Varanus Exanthematicus Research Articles

Molecular evidence of Monocercomonas and Acanthamoeba in the feces of captive reptiles

Reptiles are frequently kept as pet animals. They are considered as important reservoirs of protozoa with veterinary-medical significance. At a reptile farm in Ireland, fecal samples were collected from 98 captive reptiles, representing 43 species of three orders (Squamata, Testudines, and Crocodylia). After DNA extraction, all samples were screened by conventional PCRs, targeting the ribosomal small subunit (SSU) RNA and alpha-tubulin genes of trichomonads and SSU RNA gene of Acanthamoeba spp. One leopard gecko (Eublepharis macularius) was positive for a not yet reported species/genotype of the genus Monocercomonas, different from M. colubrorum. Various Acanthamoeba genotypes were detected in six reptilian species, i.e., Acanthamoeba genotype T11 in Eunectes notaeus and Heloderma suspectum/horridum; genotype T4 in Varanus exanthematicus, Chlamydosaurus kingii, and Macrochelys temminckii; and the genotype T13 in Iguana iguana. Some of these amoeba species might have clinicopathological significance in both humans and animals. Our findings highlight the importance to monitor pathogenic protozoa in pet as well as wildlife reptiles, as a source of possible infection for animals and humans living nearby.

Locomotor energetics in the Indonesian blue-tongued skink (Tiliqua gigas) with implications for the cost of belly-dragging in early tetrapods.

During the last decade, biomechanical and kinematic studies have suggested that a belly-dragging gait may have represented a critical locomotor stage during tetrapod evolution. This form of locomotion is hypothesized to facilitate animals to move on land with relatively weaker pectoral muscles. The Indonesian blue-tongued skink (Tiliqua gigas) is known for its belly-dragging locomotion and is thought to employ many of the same spatiotemporal gait characteristics of stem tetrapods. Conversely, the savannah monitor (Varanus exanthematicus) employs a raised quadrupedal gait. Thus, differences in the energetic efficiency of locomotion between these taxa may elucidate the role of energetic optimization in driving gait shifts in early tetrapods. Five Tiliqua and four Varanus were custom-fitted for 3D printed helmets that, combined with a Field Metabolic System, were used to collect open-flow respirometry data including O2 consumption, CO2 production, water vapor pressure, barometric pressure, room temperature, and airflow rates. Energetic data were collected for each species at rest, and when walking at three different speeds. Energetic consumption in each taxon increased at greater speeds. On a per-stride basis, energetic costs appear similar between taxa. However, significant differences were observed interspecifically in terms of net cost of transport. Overall, energy expenditure was ~20% higher in Tiliqua at equivalent speeds, suggesting that belly-dragging does impart a tangible energetic cost during quadrupedal locomotion. This cost, coupled with the other practical constraints of belly-dragging (e.g., restricting top-end speed and reducing maneuverability in complex terrains) may have contributed to the adoption of upright quadrupedal walking throughout tetrapod locomotor evolution.

Malignant Perivascular Epithelioid Cell Tumour in a Savannah Monitor (Varanus exanthematicus)

A 9-year-old male captive savannah monitor (Varanus exanthematicus) with a history of general debility was submitted for necropsy. Grossly, there were multiple white masses in the colon, mesorchium and tracheal adventitia. Histologically, the lesions were composed of epithelioid to spindloid neoplastic cells arranged in sheets to interlacing and interwoven bundles, and separated by abundant myxoid material or extensive stromal hyalinization and fibrosis with occasional chondroid metaplasia. Perivascular infiltration of epithelioid neoplastic cells was occasionally seen. Neoplastic cells were immunopositive for alpha-smooth muscle actin, melan-A and S100. The unique histological features and concurrent myogenic and melanocytic immunophenotypes suggest a malignant perivascular epithelioid cell tumour. To our knowledge, this is the first report of perivascular epithelioid cell tumours in a non-human species.

Not Goanna Get Me: Mutations in the Savannah Monitor Lizard (Varanus exanthematicus) Nicotinic Acetylcholine Receptor Confer Reduced Susceptibility to SympatricCobra Venoms.

