Hemidactylus Research Articles

Info-gap theory to determine cost-effective eradication of invasive species

Invasive species eradication campaigns often fail due to stochastic arrival events, unpredictable detectability and incorrect resource allocation. Severe uncertainty in model parameter estimates may skew the eradication policy results. Using info-gap decision theory, this research aims to provide managers with a method to quantify their confidence in realizing successful eradication of particular invasive species within their specified eradication budgets (i.e. allowed eradication cost) in face of information-gaps. The potential introduction of the Asian house gecko Hemidactylus frenatus to Barrow Island, Australia is used as a case study to illustrate the model. Results of this research demonstrate that, more robustness to uncertainty in the model parameters can be earnt by (1) increasing the allowed eradication cost (2) investment in pre-border quarantine and border inspection (i.e. prevention) or (3) investment in post-border detection surveillance. The combination of a post-border spatial dispersal model and info-gap decision theory demonstrates a novel and spatially efficient method for managers to evaluate the robustness of eradication policies for incursion of invasive species with unexpected behaviour. These methods can be used to provide insight into the success of management goals, in particular the eradication of invasive species on islands or in broader mainland areas. These insights will assist in avoiding eradication failure and wasteful budget allocation and labour investment.

Metal contents in house geckos (Squamata: Gekkonidae) from industrial and urban areas of southern Tamaulipas, Mexico and western Andalucía, Spain, may reflect airborne metal pollution

ABSTRACT House geckos share living quarters with humans in the tropical and subtropical regions inhabited by these reptiles. Gecko behavior, biological traits, continuous exposure to suspended particulate matter 0 µm in diameter (PM10) and dust, as well as status as exotic species, motivated the choice of these species to examine environmental exposure to ambient air pollutants, in particular metals, and subsequent accumulation in these organisms. One part of the study was conducted in Tamaulipas (Mexico) where Hemydactylus frenatus is abundant in urban and industrial environments, the other part was conducted in Andalucia (Spain) where Tarentola mauritanica is found in similar environments. Adult geckos were collected on buildings in locations affected by various air pollution sources. For both species, higher metal contents were observed in whole-body (including digestive tracts) analysis and were markedly different between collection sites. Contents in tails, digestive tracts, and carcasses without digestive tracts were not correlated. Based on contamination factor values, bioaccumulation in H. frenatus tissues occurred for 12 of the 15 metals analyzed. Data suggest that H. frenatus might serve as a biomonitor for Cu, Ni, Pb, Cr, Li, and V, whereas T. mauritanica might be a biomonitor for Cu, Ni, Pb, and Cr. To our knowledge, metal contents for H. frenatus are reported here for the first time. House gecko data could be integrated into a highly representative monitoring system and health risk assessments related to air quality in residential areas.

Establishment of the Smooth-scaled Tegulet (Gymnophthalmus underwoodi) and the Common House Gecko (Hemidactylus frenatus) on St. Eustatius

Within the northern Lesser Antilles, the island of Saint Martin, including the Dutch part (St. Maarten, a constituent country of The Netherlands) and the French part (the Collectivity of Saint Martin), is considered the main hub for established non-native reptiles, currently numbering ten species (Table 1) (Dewynter et al. 2022; Thorpe 2022). The islands of Saba and St. Eustatius are special municipalities of The Netherlands and frequently trade with St. Maarten. During the last five years, several new non-native reptile species have been reported on Saba and St. Eustatius, which originate from the non-native populations already present on Saint Martin: the Green Iguana, Iguana iguana (van den Burg et al. 2018, 2022) on St. Eustatius, and the Brahminy Blindsnake, Indotyphlops braminus (van den Burg et al. 2021) and Smooth-scaled Tegulet, Gymnophthalmus underwoodi on Saba (van den Burg et al. 2021). It is believed that these newly established populations have been facilitated by poor biosecurity between the islands. Here, we describe the establishment of two species, G. underwoodi and the Common House Gecko, Hemidactylus frenatus, on St. Eustatius.

Aliens on Boats? The Eastern and Western Expansion of the African House Gecko.

