Renal oxalosis in free-ranging green turtles Chelonia mydas

Eighteen green turtles Chelonia mydas recovered from the Atlantic and Gulf coasts of Florida and Tortuguero National Park, Costa Rica, were diagnosed with renal oxalosis by histopathological examination. Affected sea turtles included 14 adults and 4 immature animals, which comprised 26% (18/69) of green turtle necropsy cases available for review. Calcium oxalate deposition ranged from small to moderate amounts and was associated with granuloma formation and destruction of renal tubules. All affected turtles died from traumatic events or health problems unrelated to renal oxalosis; however, 1 immature turtle had notable associated renal injury. Crystal composition was confirmed by infrared and scanning electron microscopy and energy dispersive X-ray analysis. The source of calcium oxalate is unknown and is presumed to be of dietary origin.     

Epizootiology of spirorchiid infection in green turtles (Chelonia mydas) in Hawaii

We describe the epizootiology of spirorchiid trematode infections in Hawaiian green turtles (Chelonia mydas) by quantifying tissue egg burdens in turtles submitted for necropsy and by assessing antibody response to crude adult worm and egg antigens among a variety of age groups. Hapalotrema sp. and Laeredius sp. predominated in turtles infected with spirorchiids. Tissue egg burdens decreased with increasing size and increased with deteriorating body condition of turtles. No relationship was found between tissue egg burdens and sex or fibropapillomatosis status. Tissue egg burdens increased in turtles from southeast to northwest in the main Hawaiian Islands (Hawaii to Kauai). Hatchling and captive-reared turtles had significantly lower levels of antibodies against crude worm and egg antigens. Based on tissue egg burdens and antibody status, we hypothesize that immature turtles become infected with spirorchiids shortly after recruiting into coastal foraging pastures from the pelagic environment, that infection levels decrease with age, and that spirorchiids detrimentally affect the body condition of sea turtles independent of tumor burden. The low intensity of infection in turtles with the endemic trematode Carettacola hawaiiensis suggests either that turtles are less susceptible to infection with this parasite or that the parasite is outcompeted by species of Hapalotrema and Laeredius. Given that the 2 latter species are found in the Pacific and other oceans, they are not likely endemic and were probably introduced into Hawaii through an undetermined route.     

Dietary protein requirement for captive juvenile green turtles (Chelonia mydas)

Head-starting programs are extremely important for restoring the population of sea turtles in wild whereas husbandry conditions and feeding regimens of captive turtles are still limited. In the current study, the optimal dietary protein requirement for green turtle (Chelonia mydas) was investigated to support rearing in head-starting programs. Twenty-five-day-old turtles (44.5–46.2 g body weight, n = 45) were randomly distributed into 15 experimental plastic tanks, comprising three treatment replications of 3 turtles each. They were fed fishmeal-based feeds containing different levels of protein (30%, 35%, 40%, 45%, and 50%) for 8 weeks. At the end of feeding trial, growth performance (specific growth rate = 1.86% body weight/day) and feed utilization (protein efficiency ratio = 3.30 g gain/g protein) were highest in turtles fed with 40% protein in feed (p < .05). These nutritional responses were significantly supported by specific activities of fecal digestive enzymes, especially trypsin, chymotrypsin, amylase, and the amylase/trypsin ratio. Also, this dietary level improved the deposition of calcium and phosphorus in carapace, supporting a hard carapace and strong healthy bones. There were no negative effects in general health status of reared turtles, as indicated by hematological parameters. Based on a broken-line analysis between dietary protein levels and specific growth rate, the optimal protein level for green turtles was estimated as 40.6%. Findings from the current study support the use of artificial diets of specific protein levels to rear captive green turtle before release to natural habitats.     

