Varanus Salvator Research Articles

Identification of the linkage group of the Z sex chromosomes of the sand lizard (Lacerta agilis, Lacertidae) and elucidation of karyotype evolution in lacertid lizards.

The sand lizard (Lacerta agilis, Lacertidae) has a chromosome number of 2n = 38, with 17 pairs of acrocentric chromosomes, one pair of microchromosomes, a large acrocentric Z chromosome, and a micro-W chromosome. To investigate the process of karyotype evolution in L. agilis, we performed chromosome banding and fluorescent in situ hybridization for gene mapping and constructed a cytogenetic map with 86 functional genes. Chromosome banding revealed that the Z chromosome is the fifth largest chromosome. The cytogenetic map revealed homology of the L. agilis Z chromosome with chicken chromosomes 6 and 9. Comparison of the L. agilis cytogenetic map with those of four Toxicofera species with many microchromosomes (Elaphe quadrivirgata, Varanus salvator macromaculatus, Leiolepis reevesii rubritaeniata, and Anolis carolinensis) showed highly conserved linkage homology of L. agilis chromosomes (LAG) 1, 2, 3, 4, 5(Z), 7, 8, 9, and 10 with macrochromosomes and/or macrochromosome segments of the four Toxicofera species. Most of the genes located on the microchromosomes of Toxicofera were localized to LAG6, small acrocentric chromosomes (LAG11-18), and a microchromosome (LAG19) in L. agilis. These results suggest that the L. agilis karyotype resulted from frequent fusions of microchromosomes, which occurred in the ancestral karyotype of Toxicofera and led to the disappearance of microchromosomes and the appearance of many small macrochromosomes.

Fossil-calibrated phylogeny and historical biogeography of Southeast Asian water monitors (Varanus salvator Complex)

We utilize robust geographical genetic sampling, a multilocus dataset, a new synthesis of numerous fossil calibration points, a time-calibrated phylogeny, and the Dispersal–Extinction–Cladogenesis model to test the prediction that widespread Southeast Asian water monitor species initially diversified on the Asian mainland and subsequently invaded the island archipelagos of the Philippines, Sundaland, and Wallacea. Our results strongly contradict these expectations and instead infer an initial water monitor radiation of range-restricted but highly divergent evolutionary lineages (now recognized as endemic species) in one archipelago around 3.6mya, followed by an out-of-the-Philippines reinvasion of the mainland (2.2mya), resulting in a few, widespread species that now inhabit most the islands of the Sunda Shelf and the Southeast Asian mainland as far north as Myanmar, as well as an out-of-the-Philippines invasion of Sulawesi (2.1mya). Our analyses both confirm the importance of island archipelagos as drivers of diversification for mainland biodiversity and emphasize the global evolutionary significance and conservation priority of the Philippines for understanding processes of diversification in island archipelagos.

Karyotype evolution in monitor lizards: cross-species chromosome mapping of cDNA reveals highly conserved synteny and gene order in the Toxicofera clade

The water monitor lizard (Varanus salvator macromaculatus (VSA), Platynota) has a chromosome number of 2n = 40: its karyotype consists of 16 macrochromosomes and 24 microchromosomes. To delineate the process of karyotype evolution in V. salvator macromaculatus, we constructed a cytogenetic map with 86 functional genes and compared it with those of the butterfly lizard (Leiolepis reevesii rubritaeniata (LRE); 2n = 36) and Japanese four-striped rat snake (Elaphe quadrivirgata (EQU); 2n = 36), members of the Toxicofera clade. The syntenies and gene orders of macrochromosomes were highly conserved between these species except for several chromosomal rearrangements: eight pairs of VSA macrochromosomes and/or chromosome arms exhibited homology with six pairs of LRE macrochromosomes and eight pairs of EQU macrochromosomes. Furthermore, the genes mapped to microchromosomes of three species were all located on chicken microchromosomes or chromosome 4p. No reciprocal translocations were found in the species, and their karyotypic differences were caused by: low frequencies of interchromosomal rearrangements, such as tandem fusions, or centric fissions/fusions between macrochromosomes and between macro- and microchromosomes; and intrachromosomal rearrangements, such as paracentric inversions or centromere repositioning. The chromosomal rearrangements that occurred in macrochromosomes of the Varanus lineage were also identified through comparative cytogenetic mapping of V. salvator macromaculatus and V. exanthematicus. Morphologic differences in chromosomes 6-8 between the two species could have resulted from pericentric inversion or centromere repositioning.

