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Nicola J Nelson - One of the best experts on this subject based on the ideXlab platform.
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Survival and growth of tuatara Sphenodon punctatus following translocation from the Cook Strait to warmer locations in their historic range
Oryx, 2018Co-Authors: Stephanie J. Price, Kristine L Grayson, Brett D. Gartrell, Nicola J NelsonAbstract:AbstractPost-translocation monitoring is fundamental for assessing translocation success and identifying potential threats. We measured outcomes for four cohorts of tuatara Sphenodon punctatus translocated to warmer climates outside of their ecological region, to understand effects of climate warming. Translocation sites were on average 2–4 °C warmer than the source site. We used three short-term measures of success: survival, growth and reproduction. Data on recaptures, morphometric measurements, and reproduction were gathered over 2.5 years following release. Although decades of monitoring will be required to determine long-term translocation success in this species, we provide an interim measure of population progress and translocation site suitability. We found favourable recapture numbers, growth of founders and evidence of reproduction at most sites, with greater increases in body mass observed at warmer, less densely populated sites. Variable growth in the adult population at one translocation site suggested that higher population density, intraspecific competition, and lower water availability could be responsible for substantial weight loss in multiple individuals, and we make management recommendations to reduce population density. Overall, we found that sites with warmer climates and lower population densities were potentially beneficial to translocated tuatara, probably because of enhanced temperature-dependent and density-dependent growth rates. We conclude that tuatara could benefit from translocations to warmer sites in the short term, but further monitoring of this long-lived species is required to determine longer-term population viability following translocation. Future vulnerability to rising air temperatures, associated water availability, and community and ecosystem changes beyond the scope of this study must be considered.
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temperature selection by juvenile tuatara Sphenodon punctatus is not influenced by temperatures experienced as embryos
Journal of Thermal Biology, 2017Co-Authors: Nicola J Nelson, Susan N Keall, Kelly M HareAbstract:Abstract Most reptiles thermoregulate to achieve body temperatures needed for biological processes, such as digestion and growth. Temperatures experienced during embryogenesis may also influence post-hatching growth rate, potentially through influencing post-hatching choice of temperatures. We investigated in laboratory settings whether embryonic temperatures (constant 18 °C, 21 °C and 22 °C) influence selected body temperatures ( T sel ) of juvenile tuatara ( Sphenodon punctatus ), providing a possible mechanism for differences in growth rates. We found that incubation temperature does not influence T sel . Although the average daily mean T sel was 21.6 ± 0.3 °C, we recorded individual T sel values up to 33.5 °C in juvenile tuatara, which is higher than expected and above the panting threshold of 31–33 °C reported for adults. We found diel patterns of T sel of juvenile tuatara, observing a general pattern of two apparent peaks and troughs per day, with T sel being significantly lower around dawn and at 1500 h than any other time. When comparing our results with other studies on tuatara there is a remarkable consistency in mean T sel of ~ 21 °C across tuatara of different ages, sizes and acclimatization histories. The ability of juvenile tuatara to withstand a wide range of temperatures supports their former widespread distribution throughout New Zealand and warrants further investigation into their plasticity to withstand climate warming, particularly where they have choices of habitat and the ability to thermoregulate.
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glucocorticoids in tuatara Sphenodon punctatus some influential factors and applications in conservation management
General and Comparative Endocrinology, 2017Co-Authors: Lindsay Anderson, Nicola J Nelson, Alison CreeAbstract:Glucocorticoid (GC) hormones promote basic life processes, regulate life-history transitions, and help individuals cope with challenges and stressors, thereby playing an important fitness role. Here, we review recent evidence for several factors that influence plasma concentrations of corticosterone (CORT), the main GC in tuatara (Sphenodon punctatus), and discuss the application of CORT as a physiological tool to monitor conservation efforts. Observational studies show an association between CORT concentrations and seasonal reproductive activity, ambient temperature, and ecological habitat parameters (including presence of rats/seabird abundance, sex-ratio, and genetic diversity), and experimental studies show a positive influence of acute temperature increase on the CORT response. Recently, CORT physiology has been applied as a monitoring tool in tuatara translocation programmes. No signs of chronic stress in CORT profiles were observed during standard short- and long-term translocation and rat eradication procedures, giving confidence that current conservation efforts are supportive in population recovery. These results provide a foundation for comparative understanding of stress physiology in reptiles, and will be critical for managing future population viability of tuatara in a changing environment.
