The reptilian thyroid and parathyroid glands

RETROSPECTIVE STUDY OF MORBIDITY AND MORTALITY IN A CAPTIVE POPULATION OF CRYPTOSPORIDIUM-POSITIVE LOUISIANA PINE SNAKES (PITUOPHIS RUTHVENI)

The Louisiana pine snake (Pituophis ruthveni) is a diurnal colubrid species native to Louisiana and eastern Texas whose free-ranging populations have been declining over at least the past 30 yr. The creation and maintenance of sustainable captive breeding programs of P. ruthveni to restore native populations has also provided ample opportunity for research into this species and for P. ruthveni to serve as a research model for other colubrid snakes. However, no investigation into prevalent causes of morbidity and mortality in captive populations of this species has been described. A research population of P. ruthveni was maintained at Louisiana State University (LSU) for over 4 yr due to unsuitability for breeding after testing positive for Cryptosporidium serpentis. Since arrival at LSU, the snakes were under close veterinary surveillance. Complete postmortem examinations were performed on 12 snakes that died or were euthanized. The aim of this study was to further understanding of common factors influencing morbidity and mortality in captive P. ruthveni infected with C. serpentis, by retrospectively reviewing postmortem exam findings from the 12 deceased members of the population at LSU. A predominant finding across individuals included bacterial infections, which were responsible for major illness or death in 37.5% of the animals. Fifty percent of snakes tested positive for Cryptosporidium sp. based on PCR performed from postmortem samples; it was directly implicated as cause of death or morbidity in 83.3% of positive cases. Although infectious disease represented the most common pathologic postmortem finding, several noninfectious disease processes were identified, including gout, goiter, and neoplasia. These findings mirror those of other retrospective investigations of reptile collections at various institutions and highlight the need for appropriate emphasis on the identification, treatment, and prevention of infectious disease as part of routine veterinary care.

Updates for Reptile Pediatric Medicine

The health of hatchling, juvenile, and young adult reptiles continues to be plagued by historic nutritional deficiencies, old and emerging infectious diseases, and more recent phenotype-selective congenital abnormalities that impact welfare. Knowledge of mating seasonality, average egg counts, gestation times, and age and/or size for sexual maturity is necessary to help guide best practices for care of pediatric reptiles. Calcium, vitamin D3, and ultraviolet B (UVB) lighting recommendations vary in effectiveness amongst different species and can change with age. Phenotype-selective color patterns for spider ball pythons and scalation pattern for bearded dragons have resulted in vestibular disease, and increased evaporative water loss, respectively. Salmonellosis remains the most reported zoonotic disease for captive reptiles in the United States, despite improvements in client education and improvements in captive reptile husbandry.

Cross-species applicability of an adverse outcome pathway network for thyroid hormone system disruption

Thyroid hormone system disrupting compounds are considered potential threats for human and environmental health. Multiple adverse outcome pathways (AOPs) for thyroid hormone system disruption (THSD) are being developed in different taxa. Combining these AOPs results in a cross-species AOP network for THSD which may provide an evidence-based foundation for extrapolating THSD data across vertebrate species and bridging the gap between human and environmental health. This review aimed to advance the description of the taxonomic domain of applicability (tDOA) in the network to improve its utility for cross-species extrapolation. We focused on the molecular initiating events (MIEs) and adverse outcomes (AOs) and evaluated both their plausible domain of applicability (taxa they are likely applicable to) and empirical domain of applicability (where evidence for applicability to various taxa exists) in a THSD context. The evaluation showed that all MIEs in the AOP network are applicable to mammals. With some exceptions, there was evidence of structural conservation across vertebrate taxa and especially for fish and amphibians, and to a lesser extent for birds, empirical evidence was found. Current evidence supports the applicability of impaired neurodevelopment, neurosensory development (eg, vision) and reproduction across vertebrate taxa. The results of this tDOA evaluation are summarized in a conceptual AOP network that helps prioritize (parts of) AOPs for a more detailed evaluation. In conclusion, this review advances the tDOA description of an existing THSD AOP network and serves as a catalog summarizing plausible and empirical evidence on which future cross-species AOP development and tDOA assessment could build.

