Osmotic Regulation in Mosquito Larvae

1950 ◽  
Vol 27 (2) ◽  
pp. 145-157 ◽  
Author(s):  
J. A. RAMSAY
Keyword(s):  
Fresh Water ◽  
Sea Water ◽  
External Medium ◽  
Freezing Point ◽  
Anterior Part ◽  
Osmotic Regulation ◽  
Opposite Process ◽  
Normal Environment ◽  
Different Parts

1. The processes of osmotic regulation in the larvae of Aedes aegypti and of A. detritus have been studied by determination of the freezing-point of samples of fluid collected from different parts of the gut. 2. In A. aegypti, kept in fresh water (its normal environment), the fluid passing down the intestine to the rectum is isotonic with the haemolymph. In the rectum it becomes strongly hypotonic before being eliminated. 3. In A. detritus, kept in sea water (its normal environment), the opposite process is observed, the fluid in the rectum becoming hypertonic to the haemolymph and approximately isotonic with the external medium before being eliminated. 4. In A. detritus, which is able to live in dilute media as well as in sea water, the only two specimens from fresh water available for examination were found to have the rectal fluid hypotonic to the haemolymph. 5. The ability of A. detritus, not possessed by A. aegypti, to produce an hypertonic fluid in the rectum is tentatively associated with a region in the anterior part of the rectum and lined with an epithelium distinctly different from that in the remainder of the rectum. This anterior region has not been found in A. aegypti.

The evolution of under-ice melt ponds, or double diffusion at the freezing point

1974 ◽  
Vol 64 (3) ◽  
pp. 507-528 ◽  
Author(s):  
Seelye Martin ◽  
Peter Kauffman
Keyword(s):  
Fresh Water ◽  
Sea Water ◽  
Freezing Point ◽  
Salt Water ◽  
Ice Sheet ◽  
Water Layer ◽  
Double Diffusion ◽  
Theoretical Models ◽  
Interfacial Region ◽  
Ice Melt

In an experimental and theoretical study, we model a phenomenon observed in the summer Arctic, where a fresh-water layer at a temperature of 0°C floats both over a sea-water layer at its freezing point and under an ice layer. Our results show that the ice growth in this system takes place in three phases. First, because the fresh-water density decreases upon supercooling, the rapid diffusion of heat relative to salt from the fresh to the salt water causes a density inversion and thereby generates a high Rayleigh number convection in the fresh water. In this convection, supercooled water rises to the ice layer, where it nucleates into thin vertical interlocking ice crystals. When these sheets grow down to the interface, supercooling ceases. Second, the presence of the vertical ice sheets both constrains the temperatureTand salinitysto lie on the freezing curve and allows them to diffuse in the vertical. In the interfacial region, the combination of these processes generates a lateral crystal growth, which continues until a horizontal ice sheet forms. Third, because of theTandsgradients in the sea water below this ice sheet, the horizontal sheet both migrates upwards and increases in thickness. From one-dimensional theoretical models of the first two phases, we find that the heat-transfer rates are 5–10 times those calculated for classic thermal diffusion.

Preparation of U(VI) and Th(IV) alpha-sources from sea and fresh water samples by combining coprecipitation, solvent extraction and electrodeposition procedures

2004 ◽  
Vol 92 (3) ◽  
Author(s):  
R. Zarki ◽  
A. Elyahyaoui ◽  
A. Chiadli
Keyword(s):  
Solvent Extraction ◽  
Fresh Water ◽  
Water Samples ◽  
Sea Water ◽  
Accurate Determination ◽  
Simple Method ◽  
Considerable Saving ◽  
Initial Aqueous Solution ◽  
Initial Ph

SummaryA simple method combining coprecipitation, solvent extraction and electrodeposition for determining uranium and thorium in sea water and fresh water samples is developed. It offers a considerable saving in time, minimising chemical treatment and costs. The analytical procedure consists of enrichment of U and Th by coprecipitation with iron(III) hydroxides and subsequent extraction by diethylether solution and electrodeposition of each actinide in the extracting organic phase in which it was separated.The dependence of the coprecipitation, the extraction-electrodeposition and the overall yields of the above mentioned elements is examined in relation to the initial aqueous solution acidity and various amounts of iron carrier. At an initial pH between 6 and 10, quantitative coprecipitation of U and Th requires use of an Fe(III) quantity which depends on the acidity of these solutions. This quantity varies, under explored conditions, between 10 and 110mg/L. At a starting pH of 11, this coprecipitation becomes almost independent of Fe(III) amounts.The proposed procedure was used to analyse the content of U and Th isotopes in water samples. Recoveries of 60%-93% are obtained for uranium and 63%-86% for thorium. Good resolutions (37-56.5keV) are also achieved under optimum conditions. These resolutions allow to make accurate determination of U and Th isotopes in various water samples.

