Wild Green Turtles Research Articles

Lethal Lesions Caused by Propeller Cuts on the Endangered Green Turtle Chelonia mydas on Liuchiu Island, Taiwan

Green turtle (Chelonia mydas) is the most common sea turtle species in Taiwan. The coastal waters of Taiwan are known to contain foraging grounds for green turtles. Boat strike has been identified as the most common causes of sea turtle mortality in several sea turtle habitats worldwide. However, no relevant studies have investigated wild green turtles with boat strike injuries in Taiwan. In this field study, we conducted morphometric characteristics of 6 endangered green turtles (C. mydas) with boat strike injuries in Liuchiu Island of Pingtung County, Taiwan. This is the first report of its kind on the prevalence of documented boat strike lesions on stranded wild green turtles at their near shore foraging habitat. In 2019, a total of 14 stranded green turtles were dead when first found in Liuchiu Island of Pingtung County, Taiwan. Of these 14, 6 (42.8%) turtles showing evidence of propeller impacts. Conservation strategies including speed limits in key turtle neritic foraging habitats are required to improve their survival in Taiwan.

Haematological and biochemical reference intervals for wild green turtles (Chelonia mydas): a Bayesian approach for small sample sizes.

Animal health is directly linked to population viability, which may be impacted by anthropogenic disturbances and diseases. Reference intervals (RIs) for haematology and blood biochemistry are essential tools for the assessment of animal health. However, establishing and interpreting robust RIs for threatened species is often challenged by small sample sizes. Bayesian predictive modelling is well suited to sample size limitations, accounting for individual variation and interactions between influencing variables. We aimed to derive baseline RIs for green turtles (Chelonia mydas) across two foraging aggregations in North Queensland, Australia, using Bayesian generalized linear mixed-effects models (n = 97). The predicted RIs were contained within previously published values and had narrower credible intervals. Most analytes did not vary significantly with foraging ground (76%, 22/29), body mass (86%, 25/29) or curved carapace length (83%, 24/29). Length and body mass effects were found for eosinophils, heterophil:lymphocyte ratio, alkaline phosphatase, aspartate transaminase and urea. Significant differences between foraging grounds were found for albumin, cholesterol, potassium, total protein, triglycerides, uric acid and calcium:phosphorus ratio. We provide derived RIs for foraging green turtles, which will be helpful in future population health assessments and conservation efforts. Future RI studies on threatened species would benefit from adapting established veterinary and biomedical standards.

Antimicrobial-resistance profiles of gram-negative bacteria isolated from green turtles (Chelonia mydas) in Taiwan

The green turtle (Chelonia mydas) is listed as a globally endangered species and is vulnerable to anthropogenic threats, including environmental pollution. This study investigated the antimicrobial resistance of Gram-negative bacteria isolated from wild green turtles admitted to a sea turtle rehabilitation center in Taiwan. For this investigation, cloacal and nasal swab samples were collected from 28 green turtles between 2018 and 2020, from which a total of 47 Gram-negative bacterial isolates were identified. Among these, Vibrio spp. were the most dominant isolate (31.91%), and 89.36% of the 47 isolates showed resistance to at least one of 18 antimicrobial agents tested. Isolates resistant to one (6.38%), two (8.51%), and multiple (74.47%) antimicrobials were observed. The antimicrobial agents to which isolates showed the greatest resistance were penicillin (74.47%), followed by spiramycin, amoxicillin, and cephalexin. The antimicrobial-resistance profiles identified in this study provide useful information for the clinical treatment of sea turtles in rehabilitation facilities. The results of our study also imply that wild green turtles may be exposed to polluting effluents containing antimicrobials when the turtles traverse migratory corridors or forage in feeding habitats. To benefit sea turtle conservation, future research should focus on (1) how to prevent pollution from antimicrobials in major green turtle activity areas and (2) identifying sources of antimicrobial-resistant bacterial strains in coastal waters of Taiwan.

Trace Element Concentrations in Blood and Scute Tissues from Wild and Captive Hawaiian Green Sea Turtles (Chelonia mydas).