Antagonistic coevolutionary relationships provide intense selection pressure which drive changes in the genotype. Predator-prey interactions have caused some venomous snakes and their predators/prey to evolve α-neurotoxin resistance through changes at the orthosteric site of nicotinic acetylcholine receptors. The presence of negatively charged amino acids at orthosteric site positions 191 and 195 is the ancestral state. These negatively charged amino acids have exerted a selection pressure for snake venom α-neurotoxins to evolve with strong positive charges on their molecular surface, with the opposite-charge attraction facilitating the binding by the neurotoxins. We aimed to test the effects of a series of mutations whereby one or both negatively charged amino acids are replaced by uncharged residues to ascertain if this was a novel form of reduced venom susceptibility in the varanid species. Using a biolayer interferometry assay, we tested the relative binding of α-neurotoxin-rich snake venoms against the orthosteric sites of V. giganteus (Perentie) and V. komodoensis (Komodo dragon), which both possess the negatively charged aspartic acid at position 191; V. mertensi (Merten's water monitor), which alsohas aspartic acid at position 195; and Varanus exanthematicus (savannah monitor), which lacks negatively charged amino acids at both positions 191 and 195. The orthosteric sites of these species are otherwise identical. In order to complete the structure-function relationship examination, we also tested a mutant version with the negatively charged aspartic acid at both positions 191 and 195. It was demonstrated that the presence of a negatively charged amino acid at either position 191 or 195 is crucial for the successful binding of snake venom α-neurotoxins, with V. giganteus, V. komodoensis and V. mertensi all strongly bound. The mutant version containing a negatively charged amino acid at both positions was bound equipotently to the native forms of V. giganteus, V. komodoensis and V. mertensi. Thus, the presence of a negatively charged amino acid at both positions does not increase binding affinity. In contrast, Varanus exanthematicus, lacking a negatively charged amino acid at either position, displayed dramatically less sensitivity to neurotoxins compared with the other species. V. exanthematicus is distinguished from the other species examined in this study by being a small, terrestrial, slow-moving species living sympatrically with a high density of large cobra species that have neurotoxin-rich venoms. Thus, this vulnerable prey item seems to haveevolved a novel form of reduced susceptibility to snake venom neurotoxins under a strong selection pressures from these neurotoxic predators. These results therefore contribute to the body of knowledge of predator/prey chemical arm races while providing novel insights into the structure-activity relationships of the orthosteric site of the nicotinic acetylcholine receptor alpha-subunit.

Locomotor rib kinematics in two species of lizards and a new hypothesis for the evolution of aspiration breathing in amniotes

Most lizards walk and run with a sprawling gait in which the limbs are partly advanced by lateral undulation of the axial skeleton. Ribs and vertebrae are integral to this locomotor mode, but 3D motion of the axial skeleton has not been reported for lizard locomotion. Here, we use XROMM to quantify the relative motions of the vertebrae and ribs during slow treadmill locomotion in three savannah monitor lizards (Varanus exanthematicus) and three Argentine black and white tegus (Salvator merianae). To isolate locomotion, we selected strides with no concurrent lung ventilation. Rib rotations can be decomposed into bucket-handle rotation around a dorsoventral axis, pump-handle rotation around a mediolateral axis, and caliper rotations around a craniocaudal axis. During locomotion, every rib measured in both species rotated substantially around its costovertebral joint (8–17 degrees, summed across bucket, pump and caliper rotations). In all individuals from both species, the middle ribs rotated cranially through bucket and pump-handle motion during the propulsive phase of the ipsilateral forelimb. Axial kinematics during swing phase of the ipsilateral forelimb were mirror images of the propulsive phase. Although further work is needed to establish what causes these rib motions, active contraction of the hypaxial musculature may be at least partly responsible. Unilateral locomotor rib movements are remarkably similar to the bilateral pattern used for lung ventilation, suggesting a new hypothesis that rib motion during locomotion may have been an exaptation for the evolution of costal aspiration breathing in stem amniotes.

Testing the propulsive role of m. peroneus longus during quadrupedal walking in Varanus exanthematicus.

