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Mark Wilkinson - One of the best experts on this subject based on the ideXlab platform.

  • Itraconazole treatment of Batrachochytrium dendrobatidis (Bd) infection in captive caecilians (Amphibia: Gymnophiona) and the first case of Bd in a wild neotropical caecilian
    Journal of Zoo and Aquarium Research, 2015
    Co-Authors: Matthew Rendle, David J Gower, Benjamin Tapley, Matthew W. Perkins, Gabriela B. Bittencourt-silva, Mark Wilkinson
    Abstract:

    Batrachochytrium dendrobatidis ( Bd ) is the causative agent of the disease amphibian chytridiomycosis, one of the factors driving amphibian population declines. Bd infections are treatable in at least some cases, but in the Gymnophiona has been little reported, and restricted to heat treatment in the form of increased environmental temperature. We report the successful treatment of Bd infection in the terrestrial African caecilian Geotrypetes seraphini and the prophylactic treatment of the aquatic neotropical caecilian Potomotyphlus kaupii , using 30 minute immersions in a 0.01% solution of the antifungal itraconazole over a period of 11 days. Previously only recorded in wild African Gymnophiona, our report of Bd in P. kaupii is not only the first record of infection in a wild aquatic caecilian but also in a caecilian of neotropical origin. To improve our understanding of the impact of Bd on caecilians, Bd isolates should be obtained from wild caecilians in order to ascertain what lineages of Bd infect this order. In addition, more wild individuals should be subjected to Bd diagnostic surveys, including in Asia where caecilians have not yet been subject to such surveys.

  • Diverse anatomy of the tongue and taste organs in five species of caecilian (Amphibia: Gymnophiona)
    Zoologischer Anzeiger - A Journal of Comparative Zoology, 2015
    Co-Authors: Karolina A. Budzik, Alexander Kupfer, David J Gower, Krystyna Żuwała, Mark Wilkinson
    Abstract:

    Abstract Limited previous studies on caecilian taste organs have demonstrated the presence of very few taste buds in the oral epithelium, while providing somewhat contradictory reports of their distribution within the oropharynx and across taxa. Here we report on the gross morphology of the tongue and explore the distribution, number and morphology of taste organs of five caecilian species representing five families, focusing upon variation within the group and investigating whether larvae and adults have the same type of taste organs. We find that taste buds are widespread in the oropharynx of caecilians and that they occur both in adults and larvae of a species with a biphasic life history. Thus Gymnophiona differ substantially from Batriachia, which have distinct larval and adult taste organs.

  • Evolution of Cranial Shape in Caecilians (Amphibia: Gymnophiona)
    Evolutionary Biology, 2014
    Co-Authors: Emma Sherratt, David J Gower, Christian Peter Klingenberg, Mark Wilkinson
    Abstract:

    Insights into morphological diversification can be obtained from the ways the species of a clade occupy morphospace. Projecting a phylogeny into morphospace provides estimates of evolutionary trajectories as lineages diversified information that can be used to infer the dynamics of evolutionary processes that produced patterns of morphospace occupation. We present here a large-scale investigation into evolution of morphological variation in the skull of caecilian amphibians, a major clade of vertebrates. Because caecilians are limbless, predominantly fossorial animals, diversification of their skull has occurred within a framework imposed by the functional demands of head-first burrowing. We examined cranial shape in 141 species, over half of known species, using X-ray computed tomography and geometric morphometrics. Mapping an existing phylogeny into the cranial morphospace to estimate the history of morphological change (phylomorphospace), we find a striking pattern: most species occupy distinct clusters in cranial morphospace that closely correspond to the main caecilian clades, and each cluster is separated by unoccupied morphospace. The empty spaces in shape space are unlikely to be caused entirely by extinction or incomplete sampling. The main caecilian clades have different amounts of morphological disparity, but neither clade age nor number of species account for this variation. Cranial shape variation is clearly linked to phyletic divergence, but there is also homoplasy, which is attributed to extrinsic factors associated with head-first digging: features of caecilian crania that have been previously argued to correlate with differential microhabitat use and burrowing ability, such as subterminal and terminal mouths, degree of temporal fenestration (stegokrotaphy/zygokrotaphy), and eyes covered by bone, have evolved and many combinations occur in modern species. We find evidence of morphological convergence in cranial shape, among species that have eyes covered by bone, resulting in a narrow bullet-shaped head. These results reveal a complex history, including early expansion of morphospace and both divergent and convergent evolution resulting in the diversity we observe today.

