Reproductive hormonal profile in Eastern Pacific green turtles captured in-water (original) (raw)
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Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, 2001
From May to September of 1998, we collected monthly plasma samples from male yellow-blotched map turtles Ž. captured at two sites in the Pascagoula River drainage, Mississippi. One site Vancleave has a documented history of Ž. pollution from industrial sources principally 2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD. Fish consumption advisories at the Vancleave site were lifted in 1996 and current impacts appear minimal. However, the yellow-blotched map turtle, a federally protected species, continues to decline in numbers. To determine if endocrine disruption could be a factor in Ž. the low reproductive rates observed in Vancleave turtles, we examined levels of plasma testosterone T and Ž. Ž. estradiol-17 E from males at this site and a second site Leaksville , which has no known source of industrial 2 Ž. pollution. Plasma was also tested for vitellogenin VTG , which, in males, can be a biomarker of exposure to estrogenic contaminants. No males had detectable plasma VTG nor did mean monthly E levels differ between sites. However, 2 Ž 10% of males from the historically polluted site were found to have high levels of E equivalent to levels found in 2. females and T was significantly lower for males captured at this site for 3 of 5 months. Our data suggest that the current impact of contaminants on reproduction in this population is limited. However, a portion of the population may have been affected developmentally, as represented by differences in reproductive parameters detected between sites.
PLOS ONE, 2015
Determining sex ratios of endangered populations is important for wildlife management, particularly species subject to sex-specific threats or that exhibit temperature-dependent sex determination. Sea turtle sex is determined by incubation temperature and individuals lack external sex-based traits until sexual maturity. Previous research utilized serum/ plasma testosterone radioimmunoassays (RIA) to determine sex in immature/juvenile sea turtles. However, there has been a growing application of enzyme-linked immunosorbent assay (ELISA) for wildlife endocrinology studies, but no study on sea turtles has compared the results of ELISA and RIA. This study provides the first sex ratio for a threatened East Pacific green sea turtle (Chelonia mydas) foraging aggregation, a critical step for future management of this species. Here, we validate a testosterone ELISA and compare results between RIA and ELISA of duplicate samples. The ELISA demonstrated excellent correspondence with the RIA for providing testosterone concentrations for sex determination. Neither assay proved reliable for predicting the sex of reproductively active females with increased testosterone production. We then applied ELISA to examine the sex ratio of 69 green turtles foraging in San Diego Bay, California. Of 45 immature turtles sampled, sex could not be determined for three turtles because testosterone concentrations fell between the ranges for either sex (females: 4.1-113.1 pg/mL, males: 198.4-2,613.0 pg/mL) and these turtles were not subsequently recaptured to enable sex determination; using a Bayesian model to predict probabilities of turtle sex we predicted all three 'unknowns' were female (> 0.86). Additionally, the model assigned all turtles with their correct sex (if determined at recapture) with 100% accuracy. Results indicated a female bias (2.83F:1M) among all turtles in the aggregation; when focusing only on putative immature turtles the sex ratio was PLOS ONE |
Comparative Biochemistry and Physiology Part a Molecular Integrative Physiology, 2009
Graptemys flavimaculata, the yellow-blotched map turtle, is a long-lived, threatened, species, endemic to the Pascagoula River drainage in Mississippi. During the 1980s, one branch of the drainage (i.e. the Leaf River) was impacted by effluent from a wood pulp processing plant known to contain endocrine disrupters. A decade later, we examined seasonal reproductive parameters (i.e. monthly plasma estradiol-17β (E 2), testosterone (T), vitellogenin (VTG) and follicular development) in adult female turtles from historically polluted and reference sites in the drainage to determine if legacy exposure to pollution impacts reproduction. We found no seasonal patterns in E 2 or T and these patterns did not differ between sites. However, E 2 differed significantly among ovarian stages for the reference, but not pollutant exposed females. A significantly greater percentage of reference site females were able to produce a second clutch than females from the historically polluted site (50% and 17%). Additionally, there was a significant positive correlation between E 2 with VTG levels for reference, but not pollutant exposed females. Body and yolk tissue contaminant analysis indicated that exposure to pollutants is presently minimal and unlikely the cause of the reproductive differences observed between sites; instead, differences are potentially due to exposure history.