Testing dispersal hypotheses in foraging green sea turtles (Chelonia mydas) of Brazil

Testing theories of dispersal is challenging in highly migratory species. In sea turtles, population size, geographic distance, natal homing, and ocean currents are hypothesized to affect dispersal. Little is known, however, about these mechanisms in sea turtles foraging along the South American coast. Green sea turtles feeding at Ubatuba (UB, n = 114) and Almofala (AF, n = 117), Brazil, were sequenced at the mitochondrial DNA (mtDNA) control region (486 bp) and genotyped at 7 microsatellite loci to test dispersal hypotheses. Fifteen mtDNA haplotypes were revealed, including a previously undescribed sequence, and the average observed heterozygosity (H(o)) was 76.4%. Overall short-term temporal differences were not detected, and differentiation was less pronounced in microsatellite than in mtDNA analyses. Mitochondrial results reveal significant differentiation between the Brazilian feeding grounds and most other Atlantic groups, whereas microsatellites uncover similarities to some of the geographically closest populations. Ubatuba and Almofala are mixed stocks, drawn primarily from Ascension, with lesser contributions from Surinam/Aves and Trindade. Costa Rica is also a significant source of individuals feeding at AF. The results are consistent with a model of juvenile natal homing impacted by other factors. Effective protection of turtles foraging along the extensive Brazilian coast may enhance breeding populations thousands of kilometers away.     

Basic oxidative stress metabolites in eastern Pacific green turtles (Chelonia mydas agassizii)

Analysis of hematological and biochemical parameters, including oxidative stress indicators, is an invaluable tool in wildlife health assessment, particularly for threatened or endangered species. This study was aimed at obtaining baseline information of oxidative stress indicators in eastern Pacific green turtles (Chelonia mydas agassizii) from a relatively undisturbed habitat at Bahía Magdalena, Baja California Sur, Mexico. Tissues were analyzed for superoxide radical (O(2)(*-) production, lipid peroxidation (measured as thiobarbituric acid reactive substances, TBARS), and antioxidant enzyme activity (superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST)). Overall levels for all variables were within ranges reported for other reptile species. Results suggest differences in oxidative metabolism among tissues (p< or =0.05). Liver, lung and muscle had the highest levels of O(2)(*-) production. Liver revealed the highest TBARS levels. Liver and muscle showed the highest SOD activity, while liver and kidney had the highest CAT and GST activities. These data provide baseline values of the oxidative stress indicators in tissues from eastern Pacific green turtles. Development of a biomarker system to assess the health of wildlife species, especially one that could detect early exposure to environmental pollutants or emerging diseases, would provide a useful tool in the long-term conservation of the species.     

Hydrodynamic stability in posthatchling loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtles

Swimming animals may experience a wide range of destabilizing forces resulting from the movements of their propulsors. These forces often cause movements in directions other than the intended trajectory (i.e., recoil motions), potentially increasing locomotor costs. We quantified rectilinear swimming stability for posthatchling loggerhead (Caretta caretta) and green turtles (Chelonia mydas). Sea turtles predominantly swim via “aquatic flight”, which is characterized by synchronous dorsoventral flapping of their forelimbs. We tested four predictions about the effects of “aquatic flight” on stability: (1) it would produce little lateral recoil; (2) lateral recoil motions would be non-cyclic; (3) vertical recoil motions would be larger than lateral recoil motions; and (4) vertical recoil motions would be cyclic. Additionally, because posthatchling loggerheads possess dorsal keels on the shell that are absent in green turtles, we evaluated whether such keels might improve stability in swimming turtles. While our expectations for patterns of cyclicity in recoil motions (predictions 2 and 4) were met, our expectations for differences in their absolute and relative magnitudes (predictions 1 and 3) were not. We suggest that lateral recoil motions were greater than predicted due to slight asynchronies between the motions of the left and right foreflippers. Additionally, although minimum lateral recoil motions were smaller than minimum vertical recoil motions, maximum recoil motions were greater in the lateral direction, so that average recoil did not differ significantly between these directions. Finally, because loggerheads did not display higher levels of stability compared to green turtles, there is little evidence to support a stabilizing role for dorsal keels in loggerhead turtles.     

Feral cats (Felis catus) as predators of hatchling green turtles (Chelonia mydas)

In many parts of the world feral animals have been reported to have severe effects on marine turtle hatchling production. In this study, green turtle ( Chelonia mydas ) hatchlings were shown to be an important component of the diet of the feral cat ( Felis catus ) on Aldabra Atoll, Seychelles, and feral cat activity in the coastal areas was found to be concentrated on the beaches used most intensively by turtles for nesting. The impact of the feral cat's predation on green turtle recruitment could not be determined. However, despite cat predation, the size of the Aldabran green turtle nesting population has increased considerably since human exploitation ceased.     

