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The Rate of Feeding by Mytilus in Different Kinds of Suspension
- C. Barker Jørgensen
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- Journal:
- Journal of the Marine Biological Association of the United Kingdom / Volume 28 / Issue 2 / October 1949
- Published online by Cambridge University Press:
- 11 May 2009, pp. 333-344
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The feeding rate of small specimens of Mytilus edulis (L.) has been determined in suspensions of colloidal graphite (‘Prodag’, grade ‘C’, and ‘Aquadag’, grade ‘S’), of flagellates, and of Nitzschia dosterium. The feeding rate was measured as the volume of water cleared from particles per unit time. In graphite suspensions, with particle size of about 4–5μ, as a rule only a small percentage of the particles was retained by the gills, whereas flagellates of about the same size were normally nearly all retained.
Amphibian respiration and olfaction and their relationships: from Robert Townson (1794) to the present
- C. BARKER JØRGENSEN
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- Journal:
- Biological Reviews / Volume 75 / Issue 3 / August 2000
- Published online by Cambridge University Press:
- 01 August 2000, pp. 297-345
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- August 2000
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The present review examines the developments in the elucidation of the mechanisms of amphibian respiration and olfaction. Research in these two areas has largely proceeded along independent lines, despite the fact that ventilation of the nasobuccopharyngeal cavity is a basic element in both functions. The English naturalist Robert Townson demonstrated, in the 1790s, that amphibians, contrary to general belief, ventilated the lungs by a pressure-pump mechanism. Frogs and other amphibians respire by alternatively dilating and contracting the buccopharyngeal cavity. During dilatation, with the mouth and glottis closed, air is sucked in through the open nostrils to fill the cavity. During contraction of the throat, with nostrils closed and glottis open, the air in the buccopharyngeal cavity is pressed into the lungs. During expiration, the glottis and nostrils open and air is expelled from the lungs ‘by their own contraction from a state of distention’. Herholdt (1801), a Danish army surgeon, independently described the buccal pressure-pump mechanism in frogs, his experiments being confirmed by the commissioners of the Société Philomatique in Paris. Haro (1842) reintroduced a suction mechanism for amphibian respiration, which Panizza (1845) refuted: excision of the tympanic membranes prevented lung inflation, the air in the buccopharyngeal cavity leaving through the tympanum holes. Closure of the holes with the fingers restored lung inflation. The importance of cutaneous respiration in frogs and other amphibians was discovered by Spallanzani (1803), who found that frogs might survive excision of the lungs and that the amounts of exhaled carbon dioxide were small compared with those eliminated through the skin. Edwards (1824) confirmed and extended Spallanzani's findings, and Regnault & Reiset (1849) attempted to establish the relative importance of skin and lungs as respiratory organs in frogs. The problem was solved by Krogh (1904a) who measured respiration through the skin and lungs separately and simultaneously. Krogh (1904a) confirmed that carbon dioxide was chiefly eliminated through the skin, correlated with its high diffusion rate in water and tissue, whereas the pattern of oxygen uptake varied seasonally, the pulmonary uptake being lower than the cutaneous during autumn and winter, but substantially higher during the breeding period. Dolk & Postma (1927) confirmed this respiratory pattern. More recently, Hutchison and coworkers have examined the relative role of pulmonary and cutaneous gas exchange in a large number of amphibians, equipped with head masks for the separate measurement of the lung respiration in normally ventilating animals (Vinegar & Hutchison, 1965; Guimond & Hutchison, 1968; Hutchison, Whitford & Kohl, 1968; Whitford & Hutchison, 1963, 1965, 1966). As early as 1758, Rösel von Rosenhof suggested that the lungs of frogs in water functioned as hydrostatic organs that permitted the animal to float at the surface or rest on the bottom of the pond. The suggestion was inspired by observations made in the second half of the seventeenth century by members of the Royal Academy of Sciences in Paris. The French anatomists demonstrated that a tortoise, presumably the European freshwater turtle Emys orbicularis, could regulate its buoyancy by changing the volume of the lungs, to descend passively or ascend in the water. The hydrostatic function of the lungs has been repeatedly rediscovered, by Emery (1869) in the frog, by Marcacci (1895) in frogs, toads and salamanders, by Whipple (1906b) in a newt, by Willem (1920, 1931) in frogs and Xenopus laevis, by Speer (1942) in several anurans and urodeles, and finally by de Jongh (1972) in Xenopus laevis. In the second half of the nineteenth century a number of important papers appeared which confirmed and extended Townson's (1794) and Panizza's (1845) analysis of the normal respiratory