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

The effects of annual cycle, source population, and body condition on leukocyte profile and immune challenge in a basal reptile, the tuatara (Sphenodon punctatus)

Leukocyte profiles are broadly used to assess the health status of many species. Reference intervals, and an understanding of the factors that may influence these intervals, are necessary for adequate interpretation of leukograms. Using a data set that spans over three decades, we investigated variation in leukocyte profile in several populations of the evolutionarily unique reptile, the tuatara (Sphenodon punctatus). To do this, we first established reference intervals for each leukocyte type according to best practices. Next, we determined that source population and sampling date were the two most important predictors of leukocyte makeup. We found significant differences in the ratio of heterophils: lymphocytes (H:L) between populations, with tuatara on the more resource-stressed sampling island having a significantly higher ratio of H:L. Finally, we found that sampling location, sex, and life stage did not explain variation in the responses of tuatara to stimulation with Concanavalin A and lipopolysaccharide in both 3-(4,5-dimethylthiazol-2-yl)-2,5-di-phenyltetrazolium bromide and Griess assay experiments. Our results offer important insight into the function of leukocytes in reptiles.

Factors Predicting Apparent Ophidiomycosis in Wild Brown Watersnakes (Nerodia taxispilota)

Ophidiomycosis, also known as snake fungal disease, is caused by Ophidiomyces ophidiicola and is a threat to snake conservation worldwide. Ophidiomycosis has been reported throughout much of the eastern US, and outbreaks have been associated with local population declines of already strained populations. Previous studies report significant variability in ophidiomycosis among species sampled, with higher prevalence typically observed in Nerodia spp. Although ophidiomycosis can lead to morbidity and mortality in affected individuals, little is known about disease dynamics in free-ranging populations. Herein, we examine how individual-specific factors (e.g., life stage [immature, mature], contaminant status, sex, hemograms) may be associated with ophidiomycosis status in the brown watersnake (Nerodia taxispilota). During 2018-19, we sampled 97 N. taxispilota from five locations along the Savannah River in South Carolina and Georgia, US. Ophidiomyces ophidiicola DNA was detected in 66 snakes for a prevalence of 68% (95% confidence interval, 59-77). Mature snakes had a significantly higher risk of apparent ophidiomycosis (skin lesions present and quantitative PCR [qPCR], positive) relative to immature snakes. Snakes classified as having possible (skin lesions present, but qPCR negative) or apparent ophidiomycosis exhibited a relative azurophilia and heterophilia compared with individuals classified as negative (P≤0.037). Nerodia taxispilota in this region appear to have a high prevalence of apparent ophidiomycosis (22%; 95% CI, 14-31), similar to previous reports from the southeastern US. Additional epidemiologic investigations are warranted to further elucidate other individual-specific and environmental factors that may dictate disease risk and outcomes in affected populations.

Blood cells and hematological parameters of Chiala Mountain Salamander, Batrachuperus karlschmidti (Urodela, Hynobiidae)

Hematological parameters are essential indices for assessing the function of blood and reflecting not only the health status of animal but also their physiological adaptation to the environment. Herein, the composition of blood cells and the hematological parameters of wild Batrachuperus karlschmidti were examined for the first time, and the effects of sex, body size, body mass, and age on the hematological parameters were explored. The morphology and morphometric data of the blood cells, as well as the hematological parameters, of B. karlschmidti were slightly differ from those of its congener. However, hematological differences between sexes were only found in erythrocyte and leukocyte count, and mean cell volume (MCV), which possibly reflecting the need for better oxygen distribution and stronger immune protection for reproduction. Hematocrit (Hct) and mean cell hemoglobin (MCH) were strongly dependent on body mass. These also might have been attributed to higher oxygen requirements with larger body masses. This is a pilot project exploring the hematology of this species that may help establish hematological parameters in future for supporting species protection and monitoring studies, as well as help understanding the physiological adaptation of 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.