Metabolic heating and the prediction of sex ratios for green turtles (Chelonia mydas)

We compared incubation temperatures in nests (n=32) of the green turtle (Chelonia mydas) on Ascension Island in relation to sand temperatures of control sites at nest depth. Intrabeach thermal variation was low, whereas interbeach thermal variation was high in both control and nest sites. A marked rise in temperature was recorded in nests from 30% to 40% of the way through the incubation period and attributed to metabolic heating. Over the entire incubation period, metabolic heating accounted for a mean rise in temperature of between 0.07 degrees and 2.86 degrees C within nests. During the middle third of incubation, when sex is thought to be determined, this rise in temperature ranged between 0.07 degrees and 2.61 degrees C. Metabolic heating was related to both the number of eggs laid and the total number of hatchlings/embryos produced in a clutch. For 32 clutches in which temperature was recorded, we estimate that metabolic heating accounted for a rise of up to 30% in the proportion of females produced within different clutches. Previous studies have dismissed any effect of metabolic heating on the sex ratio of marine turtle hatchlings. Our results imply that metabolic heating needs to be considered when estimating green turtle hatchling sex ratios.     

Bacteraemia in free-ranging Hawaiian green turtles Chelonia mydas with fibropapillomatosis

Past studies of free-ranging green turtles Chelonia mydas with fibropapillomatosis (FP) in Hawaii have shown that animals become immunosuppressed with increasing severity of this disease. Additionally, preliminary clinical examination of moribund turtles with FP revealed that some animals were also bacteraemic. We tested the hypothesis that bacteraemia in sea turtles is associated with the severity of FP. We captured free-ranging green turtles from areas in Hawaii where FP is absent, and areas where FP has been endemic since the late 1950s. Each turtle was given an FP severity score ranging from 0 (no tumours) to 3 (severely affected). A fifth category included turtles that were stranded ashore and moribund with FP. We found that the percentage of turtles with bacteraemia increased with the severity of FP, and that the majority of bacteria cultured were Vibrio spp. Turtles with severe FP were more susceptible to bactaeremia, probably in part due to immunosuppression. The pattern of bacteraemia in relation to severity of disease strengthens the hypothesis that immunosuppression is a sequel to FP.     

Autopodial development in the sea turtles Chelonia mydas and Caretta caretta

The manus and pes were studied using whole-mount and histological preparations of ontogenetic series of Chelonia mydas and Caretta caretta. Patterns of connectivity and sequences of chondrification events are similar to those reported for other turtle species, with respect to both the primary axis and the digital arch. There is no evidence of anterior condensations in the region distal to the radius and the tibia, supporting the hypothesis that the radiale and tibiale are absent in turtles. The three middle metacarpals are the first elements to start ossification in the manus of C. mydas, while ossification has not started in the pes. In the hatchling of C. mydas, most carpals have started ossification, whereas tarsals are mostly still cartilaginous. In C. caretta, the first carpals to ossify are the ulnare and intermedium, followed by the pisiform. Among metatarsals, the fifth hooked metatarsal is the last one to start ossification. The fibulare and intermedium fuse early in chondrogenesis, later becoming the astragalocalcaneum. Ossification in the carpals of C. caretta starts while tarsals are still cartilaginous. The derived autopodial proportions in each autopodium of adults are laid out at the condensation stage, and features that were present in basal turtles are absent at all stages examined (developmental penetrance). In contrast to this, conservatism is expressed in the presence of similar patterns of connectivity during early chondrogenesis, and in the development of overall proportions of the manus versus pes. As in adult anatomy, the development of the autopodium of marine turtles is a mosaic of derived and plesiomorphic features.     

Amino Acid Sequence and Activity of Green Turtle (Chelonia mydas) Lysozyme

Green turtle lysozyme purified from egg white was sequenced and analyzed its activity. Lysozyme was reduced and pyridylethylated or carboxymethylated to digest with trypsin, chymotrypsin and V8 protease. The peptides yielded were purified by RP-HPLC and sequenced. Every trypsin peptide was overlapped by chymotrypsin peptides and V8 protease peptides. This lysozyme is composed of 130 amino acids including an insertion of a Gly residue between 47 and 48 residues when compared with chicken lysozyme. The amino acid substitutions were found at subsites E and F. Namely Phe34, Arg45, Thr47, and Arg114 were replaced by Tyr, Tyr, Pro, and Asn, respectively. The time course using N-acetylglucosamine pentamer as a substrate showed a reduction of the rate constant of glycosidic cleavage and transglycosylation and increase of binding free energy for subsite E, which proved the contribution of amino acids mentioned above for substrate binding at subsites E and F.     