Invasive species disrupt relations between endemics and their ecosystem and are an increasing biodiversity conservation problem. The Hemidactylus genus comprises the most successful invasive reptile species, including the worldwide-distributed Hemidactylus mabouia. In this study, we used 12S and ND2 sequences to taxonomically identify and tentatively determine the diversity and origin of these invaders in Cabo Verde while also clarifying this for several Western Indian Ocean (WIO) populations. By comparing our sequences to recently published ones, we showed, for the first time, that Cabo Verde individuals belong to the H. mabouia sensu stricto lineage and that both of its sublineages (a and b) occur there. Both haplotypes are also in Madeira, which indicates a connection between these archipelagos, possibly related to the past Portuguese trading routes. Across the WIO, results clarified the identity of many island and coastal populations, showing that this likely invasive H. mabouia lineage is widespread in the region, including northern Madagascar, with important conservation implications. Colonisation origins were difficult to access due to the wide geographical spread of these haplotypes; thus, several possible scenarios were outlined. The introduction of this species throughout western and eastern Africa may threaten endemic taxa and needs to be closely monitored.

Investigation of mechanisms underlying a light approaching behavior in a house gecko by comparative and learning experiments

Nocturnal predators of many taxa are known to come to artificial light at night for foraging on clumped food resources. Both innate and acquired light preferences seem to be possible mechanisms of light approaching behavior although empirical tests are lacking in most nocturnal predators. Here, using a Japanese gecko Gekko japonicus, we investigated whether geckos have a light preference and how foraging experiences under the light reinforce light approaching tendency. In a comparative experiment, there was no difference in light approaching behavior between urban and suburban geckos irrespective of their original light habitats. In an associative learning experiment, geckos did not significantly change light approaching behavior even after repeated opportunities to forage crickets near a lamp in the laboratory setting. These results imply that light approaching behavior of Japanese geckos may not be easily reinforced by foraging experiences under the light. Although we often witness geckos coming to artificial light at night, our findings may not suggest their light preference. Geckos may approach the light-up foraging spot based on other cues relating to the artificial light environment.

Naturally Fluorescent Field Mouse, Mus booduga (Gray, 1837) and Common House Gecko, Hemidactylus frenatus (Schlegel, 1836) as Model Organisms for Biomedical Studies

Naturally Fluorescent Field Mouse, Mus booduga (Gray, 1837) and Common House Gecko, Hemidactylus frenatus (Schlegel, 1836) as Model Organisms for Biomedical Studies

Thermal physiology of Tropical House Geckos (Hemidactylus mabouia) in a cool temperate region of South Africa.

ABSTRACT Temperature profoundly influences the functioning of ectotherms and understanding the thermal biology of invasive species affords valuable insights regarding the suitability of different habitats. Yet, this remains an understudied aspect in the field of invasion biology. Here, we investigated the thermal physiology of the highly invasive Tropical House Gecko (Hemidactylus mabouia) in a coastal region of South Africa. The study site is near to the southernmost extent of the species’ distribution and we expected the physiology of individuals at the study site to differ compared to that of individuals inhabiting tropical regions. Relative to tropical geckos, we observed a decrease of 3.4°C in preferred body temperature (Tpref) to 24.0 °C, which was likely driven by selection for improved functioning within the cooler temperate climate. However, the lower (CTmin) and upper (CTmax) critical thermal limits were higher in geckos at the study site. CTmin was similar between sexes at 11.9 °C, whereas males had a higher CTmax by ≈ 1.9 °C reaching 39.7 °C. A broader tolerance range is typical of a highly variable climate, and we presume that the increase in CTmax allows geckos to better cope with occasional high temperatures. Further, sex-specific differences are uncommon in reptiles, but our study supports claims of improved heat tolerance in male geckos, argued to be related to their aggressive and territorial behaviour. The results also support claims that tropical geckos are more adaptable than previously thought, allowing them to invade new areas. Thereafter, their aggressive behaviour, dietary flexibility and year-round activity likely provides house geckos with a competitive advantage over some native reptiles.

