Search results for "Anura"

A Globin Gene of Ancient Evolutionary Origin in Lower Vertebrates: Evidence for Two Distinct Globin Families in Animals

2004

Hemoglobin, myoglobin, neuroglobin, and cytoglobin are four types of vertebrate globins with distinct tissue distributions and functions. Here, we report the identification of a fifth and novel globin gene from fish and amphibians, which has apparently been lost in the evolution of higher vertebrates (Amniota). Because its function is presently unknown, we tentatively call it globin X (GbX). Globin X sequences were obtained from three fish species, the zebrafish Danio rerio, the goldfish Carassius auratus, and the pufferfish Tetraodon nigroviridis, and the clawed frog Silurana tropicalis. Globin X sequences are distinct from vertebrate hemoglobins, myoglobins, neuroglobins, and cytoglobins.…

Context dependent variation in corticosterone and phenotypic divergence of Rana arvalis populations along an acidification gradient

2022

Background Physiological processes, as immediate responses to the environment, are important mechanisms of phenotypic plasticity and can influence evolution at ecological time scales. In stressful environments, physiological stress responses of individuals are initiated and integrated via the release of hormones, such as corticosterone (CORT). In vertebrates, CORT influences energy metabolism and resource allocation to multiple fitness traits (e.g. growth and morphology) and can be an important mediator of rapid adaptation to environmental stress, such as acidification. The moor frog, Rana arvalis, shows adaptive divergence in larval life-histories and predator defense traits along an acidi…

Identification and Evaluation of Hazardous Pyrolysates in Bio-Based Rigid Polyurethane-Polyisocyanurate Foam Smoke

2021

In this study, rigid polyurethane (PU) and polyisocyanurate (PIR) foam samples made from renewable material (tall oil fatty acid) based polyols were analyzed by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) to obtain information about the full relative smoke content, with a focus on substance identification by their functional groups and hazardousness. The relative content of gaseous products produced during the thermal degradation was evaluated between the two samples, differenced by their assigned isocyanate (NCO) index value—150 and 300. The main thermal degradation components of the rigid PU-PIR foam were found to originate from the decomposition of isocyanate, primarily for…

Species complexes and phylogenetic lineages of Hoferellus (Myxozoa, Cnidaria) including revision of the genus: A problematic case for taxonomy

2015

Background Myxozoans are metazoan parasites whose traditional spore morphology-based taxonomy conflicts DNA based phylogenies. Freshwater species of the genus Hoferellus are parasites of the excretory system, with several members infecting food and ornamental fish species, as well as amphibians. This study aims to increase our understanding of their molecular diversity and development, aspects about which little is known, and to generate a molecular diagnostic tool to discriminate between different pathogenic and non-pathogenic Hoferellus spp. Methods SSU and ITS rDNA phylogeny, along with morphological descriptions using light and electron microscopy were used to identify and characterize …

Testing alternative vicariance scenarios in Western Mediterranean discoglossid frogs

2004

Dated molecular phylogenies are often used to interpret evolutionary history with respect to paleogeographic events. Where more than one interpretation is possible, it is desirable but difficult to assess the alternatives in an objective manner. The present work demonstrates a formalized method for testing molecular clock calibrations and biogeographic scenarios based on them. We assessed the plausibility of several previously published biogeographic hypotheses, using the frog genera Alytes, Discoglossus, and Bombina as model groups. Our data set comprised ca. 900bp of partial mitochondrial 16S and 12S rRNA gene sequences (both genes evolved in a clock-like manner across genera) from nearly…

Anisotropy of the stiffness and strength of rigid low-density closed-cell polyisocyanurate foams

2016

The cells of polymer foams are usually extended in the foam rise direction, causing a geometrical anisotropy, the degree of which, characterized by the cell aspect ratio R, depends on foam density and production method. Such elongated cell shape translates into anisotropy of the mechanical properties of foams. Rigid low-density closed-cell polyisocyanurate foams of apparent density ranging from ca. 30 to 75 kg/m3, containing polyols derived from renewable resources, have been produced and tested for the stiffness and strength in the foam rise and transverse directions in order to experimentally characterize their mechanical anisotropy. Analytical relations for foams with rectangular paralle…

Rapeseed oil-based rigid polyisocyanurate foams modified with nanoparticles of various type

2014

Polyisocyanurate foams have been developed using a polyol system partially derived from rapeseed oil (RO). The effect of nanofillers with iso-dimensional geometry (zinc oxide), nanofibers (carbon nanotubes), and nanoplatelets (organically modified montmorillonite) on stiffness and strength of the foams has been studied. It was demonstrated that the tensile properties of the filled foams are enhanced by roughly the same proportion as the stiffness and strength of monolithic filled polymers.

Out of Asia: Mitochondrial DNA Evidence for an Oriental Origin of Tiger Frogs, Genus Hoplobatrachus

2001

Most examples of intercontinental dispersal events after the Miocene contact between Africa and Asia involve mammal lineages. Among amphibians, a number of probably related groups are known from both continents, but their phylogenies are so far largely unresolved. To test the hypothesis of Miocene dispersal against a Mesozoic vicariance scenario in the context of Gondwana fragmentation, we analyzed fragments of the mitochondrial 16S rRNA gene (572 bp) in 40 specimens of 34 species of the anuran family Ranidae. Results corroborated the monophyly of tiger frogs (genus Hoplobatrachus), a genus with representatives in Africa and Asia. The African H. occipitalis was the sister group of the Asian…

CCambios seculares de la agradacion aluvial y de la meandrizacion en la Ribera Alta del Xuquer

1992

Polyurethane and Polyisocyanurate Foams in External Tank Cryogenic Insulation

2013

External tanks of the spacecrafts need not only efficient, but also safe cryogenic insulation materials and the issues of their development are still urgent. At present, polyurethane (PUR) or polyisocyanurate (PIR) foams’ cryogenic insulation is widely applied in the partially reusable launch systems. Factors influencing the cryogenic resistance of external thermal insulation performed of spray-on PUR or PIR foams are characterised based on a wide literature search. They include chemical structure and macromolecules’ architecture of polymeric matrix, physical and mechanical properties of foams, thermal stability and combustibility, cellular structure of foams etc. Experimental data on physi…