Differences in dietary and plasma fatty acids between wild and captive populations of a rare reptile, the tuatara (Sphenodon punctatus)

Tuatara (Sphenodon) are rare reptiles endemic to New Zealand. Wild tuatara on Stephens Island (study population) prey on insects as well as the eggs and chicks of a small nesting seabird, the fairy prion (Pachyptila turtur). Tuatara in captivity (zoos) are fed diets containing different insects and lacking seabirds. We compared the fatty acid composition of major dietary items and plasma of wild and captive tuatara. Fairy prions (eaten by tuatara in the wild) were rich in C20 and C22 polyunsaturated fatty acids (PUFA), especially the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In contrast, items from the diet of captive tuatara contained no C20 and C22 PUFA and were higher in medium-chain and less unsaturated fatty acids. Plasma from wild tuatara was higher in n-3 PUFA [including alpha-linoleic acid (C18:3n-3), EPA and DHA], and generally lower in oleic acid (C18:1) and palmitic acid (C16:0), than plasma from captive tuatara in the various fractions (phospholipid, triacylglycerol, cholesterol ester and free fatty acids). Plasma from wild adult tuatara showed strong seasonal variation in fatty acid composition, reflecting seasonal consumption of fairy prions. Differences in the composition of diets and plasma between wild and captive tuatara may have consequences for growth and reproduction in captivity. Accepted: 3 August 1998     

Dynamics of hematological blood parameters of white rats in postnatal ontogenesis

In experiments on Wistar rats, dynamics of blood hematologic and rheological parameters was studied from birth to the 3-month age. Results of this study indicate an intensive activity of the red bone marrow anlagen for the first 3 weeks of postnatal ontogenesis. This is manifested as an increase of the number of cells in the erythron system, a change of the erythrocyte acidic resistance, and a shift in the leukocytic formula. The boundary between the 2nd and 3rd weeks of ontogenesis is a critical period: there occur a sharp deceleration of erythropoiesis and a change of the age-related erythrocyte composition and of the blood leukocyte ratio towards the parameters characteristic of adult rats. The rise in the number of leukocytes and erythrocytes does not stop after this period. Until the 4-week age, the deformability index increases to be accompanied by an increase of hemoglobin hydration and improvement of the erythrocyte toroid shape. Subsequently, inversion of these processes occurs.     

Observations on the activity and thermoregulation of the tuatara,Sphenodon punctatus (Reptilia: Rhynchocephalia), on Stephens Island

Abstract

Observations on Stephens Island, Cook Strait, in December 1978 show that although the tuatara is generally most active at night, many animals spend much of the day at or beyond burrow entrances, apparently to increase their body temperature. During the day, tuataras tend to move further from burrows which are under shaded forest than from those in open pasture. By day, mean body temperatures (±SE) ranged from 17.2±0.5°C in forest shade to 24.6±1.1°C in full sunlight; the maximum body temperature recorded was 26.3°C. The significance of these observations is discussed.     

Ageing domestic sheep (Ovis aries L.) from growth lines in the cementum of the first incisor

First incisor teeth from known‐age domestic sheep were examined to determine whether annual lines developed, and to test 3 processing techniques. Fluorescing lines in undecalcified, unstained transverse sections indicated completed years in 44 % of teeth. Dark lines in decalcified, stained transverse sections indicated completed years in 8 % of teeth. Dark lines seen by reflected light in undecalcified roots ground transversely by hand indicated completed years in 62 % of teeth. Grinding by hand was the simplest, quickest, and most dependable method.     