Sea turtles are exposed to trace elements through water, sediment, and food. Exposure to these elements has been shown to decrease immune function, impair growth, and decrease reproductive output in wildlife. The present study compares trace element concentrations in green turtles in captivity at Sea Life Park Hawaii (n = 6) to wild green turtles in Kapoho Bay, Hawaii, USA (n = 5-7). Blood and scute samples were collected and analyzed for 11 elements via inductively coupled plasma-mass spectrometry (ICP-MS). Selenium was significantly greater (p < 0.05) in the blood of captive turtles compared with wild turtles, whereas V, Ni, and Pb were significantly greater in the blood of wild turtles. In scute, V, Cu, Se, and Cr were significantly greater in captive turtles, whereas As was significantly greater in wild turtles. Pelleted food fed to the captive turtles and representative samples of the wild turtle diet were analyzed via ICP-MS to calculate trophic transfer factors and daily intake values. Wild turtles had greater estimated daily intake than captive turtles for all elements except Cu and Se. Because captive turtles are fed a diet very different from that of their wild counterparts, captive turtles do not represent control or reference samples for chemical exposure studies in wild turtles. No toxic thresholds are known for sea turtles, but rehabilitation and managed care facilities should monitor sea turtle elemental concentrations to ensure the animals' health. Environ Toxicol Chem 2021;40:208-218. © 2020 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Recaptured Wild Green Turtles (Chelonia mydas) with Newly Documented Boat Strike Injuries in Mabul Island, Sabah, Malaysia

We conducted physical examinations of 8 green turtles (Chelonia mydas) with boat strike injuries caught repeatedly near Mabul Island (lat 4.246°N, long 118.630°E), Malaysia, where 1 adult female showed evidence of newly recorded injuries in every capture. The healing progress of boat strike injuries on this turtle and 7 other green turtles of various size classes with similar injuries was documented through repetitive captures from between August 2010 and November 2017. We provide the first report of its kind on the incidence of newly documented boat strike injuries on repeatedly captured wild green turtles at their foraging ground.

Caryospora-Like Coccidia Infecting Green Turtles (Chelonia mydas): An Emerging Disease With Evidence of Interoceanic Dissemination.

Protozoa morphologically consistent with Caryospora sp. are one of the few pathogens associated with episodic mass mortality events involving free-ranging sea turtles. Parasitism of green turtles (Chelonia mydas) by these coccidia and associated mortality was first reported in maricultured turtles in the Caribbean during the 1970s. Years later, epizootics affecting wild green turtles in Australia occurred in 1991 and 2014. The first clinical cases of Caryospora-like infections reported elsewhere in free-ranging turtles were from the southeastern US in 2012. Following these initial individual cases in this region, we documented an epizootic and mass mortality of green turtles along the Atlantic coast of southern Florida from November 2014 through April 2015 and continued to detect additional, sporadic cases in the southeastern US in subsequent years. No cases of coccidial disease were recorded in the southeastern US prior to 2012 despite clinical evaluation and necropsy of stranded sea turtles in this region since the 1980s, suggesting that the frequency of clinical coccidiosis has increased here. Moreover, we also recorded the first stranding associated with infection by a Caryospora-like organism in Hawai'i in 2018. To further characterize the coccidia, we sequenced part of the 18S ribosomal and mitochondrial cytochrome oxidase I genes of coccidia collected from 62 green turtles found in the southeastern US and from one green turtle found in Hawai'i. We also sequenced the ribosomal internal transcribed spacer regions from selected cases and compared all results with those obtained from Caryospora-like coccidia collected from green turtles found in Australia. Eight distinct genotypes were represented in green turtles from the southeastern US. One genotype predominated and was identical to that of coccidia collected from the green turtle found in Hawai'i. We also found a coccidian genotype in green turtles from Florida and Australia with identical 18S and mitochondrial sequences, and only slight inter-regional differences in the internal transcribed spacer 2. We found no evidence of geographical structuring based on phylogenetic analysis. Low genetic variability among the coccidia found in green turtle populations with minimal natural connectivity suggests recent interoceanic dissemination of these parasites, which could pose a risk to sea turtle populations.

Fast acquisition of a polysaccharide fermenting gut microbiome by juvenile green turtles Chelonia mydas after settlement in coastal habitats