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moving house long term dynamics of corticosterone secretion are unaltered in translocated populations of a rare reptile the tuatara Sphenodon punctatus
Conservation Physiology, 2015Co-Authors: Lindsay Anderson, Alison Cree, David R Towns, Nicola J NelsonAbstract:Translocations are an important conservation tool used to restore at-risk species to their historical range. Unavoidable procedures during translocations, such as habitat disturbance, capture, handling, processing, captivity, transport and release to a novel environment, have the potential to be stressful for most species. In this study, we examined acute and chronic stress (through the measurement of the glucocorticoid corticosterone) in a rare reptile (the tuatara, Sphenodon punctatus). We found that: (i) the acute corticosterone response remains elevated during the initial translocation process but is not amplified by cumulative stressors; and (ii) the long-term dynamics of corticosterone secretion are similar in translocated and source populations. Taken together, our results show that translocated tuatara are generally resistant to cumulative acute stressors and show no hormonal sign of chronic stress. Translocation efforts in tuatara afford the potential to reduce extinction risk and restore natural ecosystems.
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modulation of corticosterone secretion in tuatara Sphenodon punctatus evidence of a dampened stress response in gravid females
General and Comparative Endocrinology, 2014Co-Authors: Lindsay Anderson, Alison Cree, David R Towns, Nicola J NelsonAbstract:Abstract Baseline and stress response glucocorticoid (GC) secretion can be modulated by individuals to support activities and physiological functions connected with reproduction (migration, mating, oviposition and/or parturition, care of young). Corticosterone (CORT) is the primary GC in reptiles and, in accordance with other vertebrates, an adrenocortical stress response is observed. Modulation of CORT secretion occurs in several reptile species, such that elevated baseline CORT concentration and/or a dampened CORT response are common during reproductive life-history events. We investigated CORT secretion after 24 h capture-restraint in the oviparous tuatara ( Sphenodon punctatus ), the last living rhynchocephalian, and tested whether gravid females have a dampened CORT response compared with non-gravid females. We also included males as a comparison. We confirmed that gravid females have significantly higher baseline plasma CORT concentrations than non-gravid females, suggesting increased CORT secretion during nesting. Furthermore, we found that gravid females exhibit a dampened CORT response compared to non-gravid females and males. Our results demonstrate that female reproductive condition influences CORT secretion in tuatara, and suggest that gravid females modulate CORT secretion during nesting to maintain homeostasis, effectively increasing chances of reproductive success and promoting overall fitness.
Alison Cree - One of the best experts on this subject based on the ideXlab platform.
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Reproduction of a Rare New Zealand Reptile, the Tuatara Sphenodon punctatus, on Rat-Free and
2020Co-Authors: Alison Cree, Charles H. Daugherty, Jennifer M. HaytAbstract:We compared evidence for successful reproduction of tuatara (Sphenodon punctatus punctatus) in the presence or absence of introduced Pacific rats (kiore, Rattus exulans)for islands in the Mercury Group and Hen and Chickens Group, New Zealand. Tuatara were captured more frequently on the two kiore-free islands than on the six kiore-inhabited islands, suggesting reduced density in the presence of kiore. On the two kiore-free islands, 22.2-30.8% of all tuatara captured were juveniles or small adults (
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Comparison among three body parts and three software packages to optimise photographic identification of a reptile (tuatara, Sphenodon punctatus)
Amphibia-reptilia, 2020Co-Authors: Ricardo De Sá Rocha Mello, Scott Jarvie, Lindsay Hazley, Alison CreeAbstract:AbstractIndividually identifying animals is key to ecological research. Natural marks and patterns of animals that remain stable through time may be used to identify individuals, either manually or with the aid of software. Here we compare the performance of three body parts (chest, right side and right eye) for individual identification of tuatara (Sphenodon punctatus) using three software packages (Wild-ID, I3S and StripeSpotter). We also explored pattern stability over time for the chest and right side, and whether the identification rate differed between life-history stages (adults and juveniles) for this long-lived reptile. We used photos of 196 tuatara, including captive and free-roaming individuals. In an initial analysis with a subset of individuals, chest and right side gave better identification rates than the eye when analysed using Wild-ID (the best-performing software). In a further analysis using all photos and Wild-ID, the false rejection rate was lower for chest (0.6%) than right side (2.4%). Although the effect of time on matching scores for chest (up to 3.5 y) and right-side (up to 1.8 y) was significant, it was not large enough to reduce the matching rate; furthermore, no difference in identification rate between adults and juveniles was detected. Overall, chest was the best-performing body part and Wild-ID the best-performing software. Thus, appropriate choice of body pattern for analysis may significantly increase the matching rate, and, as previously shown, software packages vary in performance.
