Juvenile Loggerhead Sea Turtles Research Articles

Living Together but Remaining Apart: Atlantic and Mediterranean Loggerhead Sea Turtles (Caretta caretta) in Shared Feeding Grounds

Juvenile loggerhead sea turtles (Caretta caretta) from Atlantic nesting populations migrate into the western Mediterranean, where they share feeding grounds with turtles originating in the Mediterranean. In this scenario, male-mediated gene flow may lead to the homogenization of these distant populations. To test this hypothesis, we genotyped 7 microsatellites from 56 Atlantic individuals sampled from feeding grounds in the western Mediterranean and then compared the observed allele frequencies with published data of 112 individuals from Mediterranean nesting beaches. Mediterranean populations were found to be genetically differentiated from the Atlantic stock reaching the western Mediterranean (F(st) = 0.029, P < 0.001); therefore, the possible mating events between Atlantic and Mediterranean individuals are not sufficient to homogenize these 2 areas. The differentiation observed between these 2 areas demonstrates that microsatellites are sufficiently powerful for mixed stock analysis and that individual assignment (IA) tests can be performed in combination with mitochondrial DNA (mtDNA) analysis. In a set of 197 individuals sampled in western Mediterranean feeding grounds, 87% were robustly assigned to Atlantic or Mediterranean groups with the combined marker, as compared with only 52% with mtDNA alone. These findings provide a new approach for tracking the movements of these oceanic migrants and have strong implications for the conservation of the species.

BLOOD BIOCHEMISTRY REFERENCE VALUES FOR WILD JUVENILE LOGGERHEAD SEA TURTLES (CARETTA CARETTA) FROM MADEIRA ARCHIPELAGO

Standard biochemical parameters were determined in wild juvenile loggerhead sea turtles Caretta caretta living offshore Madeira Island, northeast Atlantic. We analyzed the influence of age, sex, sea surface temperature, and body condition index on biochemical parameters including uric acid, total bilirubin, total cholesterol, creatinine kinase (CK), glucose, total protein, urea nitrogen, lactate dehydrogenase, aspartate aminotranspherase (AST), gamma-glutamyl transferase (GGT), albumin, alkaline phosphatase (ALP), sodium (NA), potassium (K), chloride, calcium, phosphorus, and magnesium. Significant positive correlations were found between turtle body size and total cholesterol, total protein, and albumin. Total protein and the enzymes AST and CK were lower than reported levels in adults. Calcium levels were lower than those reported in adult or captive turtles, but similar to wild juveniles from Australian waters, and were interpreted as normal for this age category. These data may be useful to evaluate the health status of stranded or injured animals and to improve veterinary care at rehabilitation centers.

Influence of environmental and fishery parameters on loggerhead sea turtle by-catch in the longline fishery in the Azores archipelago and implications for conservation

Oceanic juvenile loggerhead sea turtles, Caretta caretta, foraging in Azorean waters, are incidentally caught in drifting longlines that target swordfish, Xiphias gladius, and blue shark, Prionace glauca. Data were recorded during a longline gear modification experiment conducted in 2000. The results show that the captures are not uniformly distributed in relation to fishing effort, with 81% of the loggerheads (N = 232) caught in one-third of the sets (N = 93). The highest turtle catch rates were around the eastern group of islands, an area characterized by the presence of mesoscale eddies induced by bathymetric features. High catch rates coincided with the presence of the thermohaline front, between August and October, and when targeting blue shark. To investigate the causes of these differences we fitted a general linear model to evaluate the influence of mean depth, minimum depth, sea surface temperature (SST), soak area, soak time, moon phase and wind force on turtle and target species catch rates. These results revealed that mean depth and SST were most important for loggerhead catch rates, while minimum depth was the only significant variable for swordfish and mean depth, SST, wind force, moon phase and soak time influenced blue shark catches. The distribution of loggerhead sea turtles can be predicted by monitoring fishing areas in relation to bathymetry and SST. The impact of longline fishing could be greatly and quickly reduced by regulating the blue shark fishery and by increasing fishermen awareness for sea turtle conservation.

