Serum gonadotropin and steroids associated with breeding activities in the green sea turtle, Chelonia mydas

Licht, Paul; Rainey, William E.; Cliffton, Kim

doi:10.1016/0016-6480(80)90102-1

Cited by 59 publications

(16 citation statements)

References 2 publications

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“…Other reptilian species examined either have low and often non-detectable levels throughout their ovarian cycles, or elevations to up to 5.7 ng/ml during the pre-ovulatory or mating period (e.g. Callard et al, 1978;Licht et al, 1979Licht et al, , 1980Licht et al, , 1982Wibbels, 1988). A high testosterone concentration during the pre-ovulatory and mating period in female tuatara may reflect the role of testosterone as a precursor in oestradiol synthesis (Callard et al, 1978).…”

Section: Femalesmentioning

confidence: 99%

Reproductive cycles of male and female tuatara (Sphenodon punctatus) on Stephens Island, New Zealand

Cockrem²,

1992

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Cycles in gonadal activity and plasma sex steroid concentrations were investigated in wild female and male tuatara on Stephens Island, New Zealand. Females nest once every four years on average. Vitellogenesis is spread over the first three years, and mating, ovulation and nesting occur in the fourth. Oviducal eggs are carried for6–8 months before nesting. Although the length of this ovarian cycle is unparalleled among oviparous reptiles, the associated cycles in plasma concentrations of sex steroids are similar to those in other reptiles. Mean plasma concentrations of oestradiol increase during vitellogenesis, peak at mating, fall rapidly before or around ovulation, are low during most of gravidity, and rise slightly during late gravidity‐nesting. Plasma concentrations of testosterone show a similarcycle. Mean plasma concentrations of progesterone are low during vitellogenesis and peak around ovulation. This periovulatory surge falls within1–2 months, and mean concentrations are low during the final 5–6 months of gravidity. Male tuatara show an annual, pre‐nuptial reproductive cycle. Mean plasma concentrations of testosterone are low during winter, rise during spring, peak during midsummer‐early autumn, when pre‐nuptial displays and mating occur, and fall in mid autumn. Limited histological data indicate that spermiogenesis occurs during midsummer‐early autumn, and also support a previous study suggesting that there may be no period of complete testicular and epididymal regression. In comparison with the pre‐nuptial cycles of other temperate‐zone reptiles, the cycle in male tuatara shows a more prolonged duration of testicular activity and of rising or elevated plasma testosterone concentrations. The prolonged reproductive cycles of male and female tuatara may be adaptations to a temperate environment with cool summers and cool, but not freezing, winters.

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Section: Femalesmentioning

confidence: 99%

Reproductive cycles of male and female tuatara (Sphenodon punctatus) on Stephens Island, New Zealand

Cockrem²,

1992

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“…Reproductively active sea turtles exhibit a relatively sharp and abrupt increase in plasma estradiol-17 concentration several weeks prior to their reproductive migration [8,[21][22][23][24], which then remains elevated for approximately four weeks [8]. Immediately prior to migrating, plasma estradiol concentration begins to decline and testosterone concentration increases sharply [20].…”

Section: Introductionmentioning

confidence: 99%

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

Smelker

Smith

Arendt

et al. 2014

Journal of Marine Biology

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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 measureCaretta carettavitellogenin 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.

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“…Radioimmunoassay measurements of circulating hormone levels in sea turtles revealed a transient increase in immunoreactive FSH coincident with the brief period of nesting (a few hours at most) and, in particular, oviposition (Licht et al 1979(Licht et al , 1980. Repeated RIA analyses of several of these blood samples using the purified neurohypophysial material as tracer confirmed that the plasma protein in question was of neurohypophysial origin.…”

Section: Discussionmentioning

confidence: 73%

“…Polyacrylamide-gel electrophoresis and subsequent fractionation studies demonstrated the neurohypophysial component comprised over 80% of the putative FSH preparation, and there was little binding of the radioactivity associated with FSH activity. In fact, purified radiolabelled FSH prepara¬ tions did not show measurable binding at antibody dilutions used routinely in radioimmunoassays to study circulating gonadotrophin levels (Licht et al 1979(Licht et al , 1980 and pituitary activities in homologous and heterologous species (Licht, 1978). In fact, the specificity of the initial RIA for the neurohypo¬ physial factor is only improved slightly by fractiona¬ tion of the tracer to remove FSH.…”

Section: Discussionmentioning

confidence: 93%

Presence of a neurophysin-like precursor in the green turtle (Chelonia mydas)

Licht¹,

Pickering²,

Papkoff³

et al. 1984

Journal of Endocrinology

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A glycoprotein of neurohypophysial origin was found to have cofractionated with FSH prepared from pituitary glands of the green turtle, Chelonia mydas. Antiserum raised against this preparation contained high antibody titres and affinity for the neurohypophysial component and allowed development of a specific radioimmunoassay to monitor its purification and distribution in the brain. Immunocytochemistry revealed that the glycoprotein was concentrated in the pars nervosa and associated nerve tracts passing through the median eminence to the supraoptic and paraventricular nuclei; similar distributions were observed in turtles and rats. The antiserum to the turtle material bound radiolabelled rat vasopressin (VP)-neurophysin and precipitated precursors of this neurophysin, but it did not cross-react with rat oxytocin-neurophysin. An amino-terminal alanine was also consistent with the structure of rat VP-neurophysin, but the turtle molecule was larger than the corresponding rat molecule. Limited tryptic digests of the turtle glycoprotein contained two components, one of which bound to lysine VP. Both components contained carbohydrate, but only the one which bound to VP cross-reacted in a radioimmunoassay for rat VP-neurophysin. The apparent surge in plasma immuno-FSH at the time of oviposition previously described in the turtle probably represented release of a neurophysin-like 'carrier' molecule associated with secretion of the neurohypophysial hormone (e.g. arginine vasotocin; AVT) responsible for oviduct contractility. These data suggest that the neurohypophysial glycoprotein represents a partially processed AVT precursor and provide the first biochemical evidence of a mammalian-like biosynthetic pathway for neurohypophysial hormones in a non-mammalian species.

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Serum gonadotropin and steroids associated with breeding activities in the green sea turtle, Chelonia mydas

Cited by 59 publications

References 2 publications

Reproductive cycles of male and female tuatara (Sphenodon punctatus) on Stephens Island, New Zealand

Reproductive cycles of male and female tuatara (Sphenodon punctatus) on Stephens Island, New Zealand

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

Presence of a neurophysin-like precursor in the green turtle (Chelonia mydas)

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