Jeanette Wyneken

The Biology of Sea Turtles

Physiology as Integrated Systems Amanda Southwood Williard Vision Kerstin A. Fritsches and Eric J. Warrant Natal Homing and Imprinting in Sea Turtles Kenneth J. Lohmann, Catherine M.F. Lohmann, J. Roger Brothers, and Nathan F. Putman The Skeleton: An In Vivo View of Structure Jeanette Wyneken Age and Age Estimation in Sea Turtles Larisa Avens and Melissa L. Snover Molecular Genetics of Sea Turtles Michael P. Jensen, Nancy N. FitzSimmons, and Peter H. Dutton Oceanic Habits and Habitats: Dermochelys coriacea Vincent S. Saba Oceanic Habits and Habitats: Caretta caretta Katherine L. Mansfield and Nathan F. Putman Feeding Biology: Advances from Field-Based Observations, Physiological Studies, and Molecular Techniques T. Todd Jones and Jeffrey A. Seminoff Predators, Prey, and the Ecological Roles of Sea Turtles Michael R. Heithaus Exposure to and Effects of Persistent Organic Pollutants Jennifer M. Keller Fisheries Bycatch of Marine Turtles: Lessons Learned from Decades of Research and Conservation Rebecca Lewison, Bryan Wallace, Joana Alfaro-Shigueto, Jeff Mangel, Sara Maxwell, and Elliott Hazen Climate Change and Marine Turtles Mark Hamann, Mariana M.P.B. Fuentes, Natalie C. Ban, and Veronique J.L. Mocellin Free-Ranging Sea Turtle Health Mark Flint Sea Turtle Epibiosis Michael G. Frick and Joseph B. Pfaller Parasites of Marine Turtles Ellis C. Greiner Index

Frenzy and Postfrenzy Swimming Activity in Loggerhead, Green, and Leatherback Hatchling Sea Turtles

Sea turtle hatchlings emerge from subsurface nests on oceanic beaches, crawl to the ocean, and swim out to sea. Once in the water, hatchlings at first swim almost continuously (a period called the frenzy). In this laboratory study, we compared the duration and diel pattern of frenzy and postfrenzy swimming activity among loggerhead, green turtle, and leatherback hatchlings frombeaches in southeastern Florida. The frenzy of all species lasted one day (24 h). After the frenzy, hatchlings continued to swim during the day. Green and loggerhead hatchlings eventually became inactive at night, but leatherback hatchlings typically swam between 15-45% of the dark period. Because the frenzy is temporally similar in all species, its function may also be the same: escape from shallow waters near shore. Postfrenzy differences in diel activity may reflect contrasts among species in foraging, predator avoidance, and energy conservation strategies.

Orientation and swimming behavior of hatchling loggerhead turtles Caretta caretta L. during their offshore migration

Loggerhead turtle Caretta caretta L. hatchlings emerging from nests on the eastern coast of Florida swim offshore toward the Florida Current. Part of the trip is accomplished during an initial 20-h period of swimming (the “frenzy”); the remainder may take a day or more of oriented swimming. Swimming speeds are slower than those of green turtles Chelonia mydas L. Hatchlings are well oriented in an offshore direction when released into the ocean during the day or night. Completion of a crawl down the beach or a plunge into the surf are unnecessary for proper orientation. Immediately after entering the ocean at night, responses to light appear essential for oriented swimming. However, present hypotheses based upon phototropotaxis may not account for orientation later in the migration.

First satellite tracks of neonate sea turtles redefine the ‘lost years’ oceanic niche

Few at-sea behavioural data exist for oceanic-stage neonate sea turtles, a life-stage commonly referred to as the sea turtle ‘lost years’. Historically, the long-term tracking of small, fast-growing organisms in the open ocean was logistically or technologically impossible. Here, we provide the first long-term satellite tracks of neonate sea turtles. Loggerheads (Caretta caretta) were remotely tracked in the Atlantic Ocean using small solar-powered satellite transmitters. We show that oceanic-stage turtles (i) rarely travel in Continental Shelf waters, (ii) frequently depart the currents associated with the North Atlantic Subtropical Gyre, (iii) travel quickly when in Gyre currents, and (iv) select sea surface habitats that are likely to provide a thermal benefit or refuge to young sea turtles, supporting growth, foraging and survival. Our satellite tracks help define Atlantic loggerhead nursery grounds and early loggerhead habitat use, allowing us to re-examine sea turtle ‘lost years’ paradigms.