Invited review: Adrenocortical function in avian and non-avian reptiles: Insights from dispersed adrenocortical cells

Herein we review our work involving dispersed adrenocortical cells from several lizard species: the Eastern Fence Lizard (Sceloporus undulatus), Yarrow's Spiny Lizard (Sceloporus jarrovii), Striped Plateau Lizard (Sceloporus virgatus) and the Yucatán Banded Gecko (Coleonyx elegans). Early work demonstrated changes in steroidogenic function of adrenocortical cells derived from adult S. undulatus associated with seasonal interactions with sex. However, new information suggests that both sexes operate within the same steroidogenic budget over season. The observed sex effect was further explored in orchiectomized and ovariectomized lizards, some supported with exogenous testosterone. Overall, a suppressive effect of testosterone was evident, especially in cells from C. elegans. Life stage added to this complex picture of adrenal steroidogenic function. This was evident when sexually mature and immature Sceloporus lizards were subjected to a nutritional stressor, cricket restriction/deprivation. There were divergent patterns of corticosterone, aldosterone, and progesterone responses and associated sensitivities of each to corticotropin (ACTH). Finally, we provide strong evidence that there are multiple, labile subpopulations of adrenocortical cells. We conclude that the rapid (days) remodeling of adrenocortical steroidogenic function through fluctuating cell subpopulations drives the circulating corticosteroid profile of Sceloporus lizard species. Interestingly, progesterone and aldosterone may be more important with corticosterone serving as essential supportive background. In the wild, the flux in adrenocortical cell subpopulations may be adversely susceptible to climate-change related disruptions in food sources and to xenobiotic/endocrine-disrupting chemicals. We urge further studies using native lizard species as bioindicators of local pollutants and as models to examine the broader eco-exposome.

Endocrine Diagnostics for Exotic Animals

Endocrine disease in exotic species is less common than in small animals. Nevertheless, the diagnostic principles used in small animals can be adapted to evaluate endocrine disease in many of the exotic species although species-specific aspects need to be considered. This article covers important diseases such as thyroid dysfunction in reptiles and birds, hyperthyroidism in guinea pigs, and hyperadrenocorticism in ferrets. Glucose metabolism in neoplasms affecting normal physiology, such as insulinoma in ferrets and gastric neuroendocrine carcinoma in bearded dragons, is discussed. Calcium abnormalities, including metabolic bone disease in reptiles and hypocalcemia in birds, are also covered.

Disruption by stealth - Interference of endocrine disrupting chemicals on hormonal crosstalk with thyroid axis function in humans and other animals

Thyroid hormones (THs) are important regulators of growth, development, and homeostasis of all vertebrates. There are many environmental contaminants that are known to disrupt TH action, yet their mechanisms are only partially understood. While the effects of Endocrine Disrupting Chemicals (EDCs) are mostly studied as "hormone system silos", the present critical review highlights the complexity of EDCs interfering with TH function through their interactions with other hormonal axes involved in reproduction, stress, and energy metabolism. The impact of EDCs on components that are shared between hormone signaling pathways or intersect between pathways can thus extend beyond the molecular ramifications to cellular, physiological, behavioral, and whole-body consequences for exposed organisms. The comparatively more extensive studies conducted in mammalian models provides encouraging support for expanded investigation and highlight the paucity of data generated in other non-mammalian vertebrate classes. As greater genomics-based resources become available across vertebrate classes, better identification and delineation of EDC effects, modes of action, and identification of effective biomarkers suitable for HPT disruption is possible. EDC-derived effects are likely to cascade into a plurality of physiological effects far more complex than the few variables tested within any research studies. The field should move towards understanding a system of hormonal systems' interactions rather than maintaining hormone system silos.

