The behavior of 5. cokei was observed in a laboratory setting. Open containers of cave water readily lost carbon dioxide, causing the pH to rise. The mysids kept their tails almost straight up at a right angle when the pH was comfortably low. As the pH rose, their tails gradually dropped in proportion to the increase; in extreme conditions, their tails were nearly horizontal. They also lowered their tails to a nearly horizontal position while walking. When the animals were forced off their substrate in the caves or the laboratory, they displayed frantic and ineffective swimming movements. The uropods spread away from the tel-son to make a wide tail fan when 5. cokei is walking. In healthy specimens, the respiratory beating of pereiopods 1-7 occurred in sequences of 3-9 seconds, followed by rest periods that lasted 2-45 seconds. As carbon dioxide levels dropped and the pH rose, their rest periods increased to as long as 50 minutes.
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