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Mark Wilkinson - One of the best experts on this subject based on the ideXlab platform.
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A new genus and species of rhinatrematid caecilian (Amphibia: Gymnophiona: Rhinatrematidae) from Ecuador
Herpetological Journal, 2021Co-Authors: Mark WilkinsonAbstract:A new genus and species of rhinatrematid caecilian, Amazops amazops gen. et sp. nov., is described based on a single specimen from Orellana, Ecuador collected in 1990. Among other features the new taxon differs from all other rhinatrematid Caecilians in having less than four annular grooves interrupted in the region of the vent and in the squamosal contributing to the bony margin of the orbit. A consideration of its distinctive morphology suggests that it is plausible that the new taxon is the sister taxon of all other rhinatrematid Caecilians. That the genus is known from a single specimen, and that this is the first new rhinatrematid species from the Andes described for more than 50 years, highlights the poor sampling (collecting) of rhinatrematid Caecilians and limited knowledge of their diversity.
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What lies beneath? Molecular evolution during the radiation of caecilian amphibians
BMC genomics, 2019Co-Authors: María Torres-sánchez, David J Gower, Mark Wilkinson, David Alvarez-ponce, Christopher J. Creevey, Diego San MauroAbstract:Evolution leaves an imprint in species through genetic change. At the molecular level, evolutionary changes can be explored by studying ratios of nucleotide substitutions. The interplay among molecular evolution, derived phenotypes, and ecological ranges can provide insights into adaptive radiations. Caecilians (order Gymnophiona), probably the least known of the major lineages of vertebrates, are limbless tropical amphibians, with adults of most species burrowing in soils (fossoriality). This enigmatic order of amphibians are very distinct phenotypically from other extant amphibians and likely from the ancestor of Lissamphibia, but little to nothing is known about the molecular changes underpinning their radiation. We hypothesised that colonization of various depths of tropical soils and of freshwater habitats presented new ecological opportunities to Caecilians. A total of 8540 candidate groups of orthologous genes from transcriptomic data of five species of caecilian amphibians and the genome of the frog Xenopus tropicalis were analysed in order to investigate the genetic machinery behind caecilian diversification. We found a total of 168 protein-coding genes with signatures of positive selection at different evolutionary times during the radiation of Caecilians. The majority of these genes were related to functional elements of the cell membrane and extracellular matrix with expression in several different tissues. The first colonization of the tropical soils was connected to the largest number of protein-coding genes under positive selection in our analysis. From the results of our study, we highlighted molecular changes in genes involved in perception, reduction-oxidation processes, and aging that likely were involved in the adaptation to different soil strata. The genes inferred to have been under positive selection provide valuable insights into caecilian evolution, potentially underpin adaptations of Caecilians to their extreme environments, and contribute to a better understanding of fossorial adaptations and molecular evolution in vertebrates.
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Musculoskeletal development of the Central African caecilian Idiocranium russeli (Amphibia: Gymnophiona: Indotyphlidae) and its bearing on the re-evolution of larvae in caecilian amphibians
Zoomorphology, 2019Co-Authors: Tobias Theska, David J Gower, Mark Wilkinson, Hendrik MullerAbstract:Few detailed accounts of the developmental morphology of caecilian amphibians exist and recent studies have highlighted problems concerning the homology of some skull elements. We investigated the embryonic and post-hatching development of the skeleton and musculature of Idiocranium russeli , a possibly miniaturized caecilian endemic to Cameroon. Idiocranium has been suggested to be direct developing; our results strongly support this hypothesis. The external morphology of different embryonic stages, the ossification sequence, and the configuration of the cranial muscles of I. russeli indicate heterochronic shifts of adult traits into embryonic development, as well as the loss or absence of various larval and metamorphic traits. For example, the tentacle, which plesiomorphically develops during metamorphosis, is already fully developed in late embryos. The maxilla and the palatine, which fuse to form the maxillopalatine (during metamorphosis in most biphasic species), fuse well before hatching. Muscles exclusive to the larva, such as the m. interhyoideus and m. hyomandibularis, are absent during development, whereas adult muscles including the m. genioglossus and m. cephalodorsosubpharyngeus, form during embryonic development. A larval ceratobranchial IV is present and fuses to the ceratobranchial III very early in ontogeny. In its near complete absence of larval traits during development, I. russeli resembles the Indian indotyphlid Gegeneophis ramaswamii ; this similarity complicates a straightforward explanation for the re-evolution of free-living larvae in Seychelles indotyphlid Caecilians.