Water temperature and internesting intervals for loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtles

Temperature loggers were attached to the carapace of green turtles (Chelonia mydas) at Ascension Island and Cyprus and to loggerhead turtles (Caretta caretta) at Cyprus, in order to record the ambient temperature experienced by individuals during the internesting interval, i.e. the period between consecutive clutches being laid. Internesting intervals were relatively short (10–14 days) and mean ambient temperatures relatively warm (27–28°C), compared to previous observations for these species nesting in Japan, although a single internesting interval versus temperature relationship described all the data for these two species from the different areas. The implication is that water temperature has both a common and a profound effect on the length of the internesting interval for these two species: internesting intervals are shorter when the water is warmer.     

Do female green turtles (Chelonia mydas) exhibit reproductive seasonality in a year-round nesting rookery?

In circumglobal populations of sea turtles, little nesting activity occurs during cold seasons when the sand temperature on a nesting beach is inappropriate for successful egg incubation. However, it is not known whether reproductive seasonality also occurs in year-round nesting rookeries where the sand temperature may be suitable throughout the year. Therefore, we examined the hypothesis that female turtles exhibit reproductive seasonality even in a year-round nesting population. To determine whether the time of nesting of individuals fluctuates between successive nesting seasons, a year-round nesting rookery of green turtles Chelonia mydas at Huyong Island, Thailand, was patrolled on foot every night for 3190 consecutive days, and nesting females were identified using microchips and metal tags. The date of first nesting within a season for an individual (nesting date) was considered the nesting season of each individual. We identified 94 females and 463 nests (including 47 unidentified nests) during the survey. Nesting dates were distributed throughout the year. Nineteen turtles remigrated to the nesting beach, and the nesting dates of the remigrated females occurred in the same seasons. This indicates that females have a fixed individual nesting season even in a year-round nesting rookery. The year-round nesting of green turtles may be attributed to a wide variation in the nesting seasons of individuals. Satellite tracking revealed that the mean travelling duration of post-nesting migrations in this population was 13.5±6.1 days. The proximity of locations for reproduction and feeding may also play an important role in sustaining year-round nesting in this population.     

Early growth and development of morphological defenses in post-hatchling flatbacks (Natator depressus) and green turtles (Chelonia mydas)

Marine turtles produce hundreds of precocial offspring (“hatchlings”) that are virtually defenseless. Many are consumed by predators. Hatchlings improve their survival prospects by migrating to offshore “nursery” areas with lower predator densities and, as they grow, by developing morphological defenses. The flatback turtle (Natator depressus), however, remains in the predator-rich coastal waters of Australia. To gain insights into how they survive there, we compared patterns of early growth and morphological development in flatbacks to their closest relative, the green turtle (Chelonia mydas), which migrates offshore. We found that morphological structures likely to be used in defense are better developed in juvenile flatbacks than in juvenile green turtles. Those structures probably represent one of a suite of characters that enable young flatbacks to survive in coastal habitats where interactions with predators are likely to be more frequent.     

Detection of low plasma estradiol concentrations in nesting green turtles (Chelonia mydas) by HPLC/Ms-Ms

In previous studies on nesting green turtles under natural conditions from different geographical regions, 17-β-estradiol (E(2) ) was either undetectable or detected at very low levels. RIA and other related techniques were not sensitive enough to measure low E(2) values in the green turtles. In this study, a sensitive method was used in detecting low hormone concentrations: high performance liquid chromatography with tandem quadruple mass spectrometry (HPLC-MS/MS). Using this technique, estradiol for the first time was detected in nesting green turtles during the peak season (June-October) at Ras Al-Hadd Reserve, Oman. The E(2) values recorded from this study were the highest ever recorded from nesting green turtles in any geographical region, but the levels did not vary significantly throughout different phases of nesting. The presence of E(2) during nesting presumably plays a role in the physiology and behavior of this species. Ras Al-Hadd hosts one of the largest nesting populations of green turtles in the world, and an understanding of their nesting patterns may be of value in conservation and management programs for this endangered species.     

