Contribution des acides aminés libres à la régulation osmotique intracellulaire chez deux crustacés euryhalins, Leander serratus F. et Leander squilla L.

anglais. The biochemical aspects of adaptation to brackish water (30 p. 100 sea water) have been studied in two species of euryhaline shrimps : Leander squilla L. and Leander serratus F. A first mechanism, consisting of an anisosmotic regulation of the blood, has been described by Pannikar in these organisms. A variation of osmotic pressure in the external medium, amounting to 1,7°C, brings about a change of only 0.°3C and 0.°6C respectively, in the blood of the two species considered. As shown by the slight change of water content of the muscles, the intracellular osmotic pressure has been approximately adjusted, in these shrimps, to the osmotic pressure of the blood. This isosmotic, intracellular regulation is accomplished for about 1/3 by the variation of concentration of a number of intracellular free amino-acids. The main rôle is played by glutamine, glycine and proline in both species. In L. serratus alanine also shows important variations. The mechanism of intracellular osmoregulation by changes of concentration of the amino-acids mentioned, has been observrd in all euryhaline Invertebrates studied so far. It appears as a general device of adaptation to changes of concentration of the internal medium, in euryhaline forms.

français. Chez deux crevettes euryhalines (Leander serratus F. et Leander squilla L.), sont décrites les variations de concentration des acides aminés libres des tissus au cours de l'adaptation à l'eau saumâtre. L'abaissement de concentration de certains acides aminés libres intracellulaires (notamment de l'alanine, de la glutamine, du glycocolle et de la proline) contribue au mécanisme de régulation isosmotique intracellulaire, déjà observé chez d'autres Invertébrés euryalins, possédant ou non une régulation anisosmotique du milieu intérieur.