Osmoregulation in Australian Freshwater Mussels (Lamellibranchiata). I. Water and Chloride Ion Exchange in Hyridella australis (Lam.)

1953 ◽  
Vol 4 (2) ◽  
pp. 317 ◽  
Author(s):  
ID Hiscock
Keyword(s):  
Water Exchange ◽  
External Medium ◽  
Chloride Ion ◽  
Pericardial Fluid ◽  
The Body ◽  
Equilibrium Level ◽  
The Difference ◽  
Effective Seal ◽  
Australian Freshwater

The chlorinities of the blood and pericardial fluid of H. australis are similar, but always exceed those of the normal external medium. A study of blood chloride changes in mussels in media of different concentrations has shown that immediately following a change of medium there is a change in blood chlorinity, which tends to assume a new equilibrium level within 24 hr. The rapidity with which this change occurs depends upon the difference between the chlorinity of the blood and that of the external medium. A study of water exchange under identical conditions has shown that significant changes occur in the hydration of the mussel. In hypotonic media the mussel can regulate its water content; in hypertonic media it cannot, but its hydration assumes a new level within 24 hr. It is concluded that some part of the body surface is permeable to both salts and water. The urine of the mussel is hypotonic to the blood; it remains remarkably stabre in chlorinity despite changes in blood chlorinity. The role of the kidney as a regulating organ is discussed. The significance of shell movements in osmoregulation is demonstrated. Shell closure has been shown to be an effective seal from the external medium, allowing the mussel to resist desiccation.

Pressure cycles and the water economy of insects

1988 ◽  
Vol 318 (1190) ◽  
pp. 377-407 ◽  
Keyword(s):  
Body Temperature ◽  
Water Exchange ◽  
Vapour Phase ◽  
The Body ◽  
Tracheal System ◽  
Water Economy ◽  
Insect Wings ◽  
Pressure Cycle ◽  
Respiratory Gases

Water exchange between insects and their environment via the vapour phase includes influx and efflux components. The pressure cycle theory postulates that insects (and some other arthropods) can regulate the relative rates of influx and efflux of water vapour by modulating hydrostatic pressures at a vapour-liquid interface by compressing or expanding a sealed, gas-filled cavity. Some such cavities, like the tracheal system, could be compressed by elevated pressure in all or part of the haemocoele. Others, perhaps including the muscular rectum of flea prepupae, could be compressed by intrinsic muscles. Maddrell Insect Physiol . 8, 199 (1971)) suggested a pressure cycle mechanism of this kind to account for rectal uptake of water vapour in Thermobia but did not find it compatible with quantitative information then available. Newer evidence conforms better with the proposed mechanism. Cyclical pressure changes are of widespread occurrence in insects and have sometimes been shown to depend on water status. Evidence is reviewed for the role of the tracheal system as an avenue for net exchange of water between the insect and its environment. Because water and respiratory gases share common pathways, most published findings fail to distinguish between the conventional view that the tracheal system has evolved as a site for distribution and exchange of respiratory gases and that any water exchange occurring in it is generally incidental and nonadaptive, and the theory proposed here. The pressure cycle theory offers a supplementary explanation not incompatible with evidence so far available. The relative importance of water economy and respiratory exchange in the functioning of compressible cavities such as the tracheal system remains to be explored. Some further implications of the pressure cycle theory are discussed. Consideration is given to the possible involvement of vapour-phase transport in the internal redistribution of water within the body. It is suggested that some insect wings may constitute internal vapour-liquid exchange sites, where water can move from the body fluids to the intratracheal gas. Ambient and body temperature must influence rates of vapour-liquid mass transfer. If elevated body temperature promotes evaporative discharge of the metabolic water burden that has been shown to accumulate during flight in some large insects, their minimum threshold thoracic temperature for sustained flight may relate to the maintenance of water balance. The role of water economy in the early evolution of insect wings is considered. Pressure cycles might help to maintain water balance in surface-breathing insects living in fresh and saline waters, but the turbulence of the surface of the open sea might prevent truly marine forms from using this mechanism.

scholarly journals From Affect to Action: Choices in Attending to Disconcertment in Interdisciplinary Collaborations

2020 ◽  
pp. 016224392097408
Author(s):  
Mareike Smolka ◽  
Erik Fisher ◽  
Alexandra Hausstein
Keyword(s):  
Science And Technology Studies ◽  
Interdisciplinary Collaboration ◽  
The Body ◽  
Affective Labor ◽  
Methodological Choices ◽  
The Social ◽  
Interdisciplinary Collaborations ◽  
Social Shaping ◽  
The Difference

