David W. Owens

Reproductive and Developmental Synchrony in Female Lepidochelys olivacea

The reproductive behavior and movements of arribada nesting olive ridley turtles (Lepido- chelys olivacea) were studied during the 1990 and 1991 nesting seasons (September through November) at Nancite Beach, Santa Rosa National Park, Guanacaste, Costa Rica. Females that normally emerge synchro- nously once a month on Nancite Beach to oviposit delayed oviposition in response to a period of very heavy rainfall. Females retained oviducal eggs for 63 days and emerged synchronously to oviposit at Nan- cite Beach after the rain had ceased. Egg retention in L. olivacea appears to be an adaptation which en- ables delayed oviposition when environmental conditions are unsuitable and may also facilitate reproduc- tive synchrony. We suggest that preovipositional arrest of developing embryos may have occurred while oviducal eggs were retained.

Incubation Temperature Effects on Hatchling Performance in the Loggerhead Sea Turtle (Caretta caretta)

Incubation temperature has significant developmental effects on oviparous animals, including affecting sexual differentiation for several species. Incubation temperature also affects traits that can influence survival, a theory that is verified in this study for the Northwest Atlantic loggerhead sea turtle (Caretta caretta). We conducted controlled laboratory incubations and experiments to test for an effect of incubation temperature on performance of loggerhead hatchlings. Sixty-eight hatchlings were tested in 2011, and 31 in 2012, produced from eggs incubated at 11 different constant temperatures ranging from 27°C to 33°C. Following their emergence from the eggs, we tested righting response, crawling speed, and conducted a 24-hour long swim test. The results support previous studies on sea turtle hatchlings, with an effect of incubation temperature seen on survivorship, righting response time, crawling speed, change in crawl speed, and overall swim activity, and with hatchlings incubated at 27°C showing decreased locomotor abilities. No hatchlings survived to be tested in both years when incubated at 32°C and above. Differences in survivorship of hatchlings incubated at high temperatures are important in light of projected higher sand temperatures due to climate change, and could indicate increased mortality from incubation temperature effects.

Diamondback terrapins, Malaclemys terrapin, as a sentinel species for monitoring mercury pollution of estuarine systems in South Carolina and Georgia, USA

Total mercury concentrations were measured in diamondback terrapin blood and scutes collected from four sites in South Carolina, USA, and at a superfund site in Brunswick, Georgia, USA. There was a strong correlation between mercury concentrations in the two terrapin body compartments (Kendalls tau = 0.79, p < 0.001). Mercury concentrations in terrapin scute and blood and in salt marsh periwinkles, Littoraria irrorata, were significantly higher in Brunswick (scute x = 3810.2 ng/g, blood x = 746.2 ng/g) than from all other sites (scute x = 309.5 ng/g, blood x = 43.2 ng/g, p < 0.001). Seasonal fluctuations of total mercury in the blood and scutes of terrapins collected in the Ashley River, South Carolina, were significantly lower in August than in April, June, or October in blood (p < 0.001); however, scute concentrations did not vary seasonally. Overall, we found higher concentrations of mercury in the scutes of females than males (n = 32, p < 0.05). Larger females may preferentially prey on larger food items, like large periwinkles, which had significantly higher mercury levels in their body tissues than smaller periwinkles (p < 0.001). Methylmercury levels in terrapin scutes were measured, revealing that 90% of the total mercury stored in this compartment was in the organic form. A methylmercury biomagnification factor of 173.5 was calculated from snails to terrapin scutes, and we found that mercury levels in scutes were representative of the mercury levels in other compartments of the ecosystem. These findings show that terrapin scutes are good predictors of mercury pollution and that this species could be used as a bioindicator for assessing mercury contamination of estuarine systems.

