THE ONTOGENY OF SWIMMING BEHAVIOR IN THE SCYPHOZOAN,AURELIA AURITA.I. ELECTROPHYSIOLOGICAL ANALYSIS

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Abstract
The strobila is a morphological and behavioral chimera of polyp and medusa presented in a developmental gradient along the oral-aboral axis. The developmental gradient expressed by the strobila was used to investigate the ontogeny of swimming behavior in a scyphozoan medusa. Particular attention was given to tentacular behavior of the polyp since the tentacles are developmentally homologous with the rhopalia of the medusa. The tentacles are the most electrically active tissue of the polyp. Tentacle contraction potentials (TCP) are conducted along the length of the tentacle but conduction to other parts of the animal was not observed. TCP fate during strobilation was followed and there is no smooth transition from TCP to marginal ganglion potentials (MGP); pacemaker activity seems to develop de novo. Two coordinated behaviors were observed in the polyp, feeding and a protective response. These coordinated responses indicate that neurological control can take place in the polyp. Feeding and the protective response are similar to feeding and spasm in the ephyra that which suggested that feeding and the protective response in the polyp are coordinated by interneural facilitation in the diffuse nerve net as in the ephyra. Comparison of polyp, ephyra and medusa behaviors show that the ephyra is a mixture of polypoid and medusoid behaviors and as development proceeds, each subsequent stage acquires some new behavior while retaining some aspect from the previous stage.

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