NOTES ON THE BEHAVIOR OF THE HYDROID, CORYMORPHA PALMA

Corymorpha, like Porpita, exhibits a synchronous oral flexion,or "concert," of its proximal tentacles. As this is unlike thecontractile writhings of siphonophoran zooids, the concert maybe a significant character in linking the behavior of Porpitamore closely to hydroids than to siphonophores. Except for thisresponse the behavior of Corymorpha and Porpita are different.In Porpita a through-conducting system forms the only link betweententacles, whereas in Corymorpha both local and through-conductingsystems connect tentacles. Corymorpha engages in rhythmic bottom-feedingusing distal tentacles which have no homologue in Porpita. Themechanical properties of the musculo-skeletal system are differentin the two, giving tentacle motions in Corymorpha a continuousappearance, and in Porpita a spasmodic appearance. Reduced glutathione, glycine, DL-serine, L-cysteine and L-glutamicacid can elicit a feeding response in Corymorpha. Sodium thioglycollateand sucrose elicit no response. Glycine is the most effectivestimulant, ca. 5 X 10^–7 M solution being effective. L-glutamicacid gives the weakest response. The presence of chemicals alonecan be sufficient to elicit the feeding reaction in starvedanimals. In moderately well-fed animals, touch may be required.In fully fed animals both touch and chemicals may be insufficient. Parker reports that when Corymorpha is shocked electricallyon its stalk it will bend the stalk so as to apply the hydranthaccurately to the stimulated spot. The response I found wasa curling of the stalk toward the side stimulated, but not toa specific spot on the stalk. Chemical or tactile stimuli maybe necessary for final location of the stimulated site. Parkerreported that the response remained accurate even after severalcuts had been made in the stalk. I could find no evidence forthis.