New locality record of Yellow-bellied House Gecko Hemidactylus flaviviridis Ruppell, 1835 a potential biological controller, from Shikohabad, Firozabad district, Uttar Pradesh (India) with its systematic account, distribution and other aspects.

Hemidactylus flaviviridis, the Yellow-bellied House Gecko, belonging to family Gekkonidae, commonly found in North India but its locality records are meagre. Recently a good number of these geckoes were sighted by the author at Shikohabad (Firozabad district, Uttar Pradesh) which is not in records and hence the gecko has been reported here for the first time from the area with its systematic account, distribution, habitat, food & feeding, breeding and trematode infestation. They are also found to be the potential biological controllers as feed on various insect pests on gardens vegetation around and mosquitoes which fly out under light in night.

De Novo Transcriptome Sequencing and Analysis of Differential Gene Expression among Various Stages of Tail Regeneration in Hemidactylus flaviviridis.

Across the animal kingdom, lizards are the only amniotes capable of regenerating their lost tail through epimorphosis. Of the many reptiles, the northern house gecko, Hemidactylus flaviviridis, is an excellent model system that is used for understanding the mechanism of epimorphic regeneration. A stage-specific transcriptome profile was generated in the current study following an autotomized tail with the HiSeq2500 platform. The reads obtained from de novo sequencing were filtered and high-quality reads were considered for gene ontology (GO) annotation and pathway analysis. Millions of reads were recorded for each stage upon de novo assembly. Up and down-regulated transcripts were categorized for early blastema (EBL), blastema (BL) and differentiation (DF) stages compared to the normal tail (NT) by differential gene expression analysis. The transcripts from developmentally significant pathways such as FGF, Wnt, Shh and TGF-β/BMP were present during tail regeneration. Additionally, differential expression of transcripts was recorded from biological processes, namely inflammation, cell proliferation, apoptosis and cell migration. Overall, the study reveals the stage-wise transcriptome analysis in conjunction with cellular processes as well as molecular signaling pathways during lizard tail regeneration. The knowledge obtained from the data can be extrapolated to configure regenerative responses in other amniotes, including humans, upon loss of a complex organ.

Concurrent 15. Presentation for: Technological advances in biosecurity monitoring

Presented on Wednesday 18 May: Session 15 Biosecurity tools are a key aspect of an effective biosecurity system, however, existing surveillance and monitoring programs are often expensive, resource intense, reliant on special expertise, long-term and deliver variable results. Advances in innovation and technology provide opportunity to improve program efficiency, reliability and cost-effectiveness. Chevron Australia developed and deployed tools to help monitor and identify non-indigenous species on Barrow Island, a Class A Nature Reserve and home to the Gorgon Natural Gas Project, operated by Chevron Australia and a joint venture of the Australian subsidiaries of Chevron (47.3%), ExxonMobil (25%), Shell (25%), Osaka Gas (1.25%), Tokyo Gas (1%) and JERA (0.417%). Tools include: The PAWS® (Print Acquisition for Wildlife Sensors) pest identification sensor pad and PAWS® live capture devices for rodent detection and monitoring, EARS (Environmental Acoustic Recognition Sensor) devices that record the male Asian house gecko’s call and can be adapted to incorporate other species if required, LAMP (Loop Mediated Isothermal Amplification) assay to identify Asian house gecko scats or tissue samples with an in situ molecular tool, Gecko identification application (app) enabling the workforce to participate in citizen science programs. These technological advances have helped to improve surveillance and biosecurity programs on Barrow Island, realising benefits including: longer monitoring periods for lower costs, resulting in greater confidence in surveillance outcomes, in situ diagnostics providing more rapid identification to enact an immediate response; deployment of live capture devices, reducing non-target captures (consequently, a more ethical tool); wider workforce participation. While these innovative tools target species likely to threaten Barrow Island’s unique biodiversity, the technology can be adapted for other environmental monitoring programs. To access the presentation click the link on the right. To read the full paper click here

