Search Results (206)

Human exploitation has been a major driver of marine turtle population declines, particularly affecting naturally scarce species such as the pantropical hawksbill turtle. Although hawksbill sea turtles have been documented in the Gulf of California since the early 20th century, data on their historical demography during periods of high exploitation in this region are nonexistent. We investigated the size structure of hawksbill turtles from the Western Central Gulf of California by examining a unique sample of decorative taxidermies, corresponding to 31 specimens captured during fishing operations near Santa Rosalía, Baja California Sur, Mexico, between 1980 and 1990. An analysis of the curved carapace measures revealed a length range (nuchal notch to posterior of supracaudals) of 29.5–59.5 cm (mean = 38.75 ± 6.67 cm) and a width range of 25.0–51.5 cm (mean = 33.63 ± 5.66 cm), with 87% of specimens having lengths between 30 and 45 cm. Based on the carapace length measurements, we estimated the ages to be between 7 and 20 years, indicating that the population included juveniles. Our findings provide baseline data for an understudied period and region, suggesting that this area previously served as an important juvenile habitat. These results contribute essential historical demographic information for conservation planning. Full article

The Kaiparowits Formation preserves one of the best fossil records of Cretaceous North America, which provides great insight into the paleoecology. In an effort to investigate the paleohydrology of the Kaiparowits Formation, stable isotope compositions (δ¹³C, δ¹⁸O-carbonate, δ¹⁸O-phosphate) of 41 hadrosaur teeth, 27 crocodile teeth, and 35 turtle shell fragments were analyzed. The mean O-isotope compositions of drinking water (δ¹⁸O_w) calculated from the O-isotope of bioapatite (phosphate-δ¹⁸O_p) are −13.76 ± 2.08‰ (SMOW) for hadrosaur, −8.88 ± 2.76‰ (SMOW) for crocodile, and −10.14 ± 2.62‰ (SMOW) for turtle, which strongly reflect niche partitioning. The Kaiparowits formation does not fit the global trend in isotopic compositions of vertebrate skeletal remains from previous studies, which suggests a unique hydrological setting of the Kaiparowits basin. High-elevation runoff from the Mogollon Highlands and sea level fluctuation may have contributed to such a unique paleohydrology. Full article

The gut microbiome of sea turtles is essential for their ecological resilience and adaptation to environmental stressors. We hypothesised that different gut microbial profiles existed between green sea turtles kept in captivity and those in the wild. The aim of this systematic review was to determine dominant bacterial phyla in the gut microbiomes of wild and captive green sea turtles. Comparison of the top four bacterial phyla revealed that Bacillota was the most abundant phylum in captive turtles (40.9–87.5%), but it only ranked second (3.5–57.8%) in wild turtles. Bacteroidota had comparable relative abundance in captive (8.7–45.6%) and wild (3.6–43.1%) populations. By contrast, the relative abundance of Pseudomonadota was higher in wild turtles (6.2–68.1%) compared to the captive population (0.1–6.6%). Verrucomicrobiota was less prevalent in wild and captive populations, with relative abundances ranging from 0.28 to 5.4% and 2.3 to 7.2%, respectively. These findings highlight a putative gut microbial shift between wild and captive green sea turtle populations. This shift may be shaped by variations in environmental factors in captivity or the wild. Nonetheless, the significance of these putative changes is still unknown; the potential to use microbial shifts to guide management, rehabilitation, and conservation of green sea turtles is promising, but remains limited. Full article

This review synthesizes current research on hydrofoil-propelled robots inspired by the swimming mechanisms of sea turtles and penguins. It begins by summarizing the swimming kinematics of these organisms, highlighting their superior aquatic performance as the primary motivation for biomimetic design. Next, established analytical methods for characterizing hydrofoil locomotion patterns are presented, along with a clear delineation of the decoupled motion components exhibited by sea turtle flippers and penguin wings. Such decoupling provides a systematic framework for guiding the design of driving mechanisms. Building on this biomechanical foundation, the review critically examines recent advances in biomimetic flexible hydrofoils that enhance propulsion efficiency through three synergistic mechanisms to enhance thrust generation, while identifying key challenges in material durability and non-linear fluid–structure interactions. The review then surveys existing hydrofoil actuation systems, which commonly reproduce coupled motions with multiple degrees of freedom (DOFs). Finally, representative biomimetic robots are examined: sea turtle-inspired forelimbs typically incorporate three DOFs, whereas penguin-inspired wings usually offer two DOFs. By aligning robotic designs with the decoupled motion patterns of the source organisms, this review offers critical insights to advance the development of hydrofoil propulsion systems for enhanced aquatic performance. Full article

