Cyclical Changes of Plasma Sex Steroids in Captive Breeding Loggerhead Turtles (Caretta caretta)

Kakizoe, Yuka; Fujiwara, Masato; Akune, Yuichiro; Kanou, Yoshihiko; Saito, Tomomi; Uchida, Itaru

doi:10.1638/2009-0254.1

Cited by 12 publications

(17 citation statements)

References 14 publications

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“…The iguanid Dipsosaurus dorsalis shows no seasonal change in plasma albumin levels associated with vitellogenesis, and while experimentally injected oestrogen decreased albumin as a proportion of total plasma protein, it had no effect on final plasma albumin concentration (Gerstle & Callard, ). In contrast to these examples, data from sea turtles suggest the opposite phenomenon: nesting Caretta caretta have higher plasma albumin levels than non‐nesting individuals (Deem et al., ), and plasma albumin concentration declines over the nesting period in Eretmochelys imbricata and Dermochelys coriacea (Honarvar et al., ; Goldberg et al., ) at the same time that plasma oestrogen concentration is declining (Wibbels et al., ; Rostal et al., ; Dobbs et al., ; Rostal, ; Kakizoe et al., ). These nesting sea turtles are actually post‐vitellogenic, but in contrast to the reptiles mentioned above, they have elevated oestrogen levels at the same time that they have elevated albumin levels.…”

Section: Lipid Metabolism During Vitellogenesismentioning

confidence: 99%

“…Levels of vitellogenin and triglycerides may rise as a side‐effect of elevated oestrogen levels (Smelker et al., ). Oestrogen is involved not only in coordinating vitellogenesis, but also other events of reproduction including nesting (Owens, ; Kakizoe et al., ). Thus the liver may be ‘incidentally’ stimulated to produce vitellogenin and triglycerides at times when they are not necessary for vitellogenesis per se .…”

Section: Lipid Metabolism During Vitellogenesismentioning

confidence: 99%

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The physiology of lipid storage and use in reptiles

Price

2016

Biological Reviews

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Lipid metabolism is central to understanding whole-animal energetics. Reptiles store most excess energy in lipid form, mobilise those lipids when needed to meet energetic demands, and invest lipids in eggs to provide the primary source of energy to developing embryos. Here, I review the mechanisms by which non-avian reptiles store, transport, and use lipids. Many aspects of lipid absorption, transport, and storage appear to be similar to birds, including the hepatic synthesis of lipids from glucose substrates, the transport of triglycerides in lipoproteins, and the storage of lipids in adipose tissue, although adipose tissue in non-avian reptiles is usually concentrated in abdominal fat bodies or the tail. Seasonal changes in fat stores suggest that lipid storage is primarily for reproduction in most species, rather than for maintenance during aphagic periods. The effects of fasting on plasma lipid metabolites can differ from mammals and birds due to the ability of non-avian reptiles to reduce their metabolism drastically during extended fasts. The effect of fasting on levels of plasma ketones is species specific: β-hydroxybutyrate concentration may rise or fall during fasting. I also describe the process by which the bulk of lipids are deposited into oocytes during vitellogenesis. Although this process is sometimes ascribed to vitellogenin-based transport in reptiles, the majority of lipid deposition occurs via triglycerides packaged in very-low-density lipoproteins (VLDLs), based on physiological, histological, biochemical, comparative, and genomic evidence. I also discuss the evidence for non-avian reptiles using 'yolk-targeted' VLDLs during vitellogenesis. The major physiological states - feeding, fasting, and vitellogenesis - have different effects on plasma lipid metabolites, and I discuss the possibilities and potential problems of using plasma metabolites to diagnose feeding condition in non-avian reptiles.

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Section: Lipid Metabolism During Vitellogenesismentioning

confidence: 99%

Section: Lipid Metabolism During Vitellogenesismentioning

confidence: 99%

The physiology of lipid storage and use in reptiles

Price

2016

Biological Reviews

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“…This has also been shown in juvenile loggerhead turtles in USA waters, where T concentrations were reliable indicators of sex only during the summer months, when water temperatures were >23°C (Braun-McNeill et al 2007), but the opposite was true for adult loggerhead turtles (Wibbels et al 1987, Owens 1997. Seasonal variation in T has also been shown for other reptiles (Gowan et al 2010, Kakizoe et al 2010, Hamlin et al 2011, Boretto et al 2012, and may maxi mise mating opportunities during the season when females are receptive. For juveniles this may serve no purpose until sexual maturity, but the drivers of the seasonal variation are currently not understood.…”

Section: Methodsmentioning

confidence: 75%

Estimating sex ratios in Caribbean hawksbill turtles: testosterone levels and climate effects

Hawkes¹,

McGowan²,

Godley³

et al. 2013

Aquat. Biol.

