Morphological, cytochemical, and ultrastructural observations on the blood cells of the reptile Tupinambis merianae (Squamata)

The hematology of captive Bobtail lizards (Tiliqua rugosa): blood counts, light microscopy, cytochemistry, and ultrastructure

INTRODUCTION

Bobtail lizards (Tiliqua rugosa) are native to Australia. The only previous study on the hematology of this species documented just 6 animals.

OBJECTIVES

The aims of this study were to characterize the light microscopy, ultrastructure and cytochemistry of blood cells, and evaluate CBCs of captive Bobtail lizards.

METHODS

Over 2 consecutive summers, heparinized venous blood was collected from the ventral coccygeal vein of 46 clinically healthy, captive indoor- or outdoor-housed adult Bobtails. Complete blood cell counts and smear evaluations were performed, and cytochemical stains and transmission electron microscopy were used to further characterize blood cells.

RESULTS

The eosinophils of this species were uniformly vacuolated: a unique feature not previously reported in reptiles. Heterophils were the predominant leukocyte, with fewer lymphocytes, azurophilic and nonazurophilic monocytes, occasional eosinophils, and basophils. Thrombocytes were frequently clumped. Slight polychromasia (0-15% of erythrocytes) was typically present. Hemogregarine parasites were seen on some smears. The range of CBC results was often wide. The PCV ranged from 11% to 38%. Total plasma proteins by refractometry were between 3.5 and 7.8 g/dL. Hemoglobin ranged between 2.6 and 12.6 g/dL by the modified hemoglobin-hydroxylamine method. Manual RBC count was 0.35-1.27 × 10⁶ /μL, and WBC count was 2.86-22.66 × 10³ /μL. Bobtail lizards housed outdoors had lower PCVs than indoor-housed animals. Bobtails with hemogregarine infections had lower PCVs than noninfected lizards.

CONCLUSIONS

Ranges for CBC data were often very wide, influenced by preanalytic and analytic factors. Hemogregarine infection is associated with a decreased PCV, suggesting that some hemogregarine species are pathogenic in this population.

Quantitative and qualitative morphologic, cytochemical, and ultrastructural characteristics of blood cells in captive Asian water monitors

BACKGROUND

The Asian water monitor (Varanus salvator) is the most common monitor lizard in Thailand. Reported data regarding hematology and morphology of blood cells for this species are scarce.

OBJECTIVES

The objective of this study was to assess routine hematologic variables and characterize the morphology, cytochemical staining, and ultrastructural features of blood cells in the Asian water monitor.

METHODS

Blood samples from 55 monitors (22 males and 33 females) were obtained for a CBC. Cytochemical staining (Sudan black B [SBB], peroxidase [PO], α-naphthyl acetate esterase [ANAE], and beta-glucuronidase [BG]), and scanning and transmission electron microscopy were performed using standard methods.

RESULTS

Determined mean (range) hematologic results of all monitors included PCV 0.32 L/L (0.20-0.44 L/L), HGB 106 g/L (62-157 g/L), WBC 15.9 × 10(9) /L (4.0-34.0 × 10(9) /L), heterophil 6.3 × 10(9) /L (1.5-17.1 × 10(9) /L, azurophil 2.6 × 10(9) /L (0.7-9.5 × 10(9) /L), basophil 0.1 (0.1-0.5 × 10(9) /L), lymphocyte 6.8 × 10(9) /L (0.5-13.1 × 10(9) /L), and monocyte 0.2 × 10(9) /L (0.04-1 × 10(9) /L) counts. Heterophils and basophils stained strongly positive with SBB, ANAE, and BG. Heterophils contained 2 types of granules, round SBB-positive and PO-negative granules, and electron-dense, large rod-shaped granules. Gamonts of Hepatozoon sp. were found in <1% RBC of 43 monitors. There was no significant difference between hematologic variables in Hepatozoon-positive and -negative monitors.

CONCLUSION

Heterophils in Asian water monitors may also function as eosinophils based on cytochemical and ultrastructural features. The quantitative results may be used as base for further studies in healthy and diseased Asian water monitors.

Understanding the ecological niche to elucidate spatial strategies of the southernmost Tupinambis lizards

Understanding factors that shape ranges of species is central in evolutionary biology. Species distribution models have become important tools to test biogeographical, ecological and evolutionary hypotheses. Moreover, from an ecological and evolutionary perspective, these models help to elucidate the spatial strategies of species at a regional scale. We modelled species distributions of two phylogenetically, geographically and ecologically close Tupinambis species (Teiidae) that occupy the southernmost area of the genus distribution in South America. We hypothesized that similarities between these species might have induced spatial strategies at the species level, such as niche differentiation and divergence of distribution patterns at a regional scale. Using logistic regression and MaxEnt we obtained species distribution models that revealed interspecific differences in habitat requirements, such as environmental temperature, precipitation and altitude. Moreover, the models obtained suggest that although the ecological niches of Tupinambis merianae and T. rufescens are different, these species might co-occur in a large contact zone. We propose that niche plasticity could be the mechanism enabling their co-occurrence. Therefore, the approach used here allowed us to understand the spatial strategies of two Tupinambis lizards at a regional scale.

Wounding in lizards results in the release of beta-defensins at the wound site and formation of an antimicrobial barrier

After tail loss in lizards no infections occur indicating the presence of an effective anti-microbial barrier in the exposed tissues of the tail stump. Previous molecular studies on the lizard Anolis carolinensis have identified some beta-defensin-like genes and the deduced peptides that may be involved in anti-infective protection. The present study has analyzed the tissues of wounded and normal tails in lizards in order to immune-localize one of the beta-defensins previously found (AcBD15) and to detect variation in its gene expression during wounding. No immunoreactivity for this beta-defensin is present in normal tissues or in the epidermis of lizards, except for some sparse granulocytes. The latter are seen during the first 1-6 days after tail amputation and AcBD15 immunoreactivity is present in their granules. Degenerating granulocytes are incorporated, together with dead erythrocytes, platelets and keratinocytes into the scab. Real time RT-PCR and western blotting analysis indicates up-regulation of AcBD15 expression during wounding with respect to normal tissues, indicating that production, storage and release of this beta-defensin from granulocytes are active following wounding. The production of beta-defensins from granulocytes would allow protection of exposed tissues from microbial invasion avoiding a persistent inflammation, a process that leads to tissue regeneration.

Structure of capsule around acanthocephalan Corynosoma strumosum from uncommon paratenic hosts-lizards of two species

Micromorphology and ultrastructure of capsule forming around acanthocephalan Corynosoma strumosum in uncommon paratenic hosts-lizards Lacerta agilis and Lacerta viridis-have been studied. Experimental infestation of the lizards by acanthocephalans obtained from naturally infested sea fishes showed that only small amount of parasites occurred in the intestine of the host was able to migrate into body cavity and to be encapsulated. Micromorphology of capsules of different ages from different species of lizards and micromorphology and ultrastructure of capsules at the age of 1.5 and 10 days appeared to be similar. In the capsule's structure cells of inflammatory rank were prevailing: mononuclear and multinuclear macrophages, eosinophils, and basophils. Fibroblasts were not numerous and were located only in the outer part of a capsule; exocellular collagen fibers were absent. Inflammatory character of capsule confirms the idea that lizards are unsuitable paratenic hosts for corynosomes.