Multiple paternity in loggerhead turtle (Caretta caretta) nests on Melbourne Beach, Florida: a microsatellite analysis

Many aspects of sea turtle biology are difficult to measure in these enigmatic migratory species, and this lack of knowledge continues to hamper conservation efforts. The first study of paternity in a sea turtle species used allozyme analysis to suggest multiple paternity in loggerhead turtle (Caretta caretta) clutches in Australia. Subsequent studies indicated that the frequency of multiple paternity varies from species to species and perhaps location to location. This study examined fine-scale population structure and paternal contribution to loggerhead clutches on Melbourne Beach, FL, USA using microsatellite markers. Mothers and offspring from 70 nests collected at two locations were analysed using two to four polymorphic microsatellite loci. Fine-scale population differentiation was not evident between the sampled locations, separated by 8 km. Multiple paternity was common in loggerhead nests on Melbourne Beach; 22 of 70 clutches had more than one father, and six had more than two fathers. This is the first time that more than two fathers have been detected for offspring in individual sea turtle nests. Paternal genotypes could not be assigned with confidence in clutches with more than two fathers, leaving the question of male philopatry unanswered. Given the high incidence of multiple paternity, we conclude that males are not a limiting resource for this central Florida nesting aggregate.     

Tetranucleotide microsatellites from the loggerhead sea turtle (Caretta caretta)

We describe primers and polymerase chain reaction conditions to amplify 15 tetranucleotide microsatellite loci from the loggerhead sea turtle (Caretta caretta). The primers were tested on 30 individuals that nested along the Georgia, USA coast. The primer pairs developed in this study yielded an average of 13.9 alleles per locus (range of 10–21), an average observed heterozygosity of 0.91 (range 0.79–1.00), and an average polymorphic information content of 0.88 (range 0.84–0.92).     

Genetic structure of loggerhead turtle (Caretta caretta) populations in Turkey

This study investigates genetic structure of loggerhead turtle (Caretta caretta) for conservation purposes using both mitochondrial and nuclear DNA markers. To evaluate overall genetic structure of C. caretta at the Turkish nesting beaches and to compare it with previously published data from other nesting sites of the Mediterranean Sea, we have studied 256 hatchlings from 18 different nesting beaches. Seven distinct haplotypes were detected, of which three have previously been reported from the Mediterranean and one from the Atlantic. The remaining three haplotypes are described for the first time for C. caretta in the present study. Distribution of these haplotypes among the nesting sites showed a significant genetic structuring, indicating that females are philopatric and that gene flow among populations is restricted. Both mtDNA and microsatellite analyses determined genetic structuring (mtDNA: γ_st = 0.214, p < 0.01; nDNA F_st = 0.0004 p < 0.05) among nesting aggregates of C. caretta throughout the study area and enabled the detection of the different haplotypes to inform conservation strategies.     

Establishing physiological blood parameters in the loggerhead sea turtle (Caretta caretta)

The loggerhead sea turtle (Caretta caretta), one of the three sea turtle species inhabiting the Mediterranean Sea, is an endangered species. However, although frequently treated in marine animal rescue centers, and the subject of several studies in literature, as yet, few studies have been conducted on large numbers of loggerhead sea turtles in order to establish physiological reference ranges that enable the identification of pathological values. The lack of studies on reference parameters probably depends on the fact that marine turtles treated in wildlife rescue centers are usually in a critical conditions, thus precluding the collection of data on healthy animals and compromising the reliability of any data obtained from them. The present biological study was therefore conducted in order to obtain a database from healthy animals in natural conditions. Serum biochemistry and serum protein electrophoresis were performed on blood samples obtained from 65 healthy adult loggerhead sea turtles captured and delivered to the Sea Turtle Rescue Center of Linosa (Italy); the blood samples were collected during the clinical examination of rescued animals. Laboratory analyses of serum samples were made in order to establish reference parameters, commonly required for laboratory diagnoses in mammals and diseased animals.

