Effect of air exposure on the growth and distribution system in the colonial hydroid Dynamena pumila (L., 1758)

. The pulsation of the stolon coenosarc of the colonial hydroid Dynamena pumila (L., 1758) was recorded using time-lapse microvideo recording. The study included several experiments: control (without air exposure) and a series of consecutive air exposure periods: 5, 10, 20, 30 min and 1 h. In general, comparison of the experiments with same colony in control and in a series of air exposure periods up to 30 min demonstrated no significant changes in the coenosarc pulsations and the hydroplasmic flow. Air exposure for 20 and 30 min caused a decrease in the amplitude of growth pulsations, and in growth increment by more than a third. The limit of permissible air exposure for D. pumila colonies is between 10 and 20 min. Such a short air exposure period does not lead to disruption of the distribution system and the growth of the growing tips, and therefore can be used in laboratory studies of colonies. A longer air exposure period, namely one hour, is critical for the colony, since it leads to disruption of its structure integrity. Tissue degradation occurs, and the inner contents begin to pour out through the holes in the burst perisarc of the growing tip.