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diet of tuatara Sphenodon punctatus translocated to ōrokonui ecosanctuary in southern new zealand
New Zealand Journal of Zoology, 2017Co-Authors: Jenny Kitchin, B I P Barratt, Scott Jarvie, Stephen C Adolph, Alison CreeAbstract:ABSTRACTScats from tuatara (Sphenodon punctatus) were investigated in autumn at Ōrokonui Ecosanctuary on South Island, New Zealand. Eighty-seven tuatara had been translocated there 5–7 months previously, either directly from Stephens Island/Takapourewa or via captivity. Tuatara at Ōrokonui fed on diverse invertebrates, including beetles, millipedes, spiders, dipteran flies and cave wētā. Prey occurrence in large scats (presumed to come from adults) was similar in frequency to that in small scats (presumed to be from medium–large juveniles), apart from a higher incidence of spiders in those from adults. Tuatara scats contained scarabaeid and large carabid beetles more frequently, and tenebrionid beetles less frequently, than reported on Stephens Island. Unlike tuatara on Stephens Island, those at Ōrokonui do not have access to seabirds or tree wētā, and showed no certain predation on passerines or reptiles. Some differences in diet composition may reflect differences in prey availability resulting from the...
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glucocorticoids in tuatara Sphenodon punctatus some influential factors and applications in conservation management
General and Comparative Endocrinology, 2017Co-Authors: Lindsay Anderson, Nicola J Nelson, Alison CreeAbstract:Glucocorticoid (GC) hormones promote basic life processes, regulate life-history transitions, and help individuals cope with challenges and stressors, thereby playing an important fitness role. Here, we review recent evidence for several factors that influence plasma concentrations of corticosterone (CORT), the main GC in tuatara (Sphenodon punctatus), and discuss the application of CORT as a physiological tool to monitor conservation efforts. Observational studies show an association between CORT concentrations and seasonal reproductive activity, ambient temperature, and ecological habitat parameters (including presence of rats/seabird abundance, sex-ratio, and genetic diversity), and experimental studies show a positive influence of acute temperature increase on the CORT response. Recently, CORT physiology has been applied as a monitoring tool in tuatara translocation programmes. No signs of chronic stress in CORT profiles were observed during standard short- and long-term translocation and rat eradication procedures, giving confidence that current conservation efforts are supportive in population recovery. These results provide a foundation for comparative understanding of stress physiology in reptiles, and will be critical for managing future population viability of tuatara in a changing environment.
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reproduction of a rare new zealand reptile the tuatara Sphenodon punctatus on rat free and
2016Co-Authors: Alison Cree, Charles H. Daugherty, Jennifer M. HaytAbstract:We compared evidence for successful reproduction of tuatara (Sphenodon punctatus punctatus) in the presence or absence of introduced Pacific rats (kiore, Rattus exulans)for islands in the Mercury Group and Hen and Chickens Group, New Zealand. Tuatara were captured more frequently on the two kiore-free islands than on the six kiore-inhabited islands, suggesting reduced density in the presence of kiore. On the two kiore-free islands, 22.2-30.8% of all tuatara captured were juveniles or small adults (<200 mm snout-vent length). In contrast, juvenile tuatara were not seen on five of the six kiore-inhabited islands and small adults were absent from three. These data support an earlier study suggesting that kiore inhibit recruitment of tuatara Both sexes of adult tuatara were present on kiore-inhabited islands, and plasma concentrations of sex hormones suggest that at least some adults remain reproductively active on most islands. Throughout their range, tuatara have become extinct this century on four islands inhabited by kiore, they are on the verge of extinction on two kiore-inhabited islands sampled in this study and two kiore-inhabited islands not sampled, and they are absent from at least six other kiore-inhabited islands on which on biogeographic grounds they would be expected to be present Although the data remain circumstantial, the most plausible explanation of these observations is that kiore can cause extinction of tuatara through competition for food and/or predation on eggs and juveniles. In the absence of kiore eradication the four worst-case populations of tuatara would probably be extinct within 10-20 years and populations on three other islands would probably be relictual or extinct within 30-50 years. Kiore eradication is being carried out on most of these islands, in part to help ensure tuatara survival. Well-monitored eradication programs will enable an exper- imental test of the hypothesis that tuatara densities and recruitment rates are enhanced in the absence of kiore.