Highly Species-Specific Centromeric Repetitive DNA Sequences in Lizards: Molecular Cytogenetic Characterization of a Novel Family of Satellite DNA Sequences Isolated from the Water Monitor Lizard (Varanus salvator macromaculatus, Platynota)

Two novel repetitive DNA sequences, VSAREP1 and VSAREP2, were isolated from the water monitor lizard (Varanus salvator macromaculatus, Platynota) and characterized using molecular cytogenetics. The respective lengths and guanine-cytosine (GC) contents of the sequences were 190 bp and 57.5% for VSAREP1 and 185 bp and 59.7% for VSAREP2, and both elements were tandemly arrayed as satellite DNA in the genome. VSAREP1 and VSAREP2 were each located at the C-positive heterochromatin in the pericentromeric region of chromosome 2q, the centromeric region of chromosome 5, and 3 pairs of microchromosomes. This suggests that genomic compartmentalization between macro- and microchromosomes might not have occurred in the centromeric repetitive sequences of V. salvator macromaculatus. These 2 sequences did only hybridize to genomic DNA of V. salvator macromaculatus, but no signal was observed even for other squamate reptiles, including Varanus exanthematicus, which is a closely related species of V. salvator macromaculatus. These results suggest that these sequences were differentiated rapidly or were specifically amplified in the V. salvator macromaculatus genome.

Multilocus phylogeny and Bayesian estimates of species boundaries reveal hidden evolutionary relationships and cryptic diversity in Southeast Asian monitor lizards

Recent conceptual, technological and methodological advances in phylogenetics have enabled increasingly robust statistical species delimitation in studies of biodiversity. As the variety of evidence purporting species diversity has increased, so too have the kinds of tools and inferential power of methods for delimiting species. Here, we showcase an organismal system for a data-rich, comparative molecular approach to evaluating strategies of species delimitation among monitor lizards of the genus Varanus. The water monitors (Varanus salvator Complex), a widespread group distributed throughout Southeast Asia and southern India, have been the subject of numerous taxonomic treatments, which have drawn recent attention due to the possibility of undocumented species diversity. To date, studies of this group have relied on purportedly diagnostic morphological characters, with no attention given to the genetic underpinnings of species diversity. Using a 5-gene data set, we estimated phylogeny and used multilocus genetic networks, analysis of population structure and a Bayesian coalescent approach to infer species boundaries. Our results contradict previous systematic hypotheses, reveal surprising relationships between island and mainland lineages and uncover novel, cryptic evolutionary lineages (i.e. new putative species). Our study contributes to a growing body of literature suggesting that, used in concert with other sources of data (e.g. morphology, ecology, biogeography), multilocus genetic data can be highly informative to systematists and biodiversity specialists when attempting to estimate species diversity and identify conservation priorities. We recommend holding in abeyance taxonomic decisions until multiple, converging lines of evidence are available to best inform taxonomists, evolutionary biologists and conservationists.

Rickettsia sp. Closely Related toRickettsia raoultii(Rickettsiales: Rickettsiaceae) in anAmblyomma helvolum(Acarina: Ixodidae) Tick From aVaranus salvator(Squamata: Varanidae) in Thailand

An engorged female Amblyomma helvolum Koch tick was removed from an adult Varanus salvator Laurenti lizard during field collection in Thailand. After using polymerase chain reaction to amplify three genes (16S rDNA, gltA, and OmpA), we discovered the presence of a Rickettsia sp. of the Spotted Fever Group. Phylogenetic analysis revealed that this Rickettsia sp. is closely related to Rickettsia raoultii Mediannikov. Therefore, we report herein for the first time the detection of a novel Spotted Fever Group Rickettsia in an Amblyomma helvolum from a Varanus salvator in Thailand.

Proposed research on home ranges and resource use of the water monitor lizard, Varanus salvator

Throughout the world, population growth and conversion of land for human development increase the potential for areas of human and wildlife activity to overlap. Anthropogenic effects on animal behavior may have ecological consequences if response to human disturbance or dependence on anthropogenic food sources prevents wildlife from carrying out traditional ecological roles. The presence of large predatory species such as the water monitor lizard, Varanus salvator, in areas of human development may also result in conflict if animals become habituated to the presence of humans or begin to compete for resources. Understanding anthropogenic effects on V. salvator resource use and activity is a key to predicting behavior and informing conflict mitigation in systems where humans and V. salvator coexist. V. salvator home ranges and resource use will be investigated on Tinjil Island, Indonesia, where radiotelemetry will be used to track V. salvator individuals across areas of varying human presence in both wet and dry seasons. Greater insight into anthropogenic influences on V. salvator resource use will contribute increased knowledge of V. salvator's ecological role in undisturbed and human-altered communities and can serve to inform the prevention of human–V. salvator conflict.