BackgroundTetrapods do not express hydrolases for cellulose and hemicellulose assimilation, and hence, the independent acquisition of herbivory required the establishment of new endosymbiotic relationships between tetrapods and microbes. Green turtles (Chelonia mydas) are one of the three groups of marine tetrapods with an herbivorous diet and which acquire it after several years consuming pelagic animals. We characterized the microbiota present in the feces and rectum of 24 young wild and captive green turtles from the coastal waters of Brazil, with curved carapace length ranging from 31.1 to 64.7 cm, to test the hypotheses that (1) the ontogenetic dietary shift after settlement is followed by a gradual change in the composition and diversity of the gut microbiome, (2) differences exist between the composition and diversity of the gut microbiome of green turtles from tropical and subtropical regions, and (3) the consumption of omnivorous diets modifies the gut microbiota of green turtles.ResultsA genomic library of 2,186,596 valid bacterial 16S rRNA reads was obtained and these sequences were grouped into 6321 different operational taxonomic units (at 97% sequence homology cutoff). The results indicated that most of the juvenile green turtles less than 45 cm of curved carapace length exhibited a fecal microbiota co-dominated by representatives of the phyla Bacteroidetes and Firmicutes and high levels of Clostridiaceae, Prophyromonas, Ruminococaceae, and Lachnospiraceae within the latter phylum. Furthermore, this was the only microbiota profile found in wild green turtles > 45 cm CCL and in most of the captive green turtles of any size feeding on a macroalgae/fish mixed diet. Nevertheless, microbial diversity increased with turtle size and was higher in turtles from tropical than from subtropical regions.ConclusionsThese results indicate that juvenile green turtles from the coastal waters of Brazil had the same general microbiota, regardless of body size and origin, and suggest a fast acquisition of a polysaccharide fermenting gut microbiota by juvenile green turtles after settlement into coastal habitats.

MtDNA Analysis Suggests Local Origin of Pelagic-Stage Juvenile Green Turtles Collected in Japanese Coastal Waters

Understanding the distribution range across the life history of endangered animals is crucial for effective conservation and management planning. However, endangered migratory green turtles with straight carapace lengths (SCLs) of <35 cm have been rarely observed in the northwestern Pacific. Information on wild green turtles with an SCL of <35 cm in this region is therefore scarce. Historically, four individuals with an SCL of <35 cm from the Japanese coasts and an oceanic area in Japan have been reported. From 2011 to 2013, we collected nine turtles with an SCL of <35 cm from Japanese coasts and coastal waters. We reviewed the existing literature and compiled records of newly collected individuals and their mitochondrial deoxyribonucleic acid haplotypes. The combined total of 13 turtles had SCLs ranging from 6.2 to 28.0 cm. Molecular analyses of nine newly collected turtles indicated that most individuals had hatched at green turtle nesting sites on the Ogasawara Islands and islands in the Ryukyu Archipelago. These results suggest that early juvenile green turtles inhabit Japanese waters, and some turtles with an SCL of <35 cm appear to have remained in Japanese waters after leaving their natal beaches in Japan without drifting with the prevailing oceanic currents to central north or eastern Pacific regions. Although the sample size in the present study was small, this is a first step in constructing comprehensive conservation and management plans for green turtles in the northwestern Pacific.

Growth rates of wild green turtles, Chelonia mydas, at a temperate foraging habitat in the northern Gulf of Mexico: assessing short‐term effects of cold‐stunning on growth

There are multiple factors that may determine individual and population growth rates and understanding the impact of extrinsic factors, such as temperature, is important for successful recovery plan stock assessment and modelling. In January 2001 and January 2003, cold‐stunning events occurred along the northern Gulf of Mexico, in St Joseph Bay, Florida. In this study we examine the short‐term effects of decreased water temperatures and repeated cold‐stunning events on the growth of juvenile green turtles in northwest Florida. There were no significant effects of number of cold‐stunning events on growth, although turtles stunned twice tended to grow slower than non‐stunned turtles. This is the first study to provide information on the growth rates of green turtles in the northern Gulf of Mexico and it is the first examination of the effects of cold‐stunning on growth in any sea turtle population.

Use of Baculovirus-Expressed Glycoprotein H in an Enzyme-Linked Immunosorbent Assay Developed To Assess Exposure to Chelonid Fibropapillomatosis-Associated Herpesvirus and Its Relationship to the Prevalence of Fibropapillomatosis in Sea Turtles

Chelonid fibropapillomatosis-associated herpesvirus (CFPHV) is an alphaherpesvirus believed to cause marine turtle fibropapillomatosis (FP). A serodiagnostic assay was developed for monitoring sea turtle populations for CFPHV exposure. CFPHV glycoprotein H (gH) expressed in recombinant baculovirus was used in an enzyme-linked immunosorbent assay (ELISA) to detect virus-specific 7S turtle antibodies. Using captive-reared green turtles (Chelonia mydas) with no history of virus exposure as "known negatives" and others with experimentally induced FP as "known positives," the assay had 100% specificity but low sensitivity, as seroconversion was detected in only half of the turtles bearing experimentally induced tumors. Antibodies were detected only in samples collected after cutaneous fibropapillomas appeared, consistent with observations that tumors are significant sites of virion production and antigen expression and the possibility that prolonged/repeated virus shedding may be required for adequate stimulation of 7S antibody responses to gH. Natural routes of infection, however, may produce higher seroconversion rates. High gH antibody seroprevalences ( approximately 80%) were found among wild green turtles in three Florida localities with different FP prevalences, including one site with no history of FP. In addition, all eight loggerhead turtles (Caretta caretta) tested were seropositive despite FP being uncommon in this species. The possibility that CFPHV infection may be common relative to disease suggests roles for environmental and host factors as modulators of disease expression. Alternatively, the possibility of other antigenically similar herpesviruses present in wild populations cannot be excluded, although antibody cross-reactivity with the lung/eye/trachea disease-associated herpesvirus was ruled out in this study.