Some varanid lizards show a prominent and highly distinctive lateral calcaneal process. It has been posited that this structure serves as a lateral "heel" to increase the moment arm for m. peroneus longus, allowing it to function as a powerful propulsive muscle. However, to confirm that m. peroneus longus serves this function requires electromyographic data showing activity during tarsal plantarflexion in the late part of the stance phase. Muscle activity patterns of m. peroneus longus, m. tibialis anterior, and mm. gastrocnemii were collected from two savannah monitors (Varanus exanthematicus) during quadrupedal walking. Across strides, m. peroneus longus shows an early onset just before hindlimb touchdown and an offset that is highly correlated with that of mm. gastrocnemii. These patterns are consistent across individuals. However, the fact that the first onset of m. peroneus longus appears to be around the end of swing phase, with activity continuing throughout the remainder of stance, suggests that this muscle likely serves other functional purposes during locomotion beside propulsion. This, paired with the fact that qualitative comparisons of m. peroneus longus activity across other lizard species reveal remarkably similar patterns, suggests the propulsive role of m. peroneus longus in V. exanthematicus was probably built upon existing muscle activity patterns present in ancestral squamates and then exaggerated through modifications to lateral calcaneal heel and the associated proximal expansion of the fifth metatarsal.

Computational Fluid Dynamics Reveals a Unique Net Unidirectional Pattern of Pulmonary Airflow in the Savannah Monitor Lizard (Varanus exanthematicus).

This report models pulmonary airflow in the savannah monitor (Varanus exanthematicus) using computational fluid dynamics simulations, which are based on computed tomography data. Simulations were validated by visualizing the flow of aerosolized lipids in excised lungs with good but not perfect agreement. The lung of this lizard has numerous successive bronchi branching off a long intrapulmonary bronchus, which are interconnected by intercameral perforations. Unidirectional flow has been documented in the lateral secondary bronchi of the savannah monitor, but patterns of airflow in the rest of the lung remain unknown, hindering our understanding of the evolution of pulmonary patterns of airflow in tetrapods. These results indicate that the lung contains a unique net unidirectional flow, where the overall flow scheme is similar during expiration and late inspiration, but dissimilar during early inspiration. Air is transported net caudally through the intrapulmonary bronchus and net craniad through secondary bronchi, much like the pattern of flow in birds. The simulations show that many chambers feature flow in multiple directions during parts of the respiratory cycle, but some regions also show robust unidirectional airflow. Air moves craniad through secondary bronchi and between adjacent secondary bronchi through intercameral perforations. The first secondary bronchus, the hilar-cranial bronchus, contains tidal flow that may improve ventilation of the central and dorsal lung parenchyma. These results expand our understanding of flow patterns in varanid lungs and suggest lungs with net unidirectional flow as an evolutionary pathway between tidal flow and complete unidirectional flow in multicameral lungs. Anat Rec, 2020. © 2019 American Association for Anatomy Anat Rec, 303:1768-1791, 2020. © 2019 American Association for Anatomy.

The roles of joint tissues and jaw muscles in palatal biomechanics of the savannah monitor (Varanus exanthematicus) and their significance for cranial kinesis.

Numerous vertebrates exhibit cranial kinesis, or movement between bones of the skull and mandible other than at the jaw joint. Many kinetic species possess a particular suite of features to accomplish this movement, including flexible cranial joints and protractor musculature. Whereas the musculoskeletal anatomy of these kinetic systems is well understood, how these joints are biomechanically loaded, how different soft tissues affect joint loading and kinetic capacity, and how the protractor musculature loads the skull remain poorly understood. Here, we present a finite element model of the savannah monitor, Varanus exanthematicus, a modestly kinetic lizard, to better elucidate the roles of soft tissue in mobile joints and protractor musculature in cranial loading. We describe the 3D resultants of jaw muscles and the histology of palatobasal, otic and jaw joints. We tested the effects of joint tissue type, bite point and muscle load to evaluate the biomechanical role of muscles on the palate and braincase. We found that the jaw muscles have significant mediolateral components that can impart stability across palatocranial joints. Articular tissues affect the magnitude of strains experienced around the palatobasal and otic joints. Without protractor muscle loading, the palate, quadrate and braincase experience higher strains, suggesting this muscle helps insulate the braincase and palatoquadrate from high loads. We found that the cross-sectional properties of the bones of V. exanthematicus are well suited for performing under torsional loads. These findings suggest that torsional loading regimes may have played a more important role in the evolution of cranial kinesis in lepidosaurs than previously appreciated.

