. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ELECTROPHYSIOLOGY OF PROBOSCIDACTYLA 245. FIGURE 7. Crumpling pulses (CrP's) stimulated at a frequency of 2/sec on the exumbrella and recorded by electrode a) attached to the exumbrella and b) attached to the subumbrella. 12 superimposed traces are shown. An arrow denotes the stimulus artifact. The horizontal bar represents 20 msec and the vertical bar, 1 mV. val between shocks is less than 1 sec (Fig. 7). During repetitive stimulation at frequencies greater than 1 shock/2 sec the conduction velocity of crumpling pulses decr
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ELECTROPHYSIOLOGY OF PROBOSCIDACTYLA 245. FIGURE 7. Crumpling pulses (CrP's) stimulated at a frequency of 2/sec on the exumbrella and recorded by electrode a) attached to the exumbrella and b) attached to the subumbrella. 12 superimposed traces are shown. An arrow denotes the stimulus artifact. The horizontal bar represents 20 msec and the vertical bar, 1 mV. val between shocks is less than 1 sec (Fig. 7). During repetitive stimulation at frequencies greater than 1 shock/2 sec the conduction velocity of crumpling pulses decreases with each successive shock until the system becomes inexcitable. This phenomenon will be called fatiguing. All parts of the ectoderm show fatiguing to the passage of closely spaced crumpling pulses, and since the phenomenon of fatiguing can be seen in preparations where the duration of the shock is less than 1 msec, increased initiation delay cannot account for fatiguing. Recovery from a fatigued state is fairly rapid with the conduction velocity returning to 90% of the original value in about 40 sec. DISCUSSION The feeding pattern seen in P. flavicirrata closely follows feeding habits in other hydromedusae. Hyman (1940) distinguishes between feeding in jellyfish having a broad, shallow bell and those having a tall, narrow bell. These characteristics are typical of the leptomedusae and anthomedusae respectively. Feeding in P. flavicirrata most closely resembles that of the flat type of jellyfish, except that tentacles holding the food contract and these tentacles are sometimes held by the manubrial lips. Low amplitude potentials have been recorded from the bases of perradial tentacles involved in a feeding response that cannot be associated with other known conduction systems (Spencer, 1971). The only analytical accounts of the mechanics of swimming in the hydro- medusae are those given by Gladfelter (1972, 1973). All the principles of propul- sion he suggests are met by
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
