights the need to deepen the knowledge of the feeding ecology and distribution of sea turtles at any developmental stage. According to their life stage, the loggerhead sea turtle (Caretta caretta) is found in a wide range of habitats, from neritic to more oceanic areas. Their feeding habits are expected to change as they develop, along with habitat use. Juvenile sea turtles are hypothesized to feed on pelagic species in oceanic areas, shifting to more benthic prey during the subadult and adult stages. We analyzed the gastrointestinal content from 150 loggerhead sea turtles stranded and/or bycaught along the Adriatic coast of the Abruzzo and Molise regions (n = 89) and the Tyrrhenian coast of the Lazio and Campania regions (n = 61) from 2018 to 2021. Food items were identified to the lowest taxonomic level, and the frequency of occurrence was calculated for each taxon and most recurrent species to assess changes in prey selection during the development. The marine litter was categorized, and the frequency of occurrence was calculated for the ingestion of litter. The most recurrent taxonomic prey group recorded in the Adriatic sample was Arthropoda (94%), followed by Mollusca (63%) and Chordata (34%). In the Tyrrhenian sample, loggerhead sea turtles fed mostly on Mollusca (84%), Arthropoda (38%), and Chordata (26%). Surprisingly, the Adriatic-Tyrrhenian sample groups showed similar feeding behavior between juveniles, subadults, and adults. A similar correlation has been observed concerning the ingestion of litter. Moreover, this study confirms the opportunistic feeding behavior of loggerhead sea turtles and their high adaptability. [ABSTRACT FROM AUTHOR]

Simple Summary: In-water behavioral observation studies of sea turtles are lacking primarily because they are highly migratory throughout their lifecycles. However, utilizing new technology, such as remote stereo-video cameras, allows researchers to collect size-specific data and view relatively natural sea turtle behavior. In this study, we completed stereo-video camera surveys at local artificial reefs, piers, and jetties within the northern Gulf of Mexico from May 2019 to August 2021. We remotely measured sea turtle straight carapace length, assessed wariness using minimum approach distance (MAD) between the turtle and camera operator, and documented behaviors during encounters. Our results indicated that green sea turtles had the smallest mean MAD before a startle response occurred, but the largest range compared to loggerhead and Kemp's ridley sea turtles. Using a linear mixed model, we found that the size of the turtle was an important predictor of MAD. Overall, our results suggest that larger sea turtles became startled at longer distances compared to the smaller individuals surveyed across all the species studied. This study supports the use of stereo-video camera systems as a non-invasive tool to conduct surveys to assess sea turtle behavioral observations in relation to body size. Our understanding of size-specific sea turtle behavior has lagged due to methodological limitations. However, stereo-video cameras (SVC) are an in-water approach that can link body-size and allow for relatively undisturbed behavioral observations. In this study, we conducted SVC dive surveys at local artificial reefs, piers, and jetties in the northern Gulf of Mexico (nGOM) from May 2019 to August 2021. Using SVCs, we measured sea turtle straight carapace length, documented behaviors, and quantified wariness by assessing minimum approach distance (MAD). In green sea turtles (Chelonia mydas), the observed MAD ranged from 0.72 to 5.99 m (mean 2.10 m ± 1.10 standard deviation (SD), n = 73). For loggerhead sea turtles (Caretta caretta), the MAD ranged between 0.93 and 3.80 m (mean 2.12 m ± 0.99 SD, n = 16). Kemp's ridley sea turtles (Lepidochelys kempii) were similar to loggerheads, and MAD ranged from 0.78 to 3.63 m (mean 2.35 m ± 0.99 SD, n = 8). We then evaluated what biological factors could impact the MAD observed by species, but we excluded Kemp's ridleys as the sample size was small. Using a linear mixed model and model selection based on AICc, the top ranked model for both green and loggerhead sea turtles included SCL as the most important factor influencing MAD. MAD did not vary with habitat type for either species. Our results showed that larger individuals, regardless of species, have a greater wariness response, becoming startled at greater distances than smaller individuals. The findings of our study support the use of SVC as an accessible, non-invasive tool to conduct ecologically relevant in-water surveys of sea turtles to link behavioral observations to body size. [ABSTRACT FROM AUTHOR]

