Pyxis Arachnoides Research Articles

Molecular Identification of Mycoplasma agassizii in Confiscated Tortoises in Madagascar.

Mycoplasmosis is of concern for chelonian conservation. We detected a Mycoplasma sp. in confiscated radiated tortoises (Astrochelys radiata) and spider tortoises (Pyxis arachnoides). Sequence analysis of the 16S-23S ribosomal RNA intergenic spacer region was consistent with Mycoplasma agassizii. Mycoplasma spp. have not been previously reported in native tortoises in Madagascar.

A novel herpesvirus from a wild-caught Madagascar spider tortoise shows evidence of host-viral coevolution with a duplication event in Durocryptodira.

Herpesviruses can be significant reptile pathogens. Herpesviral infection in a wild-caught, male spider tortoise (Pyxis arachnoides) under human care was detected during a routine wellness examination prior to transition between zoologic organizations. The tortoise had no clinical signs of illness. Oral swabs obtained during a physical examination as part of pre-shipment risk mitigation for infectious disease were submitted for consensus herpesvirus PCR assay and sequencing. Based on comparative sequence analysis, the novel herpesvirus identified is a member of the subfamily Alphaherpesvirinae. Studies of herpesviral phylogeny in chelonian species support branching patterns of turtle herpesviruses that closely mirror those of their hosts. The symmetry of these patterns is suggestive of close codivergence of turtle herpesviruses with their host species. The distribution of these viruses in both tortoises and emydids suggests a phylogenetic duplication event in the herpesviruses after host divergence of the Pleurodira and basal to the divergence of Americhelydia. Herpesviral infections have been documented to cause higher morbidity when introduced to aberrant host species, and significant consideration must be given to the presence of herpesviruses in the management of tortoise collections, particularly collections that include various species of testudines.

Immune and stress physiology of two captively-housed tortoise species.

Ecoimmunology affords us the ability to better understand immunological processes through consideration of external factors, such as the thermal microenvironment. This consideration is imperative when examining the immunological processes of ectothermic organisms like reptiles. Reptiles uniquely rely heavily on their innate immune function but remain poorly understood in immunological studies. In this study, we examined innate immunity in two zoo-housed tortoise species, the Indian star tortoise (Geochelone elegans, Schoepff, 1795) and northern spider tortoise (Pyxis arachnoides brygooi, Vuillemin & Domergue, 1972). Bacterial killing assays (BKAs) were optimized and used to assess the monthly immunocompetence of these tortoises to three different bacteria: Escherichia coli, Salmonella enterica, and Staphylococcus aureus. We evaluated differences in blood biochemistry values (lactate and glucose) among months and species as well as fecal corticosterone (CORT) between species. Lastly, we examined the potential influences of individual thermal microenvironments on bactericidal ability. Both G. elegans and P. a. brygooi demonstrated immunocompetence against all bacterial challenges, but only bactericidal ability against E. coli varied over months. Optimal BKA serum dilutions, blood glucose levels, and fecal CORT concentrations differed between the two species. Finally, there was evidence that the thermal microenvironment influenced the tortoises' bactericidal ability against E. coli. Through use of nonmodel organisms, such as tortoises, we are given insight into the inner workings of innate immunity and a better understanding of the complexities of the vertebrate immune system.

Tick (Amblyomma chabaudi) infestation of endemic tortoises in southwest Madagascar and investigation of tick-borne pathogens