Seafinding by hatchling sea turtles : role of brightness, silhouette and beach slope as orientation cues

Upon emerging from underground nests, sea turtle hatchlings immediately crawl toward the ocean. The primary cues used in orientation are visual but the nature of the visual cues was a matter of speculation. Hatchlings might also respond to secondary cues, such as beach slope. Experiments were carried out in an arena where specific visual and slope cues, simulating those present at nest sites, could be precisely controlled and manipulated. Subjects were green turtle (Chelonia mydas L.) and loggerhead (Caretta caretta L.) hatchlings. Both species oriented toward the more intensely illuminated sections of the arena. They also oriented away from dark silhouettes which simulated an elevated horizon, typical of the view toward land. Turtles responded primarily to stimuli (both silhouettes and photic differences) at or near eye level. When presented simultaneously with a silhouette and a photic gradient located in different directions, hatchlings oriented away from the silhouette and ignored photic stimuli. Under infrared light, both species oriented down slopes. However in the presence of nocturnal levels of visible light loggerheads ignored slope cues and responses of green turtles to slope were weakened. The data suggest that loggerhead and green turtle hatchlings usually find the sea by orienting away from elevated silhouettes. This is a prominent and reliable cue for species which typically nest on continental beaches.

Angiographic, Anatomic and Clinical Technique Descriptions of A Subcarapacial Venipuncture Site for Chelonians

ABSTRACT A novel technique for chelonian venipunture is described. Angiographic studies using radio-opaque iohexol, static radiography, and video fluoroscopy were undertaken in several chelonian species. Latex injected dissections were also performed to confirm the vascular anatomy. These studies indicate that a clinically useful venipuncture site is present in the anterior dorsal midline at the junction of the common intercostal veins and the caudal cervical branch of the external jugular veins, located just craniad of the last mobile cervical vertebra.

Geographical variation of persistent organic pollutants in eggs of threatened loggerhead sea turtles (Caretta caretta) from southeastern United States

Persistent organic pollutants (POPs) are recognized manmade threats to sea turtle populations, but substantial uncertainty exists surrounding their exposure to contaminants and their sensitivity to toxic effects. This uncertainty creates difficulty for conservation managers to make informed decisions for the recovery of these threatened species. To provide baseline concentrations and spatial comparisons, we measured a large suite of POPs in loggerhead sea turtle (Caretta caretta) egg yolk samples collected from 44 nests in three distinct U.S. locations: North Carolina (NC), eastern Florida (E FL), and western Florida (W FL). The POPs included polychlorinated biphenyls (PCBs), organochlorine pesticides such as dichlorodiphenyltrichloroethanes (DDTs), chlordanes, mirex, dieldin, hexachlorocyclohexanes (HCHs), hexachlorobenzene, and toxaphene congeners, as well as polybrominated diphenyl ether congeners (PBDEs). Persistent organic pollutant concentrations were lowest in W FL, intermediate in E FL, and highest in NC egg samples, with several statistically significant spatial differences. This increasing gradient along the southeast coast around the Florida peninsula to North Carolina was explained partly by the foraging site selection of the nesting females. Data from previous tracking studies show that NC nesting females feed primarily along the U.S. eastern coast, whereas W FL nesting females forage in the Gulf of Mexico and Caribbean Sea. The E FL nesting females forage in areas that overlap these two. The foraging site selection also results in exposure to different patterns of POPs. An unusual PBDE pattern was seen in the NC samples, with nearly equal contributions of PBDE congeners 47, 100, and 154. These findings are important to managers assessing threats among different stocks or subpopulations of this threatened species.