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multi tissue transcriptomes of caecilian amphibians highlight incomplete knowledge of vertebrate gene families
DNA Research, 2019Co-Authors: Maria Torressanchez, David J Gower, Mark Wilkinson, Christopher J. Creevey, Etienne Kornobis, Diego San MauroAbstract:: RNA sequencing (RNA-seq) has become one of the most powerful tools to unravel the genomic basis of biological adaptation and diversity. Although challenging, RNA-seq is particularly promising for research on non-model, secretive species that cannot be observed in nature easily and therefore remain comparatively understudied. Among such animals, the Caecilians (order Gymnophiona) likely constitute the least known group of vertebrates, despite being an old and remarkably distinct lineage of amphibians. Here, we characterize multi-tissue transcriptomes for five species of Caecilians that represent a broad level of diversity across the order. We identified vertebrate homologous elements of caecilian functional genes of varying tissue specificity that reveal a great number of unclassified gene families, especially for the skin. We annotated several protein domains for those unknown candidate gene families to investigate their function. We also conducted supertree analyses of a phylogenomic dataset of 1,955 candidate orthologous genes among five caecilian species and other major lineages of vertebrates, with the inferred tree being in agreement with current views of vertebrate evolution and systematics. Our study provides insights into the evolution of vertebrate protein-coding genes, and a basis for future research on the molecular elements underlying the particular biology and adaptations of caecilian amphibians.
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Morphological evolution and modularity of the caecilian skull
BMC evolutionary biology, 2019Co-Authors: Carla Bardua, David J Gower, Mark Wilkinson, Emma Sherratt, Anjali GoswamiAbstract:Caecilians (Gymnophiona) are the least speciose extant lissamphibian order, yet living forms capture approximately 250 million years of evolution since their earliest divergences. This long history is reflected in the broad range of skull morphologies exhibited by this largely fossorial, but developmentally diverse, clade. However, this diversity of form makes quantification of caecilian cranial morphology challenging, with highly variable presence or absence of many structures. Consequently, few studies have examined morphological evolution across Caecilians. This extensive variation also raises the question of degree of conservation of cranial modules (semi-autonomous subsets of highly-integrated traits) within this clade, allowing us to assess the importance of modular organisation in shaping morphological evolution. We used an intensive surface geometric morphometric approach to quantify cranial morphological variation across all 32 extant caecilian genera. We defined 16 cranial regions using 53 landmarks and 687 curve and 729 surface sliding semilandmarks. With these unprecedented high-dimensional data, we analysed cranial shape and modularity across Caecilians assessing phylogenetic, allometric and ecological influences on cranial evolution, as well as investigating the relationships among integration, evolutionary rate, and morphological disparity. We found highest support for a ten-module model, with greater integration of the posterior skull. Phylogenetic signal was significant (Kmult = 0.87, p < 0.01), but stronger in anterior modules, while allometric influences were also significant (R2 = 0.16, p < 0.01), but stronger posteriorly. Reproductive strategy and degree of fossoriality were small but significant influences on cranial morphology (R2 = 0.03–0.05), after phylogenetic (p
David J Gower - One of the best experts on this subject based on the ideXlab platform.
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POSTMORTEM FINDINGS IN EIGHT SPECIES OF CAPTIVE CAECILIAN (AMPHIBIA: GYMNOPHIONA) OVER A TEN-YEAR PERIOD.
Journal of zoo and wildlife medicine : official publication of the American Association of Zoo Veterinarians, 2020Co-Authors: E J Flach, David J Gower, Matthew Rendle, Matthew W. Perkins, Yedra Feltrer, Stephanie L. Jayson, Christopher J. Michaels, Ann Pocknell, Sonja Rivers, Mark F. StidworthyAbstract:Between July 2007 and June 2017 there were 86 deaths in the populations of eight caecilian species at the Zoological Society of London (ZSL) London Zoo. The mortality rate (deaths per animal-year at risk) ranged from 0.03 in the Congo caecilian (Herpele squalostoma) to 0.85 in Kaup's caecilian (Potomotyphlus kaupii). Among the 73 individuals examined post mortem, no cause of death or primary diagnosis could be established in 35 cases, but of the others the most common cause of death was dermatitis (22 cases). When all significant pathological findings were considered, skin lesions of varying types were again the commonest (56 cases), particularly among the aquatic species: Typhlonectes compressicauda (18 out of 21 cases), T. natans (8/10) and P. kaupii (12/14). Other common findings were poor gut-fill (35 cases), kidney and gastrointestinal lesions (10 cases each), generalized congestion (8 cases) and poor body condition (6 cases). This review adds to the growing body of knowledge regarding the presentations and causes of disease in captive Caecilians.