Reports from integrative researchers who have followed calls for sociotechnical integration emphasize that the potential of interdisciplinary collaboration to inflect the social shaping of technoscience is often constrained by their liminal position. Integrative researchers tend to be positioned as either adversarial outsiders or co-opted insiders. In an attempt to navigate these dynamics, we show that attending to affective disturbances can open up possibilities for productive engagements across disciplinary divides. Drawing on the work of Helen Verran, we analyze “disconcertment” in three sociotechnical integration research studies. We develop a heuristic that weaves together disconcertment, affective labor, and responsivity to analyze the role of the body in interdisciplinary collaborations. We draw out how bodies do affective labor when generating responsivity between collaborators in moments of disconcertment. Responsive bodies can function as sensors, sources, and processors of disconcerting experiences of difference. We further show how attending to disconcertment can stimulate methodological choices to recognize, amplify, or minimize the difference between collaborators. Although these choices are context-dependent, each one examined generates responsivity that supports collaborators to readjust the technical in terms of the social. This analysis contributes to science and technology studies scholarship on the role of affect in successes and failures of interdisciplinary collaboration.

Studies on the Physiology of Ascaris Lumbricoides

1952 ◽  
Vol 29 (1) ◽  
pp. 1-21
Author(s):  
A. D. HOBSON ◽  
W. STEPHENSON ◽  
L. C. BEADLE
Keyword(s):  
Osmotic Pressure ◽  
Body Fluid ◽  
Body Wall ◽  
Sea Water ◽  
External Medium ◽  
Chloride Concentration ◽  
The Body ◽  
Intestinal Fluid ◽  
The Difference ◽  
Saline Medium

1. The total osmotic pressure, electrical conductivity and chloride concentration of the body fluid of Ascaris lumbricoides and of the intestinal contents of the pig have been measured. 2. The results obtained agree with the observations of previous workers that Ascaris normally lives in a hypertonic medium and that it swells or shrinks in saline media which are too dilute or too concentrated. 3. Experiments comparing the behaviour of normal and ligatured animals show that both the body wall and the wall of the alimentary canal are surfaces through which water can pass. 4. 30% sea water has been used as a balanced saline medium for keeping the worms alive in the laboratory. This concentration was selected as being the one in which there was least change in the body weight of the animals exposed to it. 5. The osmotic pressure of the body fluid of worms kept in 30% sea water is approximately the same as in animals taken directly from the pig's intestine. The body fluid of fresh worms is hypertonic to 30% sea water and hypotonic to the intestinal fluid. In 30% sea water the normal osmotic gradient across the body wall is therefore reversed. 6. In 30% sea water the total ionic concentration (as measured by the conductivity) decreases slightly, but the chloride concentration increases by about 50%, although still remaining much below that of the external medium. 7. Experiments in which the animals were allowed to come into equilibrium with various concentrations of sea water from 20 to 40% show that there are corresponding changes in the osmotic pressure of the body fluid which is, however, always slightly above that of the saline medium. The conductivity also changes in a similar manner but is always less than that of the medium, and the difference between the two becomes progressively greater the more concentrated the medium. 8. The chloride concentration of the body fluid varies with but is always below that of the external medium, whether this is intestinal fluid or one of the saline media. In the latter the difference between the internal and external chloride concentrations is least in 20% sea water and becomes progressively greater as the concentration of the medium is increased. 9. Experiments with ligatured worms and with eviscerated cylinders of the body wall show that these share the capacity of the normal worm to maintain the chloride concentration of the body fluid below that of the environment. This power is not possessed by cylinders composed of the cuticle alone. 10. If the worms which have had their internal chloride concentration raised by exposure to 30% sea water are transferred to a medium composed of equal volumes of 30% sea water and isotonic sodium nitrate solution, the chloride concentration of the body fluid is reduced to a value below that of the external medium. This phenomenon is also displayed by worms ligatured after removal from the 30% sea water and, to an even more marked degree, by eviscerated cylinders of the body wall. 11. It is concluded that Ascaris is able to maintain the chloride concentration of the body fluid below that of the external medium by an process of chloride excretion against a concentration gradient, and that this mechanism is resident in the body wall, the cuticle being freely permeable to chloride.

