A study of strobilation in Aurelia aurita under controlled conditions

The maintenance of Aurelia aurita polyps in this laboratory has made possible the study of strobilation under well controlled laboratory conditions for the first time. The development of pulsing, statocysts and gastric filaments during normal strobilation occurring in artificial sea water at constant temperature was observed. Comparisons made of intact strobilae and segments cut from strobilae revealed that isolated segments of strobilae differentiated at a rate comparable to segments of intact strobilae. Furthermore, segments and pieces of segments which appeared morphologically to be polyp tissue and which exhibit no differentiation of structure were already “programmed” to become medusa tissue. Since isolated completed segments developed into ephyrae without further contributions of cells or substances from the parent it was postulated that segments of intact strobilae are, likewise, independent in their development once segments are completed. Studies of atypical strobilation resulting from simple environmental change emphasized that mechanisms that regulate segmentation are different from and probably independent of those that regulate metamorphosis of the segments into ephyrae. A discussion of the major processes involved in strobilation is presented and a close analogy to the metamorphosis of higher animals is drawn. The value of this primitive form of metamorphosis for studies of mechanisms involved in growth and differentiation is demonstrated.