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What lies beneath? Molecular evolution during the radiation of caecilian amphibians
BMC genomics, 2019Co-Authors: María Torres-sánchez, David J Gower, Mark Wilkinson, David Alvarez-ponce, Christopher J. Creevey, Diego San MauroAbstract:Evolution leaves an imprint in species through genetic change. At the molecular level, evolutionary changes can be explored by studying ratios of nucleotide substitutions. The interplay among molecular evolution, derived phenotypes, and ecological ranges can provide insights into adaptive radiations. Caecilians (order Gymnophiona), probably the least known of the major lineages of vertebrates, are limbless tropical amphibians, with adults of most species burrowing in soils (fossoriality). This enigmatic order of amphibians are very distinct phenotypically from other extant amphibians and likely from the ancestor of Lissamphibia, but little to nothing is known about the molecular changes underpinning their radiation. We hypothesised that colonization of various depths of tropical soils and of freshwater habitats presented new ecological opportunities to Caecilians. A total of 8540 candidate groups of orthologous genes from transcriptomic data of five species of caecilian amphibians and the genome of the frog Xenopus tropicalis were analysed in order to investigate the genetic machinery behind caecilian diversification. We found a total of 168 protein-coding genes with signatures of positive selection at different evolutionary times during the radiation of Caecilians. The majority of these genes were related to functional elements of the cell membrane and extracellular matrix with expression in several different tissues. The first colonization of the tropical soils was connected to the largest number of protein-coding genes under positive selection in our analysis. From the results of our study, we highlighted molecular changes in genes involved in perception, reduction-oxidation processes, and aging that likely were involved in the adaptation to different soil strata. The genes inferred to have been under positive selection provide valuable insights into caecilian evolution, potentially underpin adaptations of Caecilians to their extreme environments, and contribute to a better understanding of fossorial adaptations and molecular evolution in vertebrates.
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Musculoskeletal development of the Central African caecilian Idiocranium russeli (Amphibia: Gymnophiona: Indotyphlidae) and its bearing on the re-evolution of larvae in caecilian amphibians
Zoomorphology, 2019Co-Authors: Tobias Theska, David J Gower, Mark Wilkinson, Hendrik MullerAbstract:Few detailed accounts of the developmental morphology of caecilian amphibians exist and recent studies have highlighted problems concerning the homology of some skull elements. We investigated the embryonic and post-hatching development of the skeleton and musculature of Idiocranium russeli , a possibly miniaturized caecilian endemic to Cameroon. Idiocranium has been suggested to be direct developing; our results strongly support this hypothesis. The external morphology of different embryonic stages, the ossification sequence, and the configuration of the cranial muscles of I. russeli indicate heterochronic shifts of adult traits into embryonic development, as well as the loss or absence of various larval and metamorphic traits. For example, the tentacle, which plesiomorphically develops during metamorphosis, is already fully developed in late embryos. The maxilla and the palatine, which fuse to form the maxillopalatine (during metamorphosis in most biphasic species), fuse well before hatching. Muscles exclusive to the larva, such as the m. interhyoideus and m. hyomandibularis, are absent during development, whereas adult muscles including the m. genioglossus and m. cephalodorsosubpharyngeus, form during embryonic development. A larval ceratobranchial IV is present and fuses to the ceratobranchial III very early in ontogeny. In its near complete absence of larval traits during development, I. russeli resembles the Indian indotyphlid Gegeneophis ramaswamii ; this similarity complicates a straightforward explanation for the re-evolution of free-living larvae in Seychelles indotyphlid Caecilians.
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multi tissue transcriptomes of caecilian amphibians highlight incomplete knowledge of vertebrate gene families
DNA Research, 2019Co-Authors: Maria Torressanchez, David J Gower, Mark Wilkinson, Christopher J. Creevey, Etienne Kornobis, Diego San MauroAbstract:: RNA sequencing (RNA-seq) has become one of the most powerful tools to unravel the genomic basis of biological adaptation and diversity. Although challenging, RNA-seq is particularly promising for research on non-model, secretive species that cannot be observed in nature easily and therefore remain comparatively understudied. Among such animals, the Caecilians (order Gymnophiona) likely constitute the least known group of vertebrates, despite being an old and remarkably distinct lineage of amphibians. Here, we characterize multi-tissue transcriptomes for five species of Caecilians that represent a broad level of diversity across the order. We identified vertebrate homologous elements of caecilian functional genes of varying tissue specificity that reveal a great number of unclassified gene families, especially for the skin. We annotated several protein domains for those unknown candidate gene families to investigate their function. We also conducted supertree analyses of a phylogenomic dataset of 1,955 candidate orthologous genes among five caecilian species and other major lineages of vertebrates, with the inferred tree being in agreement with current views of vertebrate evolution and systematics. Our study provides insights into the evolution of vertebrate protein-coding genes, and a basis for future research on the molecular elements underlying the particular biology and adaptations of caecilian amphibians.
