Roldán A. Valverde

Olive Ridley Mass Nesting Ecology and Egg Harvest at Ostional Beach, Costa Rica

Abstract The olive ridley sea turtle (Lepidochelys olivacea), a species listed by the International Union for Conservation of Nature as vulnerable, is characterized by its mass-nesting behavior, also known as arribada. For decades, this phenomenon has facilitated the utilization of this species by coastal communities, much of it illegally. At Ostional beach, Costa Rica, a community-based egg-harvest program operates legally to generate important income for the community while promoting the protection of the ridley nesting assemblage. However, to date, no analysis exists that indicates the long-term viability of the egg harvest program as a sound management tool. To address this void, we generated baseline abundance data of the major arribada events that occurred in the period 2006–2010, as well as egg harvest data, along with preliminary hatching success. Arribadas ranged between 3564 and 476,550 egg-laying females, which indicated a large variability in the magnitude of the mass nesting events. Estimated mean egg harvest was 4746.4 and ranged from 1527 to 8138 total clutches. In relation to the estimated number of clutches laid, the estimated mean of clutches harvested was 21.2%, ranging from 1.5% to 102.4%. Estimated monthly mean hatching rates ranged from 0.0% to 32.6%. It is not clear whether arribadas underwent a significant change in abundance during the study period, although the number of years covered is too short to establish a long-term trend. However, when compared with historical data, the population appears to have declined. Based on our data, we present various management recommendations aimed at increasing hatching rates.

Amylin and Selective Glucoregulatory Peptide Alterations during Prolonged Exercise

UNLABELLED Amylin is a pancreatic β-cell peptide that facilitates the regulation of blood glucose concentration by inhibiting release of glucagon and modulating gastric emptying. Prolonged exercise may alter amylin and aid in the maintenance of blood glucose concentration; however, no studies have investigated the effects of prolonged exercise on amylin. PURPOSE This study aimed to determine the effects of 90 min of treadmill exercise on amylin and other glucoregulatory hormone responses in a postprandial state. METHODS Eight young healthy males completed a preliminary trial for VO2max and body composition determination and subsequent experimental and control trials in a counterbalanced manner. The experimental trial subjects arrived at the laboratory at 8:00 a.m., 1 h after consumption of a standard nutrient beverage (Ensure Plus®). At 9:50 a.m., subjects initiated 90 min of treadmill exercise at 60% of VO2max. Blood samples were collected twice before exercise, every 18 min during exercise, and every 20 min during 1 h of recovery. A resting control trial was conducted in an identical manner without VO2 assessment. RESULTS Plasma glucose and leptin concentrations remained stable across exercise, whereas lactate significantly increased to peak at 18 min of exercise then gradually declined. Amylin, insulin, and C-peptide values significantly declined over the trials, with no difference between exercise and control days. Glucagon area-under-the-curve concentrations were significantly greater during the exercise than the control trials. There was a significant time effect and trial effect for cortisol with a higher concentration during the experimental trial than during the control trial. CONCLUSIONS In a postprandial state, prolonged exercise stimulates glucagon and cortisol increases that are associated with stable blood glucose and leptin concentrations; however, similar to postprandial state control condition, insulin, C-peptide, and amylin concentrations decline.

Olive Ridley Sea Turtle Hatching Success as a Function of the Microbial Abundance in Nest Sand at Ostional, Costa Rica

Several studies have suggested that significant embryo mortality is caused by microbes, while high microbial loads are generated by the decomposition of eggs broken by later nesting turtles. This occurs commonly when nesting density is high, especially during mass nesting events (arribadas). However, no previous research has directly quantified microbial abundance and the associated effects on sea turtle hatching success at a nesting beach. The aim of this study was to test the hypothesis that the microbial abundance in olive ridley sea turtle nest sand affects the hatching success at Ostional, Costa Rica. We applied experimental treatments to alter the microbial abundance within the sand into which nests were relocated. We monitored temperature, oxygen, and organic matter content throughout the incubation period and quantified the microbial abundance within the nest sand using a quantitative polymerase chain reaction (qPCR) molecular analysis. The most successful treatment in increasing hatching success was the removal and replacement of nest sand. We found a negative correlation between hatching success and fungal abundance (fungal 18S rRNA gene copies g-1 nest sand). Of secondary importance in determining hatching success was the abundance of bacteria (bacterial 16S rRNA gene copies g-1 g-1 nest sand). Our data are consistent with the hypothesis that high microbial activity is responsible for the lower hatching success observed at Ostional beach. Furthermore, the underlying mechanism appears to be the deprivation of oxygen and exposure to higher temperatures resulting from microbial decomposition in the nest.

