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

A mystery revealed: an update on eosinophil and other blood cell morphology of the Argentine black and white tegu (Salvator merianae)

Reptile white blood cell (WBC) morphological features are strikingly variable across species. In the Argentine black and white tegu (Salvator merianae), red tegu (Salvator rufescens), and Savannah monitor (Varanus exanthematicus), previous reports described a WBC type with a single distinct, clear, linear- to ovoid- to crescent-shaped inclusion of presumptive monocytic origin. The objective of this study was to further investigate the origin of this unique WBC type with crescent-shaped inclusions. Blood samples from two Argentine black and white tegus, tegu 1, a 4-year-old female, and tegu 2, a 2-year-old presumed male, were submitted for routine hematological evaluation. Additional blood films were prepared and stained with these cytochemical stains: alkaline phosphatase (ALP; naphthol AS-MX phosphate substrate), alpha-naphthyl butyrate esterase, alpha-chloroacetate esterase, myeloperoxidase, Periodic acid-Schiff, and Sudan black B. Blood films from tegu 1 were also stained with a second ALP stain (5-bromo-4-chloro-3-indoxyl-phosphate and nitroblue tetrazolium substrate), Luna, luxol fast blue, and toluidine blue. The blood from tegu 1 was cytocentrifuged to isolate and fix the buffy coat in glutaraldehyde 2.5% aqueous solution for transmission electron microscopy. Six morphologically distinct WBC types were identified from tegu 1, including heterophils, basophils, monocytes, azurophils, lymphocytes, and the unique WBC type, which were identified as eosinophils with inclusions. WBC types in tegu 2 were similar; however, eosinophils lacked a discernable inclusion. Proper WBC identification will be useful in obtaining accurate hemogram data for this species.

Morphological and cytochemical characteristics of Varanus niloticus (Squamata, Varanidae) blood cells

Varanus niloticus is a lizard residing within the Varanidae family. To date no studies detailing its blood morphology and characteristics have been conducted. This study used histologically stained blood and bone marrow samples to visualize the cells and their characteristics. The erythrocytes were nucleated, these nuclei were located in the middle of the elliptical cells. Hemoglobin filled the erythrocyte cytoplasm. Eosinophils were large cells with lobed nuclei and spherical acidophilic granules. Large granulocytes called heterophils were present and characterized by their fusiform/pleomorphic cytoplasmic granules. Small spherical granulocytes, known as basophils, presented with round, deeply stained metachromatic granules that gave the cytoplasm a dusty or cobblestoned appearance which was able to cover the nucleus, which in turn had an unusual shape. Thrombocytes ranged in shape from ellipsoidal to fusiform. They featured an elliptical, centrally located nucleus and a pale cytoplasm, with small vacuoles, and fine acidophilic granulation. The smallest variety of non-granular leukocytes was the lymphocytes. Their cytoplasm was sparse, finely granular, light blue, had tiny cytoplasmic projections, featuring a high nucleus: cytoplasm ratio. Larger and smaller sized populations of lymphocytes were distinguished, with the larger cells similar in size to azurophils. In general, the pleomorphic monocytes were the biggest mononuclear leucocytes, displaying cytoplasmic projections. Their nuclei were ovoid, kidney- or bean-shaped, with vacuolated and granular cytoplasms. Round cells were common among the monocytic azurophils, and they had a granular cytoplasm, and their nuclei were typically eccentric. The present research identifies the cell types and morphologies within the Varanus niloticus. HIGHLIGHTS: H&E, PAS, toluidine blue, methylene blue, and Safranin O stains provided morphological and morphometric descriptions of Varanus niloticus blood cells from blood smears and bone marrow. The Varanus niloticus had nucleated erythrocytes and white blood cells, mostly granulocytes (heterophils, eosinophils, and basophils) and mononuclear cells (azurophils, lymphocytes, and monocytes). Aquatic vertebrate Varanus niloticus had larger erythrocytes than terrestrial counterparts. Blood cell morphological and cytochemical features were similar to other reptilian species, with some species-specific differences, which likely accommodate differing environmental conditions. These results may help clinical researchers track the pathological conditions and support conservation of these wild animals.

Haematology, biochemistry and morphological features of peripheral blood cells in captive Boa constrictor

The common boa (Boa constrictor) belongs to the family Boidae and represents one of the most popular traded and kept snake species in captivity. The early diagnosis, prevention and prophylaxis of diseases in this species, and in reptiles in general, still pose major challenges, also due to the lack of reliable reference values. This prompted us to conduct a study on clinically healthy captive B. constrictor to assess their basic health parameters in the blood (haematological and biochemical values, stress markers). Several parameters differed significantly between younger (<3 years) and older (≥3 years) boas; in the latter, the percentages of eosinophils, the haemoglobin and haematocrit levels, as well as the albumin and total protein levels, were higher. In male snakes, cholesterol levels were significantly higher than in females. Light and electron microscopy as well as immunohistochemistry served to identify and determine the morphological features of peripheral blood cells, that is, heterophils, basophils, eosinophils, azurophils, monocytes, lymphocytes, thrombocytes and erythrocytes. Leukocyte subpopulations, that is, T and B cells and monocytes, were also identified based on specific marker expression. The study provides data on haematological, biochemical and stress hormone levels, suitable as reference values, and on the blood cell morphology of B. constrictor which can serve as a guideline for further research on this species.