The postpulmonary septum of Varanus salvator and its implication for Mosasaurian ventilation and physiology

AbstractThe postpulmonary septum (PPS) is a relatively thick sheet of connective tissue covering the inferior surface of the lungs in varanid lizards. The primary connection of the PPS is to the medial surface of the ribs; additional connections occur to the inferior midline of the dorsal vertebrae, the pericardium, and a direct (through loose connective tissue) link to the surface of the lung. The PPS effectively partitions the coelomic cavity into peritoneal and pleural cavities. Investigation demonstrates that the PPS is not capable of preventing displacement of the more caudal (peritoneal) viscera, which is displaced cranially during terrestrial locomotion; this cranial displacement could impinge on the tidal volume of the lungs. Kinematic analyses of terrestrial and aquatic locomotion in Varanus salvator document the different propulsive mechanics used during movement through these two media, and, most importantly, the marked reduction in lateral displacement of the trunk during swimming. These findings, when combined with previous studies of the cardiovascular and respiratory system of varanids performing terrestrial locomotion, suggest that mosasaurs had a versatile, effective respiratory system and were likely capable of both sustained swimming and prolonged submersion, such as during ambush foraging.

Phacoemulsification for Removal of Bilateral Cataracts in a Black Water Monitor (Varanus salvator macromaculatus)

A 16-yr-old intact male, captive-born Black Water Monitor, Varanus salvator macromaculatus, was presented for evaluation of bilateral lens opacities. Examination showed bilateral cataracts, with blepharospasm, uveitis, and absence of vision in the left eye. Phacoemulsification was successfully performed on the left eye, and at six weeks postoperative, the animal was found to be visual in that eye and had complete healing of the surgical site. The right eye had phacoemulsification performed seven months later with similar results. The monitor made a full recovery and continues to have normal ocular examinations.

Isolation and characterization of novel microsatellite markers in Water monitor (Varanus salvator)

The Water monitor (Varanus salvator) is the second largest of all the monitor lizards of the world, after the Komodo dragon. It was listed in CITES Appendix II as an endangered species. Investigation of genetic variation for Varanus salvator can help to conserve and improve this endangered monitor salvator. Here, sixteen microsatellite loci were developed and twelve polymorphic loci were used to investigate the genetic variation on 30 wild individuals. The number of alleles per locus ranged from 2 to 15, with the average of 6,000. The observed and expected heterozygosity values varied from 0.2333 to 0.9000 and 0.2096 to 0.9203, respectively. Only one locus (YBJX28) significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. No significant linkage disequilibrium was detected. These polymorphic markers should be useful tool for assessing population genetics of Varanus salvator.

Two species of the genus Kalicephalus Molin, 1861 (Nematoda, Diaphanocephaloidea) from the water monitor, Varanus salvator (Laurenti, 1768) in Guangdong Province, China

AbstractTwo species of Kalicephalus Molin, 1861 were collected from the intestine of Varanus salvator (Laurenti, 1768) from Guangdong Wildlife Rescue Centre, Guangzhou, Guangdong Province, China. Kalicephalus (Kalicephalus) guangdongensis sp. nov. is similar to K. (K.) schadi Ogden, 1966 and K. (K.) schadi fotedari Kalia et Nayital, 1989 in having extremely long spicules, but differs from the latter in the relative length of spicules (spicules longer than the total body length instead of spicules almost three quarters of the total body length). Kalicephalus (Kalicephalus) schadi fotedari Kalia et Nayital, 1989 is reported for the first time in China, and Varanus salvator is a new host record.

