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Marc E H Jones - One of the best experts on this subject based on the ideXlab platform.

  • SI Additional Figures from Neutron scanning reveals unexpected complexity in the enamel thickness of an herbivorous Jurassic reptile
    2018
    Co-Authors: Marc E H Jones, Peter W. Lucas, Abigail S. Tucker, Amy P. Watson, Joseph J. W. Sertich, John R. Foster, Ruth Williams, Ulf Garbe, Joseph J. Bevitt, Floriana Salvemini
    Abstract:

    Eilenodontines are one of the oldest radiation of herbivorous lepidosaurs (snakes, lizards and tuatara) characterized by batteries of wide teeth with thick enamel that bear mammal-like wear facets. Unlike most reptiles, eilenodontines have limited tooth replacement, making dental longevity particularly important to them. We use both X-ray and neutron computed tomography to examine a fossil tooth from the eilenodontine Eilenodon (Late Jurassic, USA). Of the two approaches, neutron tomography was more successful and facilitated measurements of enamel thickness and distribution. We find the enamel thickness to be regionally variable, thin near the cusp tip (0.10 mm) but thicker around the base (0.15–0.30 mm) and notably greater than that of other rhynchocephalians such as the extant Sphenodon (0.08–0.14 mm). The thick enamel in Eilenodon would permit greater loading, extend tooth lifespan and facilitate the establishment of wear facets that have sharp edges for orally processing plant material such as horsetails (Equisetum). The shape of the enamel dentine junction indicates that tooth development in Eilenodon and Sphenodon involved similar folding of the epithelium but different ameloblast activity

  • 3D animation tooth_3 from Neutron scanning reveals unexpected complexity in the enamel thickness of an herbivorous Jurassic reptile
    2018
    Co-Authors: Marc E H Jones, Peter W. Lucas, Abigail S. Tucker, Amy P. Watson, Joseph J. W. Sertich, John R. Foster, Ruth Williams, Ulf Garbe, Joseph J. Bevitt, Floriana Salvemini
    Abstract:

    Eilenodontines are one of the oldest radiation of herbivorous lepidosaurs (snakes, lizards and tuatara) characterized by batteries of wide teeth with thick enamel that bear mammal-like wear facets. Unlike most reptiles, eilenodontines have limited tooth replacement making dental longevity particularly important to them. We use both X-ray and neutron computed tomography to examine a fossil tooth from the eilenodontine Eilenodon (Late Jurassic, USA). Of the two approaches, neutron tomography was more successful and facilitated measurements of enamel thickness and distribution. We find the enamel thickness to be regionally variable, thin near the cusp tip (0.10 mm) but thicker around the base (0.15–0.30 mm) and notably greater than that of other rhynchocephalians such as the extant Sphenodon (0.08–0.14 mm). The thick enamel in Eilenodon would permit greater loading, extend tooth lifespan and facilitate the establishment of wear facets that have sharp edges for orally processing plant material such as horsetails (Equisetum). The shape of the enamel dentine junction indicates that tooth development in Eilenodon and Sphenodon involved similar folding of the epithelium but different ameloblast activity

  • SI Table 2 from Neutron scanning reveals unexpected complexity in the enamel thickness of an herbivorous Jurassic reptile
    2018
    Co-Authors: Marc E H Jones, Peter W. Lucas, Abigail S. Tucker, Amy P. Watson, Joseph J. W. Sertich, John R. Foster, Ruth Williams, Ulf Garbe, Joseph J. Bevitt, Floriana Salvemini
    Abstract:

    Eilenodontines are one of the oldest radiation of herbivorous lepidosaurs (snakes, lizards and tuatara) characterized by batteries of wide teeth with thick enamel that bear mammal-like wear facets. Unlike most reptiles, eilenodontines have limited tooth replacement, making dental longevity particularly important to them. We use both X-ray and neutron computed tomography to examine a fossil tooth from the eilenodontine Eilenodon (Late Jurassic, USA). Of the two approaches, neutron tomography was more successful and facilitated measurements of enamel thickness and distribution. We find the enamel thickness to be regionally variable, thin near the cusp tip (0.10 mm) but thicker around the base (0.15–0.30 mm) and notably greater than that of other rhynchocephalians such as the extant Sphenodon (0.08–0.14 mm). The thick enamel in Eilenodon would permit greater loading, extend tooth lifespan and facilitate the establishment of wear facets that have sharp edges for orally processing plant material such as horsetails (Equisetum). The shape of the enamel dentine junction indicates that tooth development in Eilenodon and Sphenodon involved similar folding of the epithelium but different ameloblast activity