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Morphological evolution and modularity of the caecilian skull
BMC evolutionary biology, 2019Co-Authors: Carla Bardua, David J Gower, Mark Wilkinson, Emma Sherratt, Anjali GoswamiAbstract:Caecilians (Gymnophiona) are the least speciose extant lissamphibian order, yet living forms capture approximately 250 million years of evolution since their earliest divergences. This long history is reflected in the broad range of skull morphologies exhibited by this largely fossorial, but developmentally diverse, clade. However, this diversity of form makes quantification of caecilian cranial morphology challenging, with highly variable presence or absence of many structures. Consequently, few studies have examined morphological evolution across Caecilians. This extensive variation also raises the question of degree of conservation of cranial modules (semi-autonomous subsets of highly-integrated traits) within this clade, allowing us to assess the importance of modular organisation in shaping morphological evolution. We used an intensive surface geometric morphometric approach to quantify cranial morphological variation across all 32 extant caecilian genera. We defined 16 cranial regions using 53 landmarks and 687 curve and 729 surface sliding semilandmarks. With these unprecedented high-dimensional data, we analysed cranial shape and modularity across Caecilians assessing phylogenetic, allometric and ecological influences on cranial evolution, as well as investigating the relationships among integration, evolutionary rate, and morphological disparity. We found highest support for a ten-module model, with greater integration of the posterior skull. Phylogenetic signal was significant (Kmult = 0.87, p < 0.01), but stronger in anterior modules, while allometric influences were also significant (R2 = 0.16, p < 0.01), but stronger posteriorly. Reproductive strategy and degree of fossoriality were small but significant influences on cranial morphology (R2 = 0.03–0.05), after phylogenetic (p
Oommen V. Oommen - One of the best experts on this subject based on the ideXlab platform.
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An insight into the skin glands, dermal scales and secretions of the caecilian amphibian Ichthyophis beddomei.
Saudi journal of biological sciences, 2020Co-Authors: Damodaran Arun, Oommen V. Oommen, Mohammad Abdulkader Akbarsha, S. Sandhya, Lekha DivyaAbstract:Abstract The caecilian amphibians are richly endowed with cutaneous glands, which produce secretory materials that facilitate survival in the hostile subterranean environment. Although India has a fairly abundant distribution of Caecilians, there are only very few studies on their skin and secretion. In this background, the skin of Ichthyophis beddomei from the Western Ghats of Kerala, India, was subjected to light and electron microscopic analyses. There are two types of dermal glands, mucous and granular. The mucous gland has a lumen, which is packed with a mucous. The mucous-producing cells are located around the lumen. In the granular gland, a lumen is absent; the bloated secretory cells, filling the gland, are densely packed with granules of different sizes which are elegantly revealed in TEM. There is a lining of myo-epithelial cells in the peripheral regions of the glands. Small flat disk-like dermal scales, dense with squamulae, are embedded in pockets in the dermis, distributed among the cutaneous glands. 1-4 scales of various sizes are present in each scale pocket. Scanning electron microscopic observation of the skin surface revealed numerous glandular openings. The skin gland secretions, exuded through the pores, contain fatty acids, alcohols, steroid, hydrocarbons, terpene, aldehyde and a few unknown compounds.
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light and electron microscopic observations on the organization of skin and associated glands of two caecilian amphibians from western ghats of india
Micron, 2018Co-Authors: Arun Damodaran, Oommen V. Oommen, Beyo Reston Saroja, Ramachandran Kotharambath, Akbarsha Mohammad Abdulkader, Divya LekhaAbstract:We adopted light and electron microscopy to understand the structure of the skin of two species of Caecilians, Ichthyophis tricolor and Uraeotyphlus cf. oxyurus, from Western Ghats of Kerala, India. The surface of the skin of these Caecilians contains an irregular pattern of microridges. Oval, round and polymorphic glandular openings are randomly distributed all over the skin surface. Most of the openings are funnel shaped. The epithelial cells along the rim of the opening descend into the tunnel of the duct. A few glandular openings protrude slightly above the epithelium of the duct. The skin is formed of epidermis and dermis. Small flat disk-like dermal scales, composed of a basal plate of several layers of unmineralized collagen fibers topped with a discontinuous layer of mineralized globular squamulae, are lodged in pouches in the transverse ridges of the skin. Each pouch contains 1-4 scales, which might differ in size. The scales are almost similar between species, yet the difference can be useful in distinguishing between the two species. Flask cells and Merkel cells are present in the epidermis. Two types of glands, mucous and granular, are present in the dermis. The mucous glands are densely packed with mucous vesicles. Darkly stained mucous producing cells are located around the periphery of the gland. Secretory mucous vesicles differ in their organization and distribution. The granular glands are located perpendicular to the skin surface. The granule producing cells of the gland are located near the periphery. There are differently stained spherical secretory granules of various sizes in the cytoplasm. Thus, the use of different microscopic techniques contributed fascinatingly to the first ever understanding of organization of the skin of two selected caecilian species from Western Ghats, revealing certain features to differ between them.