Temporal and Spatial Trends of Perfluorinated Compounds in Juvenile Loggerhead Sea Turtles (Caretta caretta) along the East Coast of the United States

Perfluorinated compounds (PFCs) are globally distributed persistent environmental contaminants. This study provides temporal trends as well as large-scale spatial trends of PFC concentrations in threatened juvenile loggerhead sea turtles near or from Florida Bay (FL Bay), Cape Canaveral (FL), Charleston (SC), Core Sound (NC), and Chesapeake Bay (MD). PFCs were extracted from 163 plasma and serum samples using solid-phase extraction and quantified with LC-MS/MS. Concentrations of six compounds significantly varied by site, with MD or FL Bay turtles having the highest concentrations. Perfluorooctane sulfonate (PFOS) was the predominant PFC at all sites (range: 0.31 ng/g to 39.0 ng/g). FL Bay turtles, compared to other sites, accumulated a unique PFC pattern with a higher proportion of perfluorocarboxylates compared to PFOS. Furthermore, this study was the first to statistically correlate wildlife PFC concentrations with human population, used as a proxy for urbanization and sources of PFCs to the environment. Positive relationships were found in which human population accounted for 75 and 81% of the variance in turtle PFOS and perfluoroundecanoate (PFUnA) concentrations (p = 0.06 and 0.04), respectively. PFOS and perfluorononanoate (PFNA) significantly decreased from 2000-2008 in SC turtles annually by 20 and 11%, respectively (p </= 0.02). Future investigations should continue temporal assessments as PFC regulations change, attempt to pinpoint specific sources and transport pathways in areas with unique PFC patterns, and assess turtle health at sites with higher PFC concentrations.

Stable isotopes confirm a foraging dichotomy in juvenile loggerhead sea turtles

Differential habitat use and foraging behaviors at various life-stages within a population can have profound consequences for survivorship, stage duration, and time to maturity. While evidence for plasticity within a given life-stage in marine species is mounting, factors that contribute to this diversity remain poorly understood. We used stable isotope analysis of consumer and prey tissues to describe the trophic niche width of juvenile loggerhead turtles ( Caretta caretta) that have been tracked and previously shown to have significant variation in movement behaviors (oceanic versus neritic). Results of a Bayesian mixing model indicated that whereas benthic invertebrates dominated the recent diet of neritic turtles (determined through blood plasma), pelagic prey items contributed substantially to the diets of oceanic turtles. Analysis of temporally protracted diet composition (determined through red blood cells) reflected contributions from pelagic prey for all turtle groups, indicating that all turtles fed in the pelagic zone during overwintering periods. These results imply that the previous satellite tracking results reflect the turtles' prior foraging habits. Our study highlights the need for an integrative management approach of North Atlantic juvenile loggerheads and validates the use of stable isotopes for determining their differential habitat use.

Effect of repeated tissue sampling on growth rates of juvenile loggerhead turtles Caretta caretta

We evaluated the effect of repeated tissue sampling on growth rates of juvenile loggerhead sea turtles Caretta caretta. Samples of blood, skin, and scute (keratinized epidermal layer covering the bony shell) were collected at 3 intervals over a 120 d period from 37 loggerheads; 8 control turtles were not sampled. No infections or scarring occurred at the sampling sites, and growth in mass of experimental and control turtles was not significantly different. The sampling regime did not affect the health or physiological status of the turtles.

Satellite transmitter attachment techniques for small juvenile sea turtles

Three trials comprised of 4, 16, and 8 captive-reared juvenile loggerhead sea turtles ( Caretta caretta) were run for 164, 134, and 213 d, respectively, to evaluate platform terminal transmitter (PTT) attachment methods. Power-Fast® epoxy-only (PF-only) and Power-Fast®/Sonic-Weld® epoxy putty (PF/SW) protocols were tested in each trial, and the latter trials also included experimental, less-rigid methods incorporating 1.5 and 3.0 mm neoprene. Protocols were modified slightly for the latter trials compared to those of the first, utilizing coarser sandpaper for site preparation and discarding initial “squeezes” of epoxy. Despite a low average growth rate (0.012 cm/d), three of four PTTs were shed from the loggerheads in Trial 1. All PTTs remained attached in Trial 2 after an average straight carapace length (SCL) increase of 3.4 cm (0.024 cm/d), suggesting that protocol modifications improved upon Trial 1 methods. One 3.0-mm neoprene attachment and a PF-only attachment were shed during Trial 3 after SCL increases of 3.7 and 5.4 cm, respectively. The other six PTTs remained attached after an average SCL increase of 9.6 cm (0.045 cm/d), but significant gaps occurred along the perimeters of the three remaining non-neoprene attachments. Two neoprene attachments became loose along the edges while their centers remained secure, suggesting that carefully-applied neoprene attachments may be beneficial for tracking smaller, faster-growing sea turtles.