  • SI Segmentation Protocol from Neutron scanning reveals unexpected complexity in the enamel thickness of an herbivorous Jurassic reptile
    2018
    Co-Authors: Marc E H Jones, Peter W. Lucas, Abigail S. Tucker, Amy P. Watson, Joseph J. W. Sertich, John R. Foster, Ruth Williams, Ulf Garbe, Joseph J. Bevitt, Floriana Salvemini
    Abstract:

    Eilenodontines are one of the oldest radiation of herbivorous lepidosaurs (snakes, lizards and tuatara) characterized by batteries of wide teeth with thick enamel that bear mammal-like wear facets. Unlike most reptiles, eilenodontines have limited tooth replacement, making dental longevity particularly important to them. We use both X-ray and neutron computed tomography to examine a fossil tooth from the eilenodontine Eilenodon (Late Jurassic, USA). Of the two approaches, neutron tomography was more successful and facilitated measurements of enamel thickness and distribution. We find the enamel thickness to be regionally variable, thin near the cusp tip (0.10 mm) but thicker around the base (0.15–0.30 mm) and notably greater than that of other rhynchocephalians such as the extant Sphenodon (0.08–0.14 mm). The thick enamel in Eilenodon would permit greater loading, extend tooth lifespan and facilitate the establishment of wear facets that have sharp edges for orally processing plant material such as horsetails (Equisetum). The shape of the enamel dentine junction indicates that tooth development in Eilenodon and Sphenodon involved similar folding of the epithelium but different ameloblast activity

  • BEAST xml infile for Squamata and Sphenodon, Vellberg fossil 238myr, exponential priors with mean 4
    2017
    Co-Authors: Marc E H Jones, Susan E. Evans, Cajsa Lisa Anderson, Christy A. Hipsley, Johannes Müller, Rainer R. Schoch
    Abstract:

    BEAST xml infile for Squamata and Sphenodon, Vellberg fossil 238myr, exponential priors with mean

Charles H. Daugherty - One of the best experts on this subject based on the ideXlab platform.

  • Genetic diversity and taxonomy: a reassessment of species designation in tuatara (Sphenodon: Reptilia)
    Conservation Genetics, 2010
    Co-Authors: Stephen D. Sarre, Fred W Allendorf, David M. Lambert, Charles H. Daugherty
    Abstract:

    The identification of species boundaries for allopatric populations is important for setting conservation priorities and can affect conservation management decisions. Tuatara ( Sphenodon ) are the only living members of the reptile order Sphenodontia and are restricted to islands around New Zealand that are free of introduced mammals. We present new data of microsatellite DNA diversity and substantially increased mtDNA sequence for all 26 sampled tuatara populations. We also re-evaluate existing allozyme data for those populations, and together use them to examine the taxonomic status of those populations. Although one could interpret the data to indicate different taxonomic designations, we conclude that, contrary to current taxonomy, Sphenodon is best described as a single species that contains distinctive and important geographic variants. We also examine amounts of genetic variation within populations and discuss the implications of these findings for the conservation management of this iconic taxon.

  • The evolutionary rate of tuatara revisited
    Trends in Genetics, 2008
    Co-Authors: Hilary C. Miller, Jennifer A Moore, Fred W Allendorf, Charles H. Daugherty
    Abstract:

    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].

  • Support for a rare pattern of temperature-dependent sex determination in archaic reptiles: evidence from two species of tuatara (Sphenodon)
    Frontiers in Zoology, 2006
    Co-Authors: Nicola J Mitchell, Alison Cree, N J Nelson, Susan N Keall, Shirley Pledger, Charles H. Daugherty
    Abstract:

    Background The sex of many reptiles is determined by the temperature an embryo experiences during its development. Three patterns of temperature-dependent sex determination (TSD) have been defined, but one pattern where only males are produced above an upper temperature threshold (Type IB) is controversial. Here we report new data on the relationship between constant temperature incubation and sexual phenotype in two species of tuatara ( Sphenodon ), archaic reptiles of enormous zoological significance as the sole representatives of a once widespread reptilian order. Results In both species, the pattern observed with constant incubation temperatures from 18 to 23°C (or 24°C) supported a female→male (FM or Type IB) pattern of TSD: in Sphenodon guntheri males were produced above a pivotal temperature of 21.6°C, and in S. punctatus (unnamed subspecies on Stephens Island, Cook Strait), males were produced above a pivotal temperature of 22.0°C. The pivotal temperatures and scaling parameters differed between species (p < 0.001). The thermosensitive period (TSP), where temperature influences gonad morphogenesis, occurs between 0.25 and 0.55 of embryonic development. While it is possible that the more common female→male→female (FMF or Type II) pattern exists, with a second pivotal temperature above 23–24°C, we review several lines of evidence to the contrary. Most notably, we show that in S. punctatus , the warmest natural nests during the TSP produce predominantly males. Conclusion An FM pattern of TSD could be currently adaptive in promoting sexual size dimorphism in tuatara. However, an FM pattern has particularly serious consequences for S. guntheri because current patterns of global warming could exacerbate the male bias already present in the relic population.

  • Support for a rare pattern of temperature-dependent sex determination in archaic reptiles: evidence from two species of tuatara (Sphenodon)
    Frontiers in Zoology, 2006
    Co-Authors: Nicola J Mitchell, Alison Cree, N J Nelson, Susan N Keall, Shirley Pledger, Charles H. Daugherty
    Abstract:

    The sex of many reptiles is determined by the temperature an embryo experiences during its development. Three patterns of temperature-dependent sex determination (TSD) have been defined, but one pattern where only males are produced above an upper temperature threshold (Type IB) is controversial. Here we report new data on the relationship between constant temperature incubation and sexual phenotype in two species of tuatara (Sphenodon), archaic reptiles of enormous zoological significance as the sole representatives of a once widespread reptilian order. In both species, the pattern observed with constant incubation temperatures from 18 to 23°C (or 24°C) supported a female→male (FM or Type IB) pattern of TSD: in Sphenodon guntheri males were produced above a pivotal temperature of 21.6°C, and in S. punctatus (unnamed subspecies on Stephens Island, Cook Strait), males were produced above a pivotal temperature of 22.0°C. The pivotal temperatures and scaling parameters differed between species (p < 0.001). The thermosensitive period (TSP), where temperature influences gonad morphogenesis, occurs between 0.25 and 0.55 of embryonic development. While it is possible that the more common female→male→female (FMF or Type II) pattern exists, with a second pivotal temperature above 23–24°C, we review several lines of evidence to the contrary. Most notably, we show that in S. punctatus, the warmest natural nests during the TSP produce predominantly males. An FM pattern of TSD could be currently adaptive in promoting sexual size dimorphism in tuatara. However, an FM pattern has particularly serious consequences for S. guntheri because current patterns of global warming could exacerbate the male bias already present in the relic population.

  • Characterization of MHC class II genes from an ancient reptile lineage, Sphenodon (tuatara).
    Immunogenetics, 2005
    Co-Authors: Hilary C. Miller, Katherine Belov, Charles H. Daugherty
    Abstract:

    The organization and evolution of major histocompatibility complex (MHC) genes vary considerably among vertebrate lineages. MHC genes have been well characterized in mammals, birds, amphibians and fish, but little is known about their organization in reptiles, despite the fact that reptiles occupy an important phylogenetic position for understanding the evolutionary history of both mammalian and avian MHC genes. Here we describe the characterization of the first MHC class II B cDNA sequences from a non-avian reptile, the tuatara (Sphenodon spp.). Three class II B sequences were isolated from a tuatara cDNA library, and four additional partial sequences were isolated by reverse transcriptase-polymerase chain reaction. Six of these sequences appear to belong to the same gene family, which we have named SppuDAB. The remaining sequence (named SppuDBB) shares only 43.9% amino acid similarity with SppuDAB and thus appears to represent a separate gene family. SppuDBB may be a non-classical locus as it does not contain all the conserved residues expected of a classical MHC class II gene. Southern blot analysis indicates that only a single copy of SppuDBB exists in tuatara, but that multiple loci related to SppuDAB are present. The SppuDAB sequences have the highest amino acid similarity (57.2-62.4%) with class II B sequences from the spectacled caiman, but only 26.4-48.7% similarity with sequences from other vertebrates. The tuatara sequences do not strongly group with other reptile sequences on a phylogenetic tree, reflecting the antiquity of the Sphenodon lineage and the lack of closely related sequences for comparison.