Sea turtles use specific nesting strategies to maximize the survival of their offspring. Few studies have investigated the nesting behavior of leatherback (Dermochelys coriacea) and hawksbill (Eretmochelys imbricata) turtles. The aim of this study was to characterize the nesting behavior of these two species, taking into account anthropogenic and natural impacts, and to compare behavior between species. Nocturnal monitoring was conducted from 2020 to 2024 on three beaches in Martinique: Madiana, Diamant, and Salines. The average duration of the nesting sequence for leatherback turtles was 101.50 min, with camouflage being the dominant behavior for 27.06% of the total time. For hawksbill turtles, nesting duration was 109.49 min, with digging as the predominant activity (31.68% of total time). No effect of anthropogenic disturbances and obstacles on the behavior of leatherback turtles was observed, while that of hawksbill turtles was significantly influenced by light and the presence of roots. The results revealed behavioral differences between these two species, as well as between two other species: loggerhead (Caretta caretta) and green (Chelonia mydas) turtles. These differences could be explained by morphological differences, nesting habitat peculiarities, beach characteristics, and different evolutionary strategies. Further research is needed to better understand these behaviors and improve conservation efforts. Full article

On the beach of Linosa Island (Italy), 43 loggerhead sea turtle (Caretta caretta) unhatched eggs were recovered from nests, formalin-fixed and necropsied. The tissue samples were stained with hematoxylin-eosin (HE), Grocott, von Kossa, periodic acid-Schiff (PAS), and Movat pentachrome stains. Histologically, vacuolar degeneration (100.0%) and increased numbers of melanomacrophages (18.6%) in the liver, and edema (14.0%) in the lungs were observed. Twenty-five kidneys (58.1%) showed deposition of blue amorphous material with HE staining, which also appeared PAS-positive and black with von Kossa staining, allowing a diagnosis of calcium oxalate, confirmed by transmission electron microscopy (TEM). The hepatic lesions may be indicative of toxicosis, infection, or a defense mechanism. A statistically significant association between the nest position and renal oxalosis (renal calcium oxalate deposition) was observed. Renal oxalosis was probably due to the exceptionally high summer temperatures, which were statistically higher compared to the temperatures recorded in the previous two years. Full article

This work assessed the sexual maturity of breeding females and males of black sea turtles (Chelonia mydas agassizii) from the population in Michoacan, Mexico. This study also provides the first report of the age at sexual maturity for male black sea turtles in the eastern Pacific. Using information on juvenile growth rate, length, and age at recruitment of juveniles in the developmental habitats in Baja California (Magdalena Bay), sexual maturity was estimated from the minimum and average standard carapace lengths (SCL) of nesting females (n = 1500) on Colola Beach and males (n = 132) captured at sea using the “swim up” technique. Differential sexual maturity was found in females and males. The minimum age at sexual maturity for males was 23.0 years at a minimum size of 61.1 cm SCL and the maximum age at sexual maturity was 32.5 years at a maximum size of 76.6 cm SCL. The minimum age of sexual maturity for nesting females was 24.9 years at a minimum size of 64.2 cm SCL, while the age of sexual maturity for maximum size was 42.9 years at a 93.4 cm SCL. Differences in the age at sexual maturity influence reproductive behavior and female carapace shape, impacting mating success. Full article

Due to the high dimensional integration over latent variables, computing marginal likelihood and posterior distributions for the parameters of a general hierarchical model is a difficult task. The Markov Chain Monte Carlo (MCMC) algorithms are commonly used to approximate the posterior distributions. These algorithms, though effective, are computationally intensive and can be slow for large, complex models. As an alternative to the MCMC approach, the Laplace approximation (LA) has been successfully used to obtain fast and accurate approximations to the posterior mean and other derived quantities related to the posterior distribution. In the last couple of decades, LA has also been used to approximate the marginal likelihood function and the posterior distribution. In this paper, we show that the bias in the Laplace approximation to the marginal likelihood has substantial practical consequences. Full article

