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"Varanus."
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Mysteries of the Komodo dragon : the biggest, deadliest lizard gives up its secrets
\"For more than one hundred years, explorers have braved the dangers of Indonesia's Lesser Sunda Islands to study the deadly giant lizards that dwell there. With courage, determination, and luck, they are solving the mysteries of the Komodo dragon.\"--P. [4] of cover.
Book
Highly Differentiated ZW Sex Microchromosomes in the Australian Varanus Species Evolved through Rapid Amplification of Repetitive Sequences
Transitions between sex determination systems have occurred in many lineages of squamates and it follows that novel sex chromosomes will also have arisen multiple times. The formation of sex chromosomes may be reinforced by inhibition of recombination and the accumulation of repetitive DNA sequences. The karyotypes of monitor lizards are known to be highly conserved yet the sex chromosomes in this family have not been fully investigated. Here, we compare male and female karyotypes of three Australian monitor lizards, Varanus acanthurus, V. gouldii and V. rosenbergi, from two different clades. V. acanthurus belongs to the acanthurus clade and the other two belong to the gouldii clade. We applied C-banding and comparative genomic hybridization to reveal that these species have ZZ/ZW sex micro-chromosomes in which the W chromosome is highly differentiated from the Z chromosome. In combination with previous reports, all six Varanus species in which sex chromosomes have been identified have ZZ/ZW sex chromosomes, spanning several clades on the varanid phylogeny, making it likely that the ZZ/ZW sex chromosome is ancestral for this family. However, repetitive sequences of these ZW chromosome pairs differed among species. In particular, an (AAT)n microsatellite repeat motif mapped by fluorescence in situ hybridization on part of W chromosome in V. acanthurus only, whereas a (CGG)n motif mapped onto the W chromosomes of V. gouldii and V. rosenbergi. Furthermore, the W chromosome probe for V. acanthurus produced hybridization signals only on the centromeric regions of W chromosomes of the other two species. These results suggest that the W chromosome sequences were not conserved between gouldii and acanthurus clades and that these repetitive sequences have been amplified rapidly and independently on the W chromosome of the two clades after their divergence.
Journal Article
Endoscopic techniques for early diagnosis of cloacal pathologies and sex determination in blue spotted tree monitor (Varanus macraei) and Cuming's water monitor (Varanus cumingi)
This article attempts to present, for the first time, the usefulness and feasibility of using endoscopic techniques in the cloacal region of Varanus cumingi and Varanus macraei. This method can serve both diagnostic and therapeutic purposes, as well as offering an early approach to sex determination through the observation of the urodeum which in males ends in a blind end while in females it consists of two ostia which represent the outlets of the oviducts. In this context, commonly employed sex determination techniques, such as post-cloacal spur detection, have shown unreliability. The study involved the examination of ten specimens, approximately one year old, from a private breeding farm, following a complete clinical evaluation to confirm their general state of health. All subjects underwent sedation, which allowed the evaluation of anatomical structures, the health status of the cloaca and the determination of sex. This study and its findings may provide a critical basis for addressing population declines of these species, particularly for V. macraei, which has already been classified as 'endangered' by the IUCN.
Journal Article
Taxonomic status and phylogenetic relationships of the desert monitor Varanus griseus caspius (Squamata: Varanidae) from the territory of Uzbekistan
This study investigates the phylogenetic position and genetic diversity of Varanus griseus caspius, a widely distributed yet understudied subspecies of monitor lizard in Central Asia, with a focus on samples collected from Uzbekistan. Using DNA barcoding based on the mitochondrial cytochrome oxidase subunit I (COI) gene, molecular phylogenetic analyses were conducted via Maximum Likelihood (ML) and Bayesian Inference (BI) approaches. In addition, genetic distance and Disparity Index analyses were employed to assess evolutionary relationships among Varanus species. The V. g. caspius specimens formed a highly supported clade with V. griseus sequences in GenBank, indicating a close genetic affinity and confirming its subspecies status. Genetic distance values and substitution pattern similarities further revealed minimal divergence between V. g. caspius and other V. griseus lineages, suggesting recent common ancestry and ongoing gene flow. In contrast, significantly greater divergence was observed between V. g. caspius and other Varanus species. These findings clarify the phylogenetic placement of V. g. caspius within the V. griseus complex and provide essential baseline data for future taxonomic and conservation efforts.