Squamate reptiles from Kanapoi: Faunal evidence for hominin paleoenvironments

The squamate fossil record from Kanapoi reveals generic to higher-order similarities with modern East African herpetofaunas. The record is derived from surface collection and screen washing, and consists primarily of isolated vertebrae with a few maxillary and mandibular elements. The most abundant remains are vertebrae of large-bodied Python that are morphologically similar to extant Python sebae, and vertebrae of Varanus cf. (Varanus niloticus + Varanus exanthematicus). Additional cranial and vertebral remains indicate the presence of lygosomine skinks, indeterminate Varanus, Viperidae, cf. Atractaspididae, and multiple colubrine morphotypes in the Kanapoi ecosystem. Despite similarities with modern herpetofaunas, the Kanapoi record lacks taxa common to other East African records, including agamids, chamaeleonids, amphisbaenians, the elapid Naja, and typhlopids. The overall composition of the Kanapoi squamate record is consistent with paleoenvironments similar to modern shrub savanna habitats. There are no indicators of canopied forest environments in squamate faunal composition. The fossil record of Kanapoi suggests that assembly of squamate faunas of modern East Africa was well underway by the late Neogene.

Breathing with floating ribs: XROMM analysis of lung ventilation in savannah monitor lizards.

The structures and functions of the vertebrate lung and trunk are linked through the act of ventilation, but the connections between these structures and functions are poorly understood. We used X-ray reconstruction of moving morphology (XROMM) to measure rib kinematics during lung ventilation in three savannah monitor lizards (Varanus exanthematicus). All of the dorsal ribs, including the floating ribs, contributed to ventilation; the magnitude and kinematic pattern showed no detectable cranial-to-caudal gradient. The true ribs acted as two rigid bodies connected by flexible cartilage, with the vertebral rib and ventromedial shaft of each sternal rib remaining rigid and the cartilage between them forming a flexible intracostal joint. Rib rotations can be decomposed into bucket handle rotation around a dorsoventral axis, pump handle rotation around a mediolateral axis and caliper motion around a craniocaudal axis. Dorsal rib motion was dominated by roughly equal contributions of bucket and pump rotation in two individuals and by bucket rotation in the third individual. The recruitment of floating ribs during ventilation in monitor lizards is strikingly different from the situation in iguanas, where only the first few true ribs contribute to breathing. This difference may be related to the design of the pulmonary system and life history traits in these two species. Motion of the floating ribs may maximize ventilation of the caudally and ventrolaterally positioned compliant saccular chambers in the lungs of varanids, while restriction of ventilation to a few true ribs may maximize crypsis in iguanas.

Epipterygoid Bone Salmonella Abscess in a Savannah Monitor (Varanus exanthematicus)

Abstract A 5-year-old savannah monitor (Varanus exanthematicus) was presented for left-sided facial swelling. Examination revealed left hemi-maxilla and eyelid swelling causing caudoventral displacement of the left eye. Computed tomography (CT) of the head was conducted prior to surgical exploration, debridement, and culture of the swelling. CT images revealed a mass extending from the left retrobulbar area to the temporal muscle with extensive lysis of the epiterygoid bone resulting in compression of the brainstem. Surgical exploration allowed for partial debridement of the mass and sample collection for bacterial culture. Salmonella enterica Kintambo was isolated from the swelling and was sensitive to several antibiotics. Ceftazidime (40 mg/kg) and piperacillin (100 mg/kg) mixed with poloxamer 407 gel was subsequently injected into the swelling. Oral enrofloxacin (10 mg/kg q24h weaned to 5 mg/kg q24h) was prescribed and continued for 5 months prior to discontinuation. Over the following 5 months, extern...