Morphology and cytochemical patterns of peripheral blood cells of tiger frog (Rana rugulosa)

Background

Tiger frog (Rana rugulosa) is a national second-class protected amphibian species in China with an important ecological and economic value. In recent years, due to excessive human hunting, pollution and habitat loss, the wild population of tiger frog has declined sharply. To protect wildlife resources, the artificial breeding of tiger frogs has rapidly developed in China. Diseases are increasing and spreading among tiger frogs due to the increasing scale of artificial farming. The blood examination is the most straightforward and less invasive technique to evaluate the animal health condition. Thus, it is essential to obtain the normal hematological indicators of tiger frogs. The objective of this study was to investigate the morphometry, microstructure and cytochemical patterns of peripheral blood cells in tiger frogs.

Methods

The number of blood cells in tiger frogs was counted on a blood count board, and the cell sizes were measured by a micrometer under light microscope. The morphology and classification of blood cells were studied by Wright-Giemsa staining, and the cytochemical pateerns was investigated by various cytochemical staining including periodic acid-Schiff (PAS), Sudan black B (SBB), peroxidase (POX), alkaline phosphatase (AKP), acid phosphatase (ACP), chloroacetic acid AS-D naphthol esterase (CAE) and α-naphthol acetate esterase (ANAE) staining.

Results

Besides erythrocytes and thrombocytes, five types of leukocytes were identified in tiger frogs: neutrophils, eosinophils, basophils, lymphocytes and monocytes. The mean erythrocyte, leukocyte and thrombocyte counts were 1.33 ± 0.15 million/mm³, 3.73 ± 0.04 × 10⁴/mm³ and 1.7 ± 0.01 × 10⁴/mm³, respectively. Small lymphocytes were the most abundant leukocytes, followed by large lymphocytes, Neutrophils, eosinophils and monocytes, basophils were the fewest. Eosinophils were strongly positive for PAS, positive for SBB, POX, ACP, CAE, ANAE, while weakly positive for AKP staining; basophils were strongly positive for PAS, ACP, positive for SBB, CAE, weakly positive for ANAE, negative for AKP, POX staining; neutrophils were strongly positive for ACP, SBB, positive for PAS, POX, weakly positive for AKP, CAE and ANAE staining; monocytes were positive for PAS, SBB, ANAE, weakly positive for ACP, AKP, POX, CAE staining; large lymphocytes and thrombocytes were positive for PAS, ACP, weakly positive for ANAE, while negative for SBB, POX, AKP, CAE; small lymphocytes were similar to large lymphocytes, except for strongly positive for PAS and ACP staining.

Conclusions

The blood cell types and morphology of tiger frogs were generally similar to those of other amphibians, while their cytochemical patterns had some notable species specificity.Our study could enrich the knowledge of peripheral blood cell morphology and cytochemistry in amphibians, and provide baseline data for health condition evaluation and disease diagnosis of tiger frogs.

Statistical methodology for the evaluation of leukocyte data in wild reptile populations: A case study with the common wall lizard (Podarcis muralis)

The leukocyte profile has the potential to be a reliable method to measure health conditions and stress in wild animals, but limitations occur because current knowledge on reference intervals is largely incomplete, especially because data come from studies on captive animals involving few individuals from single populations. Here we propose a general framework for achieving reliable leukocyte reference intervals, encompassing a set of internal and external factors, potentially affecting the leukogram. To do so, we present a systematic survey of the hematology of the common wall lizard, Podarcis muralis, involving 794 lizards from 54 populations over the whole geographic range of the species in Italy. Reference intervals for white blood cell (WBC) and leukocyte differential count were obtained by using linear mixed models in a Bayesian framework. The application of the procedure clearly showed that both internal (sex and size) and external (latitude and season) factors are a source of variation of leukocyte profile. Furthermore, the leukogram of common wall lizard has a strong variability among populations, which accounts for more than 50% of the whole variation. Consequently, some common assumptions used in studies on captive individuals are no longer supported in wild populations, namely, i) any group of individuals is a representative sample, ii) any population is representative of all others, iii) geographic clines do not occur over the species range, and iv) seasonal variation has limited effects. We encourage researchers aimed at the definition of leukocyte reference intervals for wild populations of reptiles to involve a large number of populations over a wide geographic range in ad hoc statistical models to disentangle local and geographic effects on leukocyte profile variation.

