Les Transferts D'Eau En Fonction de la Salinité du Milieu Chez le Crustacé IsopodeSphaeroma serratum(Fabricius)

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Abstract
The isopod Crustacean Sphaeroma serratum is isotonic to the medium in sea water and hypertonic in diluted media. The drinking rate is 15.9 μl in SW and 3.2 μl 24 h−1 100 mg−1 wet weight in 50 % SW. The extracellular space is 28.4 % in SW and 27.0 % of the wet weight in 50 % SW. The rate of urine production, calculated from the half time for the loss of sodium diatriazoate is 11.8 mg in SW and 42.9 mg 24 h−1100 mg−1 wet weight in 50 % SW. 95 % of the diffusion fluxes of water take place through the pleopods : their surface is about 62.6 mm2 in a 100 mg weighing animal. The activation energy of water molecules is 15.0 kcal/mol between +5°C and +15 °C and 6.7 kcal/mol between +15 °C and +25 °C. The diffusion permeability coefficient Pd is 1.71 × 10−4 cm/sec in SW and 0.70 × 10−4 cm/sec in 50 % SW. The osmotic permeability coefficient Pos has a mean value of 1.91 × 10−4cm/sec in SW and 1.24 × 10−4 cm/sec in 50 % SW. Our results are compared with those obtained in other Crustaceans and in Fishes. Their validity is discussed (influence of unstirred layers, solute-solvent interaction). They are explained according to the different theories dealing with the water transit through the membranes.