Charles H. Daugherty - One of the best experts on this subject based on the ideXlab platform.
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Reproduction of a Rare New Zealand Reptile, the Tuatara Sphenodon punctatus, on Rat-Free and
2020Co-Authors: Alison Cree, Charles H. Daugherty, Jennifer M. HaytAbstract:We compared evidence for successful reproduction of tuatara (Sphenodon punctatus punctatus) in the presence or absence of introduced Pacific rats (kiore, Rattus exulans)for islands in the Mercury Group and Hen and Chickens Group, New Zealand. Tuatara were captured more frequently on the two kiore-free islands than on the six kiore-inhabited islands, suggesting reduced density in the presence of kiore. On the two kiore-free islands, 22.2-30.8% of all tuatara captured were juveniles or small adults (
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reproduction of a rare new zealand reptile the tuatara Sphenodon punctatus on rat free and
2016Co-Authors: Alison Cree, Charles H. Daugherty, Jennifer M. HaytAbstract:We compared evidence for successful reproduction of tuatara (Sphenodon punctatus punctatus) in the presence or absence of introduced Pacific rats (kiore, Rattus exulans)for islands in the Mercury Group and Hen and Chickens Group, New Zealand. Tuatara were captured more frequently on the two kiore-free islands than on the six kiore-inhabited islands, suggesting reduced density in the presence of kiore. On the two kiore-free islands, 22.2-30.8% of all tuatara captured were juveniles or small adults (<200 mm snout-vent length). In contrast, juvenile tuatara were not seen on five of the six kiore-inhabited islands and small adults were absent from three. These data support an earlier study suggesting that kiore inhibit recruitment of tuatara Both sexes of adult tuatara were present on kiore-inhabited islands, and plasma concentrations of sex hormones suggest that at least some adults remain reproductively active on most islands. Throughout their range, tuatara have become extinct this century on four islands inhabited by kiore, they are on the verge of extinction on two kiore-inhabited islands sampled in this study and two kiore-inhabited islands not sampled, and they are absent from at least six other kiore-inhabited islands on which on biogeographic grounds they would be expected to be present Although the data remain circumstantial, the most plausible explanation of these observations is that kiore can cause extinction of tuatara through competition for food and/or predation on eggs and juveniles. In the absence of kiore eradication the four worst-case populations of tuatara would probably be extinct within 10-20 years and populations on three other islands would probably be relictual or extinct within 30-50 years. Kiore eradication is being carried out on most of these islands, in part to help ensure tuatara survival. Well-monitored eradication programs will enable an exper- imental test of the hypothesis that tuatara densities and recruitment rates are enhanced in the absence of kiore.
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does nest guarding in female tuatara Sphenodon punctatus reduce nest destruction by conspecific females
Journal of Herpetology, 2009Co-Authors: Jeanine M Refsnider, Charles H. Daugherty, Susan N Keall, Nicola J NelsonAbstract:Although parental care is generally rare among reptiles, nest-guarding occurs in some species and is usually attributed to defense against nest predation. Nest-guarding also occurs in the Tuatara (Sphenodon punctatus), but nest predation on rodent-free islands does not appear to be a significant threat to nesting success in this species. We studied a population of colonially nesting Tuatara on rodent-free Stephens Island, New Zealand, over four years and tested the hypothesis that female Tuatara guard their nests to defend them from excavation by conspecific females. We located 73 nests for which females could be assigned based on observations during oviposition. Nearly 25% of these nests were subsequently excavated by another female, but only 56% of the nests were guarded by the females that constructed them. We found a trend where guarded nests were less likely to be excavated than unguarded nests. Females were more likely to guard their nests, and guarded nests for longer, as the activity of other females on the date of oviposition increased. Nest-guarding in Tuatara appears to be adaptive in that it tends to reduce the likelihood of nest excavation by other females, but social interactions may affect females' propensity to guard, because guarding behavior was influenced by the activity of conspecifics at the time of oviposition.