Visual wavelength discrimination by the loggerhead turtle, Caretta caretta

Marine turtles are visual animals, yet we know remarkably little about how they use this sensory capacity. In this study, our purpose was to determine whether loggerhead turtles could discriminate between objects on the basis of color. We used light-adapted hatchlings to determine the minimum intensity of blue (450 nm), green (500 nm), and yellow (580 nm) visual stimuli that evoked a positive phototaxis (the phototaxis "threshold" [pt]). Juvenile turtles were later trained to associate each color (presented at 1 log unit above that color's pt) with food, then to discriminate between two colors (the original rewarded stimulus plus one of the other colors, not rewarded) when both were presented at 1 log unit above their pt. In the crucial test, turtles were trained to choose between the rewarded and unrewarded color when the colors varied in intensity. All turtles learned that task, demonstrating color discrimination. An association between blue and food was acquired in fewer trials than between yellow and food, perhaps because some prey of juvenile loggerheads in oceanic surface waters (jellyfishes, polyps, and pelagic gastropods) are blue or violet in color.     

Hue discrimination in hatchling loggerhead turtles (Caretta caretta caretta)

Hatchling Atlantic loggerhead turtles (Caretta caretta caretta) were successfully trained to discriminate between broadband hues to obtain food when spatial, intensity, and other confounding cues were randomized with respect to the correct choice. Possible hue preference, the relation of these results to sea-orientation, and the suitability of these animals as subjects in behavioural studies are discussed.     

Buoyancy control in diving behavior of the loggerhead turtle,Caretta caretta

Neutral buoyancy at the stationary depth is advantageous for diving animals. The adjustment of the air inspiration before diving can be a mechanism of buoyancy control for diving animals with lungs. The stationary depth of neutral buoyancy becomes deeper with larger inspiration. Our aim was to examine whether the loggerhead sea turtle,Caretta caretta regulates the buoyancy to be neutral at the stationary depth of the dive. During an internesting period of the breeding season, we recorded the diving pattern of an adult female using a time-depth recorder and a time-swim distance recorder. The dives were classified into four types (Types 1 to 4) based on the time-depth profile. Types-3 and 4 (66% of the total dive duration) have three phases in each dive: (1) first descent, (2) gradual ascent (stationary period), and (3) final ascent. In the gradual ascent phase, the turtle stayed at a certain depth without swimming. This means that the turtle was neutrally buoyant during the gradual ascent phase. The depth of the gradual ascent phase was positively correlated with the dive duration, supporting the hypothesis that neutral buoyancy of the loggerhead turtle is achieved by the air in their lungs.     

Primary retinal targets in the Atlantic loggerhead sea turtle,Caretta caretta

Summary Autoradiographic analysis distinguished twelve primary retinal targets in the diencephalon and the mesencephalon of the Atlantic loggerhead sea turtle, Caretta caretta. While the majority of fibers terminate contralaterally, sparse labelling is seen over ipsilateral thalamic nuclei. The dorsal optic nucleus is the most expansive retinal target in the dorsal thalamus. Four nuclei ventral and one dorsal, to the dorsal optic nucleus, receive retinal input. Before terminating in the optic tectum, labelled fibers pass through the pretectum terminating in four nuclei. Within the superficial zone of the optic tectum, three terminal zones are recognized. A distinct accessory tegmental tract separates from the main optic tract terminating in the basal optic nucleus.While such a multiplicity of retinal targets occurs among other reptiles, birds and mammals, it is presently impossible to accurately recognize visual homologies among amniotic vertebrates.     

The sodium balance of the euryhaline marine loggerhead turtle,Caretta caretta

Summary The efflux of sodium ions from the loggerhead turtle,Caretta caretta, was investigated when animals were acclimated to seawater, freshwater, and during the acclimation period after transfer from seawater to freshwater. The rate of sodium loss in animals acclimated to seawater was found to be 3 M Na · g^–1 · hr^–1. Cannulation of the cloaca showed that only 5% of the gross efflux of sodium was via the cloaca and it was calculated that 60% of the gross efflux was via nasal gland secretion and 35 % via integumentary diffusional loss. Cannulation experiments indicated that a significant amount of sodium may enter the body via the cloaca. Transfer of animals from seawater to freshwater resulted in a decline of sodium efflux by 90–99 % within 6 hr, and a further decline to only approximately 0 01 M Na · g^–1· hr^–1 after 1–2 days in freshwater. Cannulation experiments of individuals acclimated to freshwater indicated that the role of the cloaca in sodium loss in freshwater was minimal. It was calculated that sodium loss in freshwater is so small that survival in freshwater for at least 20 days is possible without active extraction of sodium from the medium. No evidence could be found for active uptake of sodium ions from freshwater baths byCaretta.This research was supported by NSF grant GB 16839.     