Haematological and biochemical reference intervals for wild green turtles (Chelonia mydas): a Bayesian approach for small sample sizes

Animal health is directly linked to population viability, which may be impacted by anthropogenic disturbances and diseases. Reference intervals (RIs) for haematology and blood biochemistry are essential tools for the assessment of animal health. However, establishing and interpreting robust RIs for threatened species is often challenged by small sample sizes. Bayesian predictive modelling is well suited to sample size limitations, accounting for individual variation and interactions between influencing variables. We aimed to derive baseline RIs for green turtles (Chelonia mydas) across two foraging aggregations in North Queensland, Australia, using Bayesian generalized linear mixed-effects models (n = 97). The predicted RIs were contained within previously published values and had narrower credible intervals. Most analytes did not vary significantly with foraging ground (76%, 22/29), body mass (86%, 25/29) or curved carapace length (83%, 24/29). Length and body mass effects were found for eosinophils, heterophil:lymphocyte ratio, alkaline phosphatase, aspartate transaminase and urea. Significant differences between foraging grounds were found for albumin, cholesterol, potassium, total protein, triglycerides, uric acid and calcium:phosphorus ratio. We provide derived RIs for foraging green turtles, which will be helpful in future population health assessments and conservation efforts. Future RI studies on threatened species would benefit from adapting established veterinary and biomedical standards.

Patterns of variations in dorsal colouration of the Italian wall lizard Podarcis siculus

Research on animal colouration has grown exponentially in the last decade thanks to multidisciplinary approaches. Most studies are focused on trade-offs between communication and mimicry, which represent the two main constraints and drivers of the evolution of body colourations. Reptiles are excellent model species for investigating this field of study and lizards in particular show great variability of body colourations and their functions. We studied the lizard Podarcis siculus, analysing the variations of dorsal colour of three populations and obtained clear patterns of seasonal and ontogenetical variation of dorsal colour. According to baseline colour, males were greener and brighter than females, although no difference in saturation was recorded. According to seasonal variations, analyses showed that both sexes significantly vary in colour over the year: males reached higher peaks of hue and saturation later than females during spring, while females showed higher peaks of brightness and reached earlier similarly to hue and saturation. Ontogenetic variations were recorded only in males, which become greener, less bright and saturated with growing size. Therefore, our results suggest the occurrence of two opposing strategies in colour expression between sexes: males’ dorsal colouration plays a major role in communication, while females are more crypsis-oriented.

Summary: This research paper focuses on the dorsal chromatic variations in Mediterranean lizards, analysing the effect of seasonality and ontogeny.

Hematology, Biochemistry Reference Intervals, and Morphological Description of Peripheral Blood Cells for a Captive Population of Crocodylus intermedius in Colombia

The Orinoco crocodile (Crocodylus intermedius, Graves, 1918) is the most threatened crocodilian of South America. There is only scarce information available about the physiology of this neotropical crocodile. This study aimed to propose baseline hematological and biochemistry reference data and intervals and a morphological description of the peripheral blood cells of captive C. intermedius. Blood was collected from 318 clinically healthy individuals maintained in captivity at Villavicencio, Colombia. Eight of these individuals were sampled and resampled, and these data were compared. Reference intervals were proposed for hematological values [packed cell volume (PCV), red blood cell count, white blood cell count, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, hemoglobin, and white blood cell count differential counts] and biochemistries [total solids, alanine aminotransferase (ALT), aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase, creatine kinase, glucose, albumin, cholesterol, uric acid, creatinine, and lactate] including adults and juveniles, males and females' crocodiles. Blood cell morphology for the species is described. Significant differences between sex and age were observed. The intraindividual analysis concluded differences for total solids (P ≤ 0.01) and red blood cell counts (P ≤ 0.01). Some biochemical analytes showed a moderate correlation between them, such as ALT–alkaline phosphatase and ALT–uric acid. We present here novel and baseline data with special importance for the clinical diagnosis, improving the national reintroduction programs from either in situ and ex situ populations.