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The evolutionary rate of tuatara revisited
Trends in Genetics, 2008Co-Authors: Hilary C. Miller, Jennifer A Moore, Fred W. Allendorf, Charles H. DaughertyAbstract:Often dubbed ‘living fossils’ (because they seem not to have changed morphologically in >200 million years), tuatara (Sphenodon punctatus and Sphenodon guntheri) are endemic New Zealand reptiles that are the only extant members of an archaic order of reptiles, which diverged from squamates ∼250 million years ago. In a recent paper published in Trends in Genetics, Hay and colleagues used ancient DNA to examine the rate of molecular evolution in tuatara and suggested that tuatara have the highest rate of molecular evolution of any vertebrate studied to date [1].
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two patterns of variation among mhc class i loci in tuatara Sphenodon punctatus
Journal of Heredity, 2007Co-Authors: Hilary C. Miller, Matiu Andrewscookson, Charles H. DaughertyAbstract:The genes of the major histocompatibility complex (MHC) are a central component of the immune system in vertebrates and have become important markers of functional, fitness-related genetic variation. We have investigated the evolutionary processes that generate diversity at MHC class I genes in a large population of an archaic reptile species, the tuatara (Sphenodon punctatus), found on Stephens Island, Cook Strait, New Zealand. We identified at least 2 highly polymorphic (UA type) loci and one locus (UZ) exhibiting low polymorphism. The UZ locus is characterized by low nucleotide diversity and weak balancing selection and may be either a nonclassical class I gene or a pseudogene. In contrast, the UA-type alleles have high nucleotide diversity and show evidence of balancing selection at putative peptide-binding sites. Twenty-one different UA-type genotypes were identified among 26 individuals, suggesting that the Stephens Island population has high levels of MHC class I variation. UA-type allelic diversity is generated by a mixture of point mutation and gene conversion. As has been found in birds and fish, gene conversion obscures the genealogical relationships among alleles and prevents the assignment of alleles to loci. Our results suggest that the molecular mechanisms that underpin MHC evolution in nonmammals make locus-specific amplification impossible in some species.
Lorenzo Alibardi - One of the best experts on this subject based on the ideXlab platform.
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Microscopical observations on the regenerating tail in the tuatara Sphenodon punctatus indicate a tendency to scarring, but also influence from somatic growth.
Journal of Morphology, 2019Co-Authors: Lorenzo Alibardi, Victor Benno Meyer-rochowAbstract:: The process of tail regeneration in the tuatara (Sphenodon punctatus) is not entirely known. Similarity to and differences from lizard tail regenerations are indicated in the present histological and ultrastructural study. Regeneration is influenced by the animal's age and ambient temperature, but in comparison to that of lizards it is very slow and tends to produce outgrowths that do not reach the length of the original tail. Although microscopically similar to lizard blastemas, the mesenchyme rapidly gives rise to a dense connective tissue that contains few muscle bundles, nerves, and fat cells. The unsegmented cartilaginous tube forming the axial skeleton is not calcified after 5 months of regeneration, but calcification in the inner region of the cartilage, present after 10 months, increases thereafter. Amyelinic and myelinic peripheral nerves are seen within the regenerating tails of 2-3 mm in length and the spinal cord forms an ependymal tube inside a cartilaginous casing. Tissues of the original tail, like muscles, vertebrae and the adipose mass, are largely replaced by dense connective tissue that occupies most of the volume of the new tail at 5 and 10 months of regeneration. It is unknown whether the differentiation of the dense connective tissue is caused by the relatively low temperature that this species lives under or stems from a genetic predisposition toward scarring as with most other amniotes. Increases of muscle and adipose tissues seen in older regenerated tails derive from somatic growth of the new tail in the years following tail loss and not from a rapid regeneration process like that in lizards.