Susan E. Evans - One of the best experts on this subject based on the ideXlab platform.

  • RAG1 aligned matrix of Squamata, Sphenodon and outgroups
    2017
    Co-Authors: Marc E H Jones, Susan E. Evans, Cajsa Lisa Anderson, Christy A. Hipsley, Johannes Müller, Rainer R. Schoch
    Abstract:

    RAG1 aligned matrix of Squamata, Sphenodon and outgroup

  • BEAST xml infile for Squamata and Sphenodon, Vellberg fossil 238myr, exponential priors with mean 4
    2017
    Co-Authors: Marc E H Jones, Susan E. Evans, Cajsa Lisa Anderson, Christy A. Hipsley, Johannes Müller, Rainer R. Schoch
    Abstract:

    BEAST xml infile for Squamata and Sphenodon, Vellberg fossil 238myr, exponential priors with mean

  • The Lepidosaurian Ear: Variations on a Theme
    Evolution of the Vertebrate Ear, 2016
    Co-Authors: Susan E. Evans
    Abstract:

    Today, Lepidosauria encompasses more than 9,000 species of lizards, snakes, and amphisbaenians (Squamata), as well as the New Zealand Tuatara, Sphenodon (Rhynchocephalia). In many lizards, an efficient tympanic middle ear and an effective inner-ear compensatory mechanism permit acute hearing across a range of frequencies. Sphenodon lacks a tympanic membrane, but this is the result of secondary loss. Fossils of stem lepidosaurs and early rhynchocephalians indicate that the ancestral lepidosaurian middle ear was tympanic, although the compensatory mechanism was probably rudimentary. Derived rhynchocephalians like Sphenodon lost the tympanic ear, possibly in association with feeding specializations, whereas squamates improved it by developing a more efficient compensatory window. However, the timing of this change is uncertain as the earliest lizard fossils are uninformative in this respect. Lizards from the Early Cretaceous onward show the derived condition. Squamates are morphologically and ecologically diverse, and some specialized lifestyles have affected ear anatomy. Among extant squamates, the only obligate marine swimmers are sea snakes, but in the Cretaceous, mosasaurs dominated the marine niche. These aquatic lizards show a middle ear morphology analogous to that of extant marine turtles (bulla-like quadrate, expanded extrastapes, loss of the tympanum?). Loss of the tympanum also occurs in squamate burrowers but in conjunction with the possession of a robust stapes with an enlarged footplate and, frequently, reduction or modification of the compensatory mechanism. Ears of this type are found in the enigmatic Cretaceous Sineoamphisbaena and in amphisbaenians from the Eocene to the present day. Where known, the ears of early snakes more closely resemble those of burrowers than swimmers.

  • shearing mechanics and the influence of a flexible symphysis during oral food processing in Sphenodon lepidosauria rhynchocephalia
    Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2012
    Co-Authors: Marc E H Jones, Michael J. Fagan, Susan E. Evans, Paul Ohiggins, Neil Curtis
    Abstract:

    The New Zealand tuatara, Sphenodon, has a specialized feeding system in which the teeth of the lower jaw close between two upper tooth rows before sliding forward to slice food apart like a draw cut saw. This shearing action is unique amongst living amniotes but has been compared with the chewing power stroke of mammals. We investigated details of the jaw movement using multibody dynamics analysis of an anatomically accurate three-dimensional computer model constructed from computed tomography scans. The model predicts that a flexible symphysis is necessary for changes in the intermandibular angle that permits prooral movement. Models with the greatest symphysial flexibility allow the articulation surface of the articular to follow the quadrate cotyle with the least restriction, and suggest that shearing is accompanied by a long axis rotation of the lower jaws. This promotes precise point loading between the cutting edges of particular teeth, enhancing the effectiveness of the shearing action. Given that Sphenodon is a relatively inactive reptile, we suggest that the link between oral food processing and endothermy has been overstated. Food processing improves feeding efficiency, a consideration of particular importance when food availability is unpredictable. Although this feeding mechanism is today limited to Sphenodon, a survey of fossil rhynchocephalians suggests that it was once more widespread.

