Alison Cree

Biology of stress: interactions with reproduction, immunology and intermediary metabolism

Animals must maintain a steady physiological state, homeostasis, in response to a changing environment. An understanding of the stress response is essential if one is to appreciate the complex physiological mechanisms maintaining homeostasis in vertebrates. Moreover, a comprehensive understanding of the biology of stress is essential if we are to reduce stress in the care of any vertebrate species, including those that are not domesticated and traditional laboratory animals.

Absence of daily cycles in plasma sex steroids in male and female tuatara (Sphenodon punctatus), and the effects of acute capture stress on females

The possible existence of daily cycles in plasma concentrations of sex steroids was examined in wild male and female tuatara (Sphenodon punctatus). Samples were collected from freshly captured animals at dusk, middle of the night, dawn, and middle of the day in January (summer) and July (winter). Males showed daily cycles in mean body temperature (Tb) in both seasons but no daily cycle in mean plasma testosterone concentration in either season. Vitellogenic female tuatara in January and females in mixed reproductive condition in July also showed significant daily variation in Tb. However, there were no daily cycles in mean plasma concentrations of estradiol, testosterone, or progesterone in either group of females. Vitellogenic female tuatara subjected to an acute capture stress (3-hr confinement) in January had mean plasma concentrations of estradiol and testosterone that did not differ from those of free-roaming females. However, progesterone and Tb were significantly higher in captives than in free-roaming females. The elevation in progesterone may result from physical confinement, the difference in Tb, or both. These data suggest that seasonal fluctuations in circulating concentrations of plasma sex steroids in tuatara can be determined using samples collected at different times of the 24-hr cycle. However, the effects of acute capture stress and/or changes in Tb on plasma progesterone concentrations need to be considered in future studies on this and possibly other female reptiles.

Status and longevity of the tuatara, Sphenodon guntheri, and Duvaucel's gecko, Hoplodactylus duvaucelii, on North Brother Island, New Zealand

Abstract A herpetological survey in January 1988 of North Brother Island, Cook Strait, New Zealand, found populations of the tuatara (Sphenodon guntheri) and three species of lizards (Hoplodactylus duvaucelii, Hoplodactylus maculatus, and Leiolopisma lineoocellatum). Tuatara on North Brother I. are significantly smaller than Sphenodon punctatus on nearby Stephens Island, and the estimated density of 134/ha in good habitat is lower than reported on Stephens I. The total adult population size of tuatara is estimated at <300 adults. Two of the captured tuatara had been toe-clipped, one in 1957 and one in 1959. One H. duvaucelii, toe-clipped in 1958, had not grown in the 29 years since first capture; it was probably at least 36 years old. This may represent the longest documented survivorship of a lizard in nature.

Techniques for detecting vitellogenesis in the tuatara Sphenodon punctatus

Abstract Techniques for detecting plasma vitellogenin (the precursor to egg-yolk proteins) were investigated in a rare reptile, the tuatara (Sphenodon punctatus). A single injection of oestradiol-17β (1 μg/g bodyweight) was used to induce or increase vitellogenesis in three captive animals. In the single treated male, a unique protein (molecular weight approximately 218 kDa), with a mobility during sodium dodecyl sulphate/ polyacrylamide-gel electrophoresis (SDS/PAGE), almost identical to that of partially purified vitellogenin from the turtle Chrysemys picta, appeared in the plasma 7 days after treatment. This protein was present in the plasma of both female tuatarabefore treatment, but increased as a percentage of total plasma protein (as assessed by laser densitometry) within 2 days of oestradiol treatment. Further increases in the level of this protein occurred over at least 12 days in the three treated animals. The protein was not detected in plasma from either of two control animals (one male and on...

MORPHOLOGICAL CHANGES IN THE CORPUS LUTEUM OF TUATARA (SPHENODON PUNCTATUS) DURING GRAVIDITY

Tuatara (Sphenodon spp.) are rare reptiles, members of the reptilian order Sphenodontida, inhabiting small offshore islands of New Zealand. Females usually require about three years to yolk a clutch of eggs followed by an 8‐month period of in utero egg shelling. As in other vertebrates, the post‐ovulatory follicle forms a transitory endocrine structure, the corpus luteum. The tuatara Sphenodon punctatus exhibits a corpus luteum having several unusual morphological features as compared to turtles and squamate reptiles. Like the crocodilians, the tuatara has a corpus luteum in which the luteal cell mass never fills the central cavity and in which the thecal fibroblasts do not close the ovulation aperture. As in all oviparous reptiles examined, however, the corpus luteum appears to persist throughout gravidity based on its histological appearance. During gravidity, plasma progesterone concentrations are detectable, even though gravidity lasts an exceptionally long time (8 months) for an oviparous species. Luteolysis is initiated within two months following oviposition. The initial stages of luteolysis appear rapid, but luteal scar tissue is apparent in the ovaries of all adult females we examined and probably persists for many years post‐oviposition. J Morphol 232:79–91, 1997.

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

Abstract Female tuatara (Sphenodon punctatus) are long-lived reptiles that do not nest each year. Identification of gravid females (those carrying oviducal eggs) has in the past been achieved only with radiography or laparoscopy. Both techniques require considerable equipment and/or operator skill, and both pose an unquantified degree of risk to tuatara. For these reasons, we sought to develop a blood test for identifying females destined to nest in a given year. We observed that on Stephens Island, New Zealand, those females that nested in a given year had significantly higher plasma concentrations of oestradiol, testosterone, and progesterone at the time of mating-ovulation (February-March) than in those females that did not ovulate and nest that year. Used in conjunction, the criteria of a testosterone concentration ≥2.0 ng/ml or a progesterone concentration ≥5.8 ng/ml in plasma, obtained within 3 h of capture in February–March, can be used to distinguish females destined to nest that year from those t...

Variation in plasma constituents during the natural vitellogenic cycle of tuatara, Sphenodon Punctatus

Abstract 1. 1. The vitellogenic cycle of female tuatara was investigated by monitoring plasma levels of vitellogenin, calcium, total protein, inorganic phosphate (P1) and cholesterol. 2. 2. Vitellogenin was not detected in females in the non-reproductive condition, but was found perenially in plasma of reproducing females during vitellogenesis, which normally lasts about 3 years out of the 4 year ovarian cycle. 3. 3. No large year-to-year variations were found in the plasma constituents measured and there was no correlation between the oestradiol peak at mating and plasma levels of vitellogenin. 4. 4. The results provide further evidence that tuatara have an extraordinary prolonged and gradual vitellogenic cycle spanning several years for a single clutch of eggs. This type of reproductive cycle is unique among reptiles.