English

The genus Basidiobolus contains large groups of terrestrial fungi including the etiological agents of human gastrointestinal basidiobolomycosis (GIB). This study aimed to identify Basidiobolus species from the common house gecko and to compare them with human GIB isolates. Gecko and human GIB samples were collected from Muhayil Aseer area, south Saudi Arabia (2017-2019). Isolation of fungi from the gut contents of geckos was performed using Sabouraud dextrose agar incubated aerobically at 30°C for five days. Suspected Basidiobolus species were tentatively identified using routine bench tests and phenotypes were authenticated by phylogenetic analysis of the large subunit ribosomal RNA gene. Isolates (n = 10) were found to have zygomycete-like phenotypic characteristics. In the 28S ribosomal RNA gene phylogenetic tree, the strains assembled in the subclade encompass Basidiobolus spp. along with previously reported isolates from human’ GIB. The strains had a close resemblance with Basidiobolus haptosporus (99.97%) as well as with B. haptosporus var. minor (99.97%). One isolate (L3) falls within the subclade containing B. haptosporus strain NRRL28635. The recovery of similar isolates from both humans and gecko lizards in one geographic region is an important development toward knowing risk factors for GIB.   Key words: Zygomycetes, Entomophthoromycota, Basidiobolus, lizards.

The Global and Western Indian Ocean Dispersal of House Geckos From Asia Using Historical and Mitochondrial DNA Perspectives

Seven species of house geckos occur across the scattered islands of the Indian Ocean. Two of these, Hemidactylus frenatus and H. parvimaculatus are both widespread and possess distribution profiles that suggest pre-European, or perhaps natural dispersal to some islands. Of these, only H. frenatus currently has sufficient molecular data to begin exploring dispersal patterns. This species is one of the most successful reptile colonists, as demonstrated by its global, pantropical distribution. While in some areas, such as Australia and continental South America, its dispersal patterns are both recent and well-known, early historical records of Hemidactylus in the Indian Ocean islands suggest earlier and/or potentially non-human-mediated dispersals. Here, we reviewed the historical literature and combined those reports with an assessment of mitochondrial DNA diversity of a global sampling of H. frenatus samples that included modern and museum specimens. Our results corroborate previous studies and demonstrate the relatively high diversity within this species’ native range in Southeast Asia. In addition, the phylogenetic analysis suggests both a potential cryptic species complex, as well as global geographic structuring of different H. frenatus mitochondrial lineages. This has important implications for many comparative studies of this complex. Frequent and ongoing dispersals and colonizations complicate the identification of potentially older migration patterns. Further assessments including additional samples and analyses of additional genetic markers are necessary to disentangle older from more recent dispersals within this intriguing species.

Performance and Kinematic Differences Between Terrestrial and Aquatic Running in Anolis Sagrei.

Many animals frequently transition between different media while navigating their heterogeneous environments. These media vary in compliance, moisture content, and other characteristics that affect their physical properties. As a result, animals may need to alter their kinematics to adapt to potential changes in media while maintaining performance during predator escape and foraging. Due to its fluid nature, water is highly compliant, and although usually associated with swimming, water running has evolved in a variety of animals ranging from insects to mammals. While the best studied large water runners are the bipedal basilisk lizards (Basiliscus spp.), other lizards have also been observed to run across the surface of water, namely, Hemidactylus platyurus, a house gecko, and in this study, Anolis sagrei, the brown anole. Unlike the basilisk lizard, the primarily arboreal Anolis sagrei is not adapted for water running. Moreover, water running in A. sagrei, similar to that of the house gecko, was primarily quadrupedal. Here, we tested for performance and kinematic differences between aquatic and terrestrial running and if the variance in performance and kinematic variables differed between the two media. We found no difference in average and maximum velocity between running on land and water. We also found that Anolis sagrei had higher hindlimb stride frequencies, decreased duty factor, and shorter stride lengths on water, as well as more erect postures. Finally, we found that most kinematics did not differ in variance between the two media, but of those that were different, almost all were more variable during terrestrial running. Our findings show that animals may be capable of specialized modes of locomotion, even if they are not obviously adapted for them, and that they may do this by modulating their kinematics to facilitate locomotion through novel environments.

