In order to estimate the structure of the loggerhead turtle assemblage in Okinawan waters, we measured the straight carapace length (SCL) and sexed 35 loggerhead turtles captured by set net between 2007 and 2011. Sexual maturity in females was determined on the basis of plasma triglyceride, cholesterol, total protein, and calcium concentrations. Of the 35 captured loggerhead turtles, 18 turtles were identified as males based on their elongated tails, while 16 turtles were identified as females in the process of vitellogenesis based on highly elevated blood plasma levels. Only one turtle with low plasma measurements was of indeterminate sex. We suggest that blood plasma measurements may serve as a useful indicator of female maturity. SCL means were 865 ± 48 mm (mean ± SD) for all turtles, 865±47 mm for males, and 871±52 mm for females; the turtle of unknown gender had an SCL of 791 mm. The loggerhead turtle assemblage in Okinawan waters was found to be larger in SCL and higher in the frequency of mature individuals than those in conspecific assemblages in other areas of Japanese waters so far studied. We suggest that the loggerhead turtles migrating to Okinawan waters are primarily in active reproductive states in preparation for mating and nesting.
We determined sequences of mitochondrial control region of 16 specimens of the leatherback turtles, Dermochelys coriacea, collected in the vicinity of Japan, and estimated stock origin of Japanese migrants. As a result, we found three haplotypes (JD1, 2, and 3) in these specimens, and 14 specimens possessed JD1. In comparison with previously reported sequences, JD1 and 2 were identical to a single haplotype endemic to West Pacific stock in New Guinea and Solomon Islands, whereas JD3 was identical to a haplotype nearly endemic to Malaysian stock. Our results indicate that most of the leatherbacks foraging around Japan originate in West Pacific stock, and a few may migrate from the Malaysian nesting population.
The aim of this study was to evaluate the relationships between carapace parameters as indicators of age and plasma elements in 25 captive hawksbill sea turtles. Particle-induced X-ray emission allowed detection of 23 trace and major elements. There were significant but weak correlations between the virtual carapace surface area and plasma bromide (r= -0.552, P<0.01), phosphorus (r=0.547, P<0.01), lead (r=-0.434, P<0.05) and strontium (r=0.599, P<0.01), while there were no significant correlations with other elements. These results suggest that major and trace plasma elements in captive sea turtles show almost no variation with carapace parameters, suggesting that the increase in plasma elements seen in wild sea turtles might be the result of marine pollution.
A female pantropical spotted dolphin (Stenella attenuata) successfully mated with a mature male in captivity on April 13, 2017. This mating event was followed by an evaluation of the plasma progesterone concentration, appetite, and rectum temperature of the dolphin during pregnancy. We recorded the progesterone profiles during pregnancy, the gestation period, and the parturition events. The progesterone level (ng/mL) ranged between 0.7 and 133.4 (n = 27), and the average was 45.1 (SD = 38.5). Immediately after mating, extremely high progesterone levels were observed, which showed a decreasing trend towards the parturition day. The gestation period was 352 days. On the morning of the parturition day on March 31, the female displayed symptoms such as a drop in rectal temperature by approximately 1°C and reduced appetite. The time from the first observation of vaginal discharge to the fluke's appearance was 5.5 hr, while the subsequent period until birth was 4 hr in length. The time from parturition to the first successful nursing was approximately 4 hr, while the time from the nursing to the placental passage was less than 1 hr. To the best of our knowledge, this is the first report on the pregnancy period of pantropical spotted dolphins in captivity.
To develop ovulation induction techniques, we investigated the effects of follicle- stimulating hormone (FSH) administration on ovulation in captive hawksbill turtles Eretmochelys imbricata. Porcine FSH preparation was administered by intramuscular injection to four hawksbill turtles with fully-developed follicles (21.6–23.8 mm, measured using ultrasonography) in July or August 2009. Blood samples were obtained and subjected to plasma progesterone measurement, and ovaries and oviducts were observed by ultrasonography just before, and 1–6 days after, FSH administration. One day after the administraion, the plasma progesterone concentration significantly increased from the basal level (<0.01–0.3 ng/mL) to 0.8– 5.1 ng/mL and then dropped to nearly the basal level within 2–4 days. The formation of eggshells was observed two days after FSH administration. These data collectively indicate that in hawksbill turtles FSH administration effectively induces ovulation, progesterone secretion, and egg formation.
Abstract: In March 2015, we observed mating behavior of loggerhead turtles in the western coastal waters of Okinawa Island, Japan. Two males and one female were initially involved, of which one of the males (M1) was attempting to mount the other male (M2) that had already mounted the female. Shortly after the onset of observation, M1 dismounted from M2 and swam away. At that time, the female, initially seemingly resisting copulation with M2, became receptive. This is the first report of loggerhead turtle mating behavior that involves more than two individuals. This observation suggests that the mating season of loggerheads around Okinawa Island includes the early spring.