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immunolocalization of keratin associated beta proteins beta keratins in scales of the reptiles Sphenodon punctatus indicates that different beta proteins are present in beta and alpha layers
Tissue & Cell, 2012Co-Authors: Lorenzo AlibardiAbstract:Abstract The present ultrastructural immunocytochemical study analyzes the localization of keratin-associated beta-proteins (beta-keratins) in the epidermis of the ancient reptile Sphenodon punctatus , a relict species adapted to mid-cold conditions. The epidermis comprises two main layers, indicated as beta- and alpha-keratin layers. The beta-layer contains small beta-proteins (beta-keratins) identified by using three different antibodies while the alpha-layer is poorly or not labeled for these proteins. Using other two antibodies directed against specific amino acid sequences identified in beta-proteins of lizard it results that a high-glycine beta-protein (HgG5) is specific for the beta-layer. Another antibody that recognizes glycine–cysteine medium-rich beta-proteins (HgGC10) immuno-stains beta- and alpha-layers. This pattern of distribution suggests that both beta- and alpha-layers contain beta-proteins of different types that associate and replace intermediate-filament alpha-keratins during the terminal differentiation of keratinocytes. Therefore the different epidermal layers of the epidermis in S. punctatus , characterized by a specific cytology, material properties and consistency appear to derive from the prevalent type of beta-proteins synthesized in each epidermal layer and not from the alternation between beta- and alpha-keratins. The present observations are discussed in comparison to previous results from lizard epidermis and indicate that beta-keratins correspond to keratin-associated proteins that through their internal beta-pleated region are capable to form filaments in addition to intermediate filaments keratins.
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epidermal differentiation in embryos of the tuatara Sphenodon punctatus reptilia Sphenodontidae in comparison with the epidermis of other reptiles
Journal of Anatomy, 2007Co-Authors: Lorenzo Alibardi, B J GillAbstract:Studying the epidermis in primitive reptiles can provide clues regarding evolution of the epidermis during land adaptation in vertebrates. With this aim, the development of the skin of the relatively primitive reptile Sphenodon punctatus in representative embryonic stages was studied by light and electron microscopy and compared with that of other reptiles previously studied. The dermis organizes into a superficial and deep portion when the epidermis starts to form the first layers. At embryonic stages comparable with those of lizards, only one layer of the inner periderm is formed beneath the outer periderm. This also occurs in lizards and snakes so far studied. The outer and inner periderm form the embryonic epidermis and accumulate thick, coarse filaments (25–30 nm thick) and sparse alpha-keratin filaments as in other reptiles. Beneath the embryonic epidermis an oberhautchen and beta-cells form small horny tips that represent overlapping borders along the margin of beta-cells that overlap other beta-cells (in a tile-like arrangement). The tips resemble those of agamine lizards but at a small scale, forming a lamellate-spinulated pattern as previously described in adult epidermis. The embryonic epidermis matures by the dispersion of coarse filaments among keratin at the end of embryonic development and is shed around hatching. The presence of these matrix organelles in the embryonic epidermis of this primitive reptile further indicates that amniote epidermis acquired interkeratin matrix proteins early for land adaptation. Unlike the condition in lizards and snakes, a shedding complex is not formed in the epidermis of embryonic S. punctatus that is like that of the adult. Therefore, as in chelonians and crocodilians, the epidermis of S. punctatus also represents an initial stage that preceded the evolution of the shedding complex for moulting.
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distribution and characterization of keratins in the epidermis of the tuatara Sphenodon punctatus lepidosauria reptilia
Zoological Science, 2006Co-Authors: Lorenzo Alibardi, Mattia ToniAbstract:Abstract Reptilian scales are mainly composed of alpha- and beta-keratins. Epidermis and molts from adult individuals of an ancient reptilian species, the tuatara (Sphenodon punctatus), were analysed by immunocytochemistry, mono- and bi-dimensional electrophoresis, and western blotting for alpha-and beta-keratins. The epidermis of this reptilian species with primitive anatomical traits should represent one of the more ancient amniotic epidermises available. Soft keratins (AE1- and AE3-positive) of 40–63 kDa and with isoelectric points (pI) at 4.0–6.8 were found in molts. The AE3 antibody was diffusely localised over the tonofilaments of keratinocytes. The lack of basic cytokeratins may be due to keratin alteration in molts, following corneification or enzymatic degradation of keratins. Hard (beta-) keratins of 16–18 kDa and pI at 6.8, 8.0, and 9.2 were identified using a beta-1 antibody produced against chick scale beta-keratin. The antibody also labeled filaments of beta-cells and of the mature, compact ...