Plasma Vitellogenin in Free-Ranging Loggerhead Sea Turtles (Caretta caretta) of the Northwest Atlantic Ocean

Vitellogenin is the egg yolk precursor protein produced by oviparous vertebrates. As endogenous estrogen increases during early reproductive activity, hepatic production of vitellogenin is induced and is assumed to be complete in female sea turtles before the first nesting event. Until the present study, innate production of vitellogenin has not been described in free-ranging sea turtles. Our study describes circulating concentrations of vitellogenin in loggerhead sea turtles (Caretta caretta) from the Northwest Atlantic Ocean. We collected blood samples from juveniles and adults via in-water captures off the coast of the Southeast USA from May to August, and from nesting females in June and July at Hutchinson Island, Florida. All samples were analyzed using an in-house ELISA developed specifically to measure Caretta caretta vitellogenin concentration. As expected, plasma vitellogenin declined in nesting turtles as the nesting season progressed, although it still remained relatively elevated at the end of the season. In addition, mean vitellogenin concentration in nesting turtles was 1,000 times greater than that measured in samples from in-water captures. Our results suggest that vitellogenesis may continue throughout the nesting season, albeit at a decreasing rate. Further, vitellogenin detected in turtles captured in-water may have resulted from exposure to endocrine disrupting chemicals.

Olive Ridley Sea Turtle Hatching Success as a Function of Microbial Abundance and the Microenvironment of In Situ Nest Sand at Ostional, Costa Rica

Sea turtle hatching success at mass nesting beaches is typically lower than at solitary nesting beaches, presumably due in part to high rates of microbial metabolism resulting from the large input of organic matter from turtle eggs. Therefore, we tested the hypothesis that hatching success varies across areas of the beach in conjunction with differences in the physical nest environment and microbial abundance of in situ olive ridley sea turtle nests at Ostional, Costa Rica. We marked natural nests in high-density, low-density, and tidal-wash nesting areas of the beach and monitored clutch pO2 and temperature throughout the incubation period. We quantified hatching success and collected samples of nest sand during nest excavations. We quantified microbial abundance (bacteria and fungi) with a quantitative polymerase chain reaction (qPCR) analysis. Hatching success was lower in nests with lower pO2, higher temperatures, higher organic matter content, and higher microbial abundance. Our results suggest that the lower oxygen within the nest environment is likely a result of the high microbial abundance and rates of decomposition in the nest sand and that these factors, along with increased temperature of clutches in the high-density nesting area, are collectively responsible for the low hatching success at Ostional.

Estimation of the Net Nesting Effort of Olive Ridley Arribada Sea Turtles Based on Nest Densities at Ostional Beach, Costa Rica