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antigenic homogeneity of male mullerian gland mg secretory proteins of a caecilian amphibian with secretory proteins of the mammalian prostate gland and seminal vesicles evidence for role of the caecilian mg as a male accessory reproductive gland
Zoology, 2014Co-Authors: Arumugam Radha, Oommen V. Oommen, Sreesha Sree, Kunnathodi Faisal, Pradeep G Kumar, Mohammad Abdulkader AkbarshaAbstract:Whereas in all other vertebrates the Mullerian ducts of genetic males are aborted during development, under the influence of Mullerian-inhibiting substance, in the caecilian amphibians they are retained as a pair of functional glands. It has long been speculated that the Mullerian gland might be the male accessory reproductive gland but there has been no direct evidence to this effect. The present study was undertaken to determine whether the caecilian Mullerian gland secretory proteins would bear antigenic similarity to secretory proteins of the prostate gland and/or the seminal vesicles of a mammal. The secretory proteins of the Mullerian gland of Ichthyophis tricolor were evaluated for cross-reactivity with antisera raised against rat ventral prostate and seminal vesicle secretory proteins, adopting SDS-PAGE, two-dimensional electrophoresis and immunoblot techniques. Indeed there was a cross-reaction of five Mullerian gland secretory protein fractions with prostatic protein antiserum and of three with seminal vesicle protein antiserum. A potential homology exists because in mammals the middle group of the prostate primordia is derived from a diverticulum of the Mullerian duct. Thus this study, by providing evidence for expression of prostatic and seminal vesicle proteins in the Mullerian gland, substantiates the point that in Caecilians the Mullerian glands are the male accessory reproductive glands.
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Organization of the Corpus Luteum in a Caecilian Gegeneophis ramaswamii
Journal of Endocrinology and Reproduction, 2010Co-Authors: Reston S Beyo, Oommen V. Oommen, L Divya, K. Ramachandran, M A AkbarshaAbstract:Corpus luteum is a transient and well known endocrine gland that develops from the ruptured follicles in the female vertebrate ovaries, immediately after ovulation. A major source of progesterone, this gland is concerned with gestation in the viviparous animals and retention of eggs in the oviduct in the oviparous species. Caecilians are a group of amphibians with several aspects of reproductive anatomy and physiology unique. In as much as corpus lutem has been described in a few caecilian species, it has not been described from ultrastructural perspectives. Here in we describe the ultrastructural features of corpus luteum of a single specimen of Gegeneophis ramaswamii , which was captured immediately after it laid the eggs. The corpus luteum is formed by three types of cells, namely granulosa lutein cells, thecal lutein cells and phagocytic cells. Both the types of lutein cells are characterized by abundant mitochondria, endoplasmic reticulum and Golgi apparatus. The granulose lutein cells abound with discrete granules. The phagocytic cells engage in phagocytosing cell debris. The cellular features are discussed in relation to information from oviparous as well as viviparous vertebrates. Thus, the paper describes, for the first time the corpus luteum of a caecilian from ultrastructural perspectives.
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stages in follicle cell oocyte interface during vitellogenesis in Caecilians ichthyophis tricolor and gegeneophis ramaswamii a transmission electron microscopic study
Cell and Tissue Research, 2008Co-Authors: Reston S Beyo, Oommen V. Oommen, L Divya, Mathew Smita, M A AkbarshaAbstract:We describe the ultrastructural organization of the vitellogenic follicle stages in two caecilian species. Monthly samples of slices of ovary of Ichthyophis tricolor and Gegeneophis ramaswamii from the Western Ghats of India were subjected to transmission electron-microscopic analysis, with special attention to the follicle cell/oocyte interface. In order to maintain uniformity of the stages among the amphibians, all the stages in the caecilian follicles were assigned to stages I–VI, the vitellogenic and post-vitellogenic follicles being assigned to stages III–VI. Stage III commences with the appearance of precursors of vitelline envelope material in the perivitelline space. Stages IV and V have been assigned appropriate substages. During the transition of stage III to stage VI oocytes, a sequential change occurs in the manifestations of follicle cells, perivitelline space, vitelline envelope and oocyte cortex. The vitelline envelope becomes a tough coat through the tunnels of which the macrovilli pass to interdigitate between the microvilli. The oocyte surface forms pinocytic vesicles that develop into coated pits and, later, coated vesicles. Contributions of the oocyte cortex to the vitelline envelope and of the follicle cells to yolk material via synthesis within them are indicated. The follicle cell/oocyte interface of vitellogenic follicles of these two Caecilians resembles that in anurans and urodeles, with certain features being unique to Caecilians. Thus, this paper throws light on the possible relationships of Caecilians to anurans and urodeles with special reference to ovarian follicles.
Alexander Kupfer - One of the best experts on this subject based on the ideXlab platform.