Little is known about the role of endemic ticks as vectors for bacterial and protozoan pathogens for animals and humans in Madagascar and their interaction in anthropogenic habitats where humans, their livestock and native Malagasy species (vectors and hosts) come into more frequent contact than in natural forest ecosystems. The aims of the study were (1) to test whether habitat degradation is associated with increased infestation of tortoises by ticks and (2) to investigate whether ticks carried Babesia, Borrelia or Rickettsia species that might be pathogenic for humans and livestock. We studied hard ticks of two endemic Malagasy tortoises, Astrochelys radiata and Pyxis arachnoides in March and April 2013 in southwest Madagascar. Two tortoise habitats were compared, the National Park of Tsimanampetsotsa and the adjacent degraded pasture and agricultural land at the end of the wet season. Ticks were screened for protozoan and bacterial pathogens via PCR on DNA isolated from ticks using genus-specific primers. Only one out of 42 A. radiata collected from both habitats had ticks. The low prevalence did not allow further analyses of the effect of habitat degradation. Forty-two P. arachnoides were found in the anthropogenic habitat and 36 individuals in the national park. Tick infestation rates of P. arachnoides differed significantly between the two study sites. Tortoises inside the park had lower tick prevalence than outside (8 of 36 (22%) versus 32 of 42 individuals (76%)) and infected animals tended to have fewer ticks inside than outside the park. All ticks collected in both habitats were adults of the ixodid tick Amblyomma chabaudi, which is supposed to be a host-specific tick of P. arachnoides. Screening for Borrelia sp. and Babesia sp. was negative in all ticks. But all A. chabaudi ticks were infected with Rickettsia africae, known to cause spotted fever in humans. Thus, habitat degradation seems to be linked to higher infestation of tortoises with ticks with possible consequences for humans and their livestock.

Isolation and characterization of six polymorphic microsatellite loci for the Malagasy spider tortoise, Pyxis arachnoides and cross-amplification in Pyxis planicauda

Pyxis arachnoides is a Critically Endangered Malagasy tortoise for which little data about its natural history and genetic variation are available. This lack of knowledge complicates undertaking conservation measures considering Pyxis genetic diversity. Here, we describe six new microsatellites for Pyxis arachnoides from wild specimens and several localities, and the cross amplification of two Astrochelys radiata microsatellites. Of these microsatellites, two are monomorphic among the three distinct subspecies and a closely related species, while the remaining six are polymorphic. Microsatellite data are needed for this species to study the inter- and intra-subspecies genetic diversity, especially for the highly endangered subspecies P. a. brygooi, which currently occurs only in remote localities. The availability of polymorphic microsatellites will allow identifying the population of origin of individuals and will aid in justifying their management as separate evolutionary lineages for conservation purposes. The rationale is to preserve both evolutionary processes and adaptive potential.

Status of the relict population of the Critically Endangered Madagascar spider tortoise Pyxis arachnoides

AbstractThe Madagascar spider tortoise Pyxis arachnoides is endemic to the coastal dry forests of south-west Madagascar. In recent years its range has been reduced by c. 71%, with the species now confined to eight fragmented populations occupying a total of 2,464 km2. These remaining populations are facing a significant threat of extinction because of habitat destruction and other anthropogenic pressures. We developed methodology for a line transect distance sampling survey and applied it systematically across the species' range. The resulting distance model estimated a mean density of 226.9 tortoises km−2 (95% confidence interval, CI, 168.1–306.3) and a total population of 664,980 (95% CI 492,680–897,550). Fragmentation of the species’ range suggests the current population could be <30% of the historical population. Of the remaining population 73.5% falls within protected areas. However, nine of these 12 protected areas are designated as IUCN category III, V or VI parks, allowing some extractive activities to be undertaken. The most effective strategy for the conservation of P. arachnoides would be to reduce the threats to this species and its habitat, and to develop and expand the current community-based conservation and poverty alleviation programmes in the region.

The effect of habitat degradation on the long term survival of the Critically Endangered Madagascar spider tortoise (Pyxis arachnoides)

Pyxis arachnoides inhabits the dry, coastal forests of southwest Madagascar; a biologically unique ecoregion severely threatened by unsustainable small scale agricultural practices. Using remotely sensed data we established vegetation loss remains unabated within our study area at 1.2% year−1; consistent with ecoregion wide vegetation loss between 1990 and 2000. We monitored tortoise population density on four occasions over 8years and developed a stage class projection matrix to model the finite growth rate, matrix sensitivities and elasticities of the population. Monitoring revealed an actual mean population decline of 10.8% between 2003 and 2011. Our projection matrix model suggested the finite rate of growth to be λ=0.986, indicative of 1.4% year−1 decline for the duration of the existence of the population, with adult survival as the most sensitive parameter to overall survival of the population. Projection modeling suggests that the population would possibly become functionally non viable in approximately 170years. As our study was heavily reliant on the use of surrogate data, more information is needed on pre-adult survival and wild reproductive rates. Our study site currently represents a population of exceptional density, therefore, other less dense populations, subjected to the further stresses of poaching will likely become functionally non viable much sooner. This study highlights the utility of population projection matrices in determining the vulnerability of chelonians; a globally threatened taxon. In the case of the spider tortoise, well coordinated development programs and tighter protected area management are required to address the poverty induced drivers forcing this species closer to extinction.

