The effects of annual cycle, source population, and body condition on leukocyte profile and immune challenge in a basal reptile, the tuatara (Sphenodon punctatus).

Leukocyte profiles are broadly used to assess the health status of many species. Reference intervals, and an understanding of the factors that may influence these intervals, are necessary for adequate interpretation of leukograms. Using a data set that spans over three decades, we investigated variation in leukocyte profile in several populations of the evolutionarily unique reptile, the tuatara (Sphenodon punctatus). To do this, we first established reference intervals for each leukocyte type according to best practices. Next, we determined that source population and sampling date were the two most important predictors of leukocyte makeup. We found significant differences in the ratio of heterophils: lymphocytes (H:L) between populations, with tuatara on the more resource-stressed sampling island having a significantly higher ratio of H:L. Finally, we found that sampling location, sex, and life stage did not explain variation in the responses of tuatara to stimulation with Concanavalin A and lipopolysaccharide in both 3-(4,5-dimethylthiazol-2-yl)-2,5-di-phenyltetrazolium bromide and Griess assay experiments. Our results offer important insight into the function of leukocytes in reptiles.

Characterization of sperm and implications for male fertility in the last of the Rhynchocephalians.

Managing a species of conservation concern can be best achieved when there is information on the reproductive physiology of both sexes available; however, many species lack this critical, baseline information. One such species, the tuatara (Sphenodon punctatus), is the last surviving member of one of the four reptile orders (Rhynchocephalia) and is the only reptile known to lack a male intromittent organ. Culturally and evolutionarily significant, the conservation of this species is a global priority for the maintenance of biodiversity. In light of this, we characterized the morphology, viability and swim speed of mature tuatara sperm for the first time. We found that tuatara sperm are filiform and bear the remarkably conserved three-part sperm structure seen across the animal kingdom. Tuatara sperm are long (mean total length 166 µm), with an approximate head:midpiece:tail ratio of 15:1:17. While tuatara sperm are capable of high levels of within-mating viability (94.53%), the mean viability across all samples was 58.80%. Finally, tuatara sperm had a mean curvilinear velocity swim speed (µ × s - 1) of 82.28. At the population level, there were no differences in viability or mean swim speed between sperm collected from a male's first mating of a season and repeat matings; however, the maximum sperm swim speed increased in observed repeated matings relative to first matings. Interestingly, faster sperm samples had shorter midpieces, but had greater viability and longer head and tail sections. This work expands our understanding of male reproductive characteristics and their variation to a new order, provides wild references for the assessment of captive individuals, lays the groundwork for potential assisted reproductive techniques and highlights variation in male reproductive potential as an important factor for consideration in future conservation programs for this unique species.

Investigating the link between morphological characteristics and diet in an island population of omnivorous reptiles (Sphenodon punctatus).

The morphological characteristics that impact feeding ecology in ectotherms, particularly reptiles, are poorly understood. We used morphometric measures and stable isotope analysis (carbon-13 and nitrogen-15) to assess the link between diet and functional morphology in an island population of an evolutionarily unique reptile, the tuatara (Sphenodon punctatus). First, we established a significant positive correlation between overall body size, gape size, and fat store in tuatara (n=56). Next, we describe the relationship between stable isotope profiles created from whole blood and nail trim samples and demonstrate that nail trims offer a low-impact method of creating a long-term dietary profile in ectotherms. We used nitrogen-15 values to assess trophic level in the population and found that tuatara on Takapourewa forage across multiple trophic levels. Finally, we found a significant relationship between gape size and carbon-13 (linear regression: P<0.001), with tuatara with large gapes showing dietary profiles that suggest a higher intake of marine (seabird) prey. However, whether body size or gape size is the primary adaptive characteristic allowing for more optimal foraging is yet unknown. This article has an associated First Person interview with the first author of the paper.

Initial collection, characterization, and storage of tuatara (Sphenodon punctatus) sperm offers insight into their unique reproductive system.

Successful reproduction is critical to the persistence of at-risk species; however, reproductive characteristics are understudied in many wild species. New Zealand's endemic tuatara (Sphenodon punctatus), the sole surviving member of the reptile order Rhynchocephalia, is restricted to 10% of its historic range. To complement ongoing conservation efforts, we collected and characterized mature sperm from male tuatara for the first time. Semen collected both during mating and from urine after courting contained motile sperm and had the potential for a very high percentage of viable sperm cells (98%). Scanning electron microscopy revealed a filiform sperm cell with distinct divisions: head, midpiece, tail, and reduced end piece. Finally, our initial curvilinear velocity estimates for tuatara sperm are 2-4 times faster than any previously studied reptile. Further work is needed to examine these trends at a larger scale; however, this research provides valuable information regarding reproduction in this basal reptile.

Feeling the heat? Substantial variation in temperatures does not affect the proportion of males born in Australia.

The global proportion of male births has been shown to vary with climate, with a higher proportion of male births documented in colder climates. Here we examined the hypothesis that ambient temperature predicts fluctuations in the proportion of male births in Australia and within seven Australian states using historical annual data spanning 1910-2009. We predicted that within states with tropical ambient temperatures the proportion of male births would decrease when ambient temperatures are higher. First, considering the national composite births for the whole of Australia, the proportion of males born ranged only from 0.510 to 0.517. We observed no relationship between the proportion of male births and the mean annual temperature in the concurrent or previous years for Australia as a whole. Second, the analyses for the seven Australian regions provided a total of 14 estimated relationships. We found no association between ambient temperature in the previous or concurrent year and the proportion of males born for all 14 comparisons. Thus, we found no evidence of a negative relationship between ambient temperatures in the concurrent or previous year and the proportion of males born in the tropical regions of Australia, and no evidence of any relationship in the more temperate Australian regions or in Australia as a whole.

Whatever the weather: ambient temperature does not influence the proportion of males born in New Zealand.

BACKGROUND: The proportion of male births has been shown to be over 50% in temperate climates around the world. Given that fluctuations in ambient temperature have previously been shown to affect sex allocation in humans, we examined the hypothesis that ambient temperature predicts fluctuations in the proportion of male births in New Zealand. METHODOLOGY/PRINCIPAL FINDINGS: We tested three main hypotheses using time series analyses. Firstly, we used historical annual data in New Zealand spanning 1876-2009 to test for a positive effect of ambient temperature on the proportion of male births. The proportion of males born ranged by 3.17%, from 0.504 to 0.520, but no significant relationship was observed between male birth rates and mean annual temperature in the concurrent or previous years. Secondly, we examined whether changes in annual ambient temperature were negatively related to the proportion of male stillbirths from 1929-2009 and whether the proportion of male stillbirths negatively affected the proportion of male live births. We found no evidence that fewer male stillbirths occurred during warmer concurrent or previous years, though a declining trend in the proportion of male stillbirths was observed throughout the data. Thirdly, we tested whether seasonal ambient temperatures, or deviations from those seasonal patterns, were positively related to the proportion of male births using monthly data from 1980-2009. Patterns of male and female births are seasonal, but very similar throughout the year, resulting in a non-seasonal proportion of male births. However, no cross correlations between proportion of male births and lags of temperature were significant. CONCLUSIONS: Results showed, across all hypotheses under examination, that ambient temperatures were not related to the proportion of male births or the proportion of male stillbirths in New Zealand. While there is evidence that temperature may influence human sex allocation elsewhere, such effects of temperature are not universal.