Osmotic Behaviour of the Fairy Shrimp Chirocephalus Diaphanus Prévost

Abstract

The blood of Chirocephalus has a normal osmotic concentration equivalent to 0.44-0.5% NaCl in an external medium of 0.002% NaCl. The osmotic pressure falls rapidly when the animal is kept in glass-distilled water, but is fairly well maintained in tap water. There is an initial rise and a later return to normal even in hypotonic saline media, and this indicates active absorption of ions. The bracts are presumably the organs concerned in the salt absorption. The animal is unable to live in tap water or distilled water for more than 2-3 days without food and its general behaviour is thus markedly different from that of Daphnia.