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The evolution of parental investment in caecilian amphibians: a comparative approach
Biological Journal of The Linnean Society, 2016Co-Authors: Alexander Kupfer, Erin E. Maxwell, Sandy Reinhard, Susanne KuehnelAbstract:Parental care is widespread among vertebrates and the observed patterns of parental care and investment are extremely diverse. Among amphibians, Caecilians (Gymnophiona) exhibit considerable variation in reproductive modes, including both oviparity and viviparity, combined with highly unusual investment strategies (e.g. skin-feeding and intrauterine feeding). In the present study, current knowledge on the reproductive modes is integrated into an analysis of the evolutionary scenario of parental investment of Caecilians. Phylogenetically basal Caecilians possessing a biphasic life cycle that includes an aquatic larval stage invest in macrolecithal eggs directly corresponding to size at hatching. Some phylogenetically derived Caecilians (i.e. the Teresomata) have a smaller clutch size and show a reduction to either medium-yolked (mesolecithal) or small-yolked (microlecithal) eggs. Via alternative pathways of parental investment, such as intrauterine feeding in viviparous taxa and maternal dermatotrophy in oviparous taxa, teresomatan Caecilians increase both offspring size and quality. However, more data regarding reproductive biology are needed to obtain a fully resolved understanding of the evolution of reproduction in caecilian amphibians.
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Sexual size dimorphism in the viviparous caecilian amphibian Geotrypetes seraphini seraphini (Gymnophiona: Dermophiidae) including an updated overview of sexual dimorphism in caecilian amphibians
Amphibia-Reptilia, 2016Co-Authors: Markus Maerker, Sandy Reinhard, Peter Pogoda, Alexander KupferAbstract:Sexual size dimorphism (SSD) describing intersexual size differences of a given taxon is a widespread phenomenon in the animal kingdom. SSD plays a significant role in understanding life history and mating system evolution. The snakelike morphology of limbless caecilian amphibians lacking obvious secondary sexual characters (in contrast to frogs and salamanders) impedes an accurate comparison between sexes. Here, the phylogenetically derived teresomatan and viviparous caecilian Geotrypetes seraphini seraphini was analysed for patterns of sexual dimorphism. In terms of body size females were the larger sex, but when body length was adjusted male-biased intersexual differences in cloacal shape appeared. The larger female size is likely explained by fecundity selection as clutch size was positively correlated to female body length. Unexpectedly a cryptic, ontogeny related variation of the nuchal collars was found. An overview of SSD in Caecilians including data for 27 species of nine out of ten existing families revealed a quite high number of taxa showing sexually dimorphic head size dimensions exclusively present among phylogenetically derived teresomatan Caecilians. Still further research including insights into the behavioural ecology and molecular ecology of mating systems is warranted to better understand the evolution of sexual size dimorphism of caecilian amphibians.
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Diverse anatomy of the tongue and taste organs in five species of caecilian (Amphibia: Gymnophiona)
Zoologischer Anzeiger - A Journal of Comparative Zoology, 2015Co-Authors: Karolina A. Budzik, Alexander Kupfer, David J Gower, Krystyna Żuwała, Mark WilkinsonAbstract: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.
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Sperm storage in caecilian amphibians
Frontiers in Zoology, 2012Co-Authors: Susanne Kuehnel, Alexander KupferAbstract:Background Female sperm storage has evolved independently multiple times among vertebrates to control reproduction in response to the environment. In internally fertilising amphibians, female salamanders store sperm in cloacal spermathecae, whereas among anurans sperm storage in oviducts is known only in tailed frogs. Facilitated through extensive field sampling following historical observations we tested for sperm storing structures in the female urogenital tract of fossorial, tropical caecilian amphibians. Findings In the oviparous Ichthyophis cf. kohtaoensis , aggregated sperm were present in a distinct region of the posterior oviduct but not in the cloaca in six out of seven vitellogenic females prior to oviposition. Spermatozoa were found most abundantly between the mucosal folds. In relation to the reproductive status decreased amounts of sperm were present in gravid females compared to pre-ovulatory females. Sperm were absent in females past oviposition. Conclusions Our findings indicate short-term oviductal sperm storage in the oviparous Ichthyophis cf. kohtaoensis . We assume that in female Caecilians exhibiting high levels of parental investment sperm storage has evolved in order to optimally coordinate reproductive events and to increase fitness.
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Sexual size dimorphism in caecilian amphibians: analysis, review and directions for future research.
