Identification of female tuatara in ovulatory condition using plasma sex steroid concentrations

Cree, Alison; Guilletie, Louis J.; Cockrem, John F.

doi:10.1080/03014223.1991.10422848

Cited by 11 publications

(5 citation statements)

References 12 publications

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“…Circulating sexual steroids levels in blood from free-living tortoises obtained within 24 hours of capture were not different from levels in samples obtained over different periods of time after initial capture. These results differ from those reported on the effects of confinement on physiological processes in reptiles (Lance, 1984(Lance, , 1990Licht et al 1985;Lance and Elsey, 1986;Whittier et al 1987;Wibbels et al 1987a, b;Elsey et al 1990Elsey et al , 1991Cree et al 1991). Bolson tortoises do not exhibit a marked corticosterone-mediated stress response, and variations in steroid levels observed in both sexes mainly reflect the energetic demands imposed by environmental conditions (González, 1995).…”

Section: Discussioncontrasting

confidence: 65%

Sex-steroids associated with the reproductive cycle in male and female Bolson tortoise, Gopherus flavomarginatus

Trápaga¹,

Aguirre²,

Adest³

2000

AZM

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Estudiamos los ciclos de esteroides sexuales de machos y hembras en estado silvestre de la tortuga del Bolsón en la Reserva de la Biósfera de Mapimí (Durango). Tomamos muestras de sangre por venipunción de la yugular a intervalos bisemanales durante un período de 14 meses, determinándose los niveles circulantes de esteroides por medio de radioinmunoensayos. Los niveles hormonales mostraron tendencias estacionales. En las hembras, la testosterona tuvo un valor máximo al salir de la brumación, en asociación con el incremento en la receptividad sexual, y el nivel de estradiol aumentó después de la emergencia asociado con la maduración folicular. El nivel de estos dos esteroides se incrementó con las lluvias estacionales, cuando ocurrieron el crecimiento folicular y la vitelogénesis. La progesterona mostró niveles bajos a la emergencia, los cuales aumentaron con el incremento de la duración del dia y la temperatura, llegando al máximo antes del pico de la oviposición. La caída en los niveles de las tres hormonas estuvo asociada con la oviposición. Las hembras probablemente almacenan esperma durante parte del otoño y el invierno para usarlo en la siguiente estación reproductiva. Los machos salieron de la hibernación con bajos niveles de testosterona, pero exhibieron conductas reproductivas poco después. Junto con un incremento de la testosterona, el cortejo y la frecuencia de apareamientos se incrementaron con estímulos ambientales, prolongándose hasta principios del otoño. Los niveles de testosterona y la actividad reproductiva disminuyeron conforme se aproximaba el inicio de la hibernación. Los niveles máximos de testosterona en machos de esta especie son mayores que los conocidos para cualquier otro vertebrado.

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Section: Discussioncontrasting

confidence: 65%

Sex-steroids associated with the reproductive cycle in male and female Bolson tortoise, Gopherus flavomarginatus

Trápaga¹,

Aguirre²,

Adest³

2000

AZM

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“…obs.). Cree et al (1991c), recognising that both radiography and laparoscopy require considerable equipment and/or operator skill, and that both pose an unquantified degree of risk to tuatara, have developed a blood test for identifying …”

Section: Laying Histories Of Individual Femalesmentioning

confidence: 99%

Egg production by tuatara on Lady Alice and Stephens Island, New Zealand

Newman

Watson²,

McFadden³

1994

New Zealand Journal of Zoology

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Radiography was used to determine the proportion of female tuatara, Sphenodon punctatus, that carry eggs each year, over 6 years on Stephens Island and 5 years on Lady Alice Island. The smallest female found to be gravid, located on Stephens Island, was 170 mm snout-vent length. Between 1983 and 1987 the gravidity rate for Lady Alice Island females averaged 28.8% (range = 22.2-45.5%), while between 1982 and 1987 the gravidity rate for Stephens Island females averaged 21.9% (range = 8.2-29.6%). Excluding data from 1986, when only 11 females from Lady Alice Island were sampled, annual gravidity rates did not differ significantly between islands. There was significant annual variation in the proportion of females carrying eggs on Stephens Island, but not on Lady Alice Island. On Stephens Island, gravidity rate was especially low in 1982 (8.2%). There were significant positive, but different, correlations between clutch size and female body size on both islands. Mean clutch size for Lady Alice Island females (7.9 eggs; range = 5-13 eggs) was significantly smaller