“Africanist Presence” and the Role of Black Bodies

2020 ◽  
pp. 97-124
Author(s):  
Angela Alaimo O'Donnell
Keyword(s):  
American Literature ◽  
Essential Role ◽  
Black Body ◽  
Literary Imagination ◽  
The Body ◽  
Christian Church ◽  
Mary Douglas ◽  
Black Bodies ◽  
The Difference

Chapter 4, “‘Africanist Presence’ and the Role of Black Bodies,” taking its title and cue from Toni Morrison’s seminal study of race in American Literature, Playing in the Dark: Whiteness and the Literary Imagination, examines O’Connor’s exploration of the essential role played by African Americans in the construction of a white consciousness. It also considers the work of womanist theologian M. Shawn Copeland on “enfleshing freedom” in which she meditates on the imaging of the black body in Western culture and its implications in the Christian Church. The chapter considers the difference between what anthropologist Mary Douglas refers to as “physical bodies” and “social bodies” and the ways in which these representations and perceptions of the body enter into O’Connor’s work (73). The chapter includes analysis of “Everything that Rises Must Converge,” “The Artificial Nigger,” and “Judgement Day” (reprise).

scholarly journals Osmotic Regulation in Mosquito Larvae: The Role of the Malpighian Tubules

1951 ◽  
Vol 28 (1) ◽  
pp. 62-73 ◽  
Author(s):  
J. A. RAMSAY
Keyword(s):  
External Medium ◽  
Freezing Point ◽  
Sodium Concentration ◽  
Distal Region ◽  
Proximal Region ◽  
Malpighian Tubules ◽  
Intestinal Fluid ◽  
The Difference ◽  
Salt And Water Balance

1. The part played by the Malpighian tubules in the salt and water balance of Aedes aegypti larvae has been studied; the intestinal fluid and haemolymph have been compared in respect of freezing-point depression and sodium concentration. 2. It appears highly probable that the fluid passing down the intestine is derived from the Malpighian tubules with little or no contribution from the midgut. 3. When the larvae are kept in fresh water the intestinal fluid is very slightly hypotonic to the haemolymph (not isotonic as previously reported), but its sodium concentration is only about one-half that of the haemolymph. 4. When the larvae are kept in solutions of NaCl the difference in sodium concentration between intestinal fluid and haemolymph decreases. In an external medium of 1% NaCl the difference is abolished. 5. There is thus evidence that when the external medium is poor in salts the Malpighian tubules can contribute to the work of salt retention by excreting a fluid containing less sodium than the haemolymph; but there is no evidence that under any conditions they can excrete a fluid containing more sodium than the haemolymph. 6. Evidence of a decrease in the sodium concentration of the tubule fluid from distal region to proximal region is not statistically significant.

scholarly journals The Contribution of the Alkaline Pericardial Fluid of Freshwater Turtles to Acid Buffering During Prolonged Anoxia

1984 ◽  
Vol 109 (1) ◽  
pp. 55-62
Author(s):  
DONALD C. JACKSON ◽  
NORBERT HEISLER
Keyword(s):  
Energy Supply ◽  
Ionic Composition ◽  
Pericardial Fluid ◽  
The Body ◽  
Plasma Samples ◽  
Freshwater Turtles ◽  
Transfer Processes ◽  
Chrysemys Picta Bellii ◽  
Acid Buffering

The role of buffering of the high pericardial fluid [HCO3−] of the turtle, Chrysemys picta bellii Gray, was evaluated during prolonged anoxia at 3 and 10°C. At 3°C, pericardial fluid samples were collected from groups of animals after 0, 1, 2, 4 and 8 weeks of anoxia, and the ionic composition of these samples was compared to plasma values from the same animals. At 10 °C, pericardial and plasma samples were taken from normoxic turtles and from turtles after 11 days of anoxia. The samples were analysed for total CO2 (CCOCO2), [Cl−] and [lactate−]. At 3°C, the fall in pericardial [HCO3−] and the rise in [lactate−] lagged behind the same changes in the plasma, until after about 8 weeks of anoxia the composition of pericardial fluid became identical with that of plasma. At 10 °C, pericardial [HCO3−] fell significantly after 11 days of anoxia but was still above plasma [HCO3−], while [lactate−] was essentially the same in both fluids. We conclude that the pericardial fluid does participate in the buffering of lactic acid during prolonged anoxia. However, its involvement is delayed, possibly until the energy supply for the active carrier-mediated transfer processes responsible for the high [HCO3−] gradient breaks down as a consequence of the prolonged anoxia. Analysis of the overall buffering in the body reveals that the contribution of the pericardial fluid is minor.