Morphology and cytochemical patterns of peripheral blood cells in domestic pigeon (Columba livia)

Domestic Pigeon (Columba livia) is one of few domesticated birds with an important economic value. In this study, a comprehensive investigation on the morphology and cytochemical patterns of peripheral blood cells in domestic pigeons were conducted by using wright's and various cytochemical staining techniques including periodic acid-Schiff(PAS), sudan black B(SBB), peroxidase(POX), alkaline phosphatase(ALP), acid phosphatase(ACP), chloroacetic acid AS-D naphthol esterase(AS-D) and α-naphthol acetate esterase(α-NAE) staining. Besides erythrocytes and thrombocytes, five types of leukocytes were identified: heterophils, eosinophils, basophils, lymphocytes and monocytes. Lymphocytes were the most abundant leukocytes, followed by heterophils, eosinophils, monocytes; basophils were the fewest. Erythrocytes and thrombocytes were positive for PAS, and negative for all the other cytochemical staining. Heterophils and eosinophils exhibited positive to all cytochemical staining except for α-NAE. Basophils exhibited strongly positive for POX and AS-D, positive for PAS and ALP, while negative for SBB, ACP and α-NAE staining. Monocytes exhibited positive for PAS and α-NAE, and weakly positive for ACP, while negative for SBB, POX, ALP and AS-D staining. Lymphocytes showed positive for PAS and ACP, weakly positive for AS-D, while negative for SBB, POX, ALP and α-NAE staining. Our results add up knowledge about the domestic pigeon blood cells.

Cytochemical patterns of the peripheral blood cells in Chinese alligator (Alligator sinensis)

The Chinese alligator (Alligator sinensis) is an endemic rare crocodilian species in China. In this study, we investigated the cytochemical patterns of peripheral blood cells in Chinese alligators for the first time by a range of cytochemical staining techniques including periodic acid-Schiff(PAS), sudan black B(SBB), peroxidase(POX), alkaline phosphatase(AKP), acid phosphatase(ACP), chloroacetic acid AS-D naphthol esterase(AS-D) and α-naphthol acetate esterase(α-NAE) staining. Erythrocytes were positive for PAS, and negative for all the other staining; heterophils were strongly positive for SBB, POX, ACP, AKP, AS-D and α-NAE, while weakly positive for PAS staining; eosinophils were strongly positive for PAS, POX, AKP, ACP and AS-D, and weakly positive for SBB and α-NAE staining; basophils were strongly positive for PAS, positive for POX, ACP, AKP and α-NAE, and weakly positive for AS-D, while negative for SBB staining; monocytes were weakly positive for PAS, ACP, AKP and α-NAE, while negative for SBB, POX and AS-D staining; lymphocytes were weakly positive for PAS and α-NAE, negative for all the other staining; thrombocytes were weakly positive for PAS, and negative for all the other staining. Our results add up knowledge about Chinese alligator blood cells.

Unraveling avian and reptilian hematology: An optical and electron microscopic study of the buffy coat

BACKGROUND

Blood centrifugation and buffy coats are at the cornerstone of hematology. In mammals, the buffy coat has a layered disposition (from bottom to top) with neutrophils on top of erythrocytes, followed by monocytes/lymphocytes, and platelets. In nonmammals, this distribution is unknown. Recently, the cell tube block (CTB) technique was developed to study the buffy coat, but it was never applied to nonmammal buffy coats.

OBJECTIVES

This study aimed to evaluate using the CTB technique to study reptilian and avian buffy coats and to propose its use for clinical applications.

METHODS

Blood from five birds and eight reptiles of different species was obtained to make CTBs that were processed for optical/electron microscopy. H&E, Sirius red, and immunohistochemistry staining against CD3 (to label T lymphocytes) were applied to the CTBs.

RESULTS

In birds, the buffy coat had a layered appearance with the granulocyte layer containing granulocytes (heterophils and eosinophils) and nucleated erythrocytes followed by a mononuclear cell layer containing lymphocytes, monocytes, and thrombocytes. In some animals, a nucleated erythrocyte layer was observed admixed with the granulocyte/mononuclear cell layer. A small clot within the buffy coat was seen in seven reptiles, and less definition of layers occurred in reptiles, with only one or two layers. Lymphocytes appeared toward the top of the buffy coat.

CONCLUSIONS

From a comparative hematology perspective, the buffy coat of mammals differs from that of birds and more from that of reptiles. The CTB technique can be used to study these differences in avian and reptilian hematology, especially to study atypical circulating cells, hemoparasites, or blood cell proportions in health and disease.