Unravelling the underestimated diversity of Philippine water monitor lizards (Squamata: Varanus salvator complex), with the description of two new species and a new subspecies

Unravelling the underestimated diversity of Philippine water monitor lizards (Squamata: Varanus salvator complex), with the description of two new species and a new subspecies

Unravelling the underestimated diversity of Philippine water monitor lizards (Squamata: Varanus salvator complex), with the description of two new species and a new subspecies

Recently, the first part of the morphological revision of the Southeast Asian water monitor lizards of the Varanus salvator (Laurenti, 1768) species group provided a taxonomic overview over the members of this successful and widespread species complex (Koch et al. 2007). There, the Philippine taxa marmoratus, nuchalis and cumingi were reelevated to species status due to diagnostic morphological characteristics, e.g. significantly enlarged scales on the neck region. In this second part of the ongoing revision, these three species are re-investigated using additional voucher specimens and advanced statistical techniques including canonical variates analysis and principal component analysis. Our new investigations indicate that V. marmoratus represents a composite species, comprising at least three distinct taxa. Hence, the populations of the Sulu Archipelago (Tawi–Tawi Island) and those of the Palawan region are described as new species, viz. Varanus rasmusseni sp. nov. and V. palawanensis sp. nov., respectively. The allopatric island populations of V. cumingi inhabiting Samar, Leyte, and Bohol (the East Visayan subregion) show characteristic and geographically correlated colour patterns distinct from the type locality Mindanao (the second subregion of Greater Mindanao), warranting subspecific partition of this species. The new subspecies is named V. cumingi samarensis ssp. nov. In contrast, the taxonomic status of V. nuchalis remained unchanged, although this species shows some considerable variation in colour pattern. The systematic chapters are supplemented with notes about biology and conservation status. The hitherto underestimated diversity and zoogeography of Philippine water monitors is discussed in the light of Pleistocene sea level fluctuations. Finally, we introduce a scenario for the evolution and spread of Southeast Asian water monitor lizards and provide an identification key for the Philippine members of the V. salvator complex.

A new melanistic species of monitor lizard (Reptilia: Squamata: Varanidae) from Sanana Island, Indonesia

A new species of monitor lizard endemic to Sanana Island in the northwestern Moluccas is described from a preserved specimen and field observations. This is the only melanistic member of the Varanus indicus species group, and the only taxon in the subgenus Euprepiosaurus with prominent orange-red markings. Allied to Varanus melinus of nearby Mangole and Taliabu islands in body proportions and scutellation, the new species is convergent with melanistic populations of the Varanus salvator complex from the Sula Platform, Sulawesi and Togian Islands. On Sanana the new species reaches highest densities in coastal sago palm swamps, a habitat type that is underutilized by other species in the V. indicus group elsewhere in the Moluccas.

Preliminary Survey of Lizards of Pantai Melawi, Bachok, Kelantan, Malaysia

A survey of lizards was conducted of Pantai Melawi, Bachok on 12-14 April and 11-13 May 2009. Nine species of lizards were recorded in this preliminary survey. They were from the family Agamidae (Calotes versicolor, Leiolepis belliana), family Gekkonidae (Cosymbotus platyurus, Gehyra mutilata, Gekko monarchus, Gekko gecko and Hemidactylus frenatus), family Scincidae (Eutropis multifasciata) and family Varanidae (Varanus salvator). The common species in this area were Leiolepis belliana and Hemidactylus frenatus.

Heading East: a New Subspecies of Varanus salvator from Obi Island, Maluku Province, Indonesia, with a Discussion about the Easternmost Natural Occurrence of Southeast Asian Water Monitor Lizards

The Varanus salvator population from the Central Indonesian island of Obi, Maluku Province, is described as a new subspecies representing the most easterly confirmed occurrence of the widespread Southeast Asian water monitor lizard. The new taxon differs from the four recognized subspecies by unique characters of coloration and pattern such as a distinct dorsal pattern on the head in combination with reduced transverse rows on the anterior back which stand in contrast to the distinct and black-bordered, large light spots on the hind part of the body. In addition, the eastern border of the distribution range of the V. salvator complex is critically discussed in the light of historical voucher specimens from the Moluccas, New Guinea and even Australia. The Obi island record which had long been published but has never since been scrutinized, confirms the recently observed sympatric occurrence of members of the V. salvator and V. indicus species groups on several islands of the Moluccas. Further field investigations are needed to understand the different niche occupation between both these ecologically similar monitor lizard groups. Once more, our findings demonstrate the importance of the Central Indonesian islands of Wallacea as a global hotspot of varanid diversity and endemism.