Comparative study of hematologic and plasma biochemical variables in Eastern Atlantic juvenile and adult nesting loggerhead sea turtles (Caretta caretta)

Plasma biochemical and hematologic variables are important in the management of endangered sea turtles, such as loggerheads. However, studies on blood biochemistry and hematology of loggerheads are limited, and different concentrations according to variable criteria have been reported. The purpose of this study was to establish and compare baseline plasma chemistry and hematology values in Eastern Atlantic juvenile and adult nesting loggerhead sea turtles (Caretta caretta). Blood samples were collected from 69 healthy juvenile loggerhead sea turtles after their rehabilitation in captivity, and from 34 adult nesting loggerheads after oviposition. Fresh blood was used for leukocyte differential count and PCV determination. Heparinized blood was used for RBC and WBC counts. Plasma biochemical concentrations were measured using an automated biochemical analyzer. For the comparative study, nonparametric statistical analysis was done using the Mann-Whitney U-test. Minimum, maximum, and median concentrations were obtained for 14 hematologic and 15 plasma chemistry variables. Statistically significant differences between juvenile and adult turtles were found for PCV; RBC, WBC, and leukocyte differential counts; total protein, albumin, globulins, calcium, triglycerides, glucose, total cholesterol and urea concentrations; and lactate dehydrogenase activity. Age, size, and reproductive status cause important variations in the hematologic and plasma biochemical results of loggerheads. The reference values obtained in this study may be used as a standard profile, useful for veterinary surgeons involved in sea turtle conservation.

Helminth Component Community of the Loggerhead Sea Turtle,Caretta caretta,From Madeira Archipelago, Portugal

The helminth fauna of pelagic-stage loggerhead sea turtles, Caretta caretta, is still poorly known. Here, we describe the helminth-component community of healthy, free-ranging juvenile loggerhead sea turtles captured in the waters around Madeira Island, Portugal. Fifty-seven were used in this study. The esophagus, stomach, intestine, liver, gallbladder, spleen, kidneys, trachea, bronchi, urinary bladder, heart, left and right aortas, and coelomic cavity were macroscopically inspected; organs and tissues were removed and washed through a sieve. A search for parasites was made using a stereoscopic microscope; recovered parasites were fixed and stored in 70% alcohol until staining and identification. Prevalence, mean intensity, and mean abundance values were recorded. In total, 156 parasite specimens belonging to 9 species were found: nematodes included Anisakis simplex s.l. (larvae) and an unidentified species; digenetic trematodes present were Enodiotrema megachondrus, Rhytidodes gelatinosus, Pyelosomum renicapite, and Calycodes anthos; acanthocephalans included Bolbosoma vasculosum and Rhadinorhynchus pristis; a single cestode, Nybelinia sp., was present. Parasite infections were found to have both low prevalences and intensities. Possible reasons for this include the oligotrophic conditions of the pelagic habitat around Madeira; a 'dilution effect' because of the vastness of the area; and the small size, and thus ingestion rate, of the turtles. Results are discussed in terms of the various turtle populations that may use the waters surrounding Madeira. This work provides valuable information on the parasite fauna of a poorly known stage in the life of loggerhead sea turtles, thereby filling a fundamental gap with regard to features of the parasite fauna in this species.

