BEHAVIOR AND ELECTRICAL ACTIVITY IN THE HYDROZOAN PROBOSCIDACTYLA FLAVICIRRATA (BRANDT). I. THE HYDROID COLONY

¹ Department of Biology, University of Victoria, British Columbia, Canada

1. P. flavicirrata feeds on material collected from the brachiolar food-grooves of the host sabellid worm.

2. The feeding cycle involves wiping the tentacles through the mouth. An abortive feeding cycle can also be seen when the tentacles are not wiped through the mouth.

3. The frequency of the feeding cycle is in part controlled by activities of the host worm.

4. Tentacle contraction pulses and column contraction pulses are the electrical accompaniment to feeding and abortive feeding. Their properties are described.

5. Colonial pulses, conducted in part by epithelial cells at velocities between 1.9 and 7.3 cm/sec (13° C), cause protective retraction of all the individuals in the colony. The varying response of medusa buds as they develop is described. The colonial pulse conducting system fatigues rapidly after repetitive stimulation.

6. Colonial pulses continue to propagate after exposure to excess Mg⁺⁺ for 3 hr.