On the relative roles of selection and genetic drift in shaping MHC variation

Genes of the major histocompatibility complex (MHC) have provided some of the clearest examples of how natural selection generates discordances between adaptive and neutral variation in natural populations. The type and intensity of selection as well as the strength of genetic drift are believed to be important in shaping the resulting pattern of MHC diversity. However, evaluating the relative contribution of multiple microevolutionary forces is challenging, and empirical studies have reported contrasting results. For instance, balancing selection has been invoked to explain high levels of MHC diversity and low population differentiation in comparison with other nuclear markers. Other studies have shown that genetic drift can sometimes overcome selection and then patterns of genetic variation at adaptive loci cannot be discerned from those occurring at neutral markers. Both empirical and simulated data also indicate that loss of genetic diversity at adaptive loci can occur faster than at neutral loci when selection and population bottlenecks act simultaneously. Diversifying selection, on the other hand, explains accelerated MHC divergence as the result of spatial variation in pathogen‐mediated selective regimes. Because of all these possible scenarios and outcomes, collecting information from as many study systems as possible, is crucial to enhance our understanding about the evolutionary forces driving MHC polymorphism. In this issue, Miller and co‐workers present an illuminating contribution by combining neutral markers (microsatellites) and adaptive MHC class I loci during the investigation of genetic differentiation across island populations of tuatara Sphenodon punctatus. Their study of geographical variation reveals a major role of genetic drift in shaping MHC variation, yet they also discuss some support for diversifying selection.     

Delayed mating and the reproductive fitness of aponomma hydrosauri (Acari: Ixodidae)

, and 1992. Delayed mating and the reproductive fitness of Aponomma hydrosauri (Acari: Ixodidae). International Journal for Parasitology 22: 1197–1200. This study examines whether delayed mating influences the reproductive fitness of female reptile ticks, Aponomma hydrosauri. Delayed mating was induced by the prevention of male attachment to hosts for 20 or 40 days after females had been attached. The results showed that delayed mating had no significant influence on the number of viable progeny produced by female ticks. This may represent an important advantage for colonizing Ap. hydrosauri females in marginal population areas, particularly at parapatric boundaries.     

Fine-scale genetic structure of a long-lived reptile reflects recent habitat modification

Anthropogenic habitat fragmentation — ubiquitous in modern ecosystems — has strong impacts on gene flow and genetic population structure. Reptiles may be particularly susceptible to the effects of fragmentation because of their extreme sensitivity to environmental conditions and limited dispersal. We investigate fine-scale spatial genetic structure, individual relatedness, and sex-biased dispersal in a large population of a long-lived reptile (tuatara, Sphenodon punctatus) on a recently fragmented island. We genotyped individuals from remnant forest, regenerating forest, and grassland pasture sites at seven microsatellite loci and found significant genetic structuring (R_ST = 0.012) across small distances (< 500 m). Isolation by distance was not evident, but rather, genetic distance was weakly correlated with habitat similarity. Only individuals in forest fragments were correctly assignable to their site of origin, and individual pairwise relatedness in one fragment was significantly higher than expected. We did not detect sex-biased dispersal, but natural dispersal patterns may be confounded by fragmentation. Assignment tests showed that reforestation appears to have provided refuges for tuatara from disturbed areas. Our results suggest that fine-scale genetic structuring is driven by recent habitat modification and compounded by the sedentary lifestyle of these long-lived reptiles. Extreme longevity, large population size, simple social structure and random dispersal are not strong enough to counteract the genetic structure caused by a sedentary lifestyle. We suspect that fine-scale spatial genetic structuring could occur in any sedentary species with limited dispersal, making them more susceptible to the effects of fragmentation.     

Demographic effects of temperature‐dependent sex determination: will tuatara survive global warming?