  • Gymnophiona) inferred from mitochondrial rRNA gene sequences. Molecular Phylogenetics and Evolution 23(3):pp. 401-407.
    2014
    Co-Authors: Mark Wilkinson, Oommen V. Oommen, Jonathan A. Sheps, Bernard L. Cohenb
    Abstract:

    Phylogenetic relationships of Indian caecilians (Amphibia: Gymnophiona) inferred from mitochondrial rRNA gene sequence

  • Extreme variation in the atrial septation of caecilians (Amphibia: Gymnophiona).
    Journal of anatomy, 2014
    Co-Authors: Desiderius M. De Bakker, Mark Wilkinson, Bjarke Jensen
    Abstract:

    Caecilians (order Gymnophiona) are elongate, limbless, snake-like amphibians that are the sister-group (closest relatives) of all other recent amphibians (frogs and salamanders). Little is known of their cardiovascular anatomy and physiology, but one nearly century old study suggests that Hypogeophis (family Indotyphlidae), commonly relied upon as a representative caecilian species, has atrial septation in the frontal plane and more than one septum. In contrast, in other vertebrates there generally is one atrial septum in the sagittal plane. We studied the adult heart of Idiocranium (also Indotyphlidae) using immunohistochemistry and confirm that the interatrial septum is close to the frontal plane. Additionally, a parallel right atrial septum divides three-fourths of the right atrial cavity of this species. Idiocranium embryos in the Hill collection reveal that atrial septation initiates in the sagittal plane as in other tetrapods. Late developmental stages, however, see a left-ward shift of visceral organs and a concordant rotation of the atria that reorients the atrial septa towards the frontal plane. The gross anatomies of species from six other caecilian families reveal that (i) the right atrial septum developed early in caecilian evolution (only absent in Rhinatrematidae) and that (ii) rotation of the atria evolved later and its degree varies between families. In most vertebrates a prominent atrial trabeculation associates with the sinuatrial valve, the so-called septum spurium, and the right atrial septum seems homologous to this trabeculation but much more developed. The right atrial septum does not appear to be a consequence of body elongation because it is absent in some caecilians and in snakes. The interatrial septum of caecilians shares multiple characters with the atrial septum of lungfishes, salamanders and the embryonic septum primum of amniotes. In conclusion, atrial septation in caecilians is based on evolutionarily conserved structures but possibly exhibits greater variation than in any other vertebrate order.

David J Gower - One of the best experts on this subject based on the ideXlab platform.

  • RESEARCH ARTICLE Evolution of Cranial Shape in Caecilians (Amphibia: Gymnophiona)
    2015
    Co-Authors: Emma Sherratt, David J Gower, Christian Peter, Klingenberg Mark Wilkinson
    Abstract:

    Abstract Insights into morphological diversification can be obtained from the ways the species of a clade occupy morphospace. Projecting a phylogeny into morphospace provides estimates of evolutionary trajectories as lineages diversified information that can be used to infer the dynamics of evolutionary processes that produced patterns of morphospace occupation. We present here a large-scale investigation into evolution of morphological variation in the skull of caecilian amphibians, a major clade of verte-brates. Because caecilians are limbless, predominantly fossorial animals, diversification of their skull has occurred within a framework imposed by the functional demands of head-first burrowing. We examined cranial shape in 141 species, over half of known species, using X-ray computed tomography and geometric morphometrics. Mapping a

  • Itraconazole treatment of Batrachochytrium dendrobatidis (Bd) infection in captive caecilians (Amphibia: Gymnophiona) and the first case of Bd in a wild neotropical caecilian
    Journal of Zoo and Aquarium Research, 2015
    Co-Authors: Matthew Rendle, David J Gower, Benjamin Tapley, Matthew W. Perkins, Gabriela B. Bittencourt-silva, Mark Wilkinson
    Abstract:

    Batrachochytrium dendrobatidis ( Bd ) is the causative agent of the disease amphibian chytridiomycosis, one of the factors driving amphibian population declines. Bd infections are treatable in at least some cases, but in the Gymnophiona has been little reported, and restricted to heat treatment in the form of increased environmental temperature. We report the successful treatment of Bd infection in the terrestrial African caecilian Geotrypetes seraphini and the prophylactic treatment of the aquatic neotropical caecilian Potomotyphlus kaupii , using 30 minute immersions in a 0.01% solution of the antifungal itraconazole over a period of 11 days. Previously only recorded in wild African Gymnophiona, our report of Bd in P. kaupii is not only the first record of infection in a wild aquatic caecilian but also in a caecilian of neotropical origin. To improve our understanding of the impact of Bd on caecilians, Bd isolates should be obtained from wild caecilians in order to ascertain what lineages of Bd infect this order. In addition, more wild individuals should be subjected to Bd diagnostic surveys, including in Asia where caecilians have not yet been subject to such surveys.