Some of them came home: the Cayman Turtle Farm headstarting project for the green turtle Chelonia mydas

Headstarting is a management technique employed to enhance recruitment of turtles into diminished or extirpated marine turtle populations. Although there have been numerous projects worldwide, there has been a paucity of detailed investigations into its efficacy. Between 1980 and 2001, 16,422 captive-raised hatchlings and 14,347 yearling green marine turtles Chelonia mydas were released from the Cayman Turtle Farm. Approximately 80% of all turtles released were subject to some form of tagging, including living tags. A total of 392 tagged animals have been recaptured at intervals of up to 19 years. Of this total, 160 individuals were captured in the Cayman Islands and 232 were recorded from other locations within the wider Caribbean and southeastern USA. There was significant variation in the release-recapture intervals at the three countries with most returns (Cayman, Cuba and Nicaragua). A positive relationship exists between time at large and size at recapture and data suggest growth rates comparable to those of wild green turtles in the region. There have been at least six living tag returns, four involving turtles released as yearlings and two involving turtles released as hatchlings. This demonstrates an age at maturity that may be as short as 15–19 years, depending on stage of release. Results show that some headstarted turtles are moving around the Caribbean, surviving for long periods of time, contributing to the local breeding population, and are possibly displaying shifts in habitat utilization with age similar to those recorded by wild individuals.

Growth Rates of Wild Green Turtles (Chelonia mydas) at a Temperate Foraging Area in the Gulf of California, México

Abstract Growth rates recorded between 1995 and 2001 for green turtles in the central Gulf of California were analyzed using nonparametric regression modeling. A mixed longitudinal sampling design provided 21 growth rate estimates from 19 turtles recaptured at intervals ≥ 11 months. Initial straight carapace length (SCL) of turtles ranged from 58.6–93.8 cm. Growth rates ranged from 0.2 cm/yr to 3.4 cm/yr. The size-specific growth rate function was nonmonotonic, rising steadily from slightly under 1.0 cm/yr in the smallest sizes (approximately 60 cm SCL) to a maximum growth rate of 1.5 cm/yr at about 85 cm SCL, then declining to just over 1 cm/yr for turtles > 90 cm SCL. Mean annual growth was 1.4 cm/yr. We estimate turtles require 9–21 yr in this neritic habitat to attain maturity. These data represent the first information on wild green turtle growth in temperate regions of the Eastern Pacific Ocean.

Detection of antibodies to a disease-associated herpesvirus of the green turtle, Chelonia mydas.

Lung-eye-trachea disease-associated herpesvirus (LETV) is linked with morbidity and mortality in mariculture-reared green turtles, but its prevalence among and impact on wild marine turtle populations is unknown. An enzyme-linked immunosorbent assay (ELISA) was developed for detection of anti-LETV antibodies and could distinguish LETV-exposed green turtles from those with antibodies to fibropapillomatosis-associated herpesvirus (FPHV). Plasma from two captive-reared green turtles immunized with inactivated LETV served as positive controls. Plasma from 42 healthy captive-reared green turtles and plasma from 30 captive-reared green turtles with experimentally induced fibropapillomatosis (FP) and anti-FPHV antibodies had low ELISA values on LETV antigen. A survey of 19 wild green turtles with and 27 without FP (with and without anti-FPHV antibodies, respectively) identified individuals with antibodies to LETV regardless of their FP status. The seroprevalence of LETV infection was 13%. The presence of antibodies to LETV in plasma samples was confirmed by Western blot and immunohistochemical analyses. These results are the first to suggest that wild Florida green turtles are exposed to LETV or to an antigenically closely related herpesvirus(es) other than FPHV and that FPHV and LETV infections are most likely independent events. This is the first ELISA developed to detect antibodies for a specific herpesvirus infection of marine turtles. The specificity of this ELISA for LETV (ability to distinguish LETV from FPHV) makes it valuable for detecting exposure to this specific herpesvirus and enhances our ability to conduct seroepidemiological studies of these disease-associated agents in marine turtles.

Survey of Florida green turtles for exposure to a disease-associated herpesvirus.