Faecal Triiodothyronine Hormone Levels in Female Iguana during Weekday and Weekend in In Situ Conservation

Iguanas are exotic animals that are widely kept as pets in our society,their performance and color being their main attraction. Jogja Exotarium is anin situ conservation park that carries the back to nature concept. Animals thatare kept at the Jogja Exotarium are allowed direct contact with visitors. Thisstudy aims to determine the hormone triiodothyronine in female iguanas that are raised and conserved in situ. This study used feces obtained from iguanas kept in Jogja Exotarium, sampling was carried out on Wednesdays and Sundays for 2 weeks. The collected faecal samples were processed by usingfreeze-drying method and then extracted using 80% methanol. The extracted samples were analyzed using the enzyme immunosorbent assay (EIA) method. The results showed during the week day was 107.1 ± 7.01 ng/gr dry feces, while the week end was 119.95 ± 4.3 ng/gr dry feces. Based on the results of the study, it can be concluded that there is no difference in the hormone triiodothyronine in female iguanas during weekday and weekend

Long-term effects of in ovo exposure to an environmentally relevant dose of atrazine on the thyroid gland of Caiman latirostris

The increased incidence of human thyroid disorders, particularly in women, suggests that the exposure to endocrine-disrupting compounds (EDCs) together with sex-related factors could play a role in thyroid dysregulation. Since the herbicide atrazine (ATZ) is an environmental EDC suspected to behave as a thyroid disruptor, and Caiman latirostris is a crocodilian species highly sensitive to endocrine disruption that can be exposed to ATZ, this study aimed to describe the histoarchitecture and sexually dimorphic features of the thyroid gland of C. latirostris, and to determine the long-term effects of in ovo exposure to an environmentally relevant dose of ATZ (0.2 ppm) on its thyroid gland and growth. Control caimans showed no sexual dimorphisms. In contrast, ATZ-exposed caimans showed altered embryo growth but an unaltered temporal pattern of development and a sexually dimorphic response in the body condition index growth curves postnatally, which suggests a female-related increase in fat storage. Besides, both male and female exposed caimans showed increases in the size of the thyroid stromal compartment, content of interstitial collagen, and follicular hyperplasia, and decreases in the expression of androgen receptor in the follicular epithelium. ATZ-exposed females, but not males, also showed evidences of thyroid enlargement, colloid depletion, increased follicular epithelial height and increased presence of microfollicular structures. Our results demonstrate that prenatal exposure of caimans to ATZ causes thyroid disruption and that females were more vulnerable to ATZ than males. The effects were organizational and observed long after exposure ended. These findings alert on ATZ side-effects on the growth, metabolism, reproduction and development of non-target exposed organisms, particularly females.

A comparison of thyroid hormone levels and plasma capillary zone electrophoresis in red-eared sliders (Trachemys scripta elegans) and map turtles (Graptemys spp.) depending on season and sex

BACKGROUND

Thyroid hormones and capillary zone electrophoresis are rarely studied in reptile medicine.

OBJECTIVES

The goal of this prospective study was to establish RIs for plasma proteins and thyroid hormones, total tetraiodothyronine (tT4), free T4 (fT4), total triiodothyronine (tT3), and free T3 (fT3), as well as iodine blood levels in red-eared sliders (Trachemys scripta elegans) and map turtles (Graptemys spp.).

METHODS

Variables were measured over 1 ½ years to determine variations depending on sex and season, as well as any correlations between the parameters. A total of 131 blood samples from red-eared sliders and 51 blood samples from map turtles were collected from May 2016 to November 2017. The levels of tT4, fT4, and fT3 were measured using standardized autoanalyzer test systems; tT3 was measured by ELISA and iodine inductively coupled plasma mass spectrometry. Total protein was quantitated using the biuret method, and plasma protein fractions were measured using capillary zone electrophoresis.