Abstract Ostional Beach, Costa Rica, supports a large mass nesting (arribada) aggregation of Olive Ridley Sea Turtles (Lepidochelys olivacea). A large number of egg clutches is lost to egg harvest and to nest destruction by nesting females after every arribada. Accordingly, the purpose of our study was to generate estimates of the net number of clutches left incubating from clutch densities with the use of a quadrat methodology, and to compare these data with nesting population estimates resulting from the strip transect in time methodology that is currently applied. After the conclusion of each arribada, we randomly performed 50 excavations in 1-m2 quadrats to count the number of clutches present. We extrapolated quadrat density data to the entire nesting area of the beach to estimate the total number of clutches remaining following each arribada and egg harvest. The mean total clutch density was 4.09 ± 0.18 SE nests/m2. Our results showed that quadrat and transect estimate differences ranged from 0.04 to 52.6%, with quadrat estimates typically being lower. Our results demonstrated that, in the rainy season, a large number of clutches (47.4–99.9%) was left incubating in the beach after every arribada and egg harvest. By omitting clutches that were harvested or destroyed throughout the arribada, we evaluated the reproductive potential and estimated the magnitude of clutch loss on Ostional Beach, both of which play important roles in the management of the egg harvest as a sustainable conservation strategy. Resumen Playa Ostional, Costa Rica presenta el anidamiento masivo o arribada de la tortuga marina Lora (Lepidochelys olivacea). Un número elevado de huevos se pierde durante cada arribada debido a la cosecha de huevos y a la destrucción de nidos por parte de tortugas anidadoras. Así pues, el objetivo de este estudio fue el de generar estimados del número neto de nidos que permanecen incubándose a partir de la densidad de nidos utilizando una metodología de cuadrantes y la comparación de estos datos con los estimados poblacionales obtenidos con la metodología de transectos fijos sobre el tiempo que se está utilizando actualmente. Después de la conclusión de cada arribada, realizamos al azar 50 excavaciones en cuadrantes de 1m2 para contar el número de nidos presentes. Nosotros extrapolamos los datos de densidad de estos cuadrantes a la playa de anidación entera para estimar el número de nidos que quedan en la playa luego de cada arribada y de cada cosecha de huevos. La densidad promedio total de nidos fue de 4.09 ± 0.18 SE nidos por m2. Nuestros resultados mostraron que las diferencias entre los estimados transectos y de cuadrantes variaron de entre 0.04% a 52.6%, siendo los estimados de cuadrantes típicamente menores. Nuestros resultados demostraron que en la época lluviosa un gran número de nidos (entre el 47,4% y el 99,9%) permanecieron incubándose en la playa luego de cada arribada y cosecha de huevos. Al omitir los nidos que son destruidos por las tortugas durante cada arribada o cosechados, este nuevo procedimiento nos permitió hacer una evaluación del potencial reproductivo y de la magnitud de la destrucción de nidos en playa Ostional, ambos siendo factores que juegan un papel importante en el manejo de la cosecha de huevos como una estrategia de conservación sustentable.

Ovarian dynamics in free-ranging loggerhead sea turtles ( Caretta caretta)

Vitellogenin (VTG) is an egg yolk-precursor protein that serves as a nutrient source for developing embryos in oviparous vertebrates. The hormonal control of this protein has been studied in a variety of taxa, but details about the dynamics of this protein remain to be elucidated in sea turtle species. To investigate the dynamics of VTG in a multi-clutch species under natural conditions, 38 adult Loggerhead females entrained in the Florida Power and Light St. Lucie Nuclear Plant intake canal in Hutchinson Island, Florida were sampled from May–August of 2014. Blood samples were drawn to measure testosterone, estradiol 17β, and vitellogenin (T, E2, and VTG, respectively) using enzyme-linked immunosorbent assays. Ultrasound imaging of the gonads was used to determine ovarian status and to measure ovarian follicle and oviductal egg size. Results showed that VTG concentration increased from May (8.27 mg mL−1) to June (15.37 mg mL−1) and declined into July and August (9.44 mg mL−1); this decline corresponded with the end of the nesting season. E2 declined from 718.02 pg mL−1 in May to 95.89 pg mL−1 in July–August, and T declined from 2,008.35 pg mL−1 in May to 1,221.24 pg mL−1 in July–August. Mean concentration for both gonadal steroids was significantly higher in reproductively active females than means of reproductively inactive females, though overlapping concentrations of the steroids occurred between active and inactive animals. However, VTG concentration was high in reproductively active turtles and undetectable in gonadally quiescent turtles. We concluded that the addition of VTG measurement in conjunction with the gonadal steroids provides a more accurate and easily interpretable way to predict reproductive status of adult Loggerhead females. Finally, gonadal steroid and VTG concentration in our study corresponded only with late nesting animals, indicating that early season females do not become entrained in the intake canal of the power plant.