. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CONTRACTION PULSE PATTERNS IN HYDRA 267 activitv in II\dra should include provisions for both tvpes of pulse patterns. //. pseudoligactis will produce hursts when appropriately stimulated. Effective stimuli include: (1) increased suction of the hydra in the recording electrode; (2) intermittant light stimulation of the whole preparation; and (3) exposure to stimuli inducing a feeding reaction in the animal. When H. pseudoligactis is induced to give bursts of CP's, their temporal patterns are similar to those pre- viously not
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CONTRACTION PULSE PATTERNS IN HYDRA 267 activitv in II\dra should include provisions for both tvpes of pulse patterns. //