Patterns in the release of gaseous ammonia by terrestrial isopods

In the fall and in early spring P. scaber and O. asellus released gaseous ammonia in the form of more or less regularly spaced bursts. In the spring about twice as much ammonia was released by O. asellus than in the fall. In late spring and summer, however, both species released ammonia in a rhythmic fashion, with a maximum at noon and early in the afternoon, and a minimum early at night. Sometimes a second maximum occurred late at night.In O. asellus the addition of a moist substrate to the reaction chamber shifted the maximum of the release of ammonia from noon to late night and early morning.Fed specimens of P. scaber released only about one-third as much NH₃ as fasting animals and-at least in constant darkness-with a period of much reduced amplitude.It is concluded that the rhythmical release of ammonia is inversely related to the pattern of locomotory activity of these animals. This would implicate mechanisms that regulate either the production or the release of ammonia in such a way that the maximum occurs at a time when the animals' production of energy is at a minimum and when they are protected against loss of water by sitting in their moist retreats.