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formation of the corneous layer in the epidermis of the tuatara Sphenodon punctatus Sphenodontida lepidosauria reptilia
Zoology, 2004Co-Authors: Lorenzo AlibardiAbstract:The formation of the stratum corneum in the epidermis of the reptile Sphenodon punctatus has been studied by histochemical, immunohistochemical, and ultrastructural methods. Sulfhydryl groups are present in the mesos and pre-alpha-layer but disappear in the keratinized beta-layer and in most of the mature alpha-layer. This suggests a complete cross-linking of keratin filaments. Tyrosine increases in keratinized layers, especially in the beta-layer. Arginine is present in living epidermal layers, in the presumptive alpha-layer, but decreases in keratinized layers. Histidine is present in corneous layers, especially in the intermediate region between the alpha- and a new beta-layer, but disappears in living layers. It is unknown whether histidine-rich proteins are produced in the intermediate region. Small keratohyalin-like granules are incorporated in the intermediate region. The plane of shedding, as confirmed from the study on molts, is located along the basalmost part of the alpha-layer and may involve the degradation of whole cells or cell junctions of the intermediate region. A specific shedding complex, like that of lizards and snakes, is not formed in tuatara epidermis. AE1-, AE2-, or AE3-positive alpha-keratins are present in different epidermal layers with a pattern similar to that previously described in reptiles. The AE1 antibody stains the basal and, less intensely, the first suprabasal layers. Pre-keratinized, alpha- and beta-layers, and the intermediate region remain unlabeled. The AE2 antibody stains suprabasal and forming alpha- and beta-layers, but does not stain the basal and suprabasal layers. In the mature beta-layer the immunostaining disappears. The AE3 antibody stains all epidermal layers but disappears in alpha- and beta-layers. Immunolocalization for chick scale beta-keratins labels the forming and mature beta-layer, but disappears in the mesos and alpha-layer. This suggests the presence of common epitopes in avian and reptilian beta-keratins. Low molecular weight alpha-keratins present in the basal layer are probably replaced by keratins of higher molecular weight in keratinizing layers (AE2-positive). This keratin pattern was probably established since the beginning of land adaptation in amniotes.
Geoffrey K. Chambers - One of the best experts on this subject based on the ideXlab platform.
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purification partial characterization and peptide sequences of vitellogenin from a reptile the tuatara Sphenodon punctatus
Comparative Biochemistry and Physiology B, 1997Co-Authors: Mark A. Brown, Alan Carne, Geoffrey K. ChambersAbstract:Abstract Vitellogenin (Vg), a major precursor to egg yolk proteins, was purified from plasma of an estradiol-treated female tuatara ( Sphenodon punctatus ) by MgCl 2 –EDTA precipitation and DEAE-cellulose chromatography. The amino acid composition of tuatara Vg is similar to that of other vertebrate Vgs and contains a large proportion of serine (13.7 mol/100 mol of total amino acid). The amino acid sequences of the N-terminus of mature Vg (33 residues) and of several trypsin- and CNBr-generated peptides were determined. Six peptide sequences obtained from tuatara Vg could be aligned with Vg sequences from other vertebrates. Reduced and non-reduced forms of tuatara Vg have the same apparent molecular mass (∼218 kDa) when resolved by SDS-PAGE, indicating that inter-chain disulfide bonds are not a feature of the molecule in this species. Western blot analysis with anti-tuatara Vg antiserum indicated that at least some epitopes are shared among Vgs of turtle, alligator and tuatara.