Survival probability of a population of Madagascar spider tortoises (Pyxis arachnoides)

The spider tortoise (Pyxis arachnoides) is endemic to the coastal, dry forests of southwest Madagascar, one of the country’s most threatened habitats. Very little is known of the biology of this Critically Endangered species. We devised a three year capture-mark-recapture study to assess mean annual survival for the following cohorts; juvenile, adult male, adult female and adult of both sexes, for a population of spider tortoises using a Cormack-Jolly-Seber model. Low recapture probabilities prevented the modelling of all but the adult of both sexes cohort. Mean annual survival was 0.823 (; ). We hypothesise that habitat loss could be impacting the survival of this cohort; however establishing control data to test for this is difficult because of the widespread habitat loss, even within protected areas. Therefore we suggest extending the study across a number of gradients of impacted habitat and increase the duration of the study to assess this risk to the population and improve model robustness.

The Decline of the Critically Endangered Northern Madagascar Spider Tortoise (Pyxis arachnoides brygooi)

Abstract The northern Madagascar spider tortoise (Pyxis arachnoides brygooi), is endemic to the coastal Mikea forests of southwest Madagascar. Very little is known of P. a. brygooi's ecology; however, it is suspected that the range is now very fragmented, with remaining populations facing significant threats from habitat destruction and poaching for food and the pet trade. A line-transect survey was undertaken that systematically surveyed the suspected historical range of this subspecies. The results were incorporated into a GIS database, which revealed that the distribution was confined to 20.5% of the suspected historical range, across three fragmented populations covering 499.6 km2. It appears that a zone of intergradation has developed in a transitional area between the southern range of P. a. brygooi and the northern range of P. a. arachnoides. The results of this survey are currently being applied to management plans for newly gazetted protected areas in the region, in an effort to safeguard these r...

Chelonian type specimens at the Oxford University Museum

In the present paper, the history of the chelonian collection of the Oxford University Museum is summarized and extant type specimens are identified. Currently, there are 46 name-bearing types of 25 chelonian taxa and paralectotypes of three taxa described by Georg Baur, Thomas Bell, André Marie Constant Duméril & Gabriel Bibron, and John Edward Gray from the families Emydidae, Geoemydidae, Testudinidae, Chelidae, and Pelomedusidae. Among the name-bearing types, there are holotypes of eight taxa (Cyclemys bellii Gray, 1863; Emys speciosa var. levigata Gray, 1831; Phrynops bellii Gray, 1844; Rhinoclemys bellii Gray, 1863; Sternothaerus leachianus Bell, 1825; Sternothaerus trifasciatus Bell, 1825; Testudo hercules var. truncata Gray, 1831; Testudo tentoria Bell, 1828) and one lectotype is of Pyxis arachnoides Bell, 1827. Two additional holotypes or syntypes are of Terrapene maculata Bell, 1825 and Terrapene nebulosa Bell, 1825, and 35 syntypes represent 14 taxa (Cyclemys orbiculata Bell, 1834; Emys concentrica var. polita Gray, 1831; Emys crassicollis Gray, 1831; Emys decussata Gray, 1831; Emys hamiltonii Gray, 1831; Emys irrigata Duméril & Bibron, 1835; Emys speciosa Gray, 1831; Emys spinosa Gray, 1831; Emys tectum Gray, 1830; Emys thurjii Gray, 1831; Kinixys castanea Bell, 1827; Kinixys homeana Bell, 1827; Testudo actinodes Bell, 1828; Testudo guntheri Baur, 1889). Three paralectotypes are of Emys dentata Gray, 1831, eight paralectotypes are of Emys vulgaris Gray, 1831, and one paralectotype is of Pyxis arachnoides Bell, 1827. Except the syntype of Testudo guntheri Baur, 1889, originating from the college of Christ Church, Oxford, all type specimens belong to the former collection of Thomas Bell that was transferred to Oxford in 1862. Testudo guntheri Baur, 1889 is regarded as nomen dubium because it was based on specimens without locality data.