RESULTS

The results showed significant variations in thyroid hormone levels and plasma protein fractions depending on sex and season. Total T4 and fT4 concentrations were significantly (P < .05) correlated in both turtle species and sexes in all seasons. Thyroid hormone levels correlated with blood proteins in a few seasons, including a positive correlation between tT4 and fT4 in female red-eared sliders in fall and female map turtles in summer and fall.

CONCLUSIONS

This study demonstrates the importance of considering species, season, and sex variations when interpreting thyroid hormone and plasma protein levels. It also shows that thyroid hormone levels are not always influenced by total protein and albumin.

Applicability of Thyroxine Measurements and Ultrasound Imaging in Evaluations of Thyroid Function in Turtles

Introduction

The thyroid and parathyroid glands play a major role in maintaining physiological homeostasis in all vertebrates. Reptiles have plasma concentrations of thyroid hormones far lower than mammals. Low levels of these hormones in reptiles impede thyroid hormone detection with assays designed for the higher levels of mammals. The aim of this study was to explore teaming this with ultrasound imaging of the thyroid to appraise glandular function.

Material and Methods

Thyroid function of four pond sliders was evaluated based on the results of T4 analyses and ultrasound.

Results

The concentrations of T4 varied considerably between the examined animals from <9 nmol/L to >167.3 nmol/L. Ultrasound examination revealed uniform echogenicity and a smooth outline of the thyroid gland in all animals.

Conclusion

Monitoring of thyroid function based on T4 and electrolyte concentrations is helpful in assessing the health and living conditions of reptiles, which is important in veterinary practice but problematic. Ultrasound examinations are useful in diagnosing changes in gland structure, such as tumours and goitres, and a combination of both methods supports comprehensive assessments of the anatomy and function of the thyroid gland.

Seasonal changes in plasma concentrations of the thyroid, glucocorticoid and reproductive hormones in the tegu lizard Salvator merianae

The tegu lizard Salvator merianae is a large, widely distributed teiid lizard endemic to South America that exhibits annual cycles of high activity during the spring and summer, and hibernation during winter. This pattern of activity and hibernation is accompanied by profound seasonal changes in physiology and behavior, including endothermy during the austral spring. The unusual combination of seasonal endothermy, hibernation and oviparity, in a non-avian, non-mammalian species, makes S. merianae an interesting subject for study of comparative aspects of endocrine regulation of seasonal changes in physiology. In the present study, we first validated commercially available immunoassay kits for quantification of hormone concentrations of the reproductive (testosterone, estradiol and progesterone), adrenal (corticosterone), and thyroid [thyroxine (T₄) and triiodothyronine (T₃)] axes in plasma of an outdoor, captive adult male and female S. merianae in southeastern Brazil. All assays exhibited parallelism and accuracy with S. merianae plasma. We next assessed patterns of concentration of these hormones across the annual cycle of S. merianae. Testosterone in males and estradiol in females peaked in spring coincident with the peak in reproductive behavior. Progesterone in females was significantly elevated in October coincident with putative ovulation when gravid females build nests. Thyroid hormones, known for regulating energy metabolism, varied seasonally with some sex-dependent differences. T₄ gradually increased from an annual nadir during pre-hibernation and hibernation to high concentrations during spring in both sexes. In contrast, T₃ did not vary seasonally in males, but females showed a two-fold increase in T₃ during the spring reproductive season. T₃ may be involved in energy investment during the seasonal production of large clutches of eggs. Corticosterone was significantly elevated during the active season in both sexes, suggesting its involvement in mobilization of energy stores and modulation of behavior (territoriality) and physiology. Ours is the first investigation of concurrent changes in reproductive, thyroid and adrenal hormone concentrations in this endemic and physiologically unique South American lizard. Our findings set the stage for future investigations to determine the extent to which these hormones influence activity and thermoregulation in S. merianae.