A recently developed enzyme-linked immunosorbent assay (ELISA) was used to assess exposure of Florida wild green turtles Chelonia mydas to LETV, the herpesvirus associated with lung-eye-trachea disease (LETD). Plasma samples from 329 wild juvenile green turtles netted in the Indian River lagoon, along the Sebastian reef, or in the Trident basin (Indian River and Brevard Counties, Florida) were tested by ELISA for the presence of antibodies to LETV. Plasma samples from 180 wild juvenile green turtles were tested from these study sites to compare the prevalence of anti-LETV antibodies. While some plasma samples from each site contained anti-LETV antibodies (confirmed by Western blot analysis), plasma samples collected from the Indian River lagoon had statistically higher optical density values measured in the ELISA. No statistical differences were observed when these same plasma samples were analyzed for changes in the level of anti-LETV antibodies over 3 years (1997, 1998, and 1999). To explore the relationship between anti-LETV antibodies and fibropapillomatosis (FP), plasma from 133 green turtles scored for fibropapilloma tumor severity were tested by ELISA. There was no correlation between tumor severity and the presence of antibodies against LETV. Additional plasma samples collected from 16 tagged green turtles captured and sampled more than once (recaptures) were also tested to monitor antibody levels to LETV relative to the FP status of individual turtles over time. Again there was no clear relationship between FP tumor status and the presence of antibodies to LETV. Finally, ELISA tests on plasma from 13 nesting female turtles (9 green and 4 loggerhead) revealed high levels of anti-LETV antibodies in 11 individuals, including 2 loggerhead turtles. These results provide strong evidence that wild Florida green turtle populations at these 3 study sites are exposed to LETV or a closely related virus and that loggerhead turtles may be exposed as well. Based on a cutoff optical density value of 0.310, 71 out of the 329 wild Florida green turtles tested were seropositive for LETV antibodies (seroprevalence = 21.6%). In addition, no relationship between FP tumor severity or status and the presence of anti-LETV antibodies was found, further supporting the hypothesis that LETV and the FP-associated herpesvirus (FPHV) are separate infections of marine turtles.

BIOCHEMICAL RESPONSES TO FIBROPAPILLOMA AND CAPTIVITY IN THE GREEN TURTLE

Blood biochemical parameters were compared for green turtles (Chelonia mydas) with and without green turtle fibropapillomatosis (GTFP) from both captive and wild populations in Hawaii (USA) and from a captive population from California (USA), during the period between 1994 and 1996. Statistical analysis did not detect an influence of disease in any of the blood parameters for free-ranging turtles; however, captive turtles in Hawaii with GTFP had significantly higher levels of alkaline phosphatase and significantly lower levels of lactate compared to non-tumored captive turtles. Multivariate analysis found that biochemical profiles could be used to accurately predict if turtles were healthy or afflicted with GTFP. Discriminant function analysis correctly classified turtles as being with or without GTFP in 89% of cases, suggesting that diseased animals had a distinct signature of plasma biochemistries. Measurements of blood parameters identified numerous differences between captive and wild green turtles in Hawaii. Levels of corticosterone, lactate, triglyceride, glucose, and calcium were significantly higher in wild green turtles as compared to captive turtles, while uric acid levels were significantly lower in wild turtles as compared to captive turtles. Additionally, turtles from Sea World of California (San Diego, California, USA), which had been in captivity the longest, had higher levels of alanine aminotransferase and triglycerides as compared to nearly all other groups. Differences in diet, sampling methods, environmental conditions, and turtle size, help to interpret these results.

Growth Rates of Wild Immature Green Turtles in the Galapagos Islands, Ecuador

Despite a deluge of publications on growth in immature captive green turtles, particularly hatchlings (e.g., Harrisson, 1955; Caldwell, 1962; Lebeau and Lebrun, 1976; Garnett, 1980), or growth after release of captive-reared green turtles (e.g., Kowarsky and Capelle, 1979; Ehrhardt and Witham, 1992), growth rates of wild green turtles under completely natural conditions have received surprisingly little attention. The earliest results are those of Schmidt (1916) for wild green turtles in the U.S. Virgin Islands (then the Danish West Indies). Since then, data on growth rates of immature green turtles in the wild have been published for Bermuda (Burnett-Herkes et al., 1984), Australia (Limpus and Walter, 1980), Hawaii (Balazs, 1982), Florida (Mendonca, 1981; Wershoven and Wershoven, 1992), Bahamas (Bjorndal and Bolten, 1988), the U.S. Virgin Islands (Boulon and Frazer, 1990), and Puerto Rico (Collazo et al., 1992). This paper provides data on the growth rates of wild immature green turtles tagged in the Galapagos Islands between 1975 and 1980.