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plasma concentrations of vitellogenin and sex steroids in female tuatara Sphenodon punctatus punctatus from northern new zealand
General and Comparative Endocrinology, 1994Co-Authors: Mark A. Brown, Alison Cree, Charles H. Daugherty, Brian P Dawkins, Geoffrey K. ChambersAbstract:Abstract Vitellogenesis in tuatara ( Sphenodon punctatus ) on Stephens Island, New Zealand, at the southern (coolest) end of the geographical range of this species involves a prolonged period of about 3 years of the average 4-year reproductive cycle. These studies used a semiquantitative electrophoretic assay for vitellogenin (Vg). In the present study an ELISA was used to measure plasma levels of Vg in 138 female northern tuatara ( S.p. punctatus ) on 11 islands at the warmest end of the tuatara's range. Blood samples were collected in late summer-early autumn, just prior to the expected time of ovulation in those females that would nest the following spring. Plasma Vg levels ranged from nondetectable to 2.9 mg/ml but were not significantly correlated with plasma estradiol, testosterone, or progesterone levels. There was also no significant correlation among the three sex steroids. Plasma Vg and hormone levels were further examined as to whether females were ovulating. Incipient ovulation was inferred using endocrinological criteria derived from studies of tuatara on Stephens Island (i.e., elevated plasma testosterone). Plasma levels of Vg differed significantly between inferred ovulators and nonovulators when data for all islands were combined, although similar ranges were observed in the two groups of females (inferred ovulators: nondetectable to 2382 μg/ml, mean = 505 ± 75; inferred nonovulators: nondetectable to 2864 μg/ml, mean = 460 ± 63). Plasma levels of estradiol, but not progesterone, differed significantly between inferred ovulators and nonovulators when data for all islands were combined. Mean levels in inferred ovulators were: estradiol, 157 ± 16 pg/ml (vs. 34 ± 5 pg/ml in inferred nonovulators); progesterone, 1.1 ± 0.2 ng/ml (vs. 0.7 ± 0.1 ng/m in inferred nonovulators); and testosterone, 5.6 ± 0.5 ng/ml (vs. 0.2 ± 0 ng/ml in inferred nonovulators). Only 37% of the females sampled met the minimum hormonal criteria indicative of ovulation. This suggests that, as in S. punctatus on Stephens Island, female S.p. punctatus on northern islands do not ovulate each year.
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Slow Estradiol-induced Vitellogenesis in the Tuatara, Sphenodon punctatus
Physiological and Biochemical Zoology, 1991Co-Authors: Alison Cree, Louis J. Guillette, Mark A. Brown, Geoffrey K. Chambers, John F. Cockrem, John D. NewtonAbstract:The vitellogenic response to exogenous estradiol-17β in wild male and female tuatara (Sphenodon punctatus) is extremely slow to induce. Tuatara given slowrelease implants containing 4-11 μg estradiol/g body mass showed a marked elevation in plasma estradiol concentrations within 2 d (to levels of up to 2,967 pg/mL) but no marked increases in plasma concentrations of calcium, total protein, or inorganic phosphate within 11 d. A small increase in the amount of electrophoretically detectable vitellogenin in the plasma (expressed as a percentage of total plasma protein) was evident by 11 d. Plasma concentrations of progesterone in individual females and testosterone in individual males were low (
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slow estradiol induced vitellogenesis in the tuatara Sphenodon punctatus
Physiological and Biochemical Zoology, 1991Co-Authors: Alison Cree, Louis J. Guillette, Mark A. Brown, Geoffrey K. Chambers, John F. Cockrem, John D. NewtonAbstract:The vitellogenic response to exogenous estradiol-17β in wild male and female tuatara (Sphenodon punctatus) is extremely slow to induce. Tuatara given slowrelease implants containing 4-11 μg estradiol/g body mass showed a marked elevation in plasma estradiol concentrations within 2 d (to levels of up to 2,967 pg/mL) but no marked increases in plasma concentrations of calcium, total protein, or inorganic phosphate within 11 d. A small increase in the amount of electrophoretically detectable vitellogenin in the plasma (expressed as a percentage of total plasma protein) was evident by 11 d. Plasma concentrations of progesterone in individual females and testosterone in individual males were low (<3. 7 ng/mL and <3.8 ng/mL, respectively) during the 11 d. Several individuals captured 4-9 mo after administration of implants showed very high plasma levels of vitellogenin (up to 59% of total plasma protein), calcium (up to 61 mmol/L), total protein (up to 108 g/L), and inorganic phosphate (up to 39 mmol/L); these ...
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absence of daily cycles in plasma sex steroids in male and female tuatara Sphenodon punctatus and the effects of acute capture stress on females
General and Comparative Endocrinology, 1990Co-Authors: Alison Cree, Louis J. Guillette, Mark A. Brown, John F. Cockrem, Geoffrey K. ChambersAbstract: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.