Stereoselective degradation and thyroid endocrine disruption of lambda-cyhalothrin in lizards (Eremias argus) following oral exposure

The disturbance of the thyroid system and elimination of chiral pyrethroid pesticides with respect to enantioselectivity in reptiles have so far received limited attention by research. In this study, bioaccumulation, thyroid gland lesions, thyroid hormone levels, and hypothalamus-pituitary-thyroid axis-related gene expression in male Eremias argus were investigated after three weeks oral administration of lambda-cyhalothrin (LCT) enantiomers. In the lizard liver, the concentration of LCT was negatively correlated with the metabolite-3-phenoxybenzoic acid (PBA) level during 21 days of exposure. (+)-LCT exposure induced a higher thyroid follicular epithelium height than (-)-LCT exposure. The thyroxine levels were increased in both treated groups while only (+)-LCT exposure induced a significant change in the triiodothyronine (T3) level. In addition, the expressions of hypothalamus-pituitary-thyroid axis-related genes including thyroid hormone receptors (trs), deiodinases (dios), uridinediphosphate glucuronosyltransferase (udp), and sulfotransferase (sult) were up-regulated after exposure to the two enantiomers. (+)-LCT treatment resulted in higher expression of trs and (-)-LCT exposure led to greater stimulation of dios in the liver, which indicated PBA-induced antagonism on thyroid hormone receptors and LCT-induced disruption of thyroxine (T4) deiodination. The results suggest the (-)-LCT exposure causes higher residual level in lizard liver while induces less disruption on lizard thyroid activity than (+)-LCT.

Endocrine responses to diverse stressors of capture, entanglement and stranding in leatherback turtles (Dermochelys coriacea)

Leatherback turtles (Dermochelys coriacea) are exposed to many anthropogenic stressors, yet almost no data on stress physiology exist for this species. As a first step toward understanding the physiological responses of leatherback turtles to stress, and with the particular goal of assessment of the effect of capture, we quantified corticosterone (an adrenal stress hormone) and thyroxine (a regulator of metabolic rate, often inhibited by chronic stress) in 17 healthy leatherback turtles captured at sea for scientific study, with comparisons to 15 'distressed' leatherbacks that were found entangled in fishing gear (n = 8), confined in a weir net (n = 1) or stranded on shore (n = 6). Distressed leatherbacks had significantly elevated corticosterone (mean ± SEM 10.05 ± 1.72 ng/ml, median 8.38 ng/ml) and free thyroxine (mean 0.86 ± 0.37 pg/ml, median 0.08 pg/ml) compared with healthy leatherbacks sampled immediately before release (after ∼40 min of handling; corticosterone, mean 4.97 ± 0.62 ng/ml, median 5.21 ng/ml; and free thyroxine, mean 0.05 ± 0.05 pg/ml, median 0.00 pg/ml). The elevated thyroxine in distressed turtles compared with healthy turtles might indicate an energetic burden of entanglement and stranding. Six of the healthy leatherbacks were sampled twice, at ∼25 and ∼50 min after the time of first disturbance. In all six individuals, corticosterone was higher in the later sample (earlier sample, mean 2.74 ± 0.88 ng/ml, median 2.61 ng/ml; later sample, mean 5.43 ± 1.29 ng/ml, median 5.38 ng/ml), indicating that capture and handling elicit an adrenal stress response in this species. However, the corticosterone elevation after capture appeared relatively mild compared with the corticosterone concentrations of the entangled and stranded turtles. The findings suggest that capture and handling using the protocols described (e.g. capture duration <1 h) might represent only a mild stressor, whereas entanglement and stranding might represent moderate to severe stressors.

Vesicular, ulcerative, and necrotic dermatitis of reptiles

Vesicular, ulcerative, and necrotic dermatologic conditions are common in captive reptiles. Although these conditions have distinct differences histologically, they are commonly sequelae to each other. This article examines the anatomy and physiology of reptile skin; discusses reported causes of vesicular, ulcerative, and necrotic dermatologic conditions; and reviews various management options.

