Blood respiratory properties of a viviparous amphibian

Toews, Daniel P.; Macintyre, Doug

doi:10.1038/266464a0

Cited by 23 publications

(7 citation statements)

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“…Among the genes identified on the T. compressicauda , the gene fam13a is involved in signal transduction (GO:0007165) and has been related to different lung diseases [71, 72] with its activity induced by low levels of O 2 [73]. While cutaneous gas exchange is important in Amphibia [74], T. compressicauda has the largest lungs of any caecilian [75], is reported to have more than 90% pulmonary oxygen uptake [76], and is able to tolerate hypoxic and hypercapnic conditions [77]. Thus, changes in fam13a might be related to enhanced pulmonary function.…”

Section: Discussionmentioning

confidence: 99%

What lies beneath? Molecular evolution during the radiation of caecilian amphibians

et al. 2019

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Background 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. Results 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. Conclusions 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. Electronic supplementary material The online version of this article (10.1186/s12864-019-5694-1) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

What lies beneath? Molecular evolution during the radiation of caecilian amphibians

et al. 2019

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“…The gills are well-vascularized and have specialized microvillous epithelial surfaces [128]. Respiratory gases are likely exchanged [129], but the possible uptake of maternal nutrients by the embryo remains to be investigated [3].…”

Section: Placentae Derived From Gills and Pharyngeal Epitheliummentioning

confidence: 99%

Embryonic specializations for vertebrate placentation

Whittington

Buddle

Griffith

et al. 2022

Phil. Trans. R. Soc. B

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The vertebrate placenta, a close association of fetal and parental tissue for physiological exchange, has evolved independently in sharks, teleost fishes, coelacanths, amphibians, squamate reptiles and mammals. This transient organ forms during pregnancy and is an important contributor to embryonic development in both viviparous and oviparous, brooding species. Placentae may be involved in transport of respiratory gases, wastes, immune molecules, hormones and nutrients. Depending on the taxon, the embryonic portion of the placenta is comprised of either extraembryonic membranes (yolk sac or chorioallantois) or temporary embryonic tissues derived via hypertrophy of pericardium, gill epithelium, gut, tails or fins. These membranes and tissues have been recruited convergently into placentae in several lineages. Here, we highlight the diversity and common features of embryonic tissues involved in vertebrate placentation and suggest future studies that will provide new knowledge about the evolution of pregnancy. This article is part of the theme issue ‘Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom’.

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“…Sawaya (1941Sawaya ( , 1947, Mendes (1941), Bennett & Wake (1974), Wood et al (1975) and GonGalves & Sawaya (1976 have determined the oxygen consumption in Siphonops, Geotrypetes, Boulengerula and Typhlonectes. The haematological and respiratory properties of the African species Boulengerula taitanus and the Amazonian species Typhlonectes compressicauda were investigated by Wood et al (1975) and Toews & MacIntyre (1977, respectively.…”

Section: Introductionmentioning

confidence: 99%

A scanning and transmission electron microscopic study of the lung of a caecilian Boulengerula taitanus

Maina¹,

Maloiy

1988

Journal of Zoology

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The lung of an apodan amphibian Bouiengerula taitanus has been investigated by scanning and transmission electron microscopy. This caecilian has only a single, long tubular lung that tapers towards the caudal end of the body. The lung has a central air duct which radially opens into a single stratum of alveoli lined by well developed septa that attach to two diametrically opposite trabeculae. The trabeculae carry the pulmonary artery and vein. The septa have blood capillaries on both surfaces and supportive and contractile elements like collagen, smooth muscle, elastic tissue and fibrocytes. The alveolar surface has only a single population of pneumocytes that combine the morphological features of the mammalian type 1 and 2 cells, i.e. they contain the osmiophilic, lamellated bodies and are squamous in form. Through subepithelial cytoplasmic invaginations, the pneumocytes, together with their basement lamina, were observed to be firmly attached to the septa1 tissue elements, presumably to avoid mechanical detachment during the rapid respiratory movements. The compartmentation of the whole lung in this species is viewed as a means of increasing the surface area available for gas exchange which, coupled with other already established cardiovascular adaptations in this species, may be of significance in its fossorial mode of life, an environment that is usually hypoxic and hypercarbic.

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Blood respiratory properties of a viviparous amphibian

Cited by 23 publications

References 4 publications

What lies beneath? Molecular evolution during the radiation of caecilian amphibians

What lies beneath? Molecular evolution during the radiation of caecilian amphibians

Embryonic specializations for vertebrate placentation

A scanning and transmission electron microscopic study of the lung of a caecilian Boulengerula taitanus

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