Background/Objectives: Antimicrobial resistance (AMR) is a major global health concern with profound implications for human, animal, and environmental health. Marine ecosystems are emerging as reservoirs of resistant bacteria due to contamination from anthropogenic activities. This study aimed to investigate fluoroquinolone-resistant and multidrug-resistant bacteria in loggerhead sea turtles (Caretta caretta). Methods: Cloacal swabs were collected from 28 loggerhead sea turtles at a rescue center in southern Italy. Swabs were cultured in nutrient media supplemented with enrofloxacin. Bacterial isolates underwent identification by MALDI-TOF, antimicrobial susceptibility testing, and assessment for multidrug resistance. Conjugation experiments evaluated the transferability of enrofloxacin resistance. Results: Thirty-six enrofloxacin-resistant bacterial strains were isolated from 22 turtles. The identified species included Vagococcus fluvialis (13 strains), Citrobacter freundii (5), Escherichia coli (6), and Pseudomonas mendocina (4). Thirty-five isolates exhibited multidrug resistance, with resistance to critically important antibiotics such as imipenem observed in C. freundii and Enterobacter faecium. Conjugation experiments showed no transfer of resistance genes. Conclusions: The study highlights the prevalence of fluoroquinolone-resistant and multidrug-resistant bacteria in C. caretta, implicating marine environments as reservoirs of AMR. The findings underscore the need for stricter regulation of antimicrobial use and monitoring of resistance dissemination in marine ecosystems. These results contribute to understanding AMR dynamics within the One Health framework, emphasizing the interconnectedness of environmental, animal, and human health. Full article

Variations in the ecological roles of sea turtle species may lead to differentiations in ocular design and visual sensitivity to the colour spectrum. Behavioural colour preference studies in air and in water on hatchling and post-hatchling green turtles found evidence of a blue hue attractiveness when given a choice between blue, red, and yellow. This paper assessed and compared the colour preferences to singular colours via the behavioural responses of eleven hawksbill turtles and twelve green turtles at 15 months of age and at 22 months of age. Turtles were presented with one coloured water balloon per day (purple (400–450 nm), dark blue (450–490 nm), cyan (490–520 nm), green (520–560 nm), yellow (560–590 nm), orange (590–635 nm), and red (635–700 nm)). Time to contact balloons with beak and behaviours exhibited by turtles were recorded. Hawksbill turtles had the greatest level of interactions across both phases to shorter wavelengths with hue preference being between 450 and 490 nm. Green turtles consistently had the greatest level of interaction to longer wavelengths with a yellow (560–590 nm) hue preference. The results of this study support behavioural differences between two co-occurring turtle species that may reflect an adaptive preference for colour wavelengths associated with the optimal foraging niche for each. Full article

To develop safe and effective management policies, it is important to understand the physiologic effects of fishing interactions and scientific research methods on endangered marine species. In the present study, validated assays for plasma corticosterone, free thyroxine (fT4), and aldosterone were used to assess the endocrine status of 61 presumed healthy, wild Kemp’s ridley sea turtles (Lepidochelys kempii) that were captured for separate ecological studies using two capture methods (trawl net n = 40; manual capture n = 21). Plasma hormone concentrations were also assessed in relation to eight clinical plasma biochemical analytes. Corticosterone and aldosterone concentrations were moderately high after capture, with significantly higher concentrations in turtles captured by trawl net vs. manual capture. Free thyroxine concentrations were within previously published ranges for healthy individuals of this species. Clinical biochemical data revealed moderately elevated potassium and lactate concentrations in many individuals, with significantly greater lactate concentrations in trawl-captured turtles. Aldosterone concentrations were positively correlated with corticosterone. The results of the present study indicate that Kemp’s ridley sea turtles have robust adrenocortical activity immediately after capture, resulting in high plasma concentrations of corticosterone and aldosterone. Researchers who use such methods to access sea turtles can consider these results in planning careful and efficient field studies. Full article