Natal homing in juvenile loggerhead turtles (Caretta caretta)

Juvenile loggerhead turtles (Caretta caretta) from West Atlantic nesting beaches occupy oceanic (pelagic) habitats in the eastern Atlantic and Mediterranean, whereas larger juvenile turtles occupy shallow (neritic) habitats along the continental coastline of North America. Hence the switch from oceanic to neritic stage can involve a trans-oceanic migration. Several researchers have suggested that at the end of the oceanic phase, juveniles are homing to feeding habitats in the vicinity of their natal rookery. To test the hypothesis of juvenile homing behaviour, we surveyed 10 juvenile feeding zones across the eastern USA with mitochondrial DNA control region sequences (N = 1437) and compared these samples to potential source (nesting) populations in the Atlantic Ocean and Mediterranean Sea (N = 465). The results indicated a shallow, but significant, population structure of neritic juveniles (PhiST = 0.0088, P = 0.016), and haplotype frequency differences were significantly correlated between coastal feeding populations and adjacent nesting populations (Mantel test R2 = 0.52, P = 0.001). Mixed stock analyses (using a Bayesian algorithm) indicated that juveniles occurred at elevated frequency in the vicinity of their natal rookery. Hence, all lines of evidence supported the hypothesis of juvenile homing in loggerhead turtles. While not as precise as the homing of breeding adults, this behaviour nonetheless places juvenile turtles in the vicinity of their natal nesting colonies. Some of the coastal hazards that affect declining nesting populations may also affect the next generation of turtles feeding in nearby habitats.     

Tetranucleotide markers from the loggerhead sea turtle (Caretta caretta) and their cross-amplification in other marine turtle species

The loggerhead sea turtle (Caretta caretta) is a federally threatened species and listed as endangered by the World Conservation Union (IUCN). We describe primers and polymerase chain reaction (PCR) conditions to amplify 11 novel tetranucleotide microsatellite loci from the loggerhead sea turtle. We tested primers using samples from 22 females that nested at Melbourne Beach, Florida (USA). Primer pairs yielded an average of 11.2 alleles per locus (range of 4–24), an average observed heterozygosity of 0.83 (range 0.59–0.96), and an average polymorphic information content of 0.80 (range 0.62–0.94). We also demonstrate the utility of these primers, in addition to primers for 15 loci previously described, for amplifying microsatellite loci in four additional species representing the two extant marine turtle families: olive ridley (Lepidochelys olivacea), hawksbill (Eretmochelys imbricata), green turtle (Chelonia mydas), and leatherback (Dermochelys coriacea).     

Conservation implications of complex population structure: lessons from the loggerhead turtle (Caretta caretta)

Complex population structure can result from either sex-biased gene flow or population overlap during migrations. Loggerhead turtles (Caretta caretta) have both traits, providing an instructive case history for wildlife management. Based on surveys of maternally inherited mtDNA, pelagic post-hatchlings show no population structure across the northern Atlantic (phi(ST) < 0.001, P = 0.919), subadults in coastal habitat show low structure among locations (phi(ST) = 0.01, P < 0.005), and nesting colonies along the southeastern coast of the United States have strong structure (phi(ST) = 0.42, P < 0.001). Thus the level of population structure increases through progressive life history stages. In contrast, a survey of biparentally inherited microsatellite DNA shows no significant population structure: R(ST) < 0.001; F(ST) = 0.002 (P > 0.05) across the same nesting colonies. These results indicate that loggerhead females home faithfully to their natal nesting colony, but males provide an avenue of gene flow between regional nesting colonies, probably via opportunistic mating in migratory corridors. As a result, all breeding populations in the southeastern United States have similar levels of microsatellite diversity (H(E) = 0.70-0.89), whereas mtDNA haplotype diversity varies dramatically (h = 0.00-0.66). Under a conventional interpretation of the nuclear DNA data, the entire southeastern United States would be regarded as a single management unit, yet the mtDNA data indicate multiple isolated populations. This complex population structure mandates a different management strategy at each life stage. Perturbations to pelagic juveniles will have a diffuse impact on Atlantic nesting colonies, mortality of subadults will have a more focused impact on nearby breeding populations, and disturbances to adults will have pinpoint impact on corresponding breeding populations. These findings demonstrate that surveys of multiple life stages are desirable to resolve management units in migratory marine species.     

