A. Mostad

Cell volume regulation in osmotically adjusting marine animals

Abstract The so-called isosmotic intracellular regulation includes an adjustment of the number of moles of the intracellular solutes concomitantly to the volume regulation of the cells. For this reason, the apparent linear correlations between the specific weight, and both the water content (g water/g wet tissue) of a tissue of an isosmotic animal and the salinity of the sea water will be observed. Also, when the water content of a tissue is expressed as g water/cm 3 tissue, and is thus independent of the tissue specific weight, an apparent linear correlation between water content and the salinity of the sea water is observed. These differences in the water content between cells adjusted to different osmolalities are due to a replacement of solutes by water, or vice versa , during the cells volume regulation. This exchange process establishes thereby a mechanism which might enable the animal to maintain the volume of an osmotically adjusted tissue constant and independent of the salinity of the sea water. In the present paper, a physico-chemical treatment of the processes underlying the observed correlations is given. Simple equations describing the correlation between the water content of a tissue (in g water/cm 3 tissue) and the osmolality are presented. It is shown that the coefficient of this correlation is mainly dependent on the mean apparent molar volume of the solutes used by the tissue in the isosmotic intracellular regulation. Isosmotic common mussels ( Mytilus edulis ) were adapted to a wide range of sea water salinities, and the specific weight and the water content of the muscle tissue of these animals were measured and related to the sea water salinity. By comparison of such experimental data with those obtained by calculations according to the equations presented and the assumed composition of the intracellular fluid, it is possible to evaluate the completeness of the volume regulation. The reliability of the evaluation of the completeness of this act according to the present method is discussed and also compared to the reliability of the method usually employed. It is concluded that, in general, the present method yields the better information.

The effect of salinity and temperature on solubility of oxygen and respiratory rate in oxygen-dependent marine invertebrates

Abstract The diffusion rate of O 2 in sea water has been treated physico-chemically. It is shown that although the activity of oxygen in water remains constant when pO 2 and temperature are constant (equilibrium conditions), the diffusion rate of oxygen will nevertheless vary proportionally to the solubility of oxygen in sea water, which decreases with increasing salinity. The effect on the diffusion rate is due to a salt effect on the activity coefficient, which also implies that Ficks law can not be directly used in systems of varying salinity. It is shown that the respiratory rate of the oxygen-dependent prosobranch, Buccinum undatum L., increases with decreasing salinity when the measurements are made as usual, namely, at constant pO 2 . The respiratory rate is independent of the salinity, however, if the plot is based upon equal O 2 concentrations in water of different salinity. Physico-chemical considerations make it likely that the diffusion rate of O 2 in water is a rate-limiting factor for respiration in Buccinum . The literature shows, however, that further experimental evidence is needed before a general conclusion as to the quantitative role of the diffusion rate of oxygen in sea water on the respiratory rate can be reached. Since the solubility of O 2 in water also varies with temperature, corresponding effects regarding metabolism/temperature curves have been considered. It is shown theoretically that when the respiratory rate depends on the diffusion rate of O 2 in water, the increase of the respiratory rate with temperature is less when measured at constant pO 2 than at constant O 2 concentration. Measurements of the respiratory rate of Buccinum at different temperatures conform to this statement.

dl‐Phenyl­alaninium maleate at 123 K

In the title compound, C9H12NO2+.C4H3O4-, the amino acid molecule exists in the cationic form with a positively charged amino group and an uncharged carboxylic acid group. The maleic acid molecules exits in the mono-ionized state. In the semi-maleate anion, the intramolecular O-H...O hydrogen bond is asymmetric. The phenylalaninium cations and the semi-maleate anions form hydrogen-bonded double layers, linked together by N-H...O and O-H...O hydrogen bonds, extending along 101].