Synergistic limits to the altitudinal distribution of a high-altitude lizard, Takydromus hsuehshanensis

The geographic distribution of species can be affected by environmental factors. The adult highaltitude lizard Takydromus hsuehshanensis (altitude > 1800 m) has been shown to tolerate summer lowland air temperature; its absence in lowland areas may therefore be caused by other factors. We employed a transplant experiment to monitor survival in different life stages and female reproduction in lowland areas. We maintained the T. hsuehshanensis adults in semi-natural outdoor enclosures with sufficient food, water, and the exclusion of potential predators. The results showed that (1) the survival rates of adults gradually decreased to 23.4% from one summer to the next, (2) illness occurred in adults during the winter, and (3) reproductive capacity (2 eggs/female), hatching success (31.7%), and hatchling survival rate (0% at the end of 11 weeks) were very low during the active season. We suggest that environmental factors synergistically caused these impairments in T. hsuehshanensis across different life stages and different seasons. This may partially explain its current altitudinal distribution.

Corticosterone and thyroxine in cold-stunned Kemp's ridley sea turtles (Lepidochelys kempii)

Kemp's ridley sea turtles (Lepidochelys kempii), a critically endangered species, frequently strand on the shores of Cape Cod (Massachusetts, USA) in late autumn in a state of "cold-stunning" exhibiting low body temperature and related clinical issues. Stranded turtles are transported to the New England Aquarium (Boston, Massachusetts, USA) for treatment and rehabilitation. This study tested the hypothesis that cold-stunned sea turtles might exhibit high corticosterone ("stress hormone") or low thyroxine (which is often affected by temperature), or both, and that monitoring of both hormones may be useful for assessing recovery. In a retrospective analysis, 87 archived plasma samples were assayed from 56 cold-stunned juvenile Kemp's ridley sea turtles for corticosterone and free thyroxine (fT4). Upon admission, mean corticosterone was the highest yet reported for a population of sea turtles (39.3 +/- 2.5 ng/ml; mean +/- standard error of the mean [SEM]) and fT4 was usually undetectable. On admission, corticosterone was negatively correlated with white blood cell count but was not correlated with blood glucose. There were no differences in either hormone between survivors and nonsurvivors on admission. After 18+ days in recovery, surviving turtles' corticosterone dropped significantly to levels typical of baseline in other species (0.9 +/- 1.0 ng/ml) while fT4 increased significantly (1.3 +/- 1.5 pg/ml). During recovery, corticosterone was positively correlated with blood glucose and was not correlated with white blood cell count. Turtles that showed persistent deficits in feeding, activity, or both during recovery had significantly lower fT4 than did turtles with no such deficits. The "high corticosterone, low fT4" endocrine profile seen on admission may be a useful marker of cold-stunning in this and other species. Further studies are necessary to determine whether low thyroid hormones play a causal role in deficits in feeding and activity during recovery. Monitoring of both hormones may be useful for triage, monitoring of recovery, and assessing readiness for release.

Ultrastructural studies of cilia formation during thyroid gland differentiation in grass snake embryos

The process of ciliogenesis that accompanies the differentiation of the thyroid gland in grass snake Natrix natrix L. embryos was studied ultrastructurally. Based on this study, it can be concluded that the ciliogenesis occurred in two waves and that new centrioles duplicated via centriolar pathways. The first wave of ciliogenesis started in the post-mitotic thyrocytes before their polarisation. It ended approximately halfway through the developmental period. The second wave of ciliogenesis took place after the polarization of thyrocytes and before the resting phase of the embryonic thyroid. This wave of ciliogenesis stopped shortly before hatching when fully differentiated thyrocytes restarted their activity. During the first half of thyroid differentiation, the cilia were formed "intracellularly" but during the second half, they differentiated "extracellularly" In the differentiating thyrocytes one cilium per cell was found; however, it could not be excluded that more than one cilium per cell may be formed. These cilia lacked central fibres and therefore they had a 9+0 formula that suggested that they were immotile.