DETERMINING SEX IN POSTHATCHLING LOGGERHEAD SEA TURTLES USING MULTIPLE GONADAL AND ACCESSORY DUCT CHARACTERISTICS

The sex of young sea turtles is difficult to determine because they lack externally dimorphic characteristics and heteromorphic sex chromosomes, yet internal dimorphic morphology is defined at hatching. We tested the reliability of nine internal gonad and accessory duct characteristics to identify the sex of 558 posthatchling loggerhead sea turtles accurately. We modified existing laparoscopic procedures, previously used to classify the sex of larger sea turtles and other turtle species, for use in posthatchlings. Here we describe our approach and quantify the reliability of our morphological criteria. Sex was verified by histological examination of gonadal biopsies from a subset of the turtles. We noted seasonal shifts in early gonadal structure so that some characters which were reliable in the summer and fall were not reliable other times of the year. Thus, we confined the analysis to the six characters that were reliable year round: gonad shape, paramesonephric duct size, gonad size, paramesonephric duct lumen presence, paramesonephric duct mobility, and gonad attachment. Using discriminant analyses of the biopsy and morphological data, we found high correlations between sex from tissue biopsies and these six morphological characters; this analysis misclassified just 2% of the animals with histological verification. Applying the classification functions to animals without histology and comparing those results to our visual classification resulted in 2% reclassification. The analysis reclassified animals that we or the histology correctly identified that had both female-like and male-like characters. Our method provided accurate identification of sex in very young sea turtles. This methodology enables sex ratio assessments in early life stages, which are critical to species recovery efforts. Additionally, sex assignment data are basic to our understanding of patterns and processes directing dimorphic changes of the gonads and their ducts.

Why are hatching and emergence success low? Mercury and selenium concentrations in nesting leatherback sea turtles (Dermochelys coriacea) and their young in Florida

Leatherback sea turtles (Dermochelys coriacea) have low hatching and emergence success compared to other sea turtle species. Postmortem examinations of hatchlings showed degeneration of heart and skeletal muscle that was similar to that found in other neonates with selenium deficient mothers. Selenium deficiency can result from elevated concentrations of bodily mercury. Ingested mercury is detoxified by the liver through mercury-selenium compound formation. In animals persistently exposed to mercury, the livers ability to detoxify this element may decrease, especially if dietary selenium is insufficient. We measured mercury and selenium concentrations in nesting female leatherbacks and their hatchlings from Florida and compared the levels to hatching and emergence success. Both liver selenium and the liver selenium-to-mercury ratio positively correlated with leatherback hatching and emergence success. This study provides the first evidence for the roles of mercury and selenium in explaining low reproductive success in a globally imperiled species, the leatherback sea turtle.

Maternal Health Status Correlates with Nest Success of Leatherback Sea Turtles (Dermochelys coriacea) from Florida

Of the seven sea turtle species, the critically endangered leatherback sea turtle (Dermochelys coriacea) exhibits the lowest and most variable nest success (i.e., hatching success and emergence success) for reasons that remain largely unknown. In an attempt to identify or rule out causes of low reproductive success in this species, we established the largest sample size (n = 60–70 for most values) of baseline blood parameters (protein electrophoresis, hematology, plasma biochemistry) for this species to date. Hematologic, protein electrophoretic and biochemical values are important tools that can provide information regarding the physiological condition of an individual and population health as a whole. It has been proposed that the health of nesting individuals affects their reproductive output. In order to establish correlations with low reproductive success in leatherback sea turtles from Florida, we compared maternal health indices to hatching success and emergence success of their nests. As expected, hatching success (median = 57.4%) and emergence success (median = 49.1%) in Floridian leatherbacks were low during the study period (2007–2008 nesting seasons), a trend common in most nesting leatherback populations (average global hatching success = ∼50%). One protein electrophoretic value (gamma globulin protein) and one hematologic value (red blood cell count) significantly correlated with hatching success and emergence success. Several maternal biochemical parameters correlated with hatching success and/or emergence success including alkaline phosphatase activity, blood urea nitrogen, calcium, calcium∶phosphorus ratio, carbon dioxide, cholesterol, creatinine, and phosphorus. Our results suggest that in leatherbacks, physiological parameters correlate with hatching success and emergence success of their nests. We conclude that long-term and comparative studies are needed to determine if certain individuals produce nests with lower hatching success and emergence success than others, and if those individuals with evidence of chronic suboptimal health have lower reproductive success.