The Green sea turtle (Chelonia mydas): further observations on breeding in captivity

Mating, nesting and hatching of the Green sea turtle on Mariculture Ltd's farm on Grand Cayman Island, BWI in 1973 were recorded in a previous paper. The results described were the first of their kind, so that events in the farm breeding colony in the following year were awaited with much interest, especially as to hatchability of the eggs. The observations made in 1974, which extended and mainly confirmed those made in 1973, are described below.     

Green turtles (Chelonia mydas) foraging at Arvoredo Island in Southern Brazil: Genetic characterization and mixed stock analysis through mtDNA control region haplotypes

We analyzed mtDNA control region sequences of green turtles (Chelonia mydas) from Arvoredo Island, a foraging ground in southern Brazil, and identified eight haplotypes. Of these, CM-A8 (64%) and CM-A5 (22%) were dominant, the remainder presenting low frequencies (< 5%). Haplotype (h) and nucleotide (π) diversities were 0.5570 ± 0.0697 and 0.0021 ± 0.0016, respectively. Exact tests of differentiation and AMOVA Φ(ST) pairwise values between the study area and eight other Atlantic foraging grounds revealed significant differences in most areas, except Ubatuba and Rocas/Noronha, in Brazil (p > 0.05). Mixed Stock Analysis, incorporating eleven Atlantic and one Mediterranean rookery as possible sources of individuals, indicated Ascension and Aves islands as the main contributing stocks to the Arvoredo aggregation (68.01% and 22.96%, respectively). These results demonstrate the extensive relationships between Arvoredo Island and other Atlantic foraging and breeding areas. Such an understanding provides a framework for establishing adequate management and conservation strategies for this endangered species.     

Fibropapillomatosis Prevalence and Distribution in Immature Green Turtles (Chelonia mydas) in Martinique Island (Lesser Antilles)

Fibropapillomatosis (FP) threatens the survival of green turtle (Chelonia mydas) populations at a global scale, and human activities are regularly pointed as causes of high FP prevalence. However, the association of ecological factors with the disease’s severity in complex coastal systems has not been well established and requires further studies. Based on a set of 405 individuals caught over ten years, this preliminary study provides the first insight of FP in Martinique Island, which is a critical development area for immature green turtles. Our main results are: (i) 12.8% of the individuals were affected by FP, (ii) FP has different prevalence and temporal evolution between very close sites, (iii) green turtles are more frequently affected on the upper body part such as eyes (41.4%), fore flippers (21.9%), and the neck (9.4%), and (iv) high densities of individuals are observed on restricted areas. We hypothesise that turtle’s aggregation enhances horizontal transmission of the disease. FP could represent a risk for immature green turtles’ survival in the French West Indies, a critical development area, which replenishes the entire Atlantic population. Continuing scientific monitoring is required to identify which factors are implicated in this panzootic disease and ensure the conservation of the green turtle at an international scale.

     

Reproductive Biology of Captive Green Sea Turtles Chelonia mydas

A captive colony of green sea turtles, Chelonia mydas, has beenmaintained and observed at a commercial sea turtle farm on GrandCayman Island, B.W.I., since 1973. Observations of this breedingcolony show that the mating and nesting behaviour of the captivegreen sea turtle is similar to that observed in wild populations.Evidence indicates that mating observed prior to a female'snesting in a given season determines the hatchabilityof thatseason's egg production. Annual per female egg production ofthe captive colony appears to be two to five times greater thanthat reported for wild colonies. Observations on the reproductivebiology of green sea turtles hatched and raised under farm conditionssuggests that the minimum age of sexual maturity is eight tonine years of age. The number of eggs per nest, the number ofnests per season per female and hatch rate tend to increasewith successive seasons nesting for these turtles reaching sexualmaturity.     

Seasonality and numbers of green turtles Chelonia mydas nesting on the Pitcairn Islands

During 1991 and 1992 the first regular field observations of green turtles, Chelonia mydas , on the Pitcairn Islands (South Pacific) revealed that nesting occurs only on Henderson where about 10 females laid eggs (c. 1% of the French Polynesian population). Substrates on Pitcairn and Ducie Atoll are unsuitable for nesting and no signs of nesting were found on Oeno Atoll where the terrain appears suitable.