scholarly journals Mnéme and hénosis

2018 ◽  
Vol 12 (2) ◽  
pp. 56-70
Author(s):  
Sonja Weiss
Keyword(s):  
Mystical Experience ◽  
The State ◽  
The Body ◽  
The Other ◽  
Other Hand ◽  
The Difference ◽  
The Moment ◽  
Intelligible World

This paper reconsiders the role of memory in Plotinus' philosophy, in view of the mystical unity (hénosis) of the soul with intelligible truths, and a less desirable unification with its objects of memory during its earthly existence. As a rule, the mystical experience precludes memory, since the latter is related to time and binds a man to his individuality. Nevertheless, the capacity to remember remains an important part of the philosophical áskesis leading to this experience, since the memory is the only faculty of the soul that is able to travel through time, even though it is part of the process of discursive thinking and consequently is in a way imprisoned in time. Memory therefore turns out to be a double-edged power, which leaves us to question when we can regard it as an instrument of preserving what is inherent to us, and when, on the other hand, it is simply chaining us to the lower reality of the sensible world. The difference between the anagogical power of the Platonic recollection (anámnesis) and the memory as the state keeping us from unity with the intelligible world is important for identifying the moment when a man must let go of what he has been clinging to. This moment, however, is not set in time, but depends on the moral disposition of a man's soul leading a timeless existence outside, as well as inside, the body.

scholarly journals Quantifying predation pressure and the protective role of sheltered basking sites for small snakes in South Africa

2016 ◽  
Vol 15 (2) ◽  
pp. 155 ◽  
Author(s):  
Gareth Coombs
Keyword(s):  
South Africa ◽  
Mortality Rate ◽  
Behavioral Ecology ◽  
Predation Rate ◽  
Protective Role ◽  
The Body ◽  
Eastern Cape ◽  
The Difference ◽  
Predatory Birds

Small snakes are frequent prey of predatory birds, reptiles, and mammals. The resulting mortality rate is difficult to quantify given the low likelihood of observing such predation events. However, studies using plasticine snake models have shown that small snakes may experience relatively high rates of predation. Model snakes constructed from slow-drying clay (as a substitute to plasticine) were used to assess the predation rate on small snakes in the Eastern Cape of South Africa. The model snakes were used to test whether snakes basking in semi-shaded positions, with at least half of the body covered by overhanging vegetation are detected by bird and mammal predators. There were relatively high rates of predation, with half of the unconcealed snake models experiencing attacks. The predation rate on partially concealed models is lower than on unconcealed models, but the difference is not statistically significant. Thus, basking in sheltered areas may offer snakes protection against predators; however, predation attempts on concealed models suggests that predators actively seek out areas where prey might hide. This is the first quantification of predation on small snakes in South Africa, and the results generate numerous questions relating to the behavioral ecology of the diverse snake fauna found in this country

scholarly journals ASSESSMENT OF TIDE AND WIND EFFECTS ON THE HYDRODYNAMICS AND INTERACTIONS BETWEEN TIJUCAS BAY AND THE ADJACENT CONTINENTAL SHELF, SANTA CATARINA, BRAZIL

2014 ◽  
Vol 32 (3) ◽  
pp. 515
Author(s):  
Márcio Fabiano de Souza ◽  
Carlos Augusto França Schettini
Keyword(s):  
Continental Shelf ◽  
Residence Time ◽  
Wind Direction ◽  
River Discharge ◽  
Water Exchange ◽  
Coastal Processes ◽  
Input And Output ◽  
Continental Shelves ◽  
The Difference