SEASONAL RELIABILITY OF TESTOSTERONE RADIOIMMUNOASSAY (RIA) FOR PREDICTING SEX RATIOS OF JUVENILE LOGGERHEAD (CARETTA CARETTA) TURTLES

Because sex is determined by incubation temperatures in sea turtles and immature animals are not sexually dimorphic externally, circulating levels of testosterone measured with radioimmunoassay (RIA), in conjunction with laparoscopies, have been used to estimate sex ratios. From September to December 1995 to 1997, and from June to December 1998 to 2002, we sampled blood from 1106 juvenile loggerhead sea turtles (Caretta caretta) incidentally captured in pound nets set in Core and Pamlico Sounds, North Carolina to measure testosterone levels. Laparoscopies of 89 of these turtles revealed a sex ratio of 2.1F:1M, similar to other juvenile loggerhead populations along the southeastern coast of the USA. Laparoscopies demonstrated that testosterone levels correctly identified males during summer months (water temperatures .23 C), but were unreliable during late autumn/winter months (water temperatures #16 C). During the summer months, females (n 5 201) exhibited testosterone concentrations with an upper limit of 239.0 pg/ml, and males (n 5 69) exhibited a lower limit of 372.0 pg/ml, for a sex ratio of 2.9F:1.0M. We recommend that verification of the RIA should be conducted by laparoscoping a subset of turtles sampled in all sex ratio studies. In addition, this verification should be conducted at several different times throughout the year to evaluate any possible seasonal effects on testosterone concentrations.

Complexity and variation in loggerhead sea turtle life history

Juvenile loggerhead sea turtles spend more than a decade in the open ocean before returning to neritic waters to mature and reproduce. It has been assumed that this transition from an oceanic to neritic existence is a discrete ontogenetic niche shift. We tested this hypothesis by tracking the movements of large juveniles collected in a neritic foraging ground in North Carolina, USA. Our work shows that the shift from the oceanic to neritic waters is both complex and reversible; some individuals move back into coastal waters and then return to the open ocean for reasons that are still unclear, sometimes for multiple years. These findings have important consequences for efforts to protect these threatened marine reptiles from mortality in both coastal and open-ocean fisheries.

Morphologic and cytochemical characteristics of blood cells of juvenile loggerhead sea turtles ( Caretta caretta)

A morphologic classification based on the cytochemical characteristics of blood cells of 35 juvenile loggerhead sea turtles ( Caretta caretta) is described. Cytochemical stains included benzidine peroxidase, chloroacetate esterase, alpha-naphthyl butyrate esterase (with and without sodium fluoride), acid phosphatase (with and without tartaric acid), Sudan black B, periodic acid-Schiff, and toluidine blue. The morphologic characteristics of erythrocytes were similar to those reported in green turtles. Six types of white blood cells were identified: heterophils, eosinophils, basophils, lymphocytes, monocytes and thrombocytes. Except for the basophils, the rest of the white blood cells from loggerhead turtles had different cytochemical characteristics compared to blood cells from other sea turtle species. The leukocyte differential count was different from that reported for other sea turtle species. Heterophils were the most numerous leukocytes from these loggerhead turtles, followed by lymphocytes, eosinophils, monocytes and basophils. This paper provides a morphologic classification of blood cells of loggerhead sea turtles that is useful for veterinary surgeons involved in sea turtle conservation.

Sex ratios of juvenile loggerhead sea turtles Caretta caretta in the Mediterranean Sea

Species with environmental sex determination may have sex ratios different from 1:1, and so sex ratio is an important variable in studies on the population dynamics of these species. This is particularly important for the endangered sea turtles, in order to understand the possible effects of human impacts and conservation measures. Unfortunately, only adults show an evident external sexual dimorphism, so that sex ratio data are difficult to obtain and are limited for the juvenile class, which represents the largest part of a population. Here we present the first extensive assessment of sex ratio of juvenile loggerhead turtles (Caretta caretta) in the Mediterranean Sea. A total of 310 dead turtles from four different areas were sexed by direct examination of gonads, the most reliable sexing method. Females were 54.2% of the whole sample, and no significant differences were found between the study areas. However, this value cannot be ascribed to a single population, because specimens from different nesting sites, both within and outside the Mediterranean, share the same foraging areas and each population may potentially contribute with a different sex ratio. Although we found an unbiased sex ratio, when other information from the region about distribution, mixed stocks, and sex ratios are considered, actually present results are compatible with a hypothetical scenario in which a majority of females are produced in the Mediterranean nesting beaches.