In this work we studied total arsenic concentrations in liver, muscle and kidney of 49 individuals of two sea turtle species (loggerhead sea turtles, n = 45; leatherback turtles, n = 4) stranded in Murcia (South-eastern Spain) coastline between 2009 and 2018. In accordance with the literature, muscle was the tissue with the highest concentrations in both species, followed by liver and kidney. Although differences in arsenic concentrations were not statistically significant between the study species, loggerhead sea turtles showed concentrations two or three times higher than those of leatherback turtles, which we attribute to differences on feeding behavior and habitat preferences. Arsenic concentrations in turtles from this area increase evidence of western Mediterranean Sea as a hotspot for metal pollution. Based on the scarce existing knowledge on arsenic toxicity in sea turtles, those levels found in our study are below those responsible for liver damage. [ABSTRACT FROM AUTHOR]

With the aim of evaluating the presence of Fusarium spp. in sea turtles with and without lesions and assessing the risk factors favoring colonization and/or infection, 74 loggerhead sea turtles (Caretta caretta) admitted to rescue and rehabilitation clinics in Italy were analyzed. The study compared 31 individuals with no apparent macroscopic lesions and 43 individuals with macroscopic lesions. Shell and skin samples were analyzed using Calcofluor white with 10% potassium hydroxide, standard histopathological examination, and fungal cultures. Fusarium spp. were isolated more frequently from animals with superficial lesions (39%) than from those with no macroscopic lesions (16%). Isolates from animals with superficial lesions were Fusarium solani species complex (FSSC) lineages haplotypes 9, 12, and 27 (unnamed lineages), FSSC-2 (Fusarium keratoplasticum), Fusarium oxysporum (27%), and Fusarium brachygibbosum (3%). In contrast, only F. solani haplotypes 9 and 12 were isolated from animals with no macroscopic lesions. The presence of lesions was identified as a risk factor for the occurrence of Fusarium spp. Of the 74 animals, only 7 (9.5%) scored positive on microscopic examination with Calcofluor, and histological examination of those 7 animals revealed necrosis, inflammatory cells, and fungal hyphae in the carapace and skin. The results of this study suggest that fusariosis should be included in the differential diagnosis of shell and skin lesions in sea turtles. Direct examination using Calcofluor and potassium hydroxide was not useful to diagnose the infection. Histopathological examination and fungal culture should be performed to ensure correct treatment and infection control. [ABSTRACT FROM AUTHOR]

Abstract 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. Graphical abstract Image 1 Highlights • We examined potential PAH-related biomarkers in whole blood of loggerheads captured alive. • The PAH levels can be associated with selected gene biomarkers transcript levels. • CYP1B, NADP, LMNA and DNMT1 showed the highest gene expression levels. • Whole blood TBARS have been shown to be elevated in high PAH-exposed turtles. • We suggest links between PAH exposure and potential adverse outcomes in sea turtles. This study provides new insights into the relationship between changes in mRNA abundance profiles of specific gene biomarkers and plasma levels of total PAHs in C. caretta turtles. Our results further support the potential of using whole blood cell gene biomarkers for monitoring the impact of environmental contaminants on sea turtles. [ABSTRACT FROM AUTHOR]

Highlights: [•] Anthropogenic debris was ingested by 51.4% loggerheads in the South Indian Ocean. [•] Plastic was the debris category the most prevalent in gut content and fecal samples. [•] Debris ingestion was not significantly affected by biometric characteristics of turtles. [•] We found higher number, weight and mean length of debris in deceased sea turtles. [•] This is the first record of debris ingestion by loggerheads in the Indian Ocean. [ABSTRACT FROM AUTHOR]

We evaluated the presence of 37 organohalogen contaminants in plasma samples from 162 juvenile and 197 adult loggerhead turtles ( Caretta caretta) from the archipelagos of the Canary Islands and Cape Verde, respectively, and compared the contamination profiles found. We detected five organochlorine pesticides (OCP) and 16 polychlorinated biphenyls (PCBs). The concentrations of the two groups of contaminants were higher in turtles from the Canary Islands (OCPs, 1.04 vs. 0.37 ng/mL; PCBs, 1.92 vs. 0.08 ng/mL). We also observed a different profile of PCB contamination between the two populations. In addition, there was a negative correlation between body size and the total concentration of PCBs in the Canary Islands turtles, but not in turtles from Cape Verde. The present study presents the first data on the organochlorine contaminants (OCs) of live turtles from Canary Islands. In addition, we perform a comparison of the levels and profiles of OCs between these two different groups of loggerhead sea turtles from the Eastern Atlantic. [ABSTRACT FROM AUTHOR]