This study investigated the population dynamics, growth, reproduction, and parasitism of Penaeus aztecus over a 27-month period in Antalya Bay (Eastern Mediterranean). P. aztecus was the most abundant shrimp species, comprising 53.4% of the collected shrimp specimens. Abundance varied seasonally, with peak densities in summer. Males had a smaller mean carapace length (CL) of 25.8 mm compared to females at 30.2 mm. Females dominated larger size classes, with all individuals ≥ 46 mm CL being female. The sex ratio was balanced at 1:1, with no seasonal variations. Spawning occurred year-round, peaking in June, late summer, and November. Females displayed four ovarian stages, with the first mature size (FMS) at 36 mm CL. Parasitism by Epipenaeon ingens reduced the density of mature females, with 42% of potential spawners failing to develop gonads. The prevalence of parasitism showed seasonal variation and was inversely correlated with sea surface temperature (SST). Marine recruitment occurred from June to November, with a peak between July and September. Growth analysis revealed faster rates in females, while males reached a smaller maximum size. This study also identified inefficiencies in gear selectivity, with many juvenile shrimp (below recruitment size) being retained. Trawl efficiency improved with the use of turtle excluder devices (TEDs), which reduced bycatch of nontarget species, such as loggerhead turtles and cartilaginous fishes. The instantaneous total mortality rate (Z) ranged from 0.658 to 0.026 month⁻¹ for male shrimp and from 1.00 to 0.014 month⁻¹ for female shrimp, with survival sharply declining after recruitment, leaving only about 3.6% of individuals surviving beyond 10 months. Full article

Numerous interactions between human activities and wildlife currently impact various species. In recent decades, these activities have contributed to declining sea turtle populations. The waters around Spain serve as important staging areas for sea turtles, particularly Caretta caretta, which spend part of their life cycle there. However, these same waters threaten turtles because of various causes of stranding. This study aims to comprehensively understand the rehabilitation process for these animals at the Wildlife Rehabilitation Center (WRC) La Tahonilla in Tenerife, Canary Islands. It also seeks to explore rehabilitation efforts at different centers focused on recovering sea turtles in both the mainland and the Canary Islands. Additionally, we have examined the procedures for addressing stranded sea turtles where a recovery center does not exist. Our findings reveal the existence of varying protocols among different centers in Spain’s mainland and islands. Improving and unifying these protocols is essential for enhancing the rehabilitation of sea turtles in Spain. Full article

To investigate the impact of age on the metabolomic profile of loggerhead sea turtles (Caretta caretta), this study analyzed 100 plasma samples of individuals across two age groups—50 post-hatchlings and 50 juveniles—from various locations along the Mediterranean coastline. Both targeted and untargeted metabolomic analyses were performed on the samples. Our results demonstrated a significant age-related effect on the metabolomic profiles in both analyses. Specifically, post-hatchling turtles exhibited increased levels of urea (p < 0.001), triglyceride (p = 0.0003), cholesterol (p < 0.001), lysoPE (18:1/0:0) (p < 0.001), 7-HDoHE (p = 0.0121), pyrrolidinebutanoic acid (p < 0.001), formiminoglutamic acid (p < 0.001), pyroglutamic acid (p < 0.001), lysoPC (0:0/20:4) (p < 0.001), lysoPE (22:6/0:0) (p < 0.001), 1-acyl-sn-glycero-3-phosphocholine (p < 0.001), DL-homocysteine (p < 0.001) and gamma-Glutamyltyrosine (p < 0.001). Conversely, post-hatchlings showed reduced levels of total protein (p < 0.001), glucose (p = 0.0002), uric acid (p < 0.001), inorganic phosphorus (p = 0.0018) and calcium (p = 0.0410) compared with juveniles. These findings suggest significant physiological changes between the age groups, likely due to differentiated feeding patterns. Further research is needed to better understand the metabolic profiles and complex physiological and nutritional interactions of this species. Full article

The conservation of the olive ridley turtle (Lepidochelys olivacea) is increasingly critical due to declining global populations. This study investigates the influence of hydrometeorological conditions on the nesting season and annual hatchling sex ratios conducted at the Playón de Mismaloya Federal Reserve in Tomatlán, Jalisco, Mexico. The research specifically examines variations in sand temperature at both the beach surface and nesting depths, with extended measurements taken at multiple depths (20, 40, 60, 80, and 100 cm) to analyze the vertical temperature gradient along the beach. Atmospheric parameters were modeled using Newton’s Cooling Law and solved with the finite difference method to estimate heat loss rates from beach sand to its surroundings, shedding light on microclimatic effects on incubation and embryonic development. Meteorological data were gathered from an automatic weather station, while sand temperatures were monitored with thermographs. During the warm period (approximately 32 °C), sand temperature showed a negative correlation with depth (20–100 cm), indicating cooler temperatures at greater depths. These conditions were associated with female-biased hatchling production. Conversely, the cold period (approximately 28 °C) led to male-biased hatchling production, with a positive correlation between sand and air temperatures. This study emphasizes the importance of monitoring in situ environmental conditions and extending the protection season until February to avoid the loss of male hatchlings. Full article