The Kuroshio Extension Bifurcation Region: A pelagic hotspot for juvenile loggerhead sea turtles

Satellite telemetry of 43 juvenile loggerhead sea turtles (Caretta caretta) in the western North Pacific together with satellite-remotely sensed oceanographic data identified the Kuroshio Extension Bifurcation Region (KEBR) as a forage hotspot for these turtles. In the KEBR juvenile loggerheads resided in Kuroshio Extension Current (KEC) meanders and the associated anti-cyclonic (warm core) and cyclonic (cold core) eddies during the fall, winter, and spring when the KEC water contains high surface chlorophyll. Turtles often remained at a specific feature for several months. However, in the summer when the KEC waters become vertically stratified and surface chlorophyll levels are low, the turtles moved north up to 600 km from the main axis of KEC to the Transition Zone Chlorophyll Front (TZCF). In some instances, the loggerheads swam against geostrophic currents, and seasonally all turtles moved north and south across the strong zonal flow. Loggerhead turtles traveling westward in the KEBR had their directed westward movement reduced 50% by the opposing current, while those traveling eastward exhibited an increase in directed zonal movement. It appears, therefore, that these relatively weak-swimming juvenile loggerheads are not passive drifters in a major ocean current but are able to move east, west, north, and south through this very energetic and complex habitat. These results indicate that oceanic regions, specifically the KEBR, represent an important juvenile forage habitat for this threatened species. Interannual and decadal changes in productivity of the KEBR may be important to the species’s population dynamics. Further, conservation efforts should focus on identifying and reducing threats to the survival of loggerhead turtles in the KEBR. r 2006 Elsevier Ltd. All rights reserved.

Organochlorine contaminants in loggerhead sea turtle blood: extraction techniques and distribution among plasma and red blood cells.

Few studies have described the organochlorine (OC) contaminant concentrations found in sea turtle tissues. These studies have relied on the opportunistic sampling of either eggs or tissues from stranded carcasses. In this study, the use of whole blood samples as well as both blood components (plasma and red blood cells) were examined as a non-destructive alternative for monitoring OCs in free-ranging loggerhead sea turtles (Caretta caretta). Blood samples were collected from juvenile loggerhead sea turtles (n = 12) captured in Core Sound, North Carolina, USA and analyzed for 55 polychlorinated biphenyl (PCB) congeners and 24 OC pesticides by gas chromatography with electron capture detection and mass spectrometry. Using pooled loggerhead sea turtle whole blood, three different liquid:liquid extraction techniques were compared. Results were similar in terms of recovery of internal standards, lipids, and OC concentrations. An extraction technique, employing formic acid and 1:1 methyl-tert-butyl-ether: hexane, was found to be satisfactory. This method was applied to the extraction of OCs from whole blood, plasma, and red blood cell (RBC) samples from five loggerhead sea turtles. Plasma contained the highest OC concentrations on a wet mass basis, followed by whole blood and RBCs. The majority of each OC compound was found in the plasma rather than the RBCs, suggesting that OC compounds preferentially partition into the plasma. On average (SD), 89.4% (3.1 %) of total PCBs, 83.4% (11.9%) of total chlordanes, 74.3% (15.1%) of mirex, 72.6% (4.8%) of total DDTs, and 80.1% (16.6%) of dieldrin were found in the plasma. The concentrations of total PCBs, mirex, total chlordanes, and total DDTs measured in both components of the blood significantly correlated to those in whole blood. These are the first reported OC concentrations in sea turtle blood. They were found to be similar to previously reported levels in blood components of humans and of reptiles from relatively clean sites, but lower than those measured in blood of fish-eating birds and marine mammals. The results indicate that blood, preferably plasma, can be used to detect and monitor OC contaminants in loggerhead sea turtles.

Effect of Four Different Suture Materials on the Surgical Wound Healing of Loggerhead Sea Turtles, Caretta caretta

ABSTRACT The tissue reaction to four suture materials placed in the skin of juvenile loggerhead sea turtles, Caretta caretta, was evaluated both grossly and histologically. Chromic gut, polyglyconate, polyglactin 910, and poliglecaprone 25 were used in 258 turtles to close a wound produced at the time of laparoscopic sex determination. Gross tissue reactions were graded in 68 turtles at one week, and in the remaining 190 turtles at two weeks following surgery. Gross observations (eversion formation, holding of sutures, epibiont [organisms growing on suture site] present and crusts) were graded from one to three with one being mild and three being most severe. Gross observation scores did not differ among suture types. Crust scores were significantly greater for chromic gut and for polyglactin than for poliglecaprone 25 and polyglyconate. At the suture site, 32% of the turtles had an eversion in the incision ranging in size from 0.25 to 10 mm2 [mean 2.02 (+/− 1.95) mm2]. Eversion size did not vary signific...