Global climate change is of particular concern for small and isolated populations of reptiles with temperature-dependent sex determination because low genetic variation can limit adaptive response in pivotal temperatures, leading to skewed sex ratios. We explore the demographic consequences of skewed sex ratios on the viability of a tuatara population characterized by low genetic diversity. We studied the rare species of tuatara ( Sphenodon guntheri ) on the 4 ha North Brother Island in New Zealand over two nesting seasons and captured 477 individuals, with a 60% male bias in the adult population. Females first breed at 15 years and have extremely low rates of gravidity, producing clutches of three to eight eggs every 9 years. Simulations of the population using population viability analysis showed that the current population is expected to persist for at least 2000 years at hatchling sex ratios of up to 75% male, but populations with 85% male hatchlings are expected to become extinct within approximately 300 years (some eight generations). Incorporation of inbreeding depression increased the probability of extinction under male biased sex ratios, with no simulated populations surviving at hatchling sex ratios >75% male. Because recent models have predicted that climate change could lead to the production of all male S. guntheri hatchlings by 2085, we examined whether periodic intervention to produce mixed or female biased sex ratios would allow the population to survive if only males were produced in natural nests. We show that intervention every 2–3 years could buffer the effects of climate change on population sex ratios, but translocation to cooler environs might be more cost-effective. Climate change threatens tuatara populations because neither modified nesting behaviour nor adaptive response of the pivotal temperature can modify hatchling sex ratios fast enough in species with long generation intervals.     

Status of the tuatara,Sphenodon punctatus,on Hongiora and Ruamahua-iti Islands,Aldermen Group,New Zealand

Abstract

Results from a survey of the tuatara populations on Hongiora and Ruamahua-iti Islands, conducted in March 1986, do not support an earlier report that the Hongiora population is declining (Crook 1973). On Hongiora, 49 captures were made of 43 tuatara over 12 man-hours, and on Ruamahua-iti, 67 captures of 60 tuatara were made over 12.5 man-hours. The mean body lengths of Hongiora tuatara (male=250.4 mm, female=220.8 mm) were significantly larger than those of Ruamahua-iti animals (male= 187.6mm, female= 179.3 mm). We question the interpretation that the smaller average size of tuatara on Ruamahua-iti Island indicates that they are younger than those on Hongiora Island.     

Selective accumulation of Th2-skewing immature erythroid cells in developing neonatal mouse spleen

Environmental factors likely regulate neonatal immunity and self-tolerance. However, evidence that the neonatal immune system is suppressed or deviated is varied depending on the antigen and the timing of antigen exposure relative to birth. These disparate findings may be related to the availability of the appropriate antigen presenting cells but also point to the possibility of homeostatic changes in non-lymphoid cells in the relevant lymphoid tissues. Here we show that, while leukocytes are the most abundant cell population present in spleen during the first 4-5 days after birth, a massive accumulation of nucleated immature erythroid population in the spleen takes places on day 6 after birth. Although the relative frequency of these immature erythorid cells slowly decreases during the development of neonates, they remain one of the most predominant populations up to three weeks of age. Importantly, we show that the immature erythroid cells from neonate spleen have the capacity to modulate the differentiation of CD4 T cells into effector cells and provide a bias towards a Th2 type instead of Th1 type. These nucleated erythroid cells can produce cytokines that participate in the Th2/Th1 balance, an important one being IL-6. Thus, the selective accumulation of immature erythroid cells in the spleen during a specific period of neonatal development may explain the apparent differences observed in the type(s) of immune responses generated in infants and neonates. These findings are potentially relevant to the better management of immune deficiency in and to the design of vaccination strategies for the young.     

PERMANENT GENETIC RESOURCES: Development of microsatellite markers and analysis of their inheritance in the Australian reptile tick, Bothriocroton hydrosauri

Despite long-term study, the mechanism explaining the parapatric distribution of two Australian reptile tick species is not understood. We describe the development of primers amplifying 10 microsatellite Bothriocroton hydrosauri loci, for the study of population structure and dispersal patterns of this tick. The numbers of alleles per locus ranged from two to seven in ticks from the study site, and the observed heterozygosity between 0.28 and 0.69. Pedigree analysis indicates that one locus is inherited in a non-Mendelian manner in three families, which was not explained by null allele presence.     

Evidence of predation on a young tuatara,Sphenodon punctatus,by kiore,Rattus exulans,on Lady Alice Island

Abstract

Wounds on a juvenile tuatara discovered dead on Lady Alice Island, Chickens group, Hauraki Gulf, appear to have been inflicted by kiore. Flesh was stripped from the right abdominal wall of the tuatara exposing its ribs and liver, and part of its tail and eight digits were missing.