  • shearing mechanics and the influence of a flexible symphysis during oral food processing in Sphenodon lepidosauria rhynchocephalia
    Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2012
    Co-Authors: Marc E H Jones, Michael J. Fagan, Susan E. Evans, Paul Ohiggins, N. Curtis
    Abstract:

    The New Zealand tuatara, Sphenodon, has a specialized feeding system in which the teeth of the lower jaw close between two upper tooth rows before sliding forward to slice food apart like a draw cut saw. This shearing action is unique amongst living amniotes but has been compared with the chewing power stroke of mammals. We investigated details of the jaw movement using multibody dynamics analysis of an anatomically accurate three-dimensional computer model constructed from computed tomography scans. The model predicts that a flexible symphysis is necessary for changes in the intermandibular angle that permits prooral movement. Models with the greatest symphysial flexibility allow the articulation surface of the articular to follow the quadrate cotyle with the least restriction, and suggest that shearing is accompanied by a long axis rotation of the lower jaws. This promotes precise point loading between the cutting edges of particular teeth, enhancing the effectiveness of the shearing action. Given that Sphenodon is a relatively inactive reptile, we suggest that the link between oral food processing and endothermy has been overstated. Food processing improves feeding efficiency, a consideration of particular importance when food availability is unpredictable. Although this feeding mechanism is today limited to Sphenodon, a survey of fossil rhynchocephalians suggests that it was once more widespread. Anat Rec, 2012. © 2012 Wiley-Periodicals, Inc.

Alison Cree - One of the best experts on this subject based on the ideXlab platform.

  • evidence of food chemical discrimination in tuatara o rhynchocephalia comparison with a gekkotan lizard o squamata
    Journal of Herpetology, 2009
    Co-Authors: Anne A Besson, A Thierry, Emanuela Boros, Craig R Norrie, K Allen, S Bradley, Alison Cree
    Abstract:

    In lizards, chemical senses play important roles in ecology and behavior. Previous studies have shown that food chemical discrimination, phylogeny, and foraging modes are associated in squamates. The two major clades, Iguania and Scleroglossa, display marked differences in foraging behavior. A large majority of iguanians are primarily ambush foragers and lack prey chemical discrimination, whereas scleroglossans, mainly active foragers, are capable of prey chemical discrimination. However, evidence for prey chemical discrimination in tuatara (Sphenodon), the only living representative of the order Rhynchocephalia (the sister group of Squamata) is not clear. Here, we compare responses to food chemical stimuli between Tuatara (Sphenodon punctatus) and a gekkotan lizard, the Common Gecko (Hoplodactylus maculatus). We found that tuatara showed the same responses as Common Geckos when presented simultaneously with a series of stimuli: they spent more time in the prey zone (odor of mealworms) than the pungency or control zones; they bit only the prey stimulus; and they showed similar latency to bite and give-up time as geckos. However, unlike Tuatara, geckos showed lingual sampling (tongue flicking) toward the prey stimulus. We showed that Tuatara could use chemosensory cues to detect prey in the absence of stimulus movement. Consequently, the coding of traits used to characterized tuatara as an outgroup in chemoreception studies should be revised.

  • Support for a rare pattern of temperature-dependent sex determination in archaic reptiles: evidence from two species of tuatara (Sphenodon)
    Frontiers in Zoology, 2006
    Co-Authors: Nicola J Mitchell, Alison Cree, N J Nelson, Susan N Keall, Shirley Pledger, Charles H. Daugherty
    Abstract:

    Background The sex of many reptiles is determined by the temperature an embryo experiences during its development. Three patterns of temperature-dependent sex determination (TSD) have been defined, but one pattern where only males are produced above an upper temperature threshold (Type IB) is controversial. Here we report new data on the relationship between constant temperature incubation and sexual phenotype in two species of tuatara ( Sphenodon ), archaic reptiles of enormous zoological significance as the sole representatives of a once widespread reptilian order. Results In both species, the pattern observed with constant incubation temperatures from 18 to 23°C (or 24°C) supported a female→male (FM or Type IB) pattern of TSD: in Sphenodon guntheri males were produced above a pivotal temperature of 21.6°C, and in S. punctatus (unnamed subspecies on Stephens Island, Cook Strait), males were produced above a pivotal temperature of 22.0°C. The pivotal temperatures and scaling parameters differed between species (p < 0.001). The thermosensitive period (TSP), where temperature influences gonad morphogenesis, occurs between 0.25 and 0.55 of embryonic development. While it is possible that the more common female→male→female (FMF or Type II) pattern exists, with a second pivotal temperature above 23–24°C, we review several lines of evidence to the contrary. Most notably, we show that in S. punctatus , the warmest natural nests during the TSP produce predominantly males. Conclusion An FM pattern of TSD could be currently adaptive in promoting sexual size dimorphism in tuatara. However, an FM pattern has particularly serious consequences for S. guntheri because current patterns of global warming could exacerbate the male bias already present in the relic population.

  • Support for a rare pattern of temperature-dependent sex determination in archaic reptiles: evidence from two species of tuatara (Sphenodon)
    Frontiers in Zoology, 2006
    Co-Authors: Nicola J Mitchell, Alison Cree, N J Nelson, Susan N Keall, Shirley Pledger, Charles H. Daugherty
    Abstract:

    The sex of many reptiles is determined by the temperature an embryo experiences during its development. Three patterns of temperature-dependent sex determination (TSD) have been defined, but one pattern where only males are produced above an upper temperature threshold (Type IB) is controversial. Here we report new data on the relationship between constant temperature incubation and sexual phenotype in two species of tuatara (Sphenodon), archaic reptiles of enormous zoological significance as the sole representatives of a once widespread reptilian order. In both species, the pattern observed with constant incubation temperatures from 18 to 23°C (or 24°C) supported a female→male (FM or Type IB) pattern of TSD: in Sphenodon guntheri males were produced above a pivotal temperature of 21.6°C, and in S. punctatus (unnamed subspecies on Stephens Island, Cook Strait), males were produced above a pivotal temperature of 22.0°C. The pivotal temperatures and scaling parameters differed between species (p < 0.001). The thermosensitive period (TSP), where temperature influences gonad morphogenesis, occurs between 0.25 and 0.55 of embryonic development. While it is possible that the more common female→male→female (FMF or Type II) pattern exists, with a second pivotal temperature above 23–24°C, we review several lines of evidence to the contrary. Most notably, we show that in S. punctatus, the warmest natural nests during the TSP produce predominantly males. An FM pattern of TSD could be currently adaptive in promoting sexual size dimorphism in tuatara. However, an FM pattern has particularly serious consequences for S. guntheri because current patterns of global warming could exacerbate the male bias already present in the relic population.

  • Low genetic divergence obscures phylogeny among populations of Sphenodon, remnant of an ancient reptile lineage.
    Molecular Phylogenetics and Evolution, 2003
    Co-Authors: Jennifer M. Hay, Alison Cree, Charles H. Daugherty, Linda R. Maxson
    Abstract:

    Tuatara (two species of Sphenodon) are the last representatives of a branch of an ancient reptilian lineage, Sphenodontia, that have been isolated on the New Zealand landmass for 82 million years. We present analyses of geographic variation in allozymes, mitochondrial DNA, nuclear DNA sequences, and one-way albumin immunological comparisons. These all confirm a surprisingly low level of genetic diversity within Sphenodon for such an ancient lineage. We hypothesise a recent extended population bottleneck, probably during the Pliocene/Pleistocene glaciation cycles, to explain the current paucity of variation. All data sets reveal clear genetic differentiation between the northern populations and those in Cook Strait, but offer conflicting views of the history and taxonomic relationships of the Cook Strait population on North Brother Island, currently recognised as Sphenodon guntheri. Allozymes show this population to be the most divergent of all tuatara populations, but preliminary mitochondrial DNA data indicate few differences between S. guntheri and Cook Strait Sphenodon punctatus. Interpretation of the trees is confounded by the lack of a suitable outgroup. As in other cases of conflicting nuclear and mitochondrial data sets, the different data sets likely reveal different aspects of the animals' evolutionary history, and introgression is not uncommon between species pairs.