Zoology (Jena Germany), 2009Co-Authors: Alexander KupferAbstract:Sexual dimorphism, widespread in the animal kingdom, describes differences between the sexes in size, shape and many other traits. Sexual size dimorphism (SSD) plays a significant role in understanding life history evolution and mating systems. The snakelike morphology of limbless caecilian amphibians lacking obvious secondary sexual characters (in contrast to frogs and salamanders) impedes accurate intrasexual comparisons. In this study, sexual size dimorphism in the oviparous caecilian Ichthyophis cf. kohtaoensis, a phylogenetically basal caecilian, was analysed. Females were larger in all body and head characters tested. However, when adjusted to body size (total length), females differed only in their cloacal shape. Clutch volume was positively correlated to female body size, thus female fecundity increased with body size supporting the hypothesis of a fecundity-selected SSD in the oviparous Ichthyophis cf. kohtaoensis. A review of the present SSD data for Caecilians shows that many species are monomorphic for body size but show dimorphism in head size, while other species demonstrate female-biased SSD. Male-biased SSD has not been reported for Caecilians. To understand life history evolution in Caecilians, further studies on the reproductive biology of other taxa are urgently needed, in particular for rhinatrematids and uraeotyphlids. New data will allow phylogenetically controlled comparative analyses to fully explore the pattern of SSD among caecilian lineages.
M A Akbarsha - One of the best experts on this subject based on the ideXlab platform.
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Organization of the Corpus Luteum in a Caecilian Gegeneophis ramaswamii
Journal of Endocrinology and Reproduction, 2010Co-Authors: Reston S Beyo, Oommen V. Oommen, L Divya, K. Ramachandran, M A AkbarshaAbstract:Corpus luteum is a transient and well known endocrine gland that develops from the ruptured follicles in the female vertebrate ovaries, immediately after ovulation. A major source of progesterone, this gland is concerned with gestation in the viviparous animals and retention of eggs in the oviduct in the oviparous species. Caecilians are a group of amphibians with several aspects of reproductive anatomy and physiology unique. In as much as corpus lutem has been described in a few caecilian species, it has not been described from ultrastructural perspectives. Here in we describe the ultrastructural features of corpus luteum of a single specimen of Gegeneophis ramaswamii , which was captured immediately after it laid the eggs. The corpus luteum is formed by three types of cells, namely granulosa lutein cells, thecal lutein cells and phagocytic cells. Both the types of lutein cells are characterized by abundant mitochondria, endoplasmic reticulum and Golgi apparatus. The granulose lutein cells abound with discrete granules. The phagocytic cells engage in phagocytosing cell debris. The cellular features are discussed in relation to information from oviparous as well as viviparous vertebrates. Thus, the paper describes, for the first time the corpus luteum of a caecilian from ultrastructural perspectives.
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stages in follicle cell oocyte interface during vitellogenesis in Caecilians ichthyophis tricolor and gegeneophis ramaswamii a transmission electron microscopic study
Cell and Tissue Research, 2008Co-Authors: Reston S Beyo, Oommen V. Oommen, L Divya, Mathew Smita, M A AkbarshaAbstract:We describe the ultrastructural organization of the vitellogenic follicle stages in two caecilian species. Monthly samples of slices of ovary of Ichthyophis tricolor and Gegeneophis ramaswamii from the Western Ghats of India were subjected to transmission electron-microscopic analysis, with special attention to the follicle cell/oocyte interface. In order to maintain uniformity of the stages among the amphibians, all the stages in the caecilian follicles were assigned to stages I–VI, the vitellogenic and post-vitellogenic follicles being assigned to stages III–VI. Stage III commences with the appearance of precursors of vitelline envelope material in the perivitelline space. Stages IV and V have been assigned appropriate substages. During the transition of stage III to stage VI oocytes, a sequential change occurs in the manifestations of follicle cells, perivitelline space, vitelline envelope and oocyte cortex. The vitelline envelope becomes a tough coat through the tunnels of which the macrovilli pass to interdigitate between the microvilli. The oocyte surface forms pinocytic vesicles that develop into coated pits and, later, coated vesicles. Contributions of the oocyte cortex to the vitelline envelope and of the follicle cells to yolk material via synthesis within them are indicated. The follicle cell/oocyte interface of vitellogenic follicles of these two Caecilians resembles that in anurans and urodeles, with certain features being unique to Caecilians. Thus, this paper throws light on the possible relationships of Caecilians to anurans and urodeles with special reference to ovarian follicles.