… and Physiology-Part A: …, 2009
Graptemys flavimaculata, the yellow-blotched map turtle, is a long-lived, threatened, species, endemic to the Pascagoula River drainage in Mississippi. During the 1980s, one branch of the drainage (i.e. the Leaf River) was impacted by effluent from a wood pulp processing plant known to contain endocrine disrupters. A decade later, we examined seasonal reproductive parameters (i.e. monthly plasma estradiol-17β (E 2), testosterone (T), vitellogenin (VTG) and follicular development) in adult female turtles from historically polluted and reference sites in the drainage to determine if legacy exposure to pollution impacts reproduction. We found no seasonal patterns in E 2 or T and these patterns did not differ between sites. However, E 2 differed significantly among ovarian stages for the reference, but not pollutant exposed females. A significantly greater percentage of reference site females were able to produce a second clutch than females from the historically polluted site (50% and 17%). Additionally, there was a significant positive correlation between E 2 with VTG levels for reference, but not pollutant exposed females. Body and yolk tissue contaminant analysis indicated that exposure to pollutants is presently minimal and unlikely the cause of the reproductive differences observed between sites; instead, differences are potentially due to exposure history.
Body condition and physiological changes in male green turtles during breeding
Marine Ecology-progress Series, 2004
Investigations were made into the body condition, energy metabolite and endocrinal changes of male green turtles Chelonia mydas prior to and during their vernal breeding period in the southern Great Barrier Reef. Prior to migration, breeding males exhibited a higher body condition index than non-breeding males. However, during the migratory reproductive period, breeding males lost significant body condition. Concurrent with these physical changes, breeding males showed a reduction in plasma triglycerides and an increased level of total protein towards the mid-to late breeding period. The plasma steroids corticosterone and testosterone increased and decreased, respectively, during the migratory/breeding phase. The pattern of change in body condition and physiology allude to a high-activity fasting period during the migratory/breeding phase of the male green turtle's life history. These marked physiological events during breeding suggest a proximate basis for terminating seasonal reproductive events, and a potential basis for phenotypic variation in male reproductive tactics.
Herpetologica, 2007
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 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.
Sex ratio estimation of eastern main loggerhead sea turtle.pdf
The nesting activities of loggerhead turtles (Caretta caretta) at Anamur Beach, one of their main nesting grounds along the Mediterranean coast of Turkey, were investigated during the 2006 and 2007 nesting seasons. The mean sex ratios were estimated based on gonad histology of dead hatchlings and late stage embryos and were calculated as 72.1% and 79% as females for the years 2006 (n = 366) and 2007 (n = 271), respectively. The nest temperatures of two nests and sand temperatures at nest depths were also recorded by placing electronic temperature recorders into the nests. The recorded sand temperatures were lower when close to the sea and higher towards inland. The mean temperatures of two nests during the entire incubation period were 28.9 and 31.2 °C, with 8 days’ difference in their incubation period. Based on mean temperature during the middle third of the incubation period, which ranged from 28.6 to 30.8 °C, the sex ratios were calculated as 49.3% and 79.9% females, respectively. These data are statistically significant when compared by t test (t = 52.34, p < 0.0001) and pair wise comparison (p < 0.0001). The sex ratios among the beach sections were also different (χ2 = 16.5, df = 4, p < 0.002). The mean incubation periods of nests were slightly shorter in 2007 compared to 2006, calculated as 48.97 and 52.51 days, respectively. According to overall sex ratio, based on incubation durations, 85.2% of the hatchlings were females and the yearly estimated sex ratio was 75.6% in 2006 and 87.8% in 2007, which is roughly similar to the histological values. The spatial and temporal variations of nests and the resulting sex ratios were due to the possible effects of global warming causing changes in the nesting site preferences of adult females.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2013
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights Author's personal copy Applying generalized linear models as an explanatory tool of sex steroids, thyroid hormones and their relationships with environmental and physiologic factors in immature East Pacific green sea turtles (Chelonia mydas
The Veterinary Journal, 2011
Serum levels of gonadal steroid hormones, corticosterone and thyroxin (T 4 ), were monitored monthly in two male and one female captive Loggerhead sea turtles (Caretta caretta) over a period of 12 months in 2004 and 3 months in 2006. Ovary ultrasonography was performed in April and July 2006. The turtles were kept together in an outdoor sea pool in natural temperature and photoperiod conditions from May to November, then in separate indoor pools from December to April. Circulating hormone levels were measured by radioimmunoassay.