  • physiological effects of a fish oil supplement on captive juvenile tuatara Sphenodon punctatus
    Physiological and Biochemical Zoology, 2000
    Co-Authors: T A Blair, Alison Cree, C. Murray Skeaff, N M Grimmond
    Abstract:

    Abstract Tuatara (Sphenodon, Order Sphenodontia) are rare New Zealand reptiles whose conservation involves captive breeding. Wild tuatara eat seabirds, which contain high levels of the long‐chain n‐3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These fatty acids are absent from the captive diet, and consequently, plasma fatty acid composition of wild and captive tuatara differs. This study investigated the effects of incorporating EPA and DHA into the diet of captive juvenile tuatara (Sphenodon punctatus) in an attempt to replicate the plasma fatty acid composition of wild tuatara. Tuatara receiving a fish oil supplement containing EPA and DHA showed overall changes in their plasma fatty acid composition. Phospholipid EPA and DHA increased markedly, reaching 10.0% and 5.9 mol%, respectively, by 18 mo (cf. ≤0.9% in controls). A reduced dosage from 18 to 24 mo probably still provided a higher n‐3 PUFA content than the diet of wild juveniles. The fish oil su...

Michael B Thompson - One of the best experts on this subject based on the ideXlab platform.

  • metabolism of tuatara Sphenodon punctatus
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 1998
    Co-Authors: Michael B Thompson, Charles H. Daugherty
    Abstract:

    Abstract Rate of oxygen consumption was used as an index of metabolic rate in resting male, female and juvenile tuatara of a large range of sizes (6.8–746 g) on Stephens Island, New Zealand. Metabolic rate was measured within 72 hours of capture at 10–15°C. Metabolic rates were adjusted to 13°C and varied with mass with a metabolic scaling exponent of 0.62. Metabolic rates of juveniles were higher than expected at 13°C for lizards of similar mass, but rates for adult tuatara were approximately the same as expected for lizards at 13°C. Body temperatures of 142 active tuatara were measured during the day and night and ranged from 5.2–11.2°C. Hence, standard metabolic rates of tuatara close to their activity temperatures (at 13°C) are low compared to standard rates for lizards at their active temperatures that are normally in excess of 20°C.

  • status and longevity of the tuatara Sphenodon guntheri and duvaucel s gecko hoplodactylus duvaucelii on north brother island new zealand
    Journal of The Royal Society of New Zealand, 1992
    Co-Authors: Michael B Thompson, Alison Cree, James C. Gillingham, Charles H. Daugherty, Debbie C. French, Richard Barwick
    Abstract:

    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.

  • Status and longevity of the tuatara, Sphenodon guntheri, and Duvaucel's gecko, Hoplodactylus duvaucelii, on North Brother Island, New Zealand
    Journal of the Royal Society of New Zealand, 1992
    Co-Authors: Michael B Thompson, Alison Cree, James C. Gillingham, Charles H. Daugherty, Debbie C. French, Richard Barwick
    Abstract:

    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

  • incubation of eggs of tuatara Sphenodon punctatus
    Journal of Zoology, 1990
    Co-Authors: Michael B Thompson
    Abstract:

    Eggs of the tuatara, Sphenodon punctatus, were incubated either buried or half buried in vermiculite at constant temperatures of 15, 18, 20, 22 and 25 °C and constant water potentials between —90 and —400 kPa. Many clutches failed completely, possibly because they had been taken from females prior to proper shell development. Failed eggs were significantly smaller than successful eggs. Incubation is unsuccessful at 15 °C. Hatching success is high between 18 and 22 °C but low at 25 °C, but equally successful between 18 and 22°C. Incubation is strongly influenced by temperature, with mean incubation periods of 328 days at 18 °C, 259 days at 20 °C, 169 days at 22 °C and 150 days at 25 °C. Water potential generally has little influence on incubation time at a given temperature. Buried eggs hatch sooner than partially buried eggs at 20 °C but the large range makes significance dubious. Eggs on the driest substrata at 18 and 20 °C lose water initially but then gain water through the rest of incubation. Eggs in all other conditions gain water throughout incubation, with the rate of i water absorption being maintained or increasing late in incubation. The suggestion that increasing rate of water absorption late in incubation facilitates explosive hatching is not supported. Egg mass at the time of hatching varies from 132 to 398% of initial values, depending on incubation conditions. Final egg mass is not affected significantly by incubation temperature. Hence, rates of absorption increase with temperature. Water potential has no influence on hatchling size. However, hatchlings from buried eggs generally are significantly larger than those from partially buried eggs.