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assembly of ovarian follicles in the Caecilians ichthyophis tricolor and gegeneophis ramaswamii light and transmission electron microscopic study
Zygote, 2007Co-Authors: Reston S Beyo, Oommen V. Oommen, L Divya, P Sreejith, M A AkbarshaAbstract:Summary Though much is known about various aspects of reproductive biology of amphibia, there is littleinformation on the cellular and mechanistic basis of assembly of ovarian follicles in this group. Thisis especially true of the Caecilians. Therefore, taking advantage of the abundant distribution of Caeciliansin the Western Ghats of India, two species of Caecilians, Ichthyophis tricolor and Gegeneophis ramaswamii ,were subjected to light and transmission electron microscopic analysis to trace the sequential changesduring the assembly of ovarian follicles. The paired ovaries of these Caecilians are elongated sac-likestructures each including numerous vitellogenic follicles. The follicles are connected by a connectivetissue stroma. This stroma contains nests of oogonia, primary oocytes and pregranulosa cells as spatiallyseparated nests. During assembly of follicles the oocytes increase in size and enter the meiotic prophasewhen the number of nucleoli in the nucleus increases. The mitochondrial cloud or Balbiani vitellinebody, initially localized at one pole of the nucleus, disperses through out the cytoplasm subsequently.Synaptonemal complexes are prominent in the pachytene stage oocytes. The pregranulosa cells migratethrough the connective tissue fibrils of the stroma and arrive at the vicinity of the meiotic prophaseoocytes. On contacting the oocyte, the pregranulosa cells become cuboidal in shape, wrap the diplotenestage oocyte as a discontinuous layer and increase the content of cytoplasmic organelles and inclusions.The oocytes increase in size and are arrested in diplotene when the granulosa cells become flat andform a continuous layer. Soon a perivitelline space appears between the oolemma and granulosa cells,completing the process of assembly of follicles. Thus, the events in the establishment of follicles in thecaecilian ovary are described.Keywords: Caecilian, Follicular assembly, Granulosa cells, Mitochondrial cloud, Oocyte
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Seasonal variation in spermatogenic and androgenic activities in a caecilian testis ( Ichthyophis tricolor )
Journal of Zoology, 2005Co-Authors: Mathew Smita, Reston S Beyo, M A Akbarsha, Jancy M. George, Oommen V. OommenAbstract:Caecilians are an order of amphibians with distribution confined to several of the tropical countries. They are subterranean animals and practice a form of internal fertilization. Several species are viviparous. Published reports on seasonal variation in male reproduction in Caecilians are limited to a very few species. A study was undertaken to examine the seasonal variation of testicular activity with respect to spermatogenesis and steroidogenesis in a caecilian, Ichthyophis tricolor , fairly abundant in the Western Ghats of Kerala, India, using light and transmission electron microscopy, terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling (TUNEL) staining and biochemical determination of 3-hydroxy-Δ 5 -steroid dehydrogenase (Δ 5 -3β-HSDH) activity. Three phases in spermatogenic activity, active spermatogenesis (July–November), early regression (December–March) and spermatogenic quiescence (April–June) are identified. Apoptosis seems to be the mechanism of germ cell death during the regression phase. Leydig cells are interstitial and not peritubular. Activity of testicular Δ 5 -3β-HSDH follows the same pattern as spermatogenic activity, although histometric data on the interstitial tissue reveal higher areas during the regression and quiescent phases. Our findings will be useful in evolving strategies for conservation of Caecilians with special reference to Kerala, India.
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sertoli cells in the testis of Caecilians ichthyophis tricolor and uraeotyphlus cf narayani amphibia gymnophiona light and electron microscopic perspective
Journal of Morphology, 2003Co-Authors: Mathew Smita, Oommen V. Oommen, Jancy M. George, M A AkbarshaAbstract:The Caecilians have evolved a unique pattern of cystic spermatogenesis in which cysts representing different stages in spermatogenesis coexist in a testis lobule. We examined unsettled issues relating to the organization of the caecilian testis lobules, including the occurrence of a fatty matrix, the possibility of both peripheral and central Sertoli cells, the origin of Sertoli cells from follicular cells, and the disengagement of older Sertoli cells to become loose central Sertoli cells. We subjected the testis of Ichthyophis tricolor (Ichthyophiidae) and Uraeotyphlus cf. narayani (Uraeotyphliidae) from the Western Ghats of Kerala, India, to light and transmission electron microscopic studies. Irrespective of the functional state of the testis, whether active or regressed, Sertoli cells constitute a permanent feature of the lobules. The tall Sertoli cells adherent to the basal lamina with basally located pleomorphic nuclei extend deeper into the lobule to meet at the core. There they provide for association of germ cells at different stages of differentiation, an aspect that has earlier been misconceived as the fatty matrix. Germ cells up to the 4-cell stage remain in the intercalating region of the Sertoli cells and they are located at the apices of the Sertoli cells from the 8-cell stage onwards. The developing germ cells are intimately associated with the Sertoli cell adherent to the basal lamina until spermiation. There are ameboid cells in the core of the lobules that appear to interact with the germ cells at the face opposite to their attachment with the Sertoli cells. Adherence of the Sertoli cells to the basal lamina is a permanent feature of the caecilian testicular lobules. The ameboid cells in the core are neither Sertoli cells nor their degeneration products. J. Morphol. 258:317–326, 2003. © 2003 Wiley-Liss, Inc.