Salmonella enterica subspecies enterica serovar Paratyphi B as a disease-causing agent in reptiles in the Czech Republic

The aim of this study was to describe two case studies of reptile disease, in which the primary pathogen was apparently Salmonella enterica subspecies enterica serovar Paratyphi B. Pathological examinations, sampling from different organs and cloacal swabs was performed on a dead savannah monitor (Varanus exanthematicus) and a sick green tree python (Chondropython viridis). This material was subjected to culture examination, including selective enrichment using standard methods. Typing was performed using MALDI-TOF and strains were also serologically typified. The utilisation of d-tartrate was confirmed biochemically and also using PCR. Antibiotic susceptibility was determined by the standard disc diffusion method using Mueller-Hinton agar without blood and antibiotic discs. In both cases the detected Salmonella enterica subspecies enterica serovar Paratyphi B was positive for d-tartrate and exquisitely susceptible to chloramphenicol, tetracycline, ampicillin, amoxycillin/clavulanic acid, gentamicin, ceftazidime, enrofloxacin and piperacillin.

Case Studies in Physiology: The Case of the Giant Giraffe.

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A suite of potentially amplifiable microsatellite loci for ten reptiles of conservation concern from Africa and Asia

Here we document the addition of thousands of potentially amplifiable microsatellite loci (PALs) and associated primer sequences for public use. We conducted whole-genome shotgun sequencing to obtain ultra-low coverage, random genomic sampling from ten African and Asian squamate reptile species (representing ten genera). We used unique genomic processing methods and generated PALs for the following species: Acrochordus granulatus, Ahaetulla prasina, Cerberus rhynchops, Gonocephalus kuhlii, Ophiophagus hannah, Python bivittatus, Tribolonotus gracilis, Trimeresurus sabahi (Popeia sabahi), Uromastyx geryi and Varanus exanthematicus. All taxa included, as well as other related taxa not included in our study, are exploited heavily by the international skin and pet trades, yet researchers and conservation agencies currently lack substantial genetic resources for guiding conservation and management. Using stringent filtering methods, we generated between 467 and 8641 PALs for each of the ten species (52,164 PALs total), yielding a rich database of microsatellite loci and amplification primers for these taxa. In addition to the ten species targeted in our study, microsatellite markers provided in this database can likely be applied to a variety of closely related taxa that are also of conservation and commercial interest.

Effect of temperature on chemosensitive locus coeruleus neurons of savannah monitor lizards, Varanus exanthematicus.

Savannah monitor lizards (Varanus exanthematicus) are unusual among ectothermic vertebrates in maintaining arterial pH nearly constant during changes in body temperature in contrast to the typical α-stat regulating strategy of most other ectotherms. Given the importance of pH in the control of ventilation, we examined the CO2/H+ sensitivity of neurons from the locus coeruleus (LC) region of monitor lizard brainstems. Whole-cell patch-clamp electrophysiology was used to record membrane voltage in LC neurons in brainstem slices. Artificial cerebral spinal fluid equilibrated with 80% O2, 0.0-10.0% CO2, balance N2, was superfused across brainstem slices. Changes in firing rate of LC neurons were calculated from action potential recordings to quantify the chemosensitive response to hypercapnic acidosis. Our results demonstrate that the LC brainstem region contains neurons that can be excited or inhibited by, and/or are not sensitive to CO2 in V. exanthematicus While few LC neurons were activated by hypercapnic acidosis (15%), a higher proportion of the LC neurons responded by decreasing their firing rate during exposure to high CO2 at 20°C (37%); this chemosensitive response was no longer exhibited when the temperature was increased to 30°C. Further, the proportion of chemosensitive LC neurons changed at 35°C with a reduction in CO2-inhibited (11%) neurons and an increase in CO2-activated (35%) neurons. Expressing a high proportion of inhibited neurons at low temperature may provide insights into mechanisms underlying the temperature-dependent pH-stat regulatory strategy of savannah monitor lizards.

In situ cardiac perfusion reveals interspecific variation of intraventricular flow separation in reptiles.