Technological advances in biosecurity monitoring

Biosecurity tools are a key aspect of an effective biosecurity system, however, existing surveillance and monitoring programs are often expensive, resource intense, reliant on special expertise, long-term and deliver variable results. Advances in innovation and technology provide opportunity to improve program efficiency, reliability and cost-effectiveness. Chevron Australia developed and deployed tools to help monitor and identify non-indigenous species on Barrow Island, a Class A Nature Reserve and home to the Gorgon Natural Gas Project, operated by Chevron Australia and a joint venture of the Australian subsidiaries of Chevron (47.3%), ExxonMobil (25%), Shell (25%), Osaka Gas (1.25%), Tokyo Gas (1%) and JERA (0.417%). Tools include: The PAWS® (Print Acquisition for Wildlife Sensors) pest identification sensor pad and PAWS® live capture devices for rodent detection and monitoring, EARS (Environmental Acoustic Recognition Sensor) devices that record the male Asian house gecko’s call and can be adapted to incorporate other species if required, LAMP (Loop Mediated Isothermal Amplification) assay to identify Asian house gecko scats or tissue samples with an in situ molecular tool, Gecko identification application (app) enabling the workforce to participate in citizen science programs. These technological advances have helped to improve surveillance and biosecurity programs on Barrow Island, realising benefits including: longer monitoring periods for lower costs, resulting in greater confidence in surveillance outcomes, in situ diagnostics providing more rapid identification to enact an immediate response; deployment of live capture devices, reducing non-target captures (consequently, a more ethical tool); wider workforce participation. While these innovative tools target species likely to threaten Barrow Island’s unique biodiversity, the technology can be adapted for other environmental monitoring programs.

Three interesting fungal species associated with the Asian House Gecko in Kunming, China

A dead Asian House Gecko, infected with multiple species of fungi, was found floating in a jug of water inside a building in Kunming, China. The dead gecko was taken to the mycology laboratory at the Kunming Institute of Botany, Chinese Academy of Sciences and different fungal species were isolated. Phylogenetic analyses were carried out on the resultant isolates based on multiple gene sequences (ITS, LSU, mtSSU, rpb1, rpb2, tub2, Bloc, CAL, CHS-1, GAPDH, tef1-α). In addition to the phylogenetic analyses, morphological characteristics were also used to describe the fungal taxa. The entomopathogenic fungus Basidiobolus ranarum was isolated from the gecko’s inflamed right forelimb, while Beauveria bassiana was isolated from the gecko’s forehead. In addition, the neck skin yielded a common and important plant pathogen Colletotrichum jianxiense. Full descriptions, color plates of macro and micro structures of fungal taxa, and phylogenetic trees to show the placements of fungal taxa are provided. These findings represent either new host records or new country records for the three fungal species.

Afraid of the Dark? The Influence of Natural and Artificial Light at Night on the Behavioral Activity of a Nocturnal Gecko

Both natural and artificial light at night can strongly influence animal behavior. Nocturnal animals often alter activity dependent on lunar light levels, to increase prey capture, minimize detection by predators, or both. Trade-offs among these ecological effects are likely to have a strong influence on behavior and fitness. Here, we examined the influence of light at night on nocturnal geckos that are both predators and prey, and use both natural and anthropogenic habitats. We tested the influence of illumination on the relative abundance and behavioral activity of native geckos in natural woodlands and under laboratory conditions. We hypothesized that Australian native house geckos (Gehyra dubia) would avoid activity on nights with high moon brightness, to minimize exposure to predators, consistent with the predation risk hypothesis. Counter to our prediction, we found a positive relationship between house gecko activity and moon brightness, i.e., house geckos were more active on bright nights. This behavior may allow house geckos to better see their prey while also increasing the visibility of approaching predators. In the laboratory, house geckos had shorter latency times to emerge from a shelter under low light conditions compared to darkness equivalent to a new moon, a trend consistent with higher activity under brighter conditions in the field. Light at night, from both natural and artificial sources, clearly influences the behavior and activity of geckos, but perhaps not in the ways we expect. Reducing the risk of attack from predators in darkness, and increasing prey capture success using vision, may increase the benefits of activity in lit conditions, compared to total darkness.