Esophageal diverticulum associated with Aerococcus viridans infection in a loggerhead sea turtle (Caretta caretta)

A juvenile loggerhead sea turtle (Caretta caretta) stranded in Gran Canaria, Spain was necropsied. The turtle was underweight, had sunken eyes, and small amounts of crude oil were in the oral cavity. The most significant lesion was a large esophageal diverticulum at the junction of the esophagus and stomach. The diverticulum was full of gas and green mucoid fluid and a diffuse thick yellow fibrinonecrotic membrane covered the mucosa. The lumen of the diverticulum also contained moderate numbers of cephalopods, crustaceans, and anthropogenic debris including crude oil balls, plastics, and fishing lines. Histologically there was a severe diffuse fibrinonecrotic esophagitis. Aerococcus viridans was isolated from the diverticulum. This is the first report of an esophageal diverticulum in a sea turtle. Although A. viridans is a known pathogen of lobsters and fishes, there are no reports of A. viridans infection in sea turtles.     

Gastrointestinal helminth community of loggerhead sea turtle Caretta caretta in the Adriatic Sea

We analysed the intestinal helminth community of 70 loggerhead sea turtles Caretta caretta with a curved carapace length ranging from 25 to 85.4 cm, recovered dead in neritic foraging habitats in the Adriatic Sea in 1995 to 2004. The overall prevalence of infection was high (70.0%), with a mean abundance of 36.8 helminth parasites per turtle. Helminth fauna comprised 5 trematodes (Calycodes anthos, Enodiotrema megachondrus, Orchidasma amphiorchis, Pachypsolus irroratus, Rhytidodes gelatinosus) and 3 nematodes (Sulcascaris sulcata, Anisakis spp., Hysterothylacium sp.), with 6 taxa specific for marine turtles. In terms of infection intensity and parasite abundance, O. amphiorchis was the dominant species (mean intensity: 49.8; mean abundance: 12.8), followed by R. gelatinosus (30.5 and 8.3, respectively) and P. irroratus (23.5 and 7.0, respectively), while larval Anisakis spp. exhibited the highest prevalence (34.3%). The intensity of helminth infection ranged from 1 to 302 (mean: 52.6 ± 69.1) and was not correlated with the size of turtles; this relationship held for all species, except R. gelatinosus (rS = 0.556, p < 0.05). In comparison to other marine habitats, the helminth community of Adriatic loggerheads is characterised by higher species diversity (Shannon-Wiener H' = 1.58) and evenness (E = 0.76), and lower dominance values (Berger-Parker d = 0.35), which can be attributed to the life history and feeding ecology of sea turtles in recruited neritic grounds and the diversity of their benthic prey.     

Effect of maternal foraging habitat on offspring quality in the loggerhead sea turtle (Caretta caretta)

Exploring a trade‐off between quantity and quality of offspring allows differences in the fitness between alternative life histories to be accurately evaluated. We addressed the mechanism that maintains alternative life histories (small oceanic planktivores vs. large neritic benthivores) observed in a loggerhead sea turtle (Caretta caretta) population, which has been suggested to be environmental, based on the lack of genetic structure and a large difference in reproductive output. We examined whether maternal foraging habitat affects offspring quality, by measuring the morphology, emergence success, and righting response of hatchlings following incubation in a common open sand area over the whole nesting season at Yakushima Island, Japan, and by recording early growth and survival of offspring that were reared in a common environment at a Japanese aquarium. Furthermore, we tested whether sea turtles adjust egg size in response to temporal shifts of the incubation environment. There were no significant differences in any hatchling traits between oceanic and neritic foragers (which were classified by stable isotope ratios), except for clutches laid during the warmest period of the nesting season. There were also no significant differences in the growth and survival of offspring originating from the two foragers. The size of eggs from both foragers significantly increased as the season progressed, even though the rookery had heavy rainfall, negating the need to counteract heat‐related reduction in hatchling morphology. In comparison, the sizes of adult body and clutches from both foragers did not vary significantly. The results further support our previous suggestions that the size‐related foraging dichotomy exhibited by adult sea turtles does not have a genetic basis, but derives from phenotypic plasticity. Adjustment in reproductive investment may be associated with: (1) predation avoidance, (2) founder effect, and/or (3) annual variation in egg size.     

