[Hypoosmotic regulation in the marine cladoceran ratchet Penilia avirostris].

At average salinity of the environment 18.08% (-delta degrees C being equal to -0.99 degrees C) the depression of the hemolymph in P. avirostris is equal to -0.72 +/- 0.09 degrees C. Hypoosmotic regulation of marsupium fluid persists up to the formation of epipodites, after which the depression of this fluid becomes equal to that of the external medium. It is suggested that special epipodite cells are involved into osmoregulation. Similarity of hypoosmotic mechanisms in the marine cladoceran and Artemia salina is noted.