ABSTRACT. The importance of understanding coastal processes and their relationships to continental shelves has become increasingly important as coastal areasexperience great socio-economic growth. In this context, Tijucas Bay and its interactions with the adjacent continental shelf was a subject of study through the use ofa numerical model (MOHID Water Modeling System) for analysis of its hydrodynamics, exchanges of water masses between the bay and the continental shelf and thewater’s residence time in the bay. Simulations were run for 30 or more days. Boundary conditions for the simulations were tides, constant river discharge (24 m3.s–1)and winds. Wind time series represented typical conditions in the region, with NE winds (3 m.s–1) forcing the domain for five days, then turning in the counterclockwisedirection for 12 hours until they were oriented in the SE direction (8 m.s–1), remaining two days in this direction and again turning counterclockwise for 12 hours andending in the NE direction. Three scenarios have been proposed for the experiment; scenario 1 was forced by tides and river discharge, and scenarios 2 and 3 wereforced by tides, river discharge and winds. The difference between scenarios 2 and 3 was the wind direction at the beginning of the simulations: scenario 2 began withNE winds, and scenario 3 began with SE winds. The results showed that the hydrodynamics and water exchange of Tijucas Bay were strongly influenced by tide andwind. The tide provided the input and output water pattern in the bay, while the wind accelerated the process, increasing the speed of exchange between the bay and theadjacent shelf. Superficial layers were the most affected by the winds. The easternmost portion of the bay exhibited the greatest current speeds, with a tendency to forma gyre current with water input at one end and output at the other, depending upon wind direction. In the shallower regions, currents exhibited their greatest speeds,while in the deeper areas, the inverse was found. The residence time for scenario 1 was 75 days, and for scenarios 2 and 3, the residence times were 19 and 15 days,respectively. The hydrodynamics of Tijucas Bay is a sum of processes related to its forcings; however, it is important to highlight the role of winds as one of the majordeterminants of the dynamics of this region, directly affecting transport throughout the bay.Keywords: circulation, estuary-shelf interaction, residence time. RESUMO. Atualmente o entendimento de processos costeiros e sua relação com a plataforma continental ganha importância a medida em que as regiões costeira tornam-se áreas de grande expansão sócio-econômica. Neste contexto, a Baía de Tijucas e sua interação com a plataforma adjacente foi alvo de investigação através do uso de modelo numérico (MOHID) para análise da hidrodinâmica, troca de massas de água entre baía e plataforma e tempo de residência da baía. As simulações correram por 30 dias ou mais. As condições de fronteiras para as simulações foram maré, descarga fluvial constante (24 m3.s–1) e ventos. As séries temporais deventos representam condições típicas da região com ventos NE (3 m.s–1) forçando o domínio por 5 dias girando no sentido anti-horário durante 12 horas até a direção SE (8 m.s–1), permanecendo por 2 dias nesta direção e novamente girando no sentido anti-horário por 12 horas até a direção NE. Três cenários foram propostos parao experimento, cenário 1 foi forçado por marés e descarga fluvial, cen´arios 2 e 3 forçados por marés, descarga fluvial e ventos. A diferenc¸a entre os cenários 2 e 3 é a direçãoo do vento no início das simulações, cenário 2 começa com vento NE e cenário 3 com vento SE. Os resultados mostram que a hidrodinâmica e a troca de água da Baía de Tijucas são fortemente influenciadas pela maré e pelo vento. A maré proporciona um padrão de entrada e saída de água da baía, enquanto o vento acelera oprocesso aumentando as velocidades de troca entre baía e plataforma adjacente. As camadas superficiais são mais afetadas pelos ventos. As extremidades da baía nasua porção mais a leste apresentam as maiores velocidades das correntes, a tendência é a formação de uma corrente em forma de giro com entrada de água por uma extremidade e saída por outra, dependendo da direção do vento. Nas partes mais rasas as correntes apresentam maiores velocidades enquanto nas partes mais profundas é o inverso. O tempo de residência para o cenário 1 foi de 75 dias, enquanto os cenários 2 e 3 apresentaram tempo de residência de 19 e 15 dias, respectivamente.A hidrodinâmica da Baía de Tijucas é um somatório de processos relacionados às suas forçantes. Entretanto ´e importante destacar o papel dos ventos como um dosprincipais condicionantes da dinâmica desta região afetando diretamente o transporte baía afora.Palavras-chave: circulação, interação estuário-plataforma, tempo de residência.

The role of the Rogers–Shephard inequality in the characterization of the difference body

2017 ◽  
Vol 29 (6) ◽  
Author(s):  
Judit Abardia-Evéquoz ◽  
Eugenia Saorín Gómez
Keyword(s):  
Lower Bounds ◽  
The Body ◽  
Upper And Lower Bounds ◽  
Difference Body ◽  
The Difference

AbstractThe Rogers–Shephard and Brunn–Minkowski inequalities provide upper and lower bounds for the volume of the difference body in terms of the volume of the body itself. In this work it is shown that the difference body operator is the only continuous and

Sign in / Sign up

Export Citation Format

Share Document