Intestinal candidiasis in a loggerhead sea turtle ( Caretta caretta): an immunohistochemical study

Post mortem examination of a juvenile loggerhead sea turtle ( Caretta caretta) stranded in the Canary Islands revealed a fishing-line in the small intestine. Histologically, severe necrotic enteritis, multiple haemorrhages, and marked oedema of the intestinal submucosa were observed. Yeast cells and fungal hyphae were seen in the lamina propria of the intestinal mucosa and in the connective tissue of the submucosa. Because fungal cultures were not taken at the time of necropsy, an immunohistochemical study was performed in order to identify the fungus involved. Specific monoclonal and heterologously absorbed polyclonal antibodies served as the primary reagents for identification of aspergillosis, candidiasis, fusariosis, geotricosis, scedosporiosis, and zygomycosis, using an indirect immunofluorescence staining technique. The fungal elements were strongly stained only by a polyclonal antibody against Candida albicans and a monoclonal antibody against C. albicans. There are no known previous reports of Candida sp. causing skin disease or systemic mycotic infection in sea turtles.

Site fidelity and homing behavior in juvenile loggerhead sea turtles ( Caretta caretta )

To investigate site fidelity and homing behavior in juvenile loggerheads (Caretta caretta, L.), a mark-recapture study spanning four years (1998–2001) was conducted in Core Sound, N.C., USA. Each year of the study, approximately half of the turtles captured were tagged and released near the capture sites (n=207), while the remaining turtles were displaced 15–20 km and released (n=198). Loggerheads in both groups were recaptured in equal proportions near the original capture sites and many individuals were also recaptured in subsequent years. These data imply that juvenile loggerheads often returned to their capture sites following displacement, because if turtles dispersed randomly or remained near their release sites, then fewer displaced turtles should have been caught again. Moreover, because turtles migrate out of North Carolina sounds each winter, turtles recaptured at the same locations in different years evidently returned to specific sites following long migrations. To further investigate homing behavior, a small number of displaced turtles (n=28) were tracked using radio telemetry following their release. Although transmitters detached from most turtles within a few days, analyses of initial headings showed strong orientation in the direction of the capture site. In addition, four turtles successfully tracked for longer periods of time all returned rapidly to the vicinity of the capture location and remained in the area. Taken together, the results of this study indicate that juvenile loggerheads exhibit fidelity to specific areas during summer months and possess the navigational abilities to home to these areas following forced displacements and long-distance migrations.

Pharmacokinetics of florfenicol in loggerhead sea turtles (Caretta caretta) after single intravenous and intramuscular injections.

The pharmocodynamics of single injections of florfenicol in yearling loggerhead sea turtles (Caretta caretta) were determined. Eight juvenile loggerhead sea turtles weighing 1.25 (+/- 0.18) kg were divided into two groups. Four animals received 30 mg/kg of florfenicol i.v., and four received the same dose i.m. Plasma florfenicol concentrations were analyzed by reverse-phase high performance liquid chromatography. After the i.v. dose, there was a biphasic decline in plasma florfenicol concentration. The initial steep phase from 3 min to 1 hr had a half-life of 3 min, and there was a longer slow phase of elimination, with a half-life that ranged from 2 to 7.8 hr among turtles. The volume of distribution varied greatly and ranged from 10.46 to -60 L/kg. Clearance after the i.v. dose was 3.6-6.3 L/kg/hr. After the i.m. injection, there was a peak within 30 min of 1.4-5.6 microg/ml, and florfenicol was thereafter eliminated with a half-life of 3.2-4.3 hr. With either route, florfenicol plasma concentrations were below the minimum inhibitory concentrations for sensitive bacteria within 1 hr. Florfenicol does not appear to be a practical antibiotic in sea turtles when administered at these doses.

Use of multiple orientation cues by juvenile loggerhead sea turtles Caretta caretta

Use of multiple orientation cues by juvenile loggerhead sea turtles Caretta caretta