movements in frogs. Lung ventilation cycles, interspaced by oscillatory movements of the throat, might periodically be replaced by a sequence predominated by inspirations, resulting in lung inflation, followed by exhalations that restored normal lung volume. Babák (1912a) established that inflations were reactions to the experimental manipulations, and that in resting, undisturbed frogs, lung ventilations normally occurred singly, interspaced by series of approximately 10–50 buccal oscillations. Extensive comparative studies early in the century showed that the respiratory mechanisms and patterns were basically similar in all anurans and urodeles investigated. The modern era of investigations in amphibian respiration began with the work of de Jongh & Gans (1969). They recorded pressures in the buccal cavity, lungs and visceral cavity and electrical activity of some 15 muscles possibly associated with respiration in the bullfrog Rana catesbeiana. The respiration recorded in the frogs was predominated by cycles of lung inflation and deflation, consistent with substantially but not excessively disturbed frogs. Studies by other investigators on various anuran species showed respiratory patterns that varied strongly with respect to the frequency and degree of lung inflations, presumably reflecting degrees to which the experimental conditions affected the breathing.
The elucidation of the role of the buccopharyngeal ventilation in amphibian olfaction can be traced to the realization in the 1890s that the nasal cavity has a double function in being both the seat of the sense of smell and part of the respiratory passages. The ability of amphibians to smell and to react to air-borne or water-borne chemical cues in the environment thus depends on the oscillatory movements of the buccal floor which ventilate the nasal cavity. Experimental evidence for a sense of smell was, however, lacking, and it was first furnished in urodele feeding early in the present century. Despite the demonstration of the fundamental role of the nasobuccal oscillatory ventilation in olfactory responses to food in newts, the oscillatory throat movements in amphibians continued, however, to be referred to as respiratory. Evidence concerning the role of the buccopharyngeal ventilation in respiration had been circumstantial until Whitford & Hutchison (1963, 1965, 1966) determined the relative importance of cutaneous and pulmonary/buccopharyngeal respiration in lunged and lungless salamanders. In lungless salamanders, the buccopharyngeal mucosa accounted for approximately 25% of the total oxygen consumption, and it was concluded that buccopharyngeal oscillatory ventilation in salamanders is primarily respiratory in function, a possible olfactory function being secondary. During the last decades an extensive literature has accumulated on the role played by olfaction in the life of urodeles, but also in feeding in anurans. Often the descriptions of behaviour elicited by air-borne or water-borne odours also note increased oscillatory movements of the buccal floor, indicating the importance of the ventilation of the nasal cavity. In the elucidation of the functional significance of buccal oscillations in vertebrate evolution, the reptiles are of particular interest because such oscillations are also known in chelonians, crocodiles and some lizards. Olfaction plays a role in the life of chelonians and crocodiles which respire by means of suction mechanisms. The throat movements are thus not concerned with the ventilation of the lungs but presumably with olfaction. It is thus indicated that in lower vertebrates, including the amphibians, the shallow oscillatory movements of the buccal floor primarily serve to establish olfactory contact with the surrounding medium, air or water, whereas a respiratory function is secondary.
Role of urinary and cloacal bladders in chelonian water economy: historical and comparative perspectives
- C. BARKER JØRGENSEN
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- Journal:
- Biological Reviews / Volume 73 / Issue 4 / November 1998
- Published online by Cambridge University Press:
- 01 November 1998, pp. 347-366
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- November 1998
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The Parisian comparative anatomist Claude Perrault, dissecting an Indian giant tortoise in 1676, was the first to observe that the urinary bladder is of an extraordinary size in terrestrial tortoises. In 1799, the English comparative physiologist Robert Townson suggested that the bladder functioned as a water reservoir, as he had shown previously for frogs and toads. However, these observations went unnoticed in subsequent reports on tortoise water economy that were made by travellers and naturalists visiting the Galapagos Archipelago and marvelling over the huge numbers of giant tortoises that inhabited these desert-like islands. The first such report was by an American naval officer, David Porter, who was a privateer in the 1812–15 war with England. In his journal he referred to the constant supply of water which the Galapagos tortoises carried with them. References to the location in the body, as well as the amounts and quality of the water stored, were, however, contradictory.