Hormones and Reproductive Cycles in Turtles

Publisher Summary Various adaptations and flexibilities of reproductive patterns have evolved to allow turtles to reproduce successfully from oceans to deserts and from tropical to temperate zones throughout the world. The major life-history challenge for a turtle is to survive to adulthood. However, once they are adults, they repeatedly cycle for reproduction for up to several decades. The anatomical, behavioral, endocrinological, and regulatory organization of the many forms these cycles take is both fascinating and complicated. Radiography, laparoscopy, and ultrasonography have been used on a few species of turtle to describe a diversity of ovarian and testicular cycles. Radioimmunoassays (RIAs) have provided evidence of the dynamic cycling of peptides and steroid hormones within a reproductive season. All turtles are cyclic breeders and show a range of annual and multiannual reproductive patterns—regulated by nutritional status and environmental conditions—which are most often described as prenuptial or postnuptial. These cycles may be seasonally coordinated by an active pineal gland in the brain via melatonin secretion affecting the hypothalamus. Moreover, the steroid hormone cycles can be rapid and dynamic, and steroid hormones stimulate a carefully orchestrated mating receptivity period: a series of rapid ovulations in the case of multiclutched turtles, egg production, and oviposition events.

ULTRASOUND IMAGING OF THE INGUINAL REGION OF ADULT MALE LOGGERHEAD SEA TURTLES (CARETTA CARETTA)

Abstract The biology and reproductive anatomy of male loggerhead sea turtles (Caretta caretta) have been difficult to study. The principle method for evaluation of the coelomic cavity in both adult and juvenile male sea turtles is celioscopy. The purpose of this study was to describe the technique and structures seen when scanning the inguinal region of live, wild-caught, adult male loggerhead sea turtles and to compare these findings to those resulting from celioscopy and necropsy. Twenty-one adult male loggerhead sea turtles were collected by trawling in the Cape Canaveral shipping channel in April 2007. All turtles were placed in dorsal recumbency and imaged with a Sonosite 180 Vet Plus (Sonosite, Inc., Bothell, Washington 98021, USA) and a microconvex, 4–7-MHz curvilinear array probe. The inguinal region was divided into four quadrants: cranial, lateral, medial, and caudal. Celioscopy was performed on 13 turtles, and biopsies were obtained of the testes and the epididymides to confirm correct identification of the structures. In the cranial aspect of the inguinal region, the urinary bladder and large and small intestines were identified. In the lateral inguinal region, the lung and kidney were seen. In the medial aspect of the inguinal region, the testis and epididymis were routinely identified. In the caudal aspect of the inguinal region, the coxofemoral joint was seen. A small learning curve was required; however, correlation with celioscopy and biopsy showed that consistent, repeatable identification of caudal coelomic structures was easily achieved. Ultrasound provided an inexpensive, rapid, noninvasive method to evaluate the reproductive anatomy of live-captured, male loggerhead sea turtles.

Female-Bias in a Long-Term Study of a Species with Temperature-Dependent Sex Determination: Monitoring Sex Ratios for Climate Change Research.

Alterations have occurred and continue to manifest in the Earth’s biota as a result of climate change. Animals exhibiting temperature dependent sex determination (TSD), including sea turtles, are perhaps most vulnerable to a warming of the Earth as highly skewed sex ratios can result, potentially leading to population extinction resulting from decreased male recruitment. Recent studies have begun to quantify climate change impacts to sea turtle populations, especially in terms of predicting effects on hatchling sex ratios. However, given the inherent difficulty in studying sex ratios at this life stage, a more accurate assessment of changes in population sex ratios might be derived by evaluating the juvenile portion of foraging aggregations. We investigated the long-term trend in sex ratio of a juvenile loggerhead (Caretta caretta) sea turtle population inhabiting Pamlico and Core Sounds, North Carolina, USA. We used plasma testosterone reference ranges measured using radioimmunoassay (RIA) to assign sex for 959 turtles and confirmed sex assignment of a subset (N = 58) of the sampled turtles through laparoscopic examination of their gonads. Our results demonstrate that for this particular population of loggerheads, sex ratios (3Females:1Male) had not significantly changed over a 10 year period (1998–2007), nor showed any significant difference among 5-cm straight carapace length (SCL) size classes. Ultimately, these findings provide a basis for comparison with future sex ratios, and highlight the importance of establishing similar long-term studies monitoring secondary, rather than primary, sex ratios, so that needed mitigation measures to climate change impacts can be implemented.