Journal Article
A new blue-tailed Monitor lizard (Reptilia, Squamata, Varanus) of the Varanus indicus group from Mussau Island, Papua New Guinea
We describe a new species of Varanus from Mussau Island, north-east of New Guinea. The new species is a member of the Varanus indicus species group and is distinguished from all other members by both morphological and molecular genetic characters. It is the third species of Varanus reported from the Bismarck Archipelago and the first record of a yellow tongued member of the Varanus indicus species group from a remote oceanic island. The herpetofauna of Mussau Island has not been well studied but the discovery of this new species is in accordance with recent findings indicating that the island may harbor several unknown endemic vertebrates. The distribution of the closely related Varanus finschi is also discussed in the light of recent fieldwork and a review of old records.
Journal Article
Anticancer properties of peptides and protein hydrolysates derived from Asian water monitor (Varanus salvator) serum
This study investigated the anticancer efficacy of <3 kDa fractions derived from native peptides and protein hydrolysate of Varanus saltator serum. The inhibitory effects of these fractions were evaluated against a panel of cancer cell lines (A375, CaCO2, CAL27, NCI-H460, HeLa, HCT8, HT29, HepG2, KATO III, MCF-7, MDA-MB-231, Raw264.7, SKOV-3, SW620, T47D, and U937) and normal cell lines (HaCaT, MRC5, and Vero). Native peptides demonstrated higher anticancer activity compared to protein hydrolysates, inhibiting 16 cell lines and exhibiting high efficacy (≥70% inhibition) against CaCO2, CAL27, HaCaT, HT29, HepG2, MCF-7, MRC5, and U937. These native peptides were further fractionated by stepwise reverse-phase column chromatography. The hydrophilic (C18 unbound) peptide fraction exhibited greater anticancer activity than the hydrophobic (C18 bound) fraction. In addition, by LC-MS analysis, the peptide sequences were screening in silico . The predictions showed that 159 of the 432 Varanus peptides had the potential to be anticancer peptides (ACPs), of which the top twenty had a probability of more than 75%. The anticancer mechanism of peptides may be explained by the mechanism of cell entry or action. Further peptide synthesis and modification should be the next step to enhance the anticancer efficacy of these peptides with less toxicity to Vero cells. This finding sets the way for the development of new anticancer drugs originating from Varanus salvator serum peptides.
Journal Article
Hematology and Plasma Biochemistry Reference Values of the Subgenus Hapturosaurus (Varanus macraei, Varanus prasinus, Varanus beccarii) Under Human Care
The tree monitor lizards of the subgenus Hapturosaurus are an understudied but increasingly important group of reptiles in zoos. The routine blood analysis of reptiles in captivity is highly recommended; however, the lack of reliable reference values for many species severely limits their clinical use. This study aims to establish preliminary reference values (RV) for the main hematological and biochemical parameters in three species of the subgenus Hapturosaurus (Varanus macraei, Varanus prasinus and Varanus beccarii). Blood samples were taken from healthy adult individuals (n = 34), females (n = 18) and males (n = 16), maintained under controlled conditions in a zoo. A complete biochemical analysis was performed on all individuals, including alanine-aminotransferase, alkaline phosphatase, gamma-glutamyl transpeptidase, aspartate-aminotransferase, creatine kinase, bile acids, urea, uric acid, total solids, total proteins, albumin, glucose, fructosamine, lactate, cholesterol, triglycerides, amylase, calcium, phosphorus, calcium:phosphorus ratio, and magnesium. In addition, a complete hematological analysis was conducted on these individuals, including hematocrit, hemoglobin concentration, total erythrocyte and leukocyte counts, and leukocyte differential count. From the data obtained, reference intervals were established following the guidelines provided by the American Society for Veterinary Clinical Pathology (ASVCP). In this study, the results of the three species were unified to increase the sample size and to obtain more representative reference intervals. This unification was supported by a statistical analysis using the one-factor ANOVA test, which showed no statistically significant differences between species (p < 0.050). These data constitute an essential first step for the clinical practice and management of these Hapturosaurus species in zoos and specialized centers. Future collaboration with other institutions will help expand the dataset and enhance the accuracy of the established reference values.