  • Diverse anatomy of the tongue and taste organs in five species of caecilian (Amphibia: Gymnophiona)
    Zoologischer Anzeiger - A Journal of Comparative Zoology, 2015
    Co-Authors: Karolina A. Budzik, Alexander Kupfer, David J Gower, Krystyna Żuwała, Mark Wilkinson
    Abstract:

    Abstract Limited previous studies on caecilian taste organs have demonstrated the presence of very few taste buds in the oral epithelium, while providing somewhat contradictory reports of their distribution within the oropharynx and across taxa. Here we report on the gross morphology of the tongue and explore the distribution, number and morphology of taste organs of five caecilian species representing five families, focusing upon variation within the group and investigating whether larvae and adults have the same type of taste organs. We find that taste buds are widespread in the oropharynx of caecilians and that they occur both in adults and larvae of a species with a biphasic life history. Thus Gymnophiona differ substantially from Batriachia, which have distinct larval and adult taste organs.

  • Evolution of Cranial Shape in Caecilians (Amphibia: Gymnophiona)
    Evolutionary Biology, 2014
    Co-Authors: Emma Sherratt, David J Gower, Christian Peter Klingenberg, Mark Wilkinson
    Abstract:

    Insights into morphological diversification can be obtained from the ways the species of a clade occupy morphospace. Projecting a phylogeny into morphospace provides estimates of evolutionary trajectories as lineages diversified information that can be used to infer the dynamics of evolutionary processes that produced patterns of morphospace occupation. We present here a large-scale investigation into evolution of morphological variation in the skull of caecilian amphibians, a major clade of vertebrates. Because caecilians are limbless, predominantly fossorial animals, diversification of their skull has occurred within a framework imposed by the functional demands of head-first burrowing. We examined cranial shape in 141 species, over half of known species, using X-ray computed tomography and geometric morphometrics. Mapping an existing phylogeny into the cranial morphospace to estimate the history of morphological change (phylomorphospace), we find a striking pattern: most species occupy distinct clusters in cranial morphospace that closely correspond to the main caecilian clades, and each cluster is separated by unoccupied morphospace. The empty spaces in shape space are unlikely to be caused entirely by extinction or incomplete sampling. The main caecilian clades have different amounts of morphological disparity, but neither clade age nor number of species account for this variation. Cranial shape variation is clearly linked to phyletic divergence, but there is also homoplasy, which is attributed to extrinsic factors associated with head-first digging: features of caecilian crania that have been previously argued to correlate with differential microhabitat use and burrowing ability, such as subterminal and terminal mouths, degree of temporal fenestration (stegokrotaphy/zygokrotaphy), and eyes covered by bone, have evolved and many combinations occur in modern species. We find evidence of morphological convergence in cranial shape, among species that have eyes covered by bone, resulting in a narrow bullet-shaped head. These results reveal a complex history, including early expansion of morphospace and both divergent and convergent evolution resulting in the diversity we observe today.

  • a visceral synapomorphy of scolecomorphus boulenger 1883 amphibia Gymnophiona scolecomorphidae
    African Journal of Herpetology, 2013
    Co-Authors: Mark Wilkinson, Simon P Loader, David J Gower, Hendrik Muller
    Abstract:

    We describe the distinctive but previously overlooked shape and position of the fat bodies of some scolecomorphid caecilians. Anteriorly positioned, finger-like fat bodies projecting into the coelom from narrow bases in the genital mesenteries are found in both sexes of all species of the East African caecilian genus Scolecomorphus and are unknown elsewhere. We interpret this as a visceral synapomorphy of Scolecomorphus that may be related to viviparity in this genus.

Wilkinson Mark - One of the best experts on this subject based on the ideXlab platform.

Gower, David J. - One of the best experts on this subject based on the ideXlab platform.

Felicity Wynne - One of the best experts on this subject based on the ideXlab platform.

  • batrachochytrium dendrobatidis infection and lethal chytridiomycosis in caecilian amphibians Gymnophiona
    Ecohealth, 2013
    Co-Authors: David J Gower, Felicity Wynne, Simon P Loader, Mark Wilkinson, Benjamin Tapley, Thomas M Dohertybone, Marcel T Kouete, Frances Orton, Olivia Daniel
    Abstract:

    Batrachochytrium dendrobatidis (Bd) is commonly termed the ‘amphibian chytrid fungus’ but thus far has been documented to be a pathogen of only batrachian amphibians (anurans and caudatans). It is not proven to infect the limbless, generally poorly known, and mostly soil-dwelling caecilians (Gymnophiona). We conducted the largest qPCR survey of Bd in caecilians to date, for more than 200 field-swabbed specimens from five countries in Africa and South America, representing nearly 20 species, 12 genera, and 8 families. Positive results were recovered for 58 specimens from Tanzania and Cameroon (4 families, 6 genera, 6+ species). Quantities of Bd were not exceptionally high, with genomic equivalent (GE) values of 0.052–17.339. In addition, we report the first evidence of lethal chytridiomycosis in caecilians. Mortality in captive (wild-caught, commercial pet trade) Geotrypetes seraphini was associated with GE scores similar to those we detected for field-swabbed, wild animals.