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“…Plasma T concentrations can be used as a gauge for reproductive activity in males, where increased T implies increased sperm production, territoriality, courtship, and mating events (Cree et al, 1992;Gillingham et al, 1995). In females, plasma T concentrations are normally lower than males; however, results can be used to gauge percentage of reproductively active females in each population, as elevated T concentrations (obtained within 3 h of capture) in February-March distinguish female tuatara in ovulatory condition (Cree et al, 1991b).…”

Section: Reproductive Activity: Testosterone (T) Secretionmentioning

confidence: 99%

Corticosterone secretion in tuatara (Sphenodon punctatus): Influential factors and conservation applications

Anderson¹

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<p>Animals are regularly exposed to environmental, social and physiological challenges. In reaction to these challenges, individuals adjust their physiology and behaviour to maintain essential processes and optimise fitness. The most widely used indicators of physiological stress in vertebrates are glucocorticoid hormones (corticosterone (CORT) or cortisol), which are commonly referred to as ‘stress hormones’. The use of CORT as a tool to understand how individuals respond to natural or human-caused challenges is central to stress physiology research. Here, I investigated intrinsic and extrinsic factors associated with CORT secretion, CORT secretion as an indicator of physiological response to challenges/stressors, and the value of CORT secretion as conservation tool in an iconic protected reptile (the tuatara, Sphenodon punctatus). A capture-restraint time series revealed a significant CORT response over a 24 h period in male and female (non-gravid and gravid) tuatara. Baseline CORT and the CORT response to capture and restraint (i.e. a standardised capture-stress protocol) were similar between sexes; however, female reproductive condition was correlated with CORT secretion in that higher baseline CORT and a lower CORT response were observed in gravid females. An observational study incorporating data across a wide range of ambient temperatures (from four island sites) confirmed that body temperature (Tb) is positively correlated with baseline CORT in gravid females only, and revealed a positive correlation between the CORT response and higher Tb in all adults. A supporting experimental study showed that acute ambient temperature increase (in which mean Tb reached 21.4±0.4°C) elicits a significant CORT response to capture-restraint in gravid females. These results confirmed that gravid females are not secreting CORT maximally during nesting, but actively modulate secretion. An inter-island comparison of CORT secretion (for four populations) revealed that baseline CORT secretion was similar among populations during the non-breeding and breeding seasons; however, the CORT response to capture-restraint varied significantly among populations. Inter-population variation in testosterone (T) was observed in males (but not females) and was positively linked with increased baseline CORT from the non-breeding season to the breeding season, suggesting male reproductive activity may drive seasonal change of baseline CORT. Significant correlations were observed between the CORT response to capture-restraint (but not baseline CORT) and habitat elements of latitude, tuatara density and seabird abundance and 2) demogenetic factors of sex ratio and genetic diversity. The measurement of CORT as a physiological monitoring tool indicated that short- and long- term dynamics of CORT secretion in tuatara are not altered through translocation to a new island, as the acute CORT response remained stable throughout exposure to cumulative stressors and long-term dynamics of CORT secretion in translocated populations simultaneously mirrored those in source populations. These findings deliver the most detailed study of CORT secretion patterns in tuatara to date. Moreover, as the first study to apply CORT secretion data as an conservation physiology monitoring tool in tuatara, these results serve as a baseline reference for future research and monitoring of conservation efforts.</p>

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Identification of female tuatara in ovulatory condition using plasma sex steroid concentrations

Cited by 11 publications

References 12 publications

Sex-steroids associated with the reproductive cycle in male and female Bolson tortoise, Gopherus flavomarginatus

Sex-steroids associated with the reproductive cycle in male and female Bolson tortoise, Gopherus flavomarginatus

Egg production by tuatara on Lady Alice and Stephens Island, New Zealand

Corticosterone secretion in tuatara (Sphenodon punctatus): Influential factors and conservation applications

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