The ventricles of non-crocodilian reptiles are incompletely divided and provide an opportunity for mixing of oxygen-poor blood and oxygen-rich blood (intracardiac shunting). However, both cardiac morphology and in vivo shunting patterns exhibit considerable interspecific variation within reptiles. In the present study, we develop an in situ double-perfused heart approach to characterise the propensity and capacity for shunting in five reptile species: the turtle Trachemys scripta, the rock python Python sebae, the yellow anaconda Eunectes notaeus, the varanid lizard Varanus exanthematicus and the bearded dragon Pogona vitticeps To simulate changes in vascular bed resistance, pulmonary and systemic afterloads were independently manipulated and changes in blood flow distribution amongst the central outflow tracts were monitored. As previously demonstrated in Burmese pythons, rock pythons and varanid lizards exhibited pronounced intraventricular flow separation. As pulmonary or systemic afterload was raised, flow in the respective circulation decreased. However, flow in the other circulation, where afterload was constant, remained stable. This correlates with the convergent evolution of intraventricular pressure separation and the large intraventricular muscular ridge, which compartmentalises the ventricle, in these species. Conversely, in the three other species, the pulmonary and systemic flows were strongly mutually dependent, such that the decrease in pulmonary flow in response to elevated pulmonary afterload resulted in redistribution of perfusate to the systemic circuit (and vice versa). Thus, in these species, the muscular ridge appeared labile and blood could readily transverse the intraventricular cava. We conclude that relatively minor structural differences between non-crocodilian reptiles result in the fundamental changes in cardiac function. Further, our study emphasises that functionally similar intracardiac flow separation evolved independently in lizards (varanids) and snakes (pythons) from an ancestor endowed with the capacity for large intracardiac shunts.

English

The herpetofaunal species in Ghana are under serious threat from habitat loss and degradation, global climate change, disease and parasitism, introduced invasive species and unsustainable use. The herpetofaunal species of the Kogyae Strict Nature Reserve of Ghana were surveyed using two methods: refuge examination via direct searches, visual/audio surveys and interviews of local residents. Data were obtained during two visits to two study sites in 2012: savanna woodland and riparian forest mosaic. The first visit was in the dry season in January, 2012 for five days and the second visit in the rainy season in June, 2012 for six days. Thirty-six herpetofaunal species were recorded, comprising of 14 amphibians and 22 reptiles. Ten of the reptiles were recorded only from interviews. The savanna woodland recorded a higher number of species (33) than the riparian forest mosaic (22), and there was low similarity in species between the two sites (Sorenson’s similarity index, CS = 0.42). Four species were frequently encountered at both sites in high numbers: Phrynobatrachus natalensis, Phrynobatrachus latifrons, Arthroleptis spp. and Trachylepis affinis. Two lizard (Varanus niloticus and Varanus exanthematicus) and two snake (Python sebae and Python regius) species are of both local and global conservation significance. The lizards are categorized under Schedule I (complete protection) and the pythons under Schedule II (partial protection) of the Ghana Wildlife Conservation Regulations. The main threats to the herpetofaunal species of the study area include habitat destruction due to annual bushfires and killing of large reptiles like the monitors as well as snakes. It is recommended that riparian vegetation bordering streams should be particularly targeted to conserve herpetofauna of the study area.   Key words: Africa, biodiversity, Ghana, herpetofauna, Kogyae, protected area, reserve. &nbsp

Chemosensitive locus coeruleus neurons in the Savannah monitor lizard, Varanus exanthematicus (879.13)

Savannah monitor lizards, Varanus exanthematicus, are unusual among air‐breathing, ectothermic vertebrates by maintaining arterial pH nearly constant during changes in body temperature (‐0.003 U °C‐1) in contrast to the typical α‐stat regulating strategy (‐0.015 to ‐0.017 U °C‐1) of most other ectotherms. Given the importance of pH in the control of ventilation, we examined the CO2/H+ sensitivity of neurons from the locus coeruleus (LC) region of Savannah monitor lizard brainstems. Whole‐cell patch clamp electrophysiology was used to record membrane voltage (Vm) in neurons within the LC region in brainstem slices; changes in firing rate of LC neurons were calculated from action potential recordings. Upon exposure to hypercapnic acidosis (HA) at 20°C, 60% of neurons significantly decreased firing rate (1.8±0.3 vs. 0.6±0.1 Hz; P<0.05). The percentage of LC neurons inhibited by HA is high at 20°C compared with published percentages from bullfrogs and rats. Increasing temperature to 30°C abolished the inhibited response to HA (2.4±0.9 Hz vs. 2.6±1.0 Hz; P=1.0). The large proportion of neurons inhibited by HA at 20°C may provide a mechanism whereby retention of whole body CO2 stores with cooling enables the pH‐stat regulation strategy of Varanus exanthematicus.Grant Funding Source: Supported by NSF IOS 1257338