Journal Article
Habitat use and distribution of Nile monitors (Varanus niloticus) in a mosaic of land use types and human population densities in KwaZulu-Natal, South Africa
Context
Globally, with the continuous increase in human populations, unprecedented changes in land use are taking place. Little is known about how African reptiles respond to this rapid land use change.
Objectives
We used sightings to establish if Nile monitors (
Varanus niloticus
) are persisting in a mosaic of human population densities and land use types in KwaZulu-Natal Province, South Africa.
Methods
We collected sighting data throughout KwaZulu-Natal between April 2022 and July 2023, using three main methods, namely urban sightings obtained from reptile relocation groups and collaborations with reptile relocators; sightings obtained from personal encounters and citizen scientist observations using social media,s posters, newspaper articles and interviews; and sightings from iNaturalist observations.
Results
We obtained and used 419 sightings and then identified two hotspot areas in the province on which we chose to focus. Site A was dominated by natural habitat, and anthropogenic land use types dominated site B. We found a significant relative selection strength for most tested land covers over anthropogenic cover in site A, whereas most were insignificant in site B. Our results suggest that the use of anthropogenic land use types by Nile monitors in KwaZulu-Natal may be driven by habitat transformation and loss. Nile monitors were found persisting in urban mosaic landscapes and, when compared with available cover, were found in increasingly wooded (natural and urban vegetation) areas with increased human populations. Furthermore, they used small anthropogenic water bodies (e.g., swimming pools and storm drains), making them less reliant on rivers in urban environments. Their population demographics were similar in low and high human population density, but there appeared to be a skew towards smaller and younger individuals in medium human population density areas. Reproduction was occurring successfully in urban environments, but the detection of larger monitors by potential wild and domestic predators and negative human interactions pose risks. Our study outlined the importance of natural and managed (e.g., gardens, parks, golf courses) green spaces in urban mosaic landscapes for wildlife persistence, specifically Nile monitors, and supporting human well-being as well as reptile conservation. There is an overall need for more research on this highly exploited yet understudied reptilian urban adapter.
Journal Article
Phylogenomics of Monitor Lizards and the Role of Competition in Dictating Body Size Disparity
Organismal interactions drive the accumulation of diversity by influencing species ranges, morphology, and behavior. Interactions vary from agonistic to cooperative and should result in predictable patterns in trait and range evolution. However, despite a conceptual understanding of these processes, they have been difficult to model, particularly on macroevolutionary timescales and across broad geographic spaces. Here, we investigate the influence of biotic interactions on trait evolution and community assembly inmonitor lizards (Varanus). Monitors are an iconic radiation with a cosmopolitan distribution and the greatest size disparity of any living terrestrial vertebrate genus. Between the colossal Komodo dragon Varanus komodoensis and the smallest Australian dwarf goannas, Varanus length and mass vary by multiple orders of magnitude. To test the hypothesis that size variation in this genus was driven by character displacement, we extended existing phylogenetic comparative methods which consider lineage interactions to account for dynamic biogeographic history and apply these methods to Australian monitors and marsupial predators. Incorporating both exon-capture molecular and morphological data sets we use a combined evidence approach to estimate the relationships among living and extinct varaniform lizards. Our results suggest that communities of Australian Varanus show high functional diversity as a result of continent-wide interspecific competition among monitors but not with faunivorous marsupials. We demonstrate that patterns of trait evolution resulting from character displacement on continental scales are recoverable from comparative data and highlight that these macroevolutionary patterns may develop in parallel across widely distributed sympatric groups.
Journal Article