Propofol anesthesia in loggerhead (Caretta caretta) sea turtles

Rapid, safe, and effective methods of anesthetic induction and recovery are needed for sea turtles, especially in cases eligible for immediate release. This study demonstrates that intravenous propofol provides a rapid induction of anesthesia in loggerhead (Caretta caretta) sea turtles and results in rapid recovery, allowing safe return to water shortly after the procedure. Forty-nine loggerhead sea turtles were recovered as local fishery by-catch in pound nets and transported to a surgical suite for laparoscopic sex determination. Treatment animals (n = 32) received 5 mg/kg propofol intravenously (i.v.) as a rapid bolus, whereas control animals (n = 17) received no propofol. For analgesia, all animals received a 4 ml infusion of 1% lidocaine, locally, as well as 2 mg/kg ketoprofen intramuscularly (i.m.). Physiologic data included heart and respiratory rate, temperature, and a single blood gas sample collected upon termination of the laparoscopy. Subjective data included jaw tone and ocular reflex: 3 (vigorous) to 0 (none detected). Anesthetic depth was scored from 1, no anesthesia, to 3, surgical anesthesia. Turtles receiving propofol became apneic for a minimum of 5 min with a mean time of 13.7 +/- 8.3 min to the first respiration. Limb movement returned at a mean time of 21.1 +/- 16.8 min. The treatment animals were judged to be sedated for approximately 30 min (mean anesthetic depth score > or = 1.5) when compared to controls. Median respiratory rates for treatment animals were slower compared to controls for the first 15 min, then after 35 min, they became significantly faster than the controls. Median heart rates of control animals became significantly slower than treatment animals between 40 and 45 min. Physiologic differences between groups persisted a minimum of 55 min. Possible explanations for heart rate and respiratory rate differences later in the monitoring period include a compensatory recovery of treatment animals from anesthesia-induced hypoxia and hypercapnia or, alternatively, an induced response of the nonsedated control animals. The animals induced with propofol were easier to secure to the restraint device and moved less during laparoscopy. In conclusion, propofol is a safe and effective injectable anesthetic for use in free-ranging loggerhead sea turtles that provides rapid induction and recovery.     

An assessment of initial body size in loggerhead sea turtle (Caretta caretta) hatchlings in Turkey

Eggs, hatchlings, and adult loggerhead turtles, and incubation durations of clutches, were measured on three Turkish beaches (Dalyan, Fethiye and G?ksu Delta), and some physical features of nests were compared. These features were not statistically different among the beaches, except for nest depth and distance to the high water mark. There was a positive relationship between hatchling mass and egg size. The carapace length of hatchlings was correlated with both egg diameter and incubation duration. The duration of asynchronous emergence of hatchlings on Fethiye beach was slightly longer than on the other two beaches, and the size of hatchlings decreased as asynchronous emergence proceeded. Of the hatchlings that emerged first, those that died were significantly smaller in SCL and mass than those that lived. These results suggest that smaller hatchlings may not be vigorous enough to emerge earlier from nests, and that they may be less fit.     

Clutch size for Mediterranean loggerhead turtles (Caretta caretta)

We investigated the number of eggs laid and the total clutch volume for loggerhead turtles ( Caretta caretta L.) nesting on the Greek island of Cephalonia (38° 09' N, 20° 33' E) during 1990. Both the number of eggs laid and clutch volume were positively related to female body size, and the mean explained variation for these relationships (36·6% and 37·7%, respectively) were not significantly different. Clutch volume decreased as the season progressed because individuals laid successively smaller clutches. The inter-nesting interval (range 15–19 days) did not significantly influence the number of eggs laid or clutch volume. For individuals seen laying more than once, female size in combination with the number of a clutch in relation to all the clutches observed for that individual, together explained 65·5% of the variation in clutch volume.     

Twelve new polymorphic microsatellite markers from the loggerhead sea turtle (Caretta caretta) and cross-species amplification on other marine turtle species

We describe 12 new polymorphic dinucleotide microsatellite loci and multiplex Polymerase Chain Reaction conditions from the loggerhead sea turtle Caretta caretta. Levels of polymorphism were assessed in 50 individuals from the nesting population of the Cape Verde Islands. Number of alleles ranged from 3 to 13 (average of 7.33) and the values of observed heterozygosities from 0.32 to 0.80 (average of 0.61). Cross-species amplification on three other marine turtles, Chelonia mydas, Eretmochelys imbricata and Dermochelys coriacea, revealed polymorphism and variability at eight, eleven and three loci, respectively.