Distribution patterns and predilection muscles of Trichinella zimbabwensis larvae in experimentally infected Nile crocodiles (Crocodylus niloticus Laurenti).

No controlled studies have been conducted to determine the predilection muscles of Trichinella zimbabwensis larvae in Nile crocodiles (Crocodylus niloticus) or the influence of infection intensity on the distribution of the larvae in crocodiles. The distribution of larvae in muscles of naturally infected Nile crocodiles and experimentally infected caimans (Caiman crocodilus) and varans (Varanus exanthematicus) have been reported in literature. To determine the distribution patterns of T. zimbabwensis larvae and predilection muscles, 15 crocodiles were randomly divided into three cohorts of five animals each, representing high infection (642 larvae/kg of bodyweight average), medium infection (414 larvae/kg of bodyweight average) and low infection (134 larvae/kg of bodyweight average) cohorts. In the high infection cohort, high percentages of larvae were observed in the triceps muscles (26%) and hind limb muscles (13%). In the medium infection cohort, high percentages of larvae were found in the triceps muscles (50%), sternomastoid (18%) and hind limb muscles (13%). In the low infection cohort, larvae were mainly found in the intercostal muscles (36%), longissimus complex (27%), forelimb muscles (20%) and hind limb muscles (10%). Predilection muscles in the high and medium infection cohorts were similar to those reported in naturally infected crocodiles despite changes in infection intensity. The high infection cohort had significantly higher numbers of larvae in the sternomastoid, triceps, intercostal, longissimus complex, external tibial flexor, longissimus caudalis and caudal femoral muscles (p < 0.05) compared with the medium infection cohort. In comparison with the low infection cohort, the high infection cohort harboured significantly higher numbers of larvae in all muscles (p < 0.05) except for the tongue. The high infection cohort harboured significantly higher numbers of larvae (p < 0.05) in the sternomastoid, triceps, intercostal, longissimus complex, external tibial flexor, longissimus caudalis and caudal femoral muscles compared with naturally infected crocodiles. Results from this study show that, in Nile crocodiles, larvae of T. zimbabwensis appear first to invade predilection muscles closest to their release site in the small intestine before occupying those muscles situated further away. The recommendation for the use of masseter, pterygoid and intercostal muscles as sampling sites for the detection of T. zimbabwensis in crocodiles is in contrast to the results from this study, where the fore- and hind limb muscles had the highest number of larvae. This study also supports the use of biopsy sampling from the dorso-lateral regions of the tail for surveillance purposes in both wild and commercial crocodile populations.

Coelomic and Pericardial Effusion Associated with Mesothelioma in a Savannah Monitor (Varanus exanthematicus)

An adult male Savannah monitor (Varanus exanthematicus) was evaluated for lethargy, anorexia, and coelomic distension. Ultrasonographic investigation identified both pericardial and coelomic effusion. Clinical laboratory investigations and radiographs did not identify a definitive disease process, and culture of the coelomic fluid was negative for bacterial growth. A tentative diagnosis of neoplasia, with mesothelioma as a potential type, was made after cytological examination of the coelomic fluid and echocardiography. Surgical exploration and excisional biopsy of the pericardium for drainage of the fluid and determination of a final diagnosis was carried out. The lizard died 16 h post-anesthesia. Histopathology confirmed changes throughout the coelomic cavity consistent with a diagnosis of mesothelioma. Mesothelioma is a rarely reported neoplasm in all animals but particularly in reptiles. This case report provides a detailed clinical and pathologic description of the lesions associated with mesothelioma in a monitor lizard. In addition, this is the first known report of a surgical pericardectomy in a reptile.