The Site of Formation of Hypotonic Urine in the Nephridium of Lumbricus

1949 ◽  
Vol 26 (1) ◽  
pp. 65-75 ◽  
Author(s):  
J. A. RAMSAY
Keyword(s):  
Osmotic Pressure ◽  
Freezing Point ◽  
Freezing Point Depression ◽  
Narrow Tube ◽  
Wide Tube ◽  
Different Parts

1. Methods for the collection of samples of urine from different parts of the nephridium of Lumbricus are described. 2. The osmotic pressures of these samples have been measured by determination of freezing-point depression and have been compared with the osmotic pressure of the medium surrounding the nephridium. 3. The results of this comparison indicate that the ability to form hypotonic urine is certainly present in the wide tube, is possibly present in the middle tube and is probably not present in the narrow tube. 4. The analogy between the nephridium and the vertebrate nephron is discussed.

Osmotic regulation in the embryo of the herring (Clupea harengus)

1965 ◽  
Vol 45 (2) ◽  
pp. 305-311 ◽  
Author(s):  
F. G. T. Holliday ◽  
M. Pattie Jones
Keyword(s):  
Sea Water ◽  
Freezing Point ◽  
Body Fluids ◽  
Clupea Harengus ◽  
Osmotic Regulation ◽  
Osmotic Concentration ◽  
Significant Change

Just before spawning the semen of the herring is isosmotic with the parent blood, the eggs are hyposmotic. Immediately the eggs are placed in sea water of salinities 5, 17·5, 35 and 50 %0 there is a change in the freezing-point of the yolk indicating that it has approached close to being isosmotic with the water. Changes in the freezing-point of the yolk during development indicate that the overgrowing embryo gradually regulates the osmotic concentration of the yolk, although full regulation is not achieved until after the closing of the blastopore. After this point there is no significant change in the freezing-point of the yolk or body fluids. Regulation is most probably brought about by the activity of the cells of the ectoderm.

Preconcentration and determination of trace elements in fresh water and sea water

1978 ◽  
Vol 291 (4) ◽  
pp. 273-277 ◽  
Author(s):  
P. Burba ◽  
K. H. Lieser ◽  
V. Neitzert ◽  
H. -M. Röber
Keyword(s):  
Trace Elements ◽  
Fresh Water ◽  
Sea Water

scholarly journals Considérations physiques sur le passage Nord-ouest; by the same. Communicated by the Right Hon. the Earl of Minto, G. C. B. F. R. S

1837 ◽  
Vol 3 ◽  
pp. 484-484
Keyword(s):  
Sea Water ◽  
Freezing Point ◽  
Atmospheric Temperature ◽  
North West ◽  
The North ◽  
The Mean ◽  
Coppermine River ◽  
The Right ◽  
North Latitude

The author of this memoir, considering that the practicability of a North-west Arctic passage must depend on the mean summer atmospheric temperature of the most northern point of the continent of America being above that at which the congelation of sea water takes place, applies himself to the determination of these temperatures. The results of his calculations are given in a table, exhibiting the extreme and the mean temperatures of the atmosphere for each of the summer months, from May to September, at all degrees of latitude, from 60° to 80° inclusive. According to this table, the temperature of zero, which is about the freezing point of sea water, prevails, at 60° of latitude, on the 10th of May; at 61° lat. on the 20th of May; at 63°, on the 1 st of June; at 65°, on the 10th of June; at 67°, on the 20th of June; and at 71°, during the whole of the months of July and August. The author concludes that navigators can reach, without danger of being obstructed by ice, the latitude of 71° during these latter months: and that since the American continent does not probably extend beyond 70° north latitude a passage to the North-west is then open. He recommends, however, that instead of attempting it by the dangerous navigation of the polar sea, a coasting voyage between the continent and the numerous islands which exist in that ocean should be undertaken; or, what he thinks still more promising of success, an expedition by land for exploring the country intervening between the Coppermine River and Hudson’s Bay.

scholarly journals On the absorption of carbonic acid by saline solutions

1874 ◽  
Vol 22 (148-155) ◽  
pp. 483-495
Keyword(s):  
Carbonic Acid ◽  
Sea Water ◽  
Point Of View ◽  
Property A ◽  
Partial Pressures ◽  
Cause Of Error ◽  
Series Of Experiments ◽  
Saline Solutions ◽  
Different Parts