Proliferative thyroid lesions in three diplodactylid geckos: Nephrurus amyae, Nephrurus levis, and Oedura marmorata

Over a 5-mo period, three diplodactylid geckos housed at the National Aquarium were diagnosed with proliferative thyroid lesions: a rough knob-tail gecko (Nephrurus amyae), a smooth knob-tail gecko (Nephrurus levis), and a marbled velvet gecko (Oedura marmorata). Clinical signs included an intraoral mass or ventral throat swelling (or both), oral bleeding, and weight loss. Both of the knob-tail geckos died. The histologic diagnosis for the rough knob-tail gecko was thyroid carcinoma with metastases to the liver and lungs, and thyroid carcinoma with no metastases was reported in the smooth knob-tail gecko. A thyroidectomy was performed on the marbled velvet gecko with a histologic diagnosis of adenomatous hyperplasia. Postoperative weight loss and bradycardia resolved following oral supplementation with levothyroxine. The animal is in normal health 10 mo post-surgery. Five other diplodactylid geckos in the collection remain unaffected, giving a 38% prevalence of proliferative thyroid lesions (3/8). The etiology remains undetermined. This is the first report of a cluster of proliferative thyroid lesions in geckos.

A survey of the husbandry of captive tuatara (Sphenodon spp.) in relation to factors implicated in nutritional secondary hyperparathyroidism

AIM

To examine selected aspects of the diet and husbandry of captive tuatara (Sphenodon spp.) in New Zealand, in order to develop recommendations on provision of ultraviolet B light and diet, to reduce the incidence of nutritional secondary hyperparathyroidism (NSHP).

METHODS

Information was collected from 18/20 institutions holding tuatara in New Zealand, on the numbers kept, dimensions and type of enclosures, and type of light sources used. Historical information on breeding activity and problems known to be associated with NSHP, and standardised measurements of levels of ultraviolet B light in enclosures were also recorded. Diet samples were collected (n=17) and analysed for Ca, P and vitamin D content.

RESULTS

The intensity of ultraviolet B light was lower where there was a history of previous high, compared with medium or low, risk of NSHP for tuatara kept indoors (p>0.001). Light sources varied significantly in both output of ultraviolet B light (spectral irradiance) at the source, and fractional reduction in electromagnetic fluence with increasing distance from the source. The average exposure to ultraviolet B light of captive tuatara kept indoors was 26.44 (SE 4.29) microW/cm2, and there was significant variation between enclosures, with 4/14 (29%) institutes having no measurable ultraviolet B light present. For tuatara kept outdoors ultraviolet B light at ground level was influenced by weather conditions (p< or =0.007), roofing material (p=0.004), and substrate shading (p=0.003). The Ca:P ratio of dietary samples was 2.3 (SE 1.9), but this included one extreme outlier (32.7). When the outlier was excluded, it was 0.53 (SE 0.16). The levels of vitamin D in the feed samples were below the minimum detectable level of the assay (<20 IU/100 g) for all but one sample (72 IU/100 g) that had been dusted with vitamin/mineral supplement prior to freezing.

CONCLUSIONS AND CLINICAL RELEVANCE

The current diet and husbandry of captive tuatara in New Zealand predisposes the animals to NSHP. The ultraviolet B light emitted from commercial light sources dissipates rapidly with increasing distance from the source. Regular direct measurement of ultraviolet B light at substrate level is recommended for indoor enclosures, whereas tuatara kept outdoors should have access to an unshaded basking area through a wire-meshed roof. The Ca:P ratio and concentration of vitamin D of most common food items fed to tuatara is deficient, and reptile vitamin and mineral supplements should be provided by dusting or gut-loading insect food items.