PREDATION EVENT OF MILK FROG Trachycephalus typhonius (ANURA: HYLIDAE) ON A COMMON HOUSE GECKO Hemidactylus frenatus (SQUAMATA: GEKKONIDAE)

Observations of predation events are rare. These events are important to help understand trophic networks of biological communities in general and of introduced species in particular. Milk frogs (Trachycephalus typhonius) feed on insects and other arthropods, but some cases of vertebrates have been reported in its diet: a Sheep toad (Hypopachus variolosus) in México, a Black Myotis (Myotis nigrescens) in the Pantanal of Brazil, and an adult tree frog of Dendropsophus soaresi also in Brazil. Here we report the predation of an adult Milk frog on a Common house gecko (Hemidactylus frenatus) in Bajamar, Puntarenas, Costa Rica. The observation was made in a house in an area of pastures with trees near a mangrove swamp.

First Report of Anuran Trypanosoma DNA in Flat-Tailed House Geckos (Reptilia: Gekkonidae) Collected from Southern Thailand: No Evidence as a Reservoir for Human Trypanosomatids.

Over the years, cases of autochthonous leishmaniasis have been dramatically increasing in Thailand. Recently, several publications have claimed certain species of the phlebotomine sand flies and biting midges potentially serve as natural vectors of Leishmania and Trypanosoma species in this country. However, more information regarding the vector–parasite relationships, as well as their natural reservoirs in the country, still needs to be explored. Herein, we hypothesized that synanthropic reptiles in the leishmaniasis-affected area might be a natural reservoir for these parasites. In this present study, a total of nineteen flat-tailed house geckos were collected from the house of a leishmaniasis patient in Songkhla province, southern Thailand, and then dissected for their visceral organs for parasite detection. Small subunit ribosomal RNA (SSU rRNA) gene and internal transcribed spacer 1 (ITS-1)-specific amplifications were conducted to verify the presence of Trypanosoma and Leishmania parasites, respectively. Only Trypanosoma DNA was screened positive in eight gecko individuals by SSU rRNA-PCR in at least one visceral organ (4, 4, and 6 of the heart, liver, and spleen, respectively) and phylogenetically related to the anuran Trypanosoma spp. (An04/Frog1 clade) previously detected in three Asian sand fly species (Phlebotomus kazeruni, Sergentomyia indica, and Se. khawi). Hence, our data indicate the first detection of anuran Trypanosoma sp. in the flat-tailed house geckos from southern Thailand. Essentially, it can be inferred that there is no evidence for the flat-tailed house gecko (Hemidactylus platyurus) as a natural reservoir of human pathogenic trypanosomatids in the leishmaniasis-affected area of southern Thailand.

Predation attempt by a Tropical House Gecko, Hemidactylus mabouia (Gekkonidae), on a Cuban Blue Anole, Anolis allisoni (Dactyloidae) in south-central Cuba

Predation attempt by a Tropical House Gecko, Hemidactylus mabouia (Gekkonidae), on a Cuban Blue Anole, Anolis allisoni (Dactyloidae) in south-central Cuba

Habitat Preference and Population Study of House Gecko (Gekko gecko) in Seribu Islands, Special Capital Region of Jakarta

The house gecko (Gekko gecko) or tokek is a reptile species known widely used as an export commodity. Overexploitation can threaten wild populations of tokek in the wild. The research was conducted through a Visual Encounter Survey on the islands of Tidung, Pari, and Untung Jawa from 27 November to 02 December 2021. We also distributed questionnaires about the insight and presence of geckos in residents' homes or buildings. The number of respondents have been interviewed are 117 people, while for direct observation the results obtained are 273 individuals. The highest number of geckos was found on Pari Island and the least was on Untung Jawa Island. The house gecko is distributed throughout on these islands and is relatively more abundant in residential areas. The house gecko is most found on power poles and building walls and in breadfruit trees (Artocarpus altilis). Area of The Kepulauan Seribu is about 474562 hectares with a land area of 877 hectares. The population density of tokek based on direct observation was 13.60 individuals/ha. Therefore, the estimated population of tokek; in the Seribu Islands based on direct observations is around 11930.12 individuals.