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Evolutionary theory predicts that male and female offspring should be produced at a 1:1 ratio, but this may rarely be the case for species in which sex is determined during incubation by temperature, such as marine turtles. Estimates of primary sex ratio suggest that marine turtle sex ratios are highly skewed, with up to 9 females per male. We captured juvenile hawksbill turtles Eretmochelys imbricata in waters around Anegada, British Virgin Islands, a regionally important foraging aggregation, and analysed concentrations of plasma testosterone and oestradiol-17β from 62 turtles to estimate sex ratio. There were 2.4 to 7.7 times more females than males. Testosterone concentrations correlated with sampling date and sea surface temperature (SST), with higher con centrations in the late summer when SST was highest, suggesting that assigning sex through threshold values of sex hormones must be carried out cautiously. The sex ratio in the juvenile foraging aggregation around Anegada is more male biased than at other locations, suggesting that turtles at Anegada have resilience against feminising effects of climate change. Future work should (1) integrate the relative contributions of different genetic stocks to foraging aggregations and (2) investigate the annual and seasonal cycles of sex hormones, and differences among individuals and life history stages. KEY WORDS: Marine turtles · Sex ratio · Climate change · HormonesResale or republication not permitted without written consent of the publisher Aquat Biol 18: 9-19, 2013 Skewed sex ratios may be advantageous under specific biological circumstances (e.g. if pa rental investment in the sexes is unequal, if one sex helps their parents or if male siblings compete for mates), but also in some environmental circumstances (Warner & Shine 2008). The Charnov-Bull model (Charnov & Bull 1977) was proposed to ex plain this and has been demonstrated for a lizard species, such that offspring raised in conditions that promote high fitness for females had higher lifetime reproductive success if they were female than male (males were produced by hormonal manipulation at temperatures that usually lead to the development of females; Warner & Shine 2008). Temperature-dependent sex determinationIn marine turtles, sex is determined by the temperature experienced during the middle third of the embryo incubation period (temperature-dependent sex determination [TSD], a type of ESD), where males are produced at lower temperatures and females at higher temperatures (Yntema & Mrosovsky 1980, 1982, Mrosovsky 1988. The majority of research into sex ratios of marine turtles has been carried out on the nesting beach at the hatchling stage, and approaches using the modelled relationship between incubation temperature and sex ratio, as well as incubation duration and sex ratio, have enabled estimation of 'primary' sex ratio for a large number of rookeries (reviewed in Hawkes et al. 2009). Primary sex ratios vary among beaches and within clutches, as well as during the course of a nest...

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“…It was thought that it was caused by the effective accumulation of Ca which was to be used in the next nesting period. In the annual observation of Ca and the ratio of Ca/P, it was found that they increased from previous autumn as estradiol [9], TP, and lipids did. Therefore, it shows that females prepare Ca along with TP and lipids for half a year for the next egg laying.…”

Section: Discussionmentioning

confidence: 93%

“…Both Ca and P indicated higher values in the egg laying time than those between egg layings. Moreover, considering ovulation is expected to occur within several days after egg laying based on progesterone concentration change; the preparation for the next egg formation has already started at the time of egg laying in sea turtles like the poultries [9]. Although the ratio of Ca/P indicated the extremely high value on the seventh day after each egg laying, it is considered that eggs go into shell gland and their egg formation is undertaken actively at this time.…”

Section: Discussionmentioning

confidence: 99%

Change of Plasma Chemistry Values in Captive Breeding Loggerhead Turtles (Caretta caretta)

Kakizoe¹,

Sakaoka²,

Akune³

et al. 2013

ISRN Zoology

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Loggerhead turtles, Caretta caretta, have been laying eggs in an indoor artificial beach since 1995, at the Port of Nagoya Public Aquarium (PNPA). Two males and four females were mated and those four landed and laid eggs several times during the breeding period in 1996. In 1998 egg laying was observed from April to July and mating was one or two months prior to the nesting season. Blood samples from these individuals were collected monthly in the previously mentioned years in order to investigate the changes in sex steroid hormones (testosterone, estradiol, and progesterone). Moreover, blood chemistry values (total protein, albumin, triglyceride, total cholesterol, total calcium, and inorganic phosphorus) were investigated. In 1998, for the two males, changes in testosterone levels were additionally examined. Blood chemistry values of each turtle changed periodically as sex steroids did based on the breeding period and laying cycle. Data from a completely artificial environment such as the one at the PNPA provide elucidation of the reproductive physiology in these endangered species.

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Cyclical Changes of Plasma Sex Steroids in Captive Breeding Loggerhead Turtles (Caretta caretta)

Cited by 12 publications

References 14 publications

The physiology of lipid storage and use in reptiles

The physiology of lipid storage and use in reptiles

Estimating sex ratios in Caribbean hawksbill turtles: testosterone levels and climate effects

Change of Plasma Chemistry Values in Captive Breeding Loggerhead Turtles (Caretta caretta)

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