Population density and seasonal activity of the threatened Madagascar spider tortoise (Pyxis arachnoides arachnoides) of the southern dry forests; South West Madagascar

The Madagascar spider tortoise Pyxis arachnoides is facing pressure from habitat destruction, hunting for food and collection for the exotic pet-trade. Very little is known of the biology and ecology of P. arachnoides. This study centres on a subspecies population of P. arachnoides arachnoides, within the southern dry forests of the Anakao region of southwest Madagascar. Surveys were carried out across 83, one hectare, quadrants over 12 months, during both the wet and dry seasons, with respective seasonal mean population densities recorded at 4.63 and 2.08 individuals per ha. This significant variation was accompanied by a variation in micro habitat preference between the seasons, with P. a. arachnoides moving to areas of greater vegetation cover during the warmer wet season. P. a. arachnoides was only recorded as feeding during the wet months, a period of increased activity. The subspecies became less active during the dry season, with some individuals entering a dormant phase. There was generally a greater abundance of females encountered throughout the year, usually weighing less than males. Juvenile abundance peaked during February and March. Six-year-old specimens were the most regularly encountered individuals and a mean age throughout the survey was recorded at 11.25 years.

Amoebosis in the Flat-shelled Spider Tortoise

Amoebosis is one of the most common protozoal diseases of reptiles, but has rarely been reported in tortoises. Six cases of amoebosis were identified in flat-shelled spider tortoises immediately after their importation from Madagascar to Japan. Necropsy revealed an extensive green pseudomembrane of ulceration along the length of the thickened wall of the colon, and disseminated green foci in the liver. Histologically, the colonic wall was severely ulcerated and covered with a fibrinonecrotic pseudomembrane, and many amoebic trophozoites were seen in the submucosa. Multifocal necrosis with intralesional amoebic trophozoites corresponded to the disseminated green foci in the liver. Amoebic trophozoites invaded many blood vessels in the colon and liver. All tortoises exhibited severe colonic lesions, but the severity of the hepatic lesions varied. These findings suggest that amoebic colitis was the primary lesion with spread of amoebae to the liver via the portal system.

A Molecular Phylogeny of Four Endangered Madagascar Tortoises Based on MtDNA Sequences

Four of the five tortoise species in Madagascar,Pyxis arachnoides, P. planicauda, Geochelone radiata,andG. yniphora,are endemic and on the verge of extinction. Their phylogenetic relationships remain controversial and unresolved. Here we address the phylogeny of this group using DNA sequences for the 12S and 16S rDNA and cytbgenes in mitochondrial DNA. As outgroups we used two species ofGeochelone, pardalis(mainland Africa) andnigra(Galápagos), as well as a more distant North American tortoise,Gopherus polyphemus.We conclude that the twoPyxisspecies are sister taxa and are imbedded in the genusGeochelone,rendering this latter genus paraphyletic. There is moderate support for the sister status of the two MadagascarGeocheloneand for the monophyletic origin of all four endemics, suggesting a single colonization of the island. The separation of Madagascar from other land masses (90–165 mya) predates the origin of the endemic tortoises (estimated to be 14–22 mya). This suggests founding by rafting, a process known to have occurred with other tortoises. The derived morphological divergence of thePyxisspecies in a relatively short period of time (13–20 my) stands in contrast to the notoriously slow rate of morphological evolution in most lineages of Chelonia.

Etude systématique du genre endémique malgache Pyxis Bell, 1827 (Reptilia, Chelonii) (Note complémentaire)

SPyxis arachnoïdes oblonga Gray, 1869 is recognized as a valid senior synonym of Pyxis arachnoides matzi Bour, 1979 ; the holotypus is still in the collection of the British Museum (Natural History) ; the designated terra typica is Cap Sainte-Marie, southern Madagascar.