The dash of freshly emerged hatchlings to the sea is a short but critical phase in the life cycle of sea turtles. We examine the time spent on a Mediterranean beach from the perspective of substrate composition and temperature, marine debris, and hatchling crawling speeds and times. Crawling speeds depended on beach quality. The hatchlings crawled significantly faster on sand than on cobbles, and cooler temperatures considerably prolonged the crawls. Marine debris was a major impediment: hatchlings were severely entangled in fishing nets and entrapped in simple containers such as plastic cups and cut-open canisters. They never avoided contact with such experimentally deployed debris or reversed their direction to escape. The overall debris density at the study site averaged 1.03 items m-2, mostly plastic, and 2 out of 3 hatchlings had contact with such debris on the way to the sea. Marine debris is a new aspect of habitat quality for sea turtle nesting site monitoring and conservation efforts and may help explain the long-term decline in nest numbers on this beach. This serves as a case study for the role of habitat quality in the survival of endangered species. [ABSTRACT FROM AUTHOR]

BACKGROUND: Mercury is a pervasive environmental pollutant whose toxic effects have not been studied in sea turtles in spite of their threatened status and evidence of immunosuppression in diseased populations. OBJECTIVES: In the present study we investigate mercury toxicity in loggerhead sea turtles (Caretta caretta) by examining trends between blood mercury concentrations and various health parameters. METHODS: Blood was collected from free-ranging turtles, and correlations between blood mercury concentrations and plasma chemistries, complete blood counts, lysozyme, and lymphocyte proliferation were examined. Lymphocytes were also harvested from free-ranging turtles and exposed in vitro to methylmercury to assess proliferative responses. RESULTS: Blood mercury concentrations were positively correlated with hematocrit and creatine phosphokinase activity, and negatively correlated with lymphocyte cell counts and aspartate aminotransferase. Ex vivo negative correlations between blood mercury concentrations and B-cell proliferation were observed in 2001 and 2003 under optimal assay conditions. In vitro exposure of peripheral blood leukocytes to methylmercury resulted in suppression of proliferative responses for B cells (0.1 μg/g and 0.35 μg/g) and T cells (0.7 μg/g). CONCLUSIONS: The positive correlation between blood mercury concentration and hematocrit reflects the higher affinity of mercury species for erythrocytes than plasma, and demonstrates the importance of measuring hematocrit when analyzing whole blood for mercury. In vitro immunosuppression occurred at methylmercury concentrations that correspond to approximately 5% of the individuals captured in the wild. This observation and the negative correlation found ex vivo between mercury and lymphocyte numbers and mercury and B-cell proliferative responses suggests that subtle negative impacts of mercury on sea turtle immune function are possible at concentrations observed in the wild. [ABSTRACT FROM AUTHOR]

The present study sought to determine bioaccumulation and potential molecular effects of four of the most environmentally significant sunscreen agents in juvenile loggerhead sea turtles (Caretta caretta) from the Italian coasts of the central Adriatic Sea. Each of these sunscreen agents were found in most of the plasma samples analyzed, with benzophenone-3 as the dominant species. Total concentrations of the sunscreen agents ranged from not detected (−1. Almost all of the gene biomarkers of inflammation, oxidative stress and hormonal activity assessed by RT-qPCR in blood tissue showed significant positive correlations with total sunscreen agent concentrations. The present study is the first to provide data on contamination by sunscreen agents in loggerheads, and indicates that these chemicals tend to bioaccumulate and exert potential adverse effects in sea turtles. • Environmentally relevant sunscreen agents were detected in Adriatic loggerheads. • Total concentrations of the UV filters ranged from not detected to 28.43 g mL−1. • Blood gene expression biomarkers were positively associated with total UV filters. [ABSTRACT FROM AUTHOR]