Ionic Regulation in the Palaemonid Prawn Palaemon (=Leander) Serratus

Abstract

1. Analyses have been made of the blood and urine of Palaemon serratus for the inorganic ions Na, K, Ca, Mg, Cl, SO4 the animals being kept in 50, 100 and 120% sea water. 2. When the animal is in 100% sea water the concentrations of ions in the blood, expressed as percentages of their concentrations in the medium (to the nearest 5%) are as follows: Na, K and Cl, 85% Ca, 105% Mg, 20% SO4 10%. 3. When the animal is in 50% sea water the corresponding figures are: Na and Cl, 105%K, 120%; Ca, 200%; Mg, 20%; SO4 10%. 4. When the animal is in 120% sea water the corresponding figures are: Na, K and Cl, 85% Ca, 115% Mg, 30% SO4 20%. 5. The concentrations of Na, K and Ca in the urine are always slightly (≤20%) less than their concentrations in the blood. The concentration of Cl is slightly greater in the urine than in the blood (10-20%) and the concentrations of Mg and SO4 are very much greater, by factors of up to 7 times. The relative concentrations of ions blood and urine do not change substantially with changes in the external medium. 6. The antennal gland, although it plays no part in purely osmotic regulation, is no doubt partly responsible for maintaining the low blood concentrations of Mg and SO4.