In the examination of sea-water, whether it be regarded from a chemical or from a zoological point of view, the determination of and the variations in the amount of carbonic acid in different parts of ocean must always be an object of importance. This is more especially so when a parallel series of observations on the quantity of oxygen present is carried out. At the surface we should expect to find the quantities of these gases following the law of partial pressures; at greater depths, however, where the water for long periods only comes in contact with water, we should expect to find the quantity of oxygen decreasing and that of carbonic acid increasing with the amount of animal life. The investigation from this point of view of the bottom-water, at greater and smaller depths, presents perhaps a more interesting field of observation than that of intermediate depths. Down to nearly 2000 fathoms life is still abundant; below this depth, however, the amount rapidly decreases till, at about 2800 fathoms, it is, for carbonic acid producing purposes, practically extinct. "We have, then, to settle the variation of the carbonic acid with latitude and longitude, with depth, with nature of bottom, and with nature of atmosphere. In order to solve these problems, it is before all necessary to have a reliable method for the determination of the carbonic acid. For the discovery of a cause of error in the old method, and for the invention of a new one, we are indebted to Dr. Jacobsen, of Kiel. Dr. Jacobsen found that sea-water could not, as had been till then assumed, be thoroughly freed from its dissolved carbonic acid by merely boiling in vacuo . He found that it was necessary to boil down almost to dryness before the last traces of carbonic acid could be expelled. Being particularly interested in the matter, I immediately commenced a series of experiments to determine, if possible, the salt or salts to which sea-water owes this peculiar property. A short résumé of the results of these experiments have been published as an appendix to Professor Wyville Thomson’s Depths of the Sea.’

scholarly journals Salt and Water Balance in the East African Fresh-Water Crab, Potamon Niloticus (M. Edw.)

1959 ◽  
Vol 36 (1) ◽  
pp. 157-176 ◽  
Author(s):  
J. SHAW
Keyword(s):  
Water Balance ◽  
Fresh Water ◽  
Sea Water ◽  
Freezing Point ◽  
Salt Content ◽  
The Body ◽  
Sodium Balance ◽  
East African ◽  
Sodium Loss ◽  
Salt And Water Balance

1. The mechanisms of salt and water balance in the East African fresh-water crab, Potamon niloticus, have been investigated. 2. The freezing-point depression of the blood is equivalent to that of a 271 mM./l. NaCl solution. 3. The animals cannot survive in solutions more concentrated than 75% sea water. Above the normal blood concentration, the blood osmotic pressure follows that of the medium. 4. The urine is iso-osmotic with the blood and is produced at a very slow rate. The potassium content is only half that of the blood. 5. The animal loses sodium at a rate of 8 µM./10 g./hr. mainly through the body surface. Potassium loss occurs at one-sixteenth of this rate. 6. Sodium balance can be maintained at a minimum external concentration of 0.05 mM./l. Potassium requires a concentration of 0.07 mM./l. 7. Active absorption of both sodium and potassium occurs. The rate of uptake of sodium depends on the extent of previous sodium loss. The rate of sodium uptake may be affected by such environmental factors as the salt content of the water, temperature and oxygen tension. 8. The normal oxygen consumption rate is 0.72 mg./10 g./hr. A minimum of 2.3% is used in doing osmotic work to maintain salt balance. 9. The salt and water balance in Potamon is discussed in relation to the adaptation of the Crustacea to fresh water. The importance of permeability changes is stressed.

Studies on Salt and Water Balance in Myxine Glutinosa (L.)

1965 ◽  
Vol 42 (2) ◽  
pp. 359-371
Author(s):  
R. MORRIS
Keyword(s):  
Water Balance ◽  
Sea Water ◽  
External Medium ◽  
Freezing Point ◽  
Freezing Point Depression ◽  
High Concentration ◽  
After Effects ◽  
Monovalent Ions ◽  
Calcium Magnesium ◽  
Salt And Water Balance

1. Measurements of freezing-point depression and chemical analysis have been made of the plasma and urine of Myxine. 2. The plasma is generally slightly hypertonic to sea water whilst the urine tends to be slightly hypotonic to the blood. 3. The urinary output is low (5·4±1·6 ml./kg./day) and the majority of animals do not swallow sea water. 4. Analyses of plasma and urine indicate that the kidney participates in ionic regulation by reducing the concentrations of calcium, magnesium and sulphate in the plasma relative to sea water. Chloride seems to be conserved whilst potassium may be conserved or excreted. The high concentration of magnesium in the plasma of animals kept in static sea water may be caused by the after effects of urethane. These animals continue to excrete magnesium at normal rates. 5. The rates at which calcium, magnesium and sulphate enter an animal which does not swallow sea water are proportional to the diffusion gradients which exist between the external medium and the plasma. The situation is more complicated for monovalent ions, but there is no evidence of specialized ion-transporting cells within the gill epithelium. 6. In those animals which swallow sea water the amounts of ions absorbed from the gut are very large compared with the renal output and it would therefore seem unlikely that swallowing is part of the normal mechanism of salt and water balance. 7. It is argued that the mechanism of salt and water balance in Myxine is likely to be primitive and that the vertebrate glomerulus was probably developed originally in sea water as an ion-regulating device.

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