Entamoeba invadens Myositis in a Common Water Monitor Lizard (Varanus salvator)

Amoebiasis is one of the most common protozoal diseases of reptiles, but amoebic myositis has not been reported in any animal species. An 11-year-old, male common water monitor lizard (Varanus salvator) was found dead with several subacute ulcerated skin wounds. Gross examination revealed multiple discrete to coalescing, white-yellow to gray, caseous foci scattered in the skeletal muscles and liver. The mucosa of small intestine was thickened, red, and contained many variably sized, dark red ulcers, with depressed and hemorrhagic centers. Histopathologic examination revealed severe necrotizing and granulomatous myositis, hepatitis, and enteritis accompanied by large numbers of intralesional, 10-20-microm diameter, periodic acid-Schiff-positive, amoeboid protozoa. Gene sequence analysis of a 136-bp region of the 18S ribosomal RNA amplified by polymerase chain reaction revealed 98-100% similarity with Entamoeba invadens. Aside from intestinal and hepatic involvement, no other internal organs were affected. The muscular infection by E. invadens likely resulted from a combination of direct invasion of trophozoites via skin wounds and hematogenous spread.

New and Already Known Acanthocephalans Mostly from Mammals in Vietnam, with Descriptions of Two New Genera and Species in Archiacanthocephala

Adults of 2 new species and 2 new genera of acanthocephalans in class Archiacanthocephala, collected between 1998 and 2004 in Vietnam from the intestines of mammals, are described, i.e., Cucullanorhynchus constrictruncatus n. gen., n. sp. (Oligacanthorhynchidae) from a leopard Panthera pardus (Linnaeus) (Mammalia: Felidae) and Paraprosthenorchis ornatus n. gen. n. sp. (Oligacanthorhynchidae) from the Chinese pangolin Manis pentadactyla (Linnaeus) (Mammalia: Manidae). Adult Sphaerechinorhynchus macropisthospinus Amin, Wongsawad, Marayong, Saehoong, Suwattanacoupt, and Sey, 1998 (Plagiorhynchidae) are described for the first time from 2 females collected from a tiger Panthera tigris (Linnaeus) (Mammalia: Felidae) and from 1 male from a water monitor Varanus salvator Laurenti (Reptilia: Varanidae). Characteristic features distinguishing the new species or genera from related taxa are as follows. The trunk of C. constrictruncatus has an anterior hood in both sexes and a posterior constriction in females. The anterior trunk of P. ornatus has many small festoons and proboscis hooks are inserted in elevated papillae separated by beady, near hexagonal, ornate grids.

Tracing the diet of the monitor lizard Varanus mabitang by stable isotope analyses (delta(15)N, delta(13)C).

In this study, we used analyses of stable isotopes of nitrogen (delta(15)N) and carbon (delta(13)C) to determine the trophic ecology of the monitor lizard Varanus mabitang. Stable isotopes from claws, gut contents, and soft tissues were measured from the type specimen. Samples from Varanus olivaceus, Varanus prasinus, Varanus salvator, the herbivorous agamid lizard Hydrosaurus pustulatus, and some plant matter were included for comparison. Our data show a rapid decrease in delta(13)C (about 10 per thousand) from food plants towards gut contents and soft tissues of herbivorous species. For the varanids, we found a significant linear correlation of decreasing delta(13)C and increasing delta(15)N from herbivorous towards carnivorous species. In terms of trophic isotope ecology, the type specimen of V. mabitang is a strict herbivore. Thus it differs significantly in its isotopic composition from the morphologically next closest related species V. olivaceus. The most highly carnivorous species is V. salvator, while delta(15)N values for V. prasinus and V. olivaceus are intermediate. Claws provide very valuable samples for such measurements, because they can be sampled from living animals without harm. Additionally, their range of variability is relatively small in comparison with measurements from soft tissues.

A NOVEL INTEGRON IN THE GENOME OF ESCHERICHIA COLI ISOLATED FROM INDONESIAN MONITOR LIZARD (VARANUS SPP).

The genotype of antibiotic resistance in natural isolates of Escherichia coli was determined through integron detection and characterization of the associated antibiotic resistance. E. coli SG2 isolated from Varanus salvator of Java demonstrated resistance to spectinomycin (50ng/ml) and streptomycin (SOng/ml). Integron detection indicated that eight isolates out of nine E. coli isolates possessed a conserved segment of the integron. Amplification of the inserted cassette of the integron in this SG2 isolate yielded a 1-kb DNA fragment. Sequence analyses indicated that this fragment was homologous with aad gene, which confirmed the resistance to spectinomycin/streptomycin. This is the first report on the presence of integron in the E. coli isolated from the environment. Key words: Integron / antibiotic resistance / Escherichia coli