The confusion concerning the anatomical identity of the water reservoir in the Galapagos tortoise, Geochelone elephantopus, persisted throughout the nineteenth century, and continued when studies of tortoise water economy and drinking behaviour in arid environments were taken up independently in the desert tortoise, Gopherus agassizii, which inhabits the desert regions in the south-western United States. In 1881 Cox found large sacs filled with clear water under the carapace, but it was half a century later that these sacs were identified as the large bilobed bladder; references to specific water sacs continued to appear in the literature until the 1960s.
Since 1970, information on the water economy of desert tortoises has been obtained from extensive field studies. Rates of disappearance of tritiated water injected into the body have shown that during the drought periods of the summer, water turnover (intake) rates do not differ from the rates of metabolic water production. Under these conditions urine is not voided, but is stored in the large bladder. During a drought period the bladder urine increases from initially low osmolality finally to reach isosmolality with the blood plasma. Soluble K+ is the major cation of the urine, but large amounts of K+ are also present as precipitated urates. During a drought period the body is in negative water balance, but despite substantial losses of total body water, the plasma concentrations of Na+ and Cl− can remain constant for many months, indicating regulation of the extracellular fluid and water content of the body tissues by reabsorption of water from the urinary bladder. The bladder thus acts both as a store for nitrogenous waste and K+ and as a water reservoir during droughts. Following rain showers, there is a sharp decline in tritium activity correlated with copious drinking from temporary pools of rain water. The old bladder urine is voided and most of the water drunk is stored as a highly dilute urine.
In 1676 Perrault observed that in a freshwater turtle, Emys orbicularis, but not in the giant tortoise, two other bladders opened into the cloaca. By the mid-twentieth century it had been established that these cloacal bladders typically were restricted to species of chelonians that led a semi-terrestrial or semi-aquatic life. The function of the bladders has been debated since Townson observed in 1799 that dehydrated freshwater turtles took up water by anal drinking, suggesting that anal drinking served in the water economy of semi-terrestrial turtles. Since then, the bladders have been ascribed hydrostatic and respiratory functions, but the recent literature mostly argues for a respiratory function. The possible role of the cloacal bladders as a water reservoir in amphibious turtles is still open.
Terrestrial amphibians and tortoises are unique among vertebrates in possessing large urinary bladders that may function as water reservoirs in dry environments. This function depends upon copious water intake when water becomes available combined with discontinued voiding of urine in the absence of water. Adaptation to terrestrial habitats in ureotelic amphibians is correlated with tolerance of high urea concentrations in the body fluids. In arid-zone tortoises and uricotelic tree frogs, nitrogenous waste products are precipitated in the bladder, which functions as the main sink. Renewed contact with water releases drinking behaviour and voiding of the bladder urine until the accumulated excretory products are eliminated from the body and/or bladder, preparing the organism for re-exposure to arid conditions.
200 YEARS OF AMPHIBIAN WATER ECONOMY: FROM ROBERT TOWNSON TO THE PRESENT
- C. BARKER JØRGENSEN
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- Journal:
- Biological Reviews / Volume 72 / Issue 2 / May 1997
- Published online by Cambridge University Press:
- 01 May 1997, pp. 153-237
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- May 1997
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In the 1790s, Robert Townson established the main features of the water economy of terrestrial amphibians: rapid evaporative water loss in dry surroundings, ‘drinking’ by absorption of water through the abdominal skin pressed against moist substrates, and use of the urinary bladder as a reservoir from which water is reabsorbed on land. This knowledge was of little interest to the establishment in the first half of the nineteenth century of experimental physiology as a basic medical discipline, when frogs became models in the elucidation of general physiological processes. Townson's pioneer contributions to amphibian physiology were forgotten for 200 years (Jørgensen 1994b). Durig (1901) and particularly Overton (1904) restored knowledge about amphibian water economy to the level reached by Townson, but the papers had little impact on the young science of animal physiology because they primarily aimed at elucidating the transport of fluids across membranes. Frog skin remained a model preparation in such studies throughout the century. With the establishment of terrestrial ecology early in the century, the relations of animals, including amphibians, to water became a central theme. Concurrently with comparative studies of amphibian water economy in an ecological setting, the subject proceeded as an aspect of animal osmoregulation. Adolph (1920–1930) and Rey (1937a) established the highly dynamic nature of water balance in amphibians in water and on land. Their observations indicated functional links between environment, skin and kidneys, the nature of which remained to be explored. Thorson & Svihla (1943) reopened the ecological approach in a comparative study of the relations between amphibian habitat and tolerance of dehydration. By mid-century, the central themes of amphibian adaptations to terrestrial modes of life were re-established, except for the function of the bladder as a water-depot. During the following decades, a rich literature appeared, particularly focusing on adaptations of amphibians to arid environments. Thus, in the 1970s, it was found that ‘waterproofing’ of the highly permeable skins by means of skin secretions had evolved independently in several families of tropical arboreal frogs, and that a number of amphibians that aestivate whilst burrowed in dry soil could reduce evaporation by forming cocoons from shed strata cornea. In 1950–1970 the role of bladder urine as a water depot in terrestrial amphibians was recognized: this did not change the established view of water balance in terrestrial amphibians as alternating between dehydration on land and rehydration in response to the deficit in body water. Amphibians may, however, maintain normal water balance whether the ambient medium is water or air by means of little understood integrated mechanisms in control of cutaneous drinking behaviour, water permeability of the skin and bladder wall, and urine production.
6 - Modern Mat-Building Microbial Communities: a Key to the Interpretation of Proterozoic Stromatolitic Communities
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- By Beverly K. Pierson, University of Puget Sound, John Bauld, Bureau of Mineral Resources, Richard W. Castenholz, University of Oregon, Elisa D'Amelio, Ames Research Center, David J. Des Marais, Ames Research Center, Jack D. Farmer, University of California, John P. Grotzinger, Massachusetts Institute of Technology, Bo Barker Jørgensen, University of Aarhus, Douglas C. Nelson, University of California, Anna C. Palmisano, Ivorydale Technical Center, J. William Schopf, University of California, Roger E. Summons, Bureau of Mineral Resources, Geology and Geophysics, Australia, Malcolm R. Walter, M. R. Walter Pty. Ltd, David M. Ward, Montana State University
- Edited by J. William Schopf, University of California, Los Angeles, Cornelis Klein, University of New Mexico
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- Book:
- The Proterozoic Biosphere
- Published online:
- 04 April 2011
- Print publication:
- 26 June 1992, pp 245-342
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Summary
Introduction
Modern microbial mats are structurally coherent macroscopic accumulations of microorganisms. Mats are widely distributed on earth. They are found in a surprisingly large number of diverse environments from the equatorial zones to both polar regions. They vary in size from extensive terrestrial and hypersaline mats that cover areas several square kilometers in extent to minute mats only a few square centimeters in area found in small thermal springs. They vary in thickness from massive accumulations measured in meters, such as those in the Persian Gulf and the Red Sea region, to thin films less than a few millimeters in thickness. In addition to being highly varied in size, modern microbial mats are also very diverse in morphology, community structure, and physiological characteristics. What do such mats have in common? Under what conditions do they form? What is the basis of their diversity? What insight do they provide, if any, to the interpretation of the widespread stromatolites of the Proterozoic?
A Terminology
Microbial mats are accretionary cohesive microbial communities which are often laminated and found growing at the sediment-water (occasionally sediment-air) interface. Most mats stabilize unconsolidated sediment. The mats are comprised of the various microorganisms that accumulate along with their metabolic products. The most conspicuous of these products is usually a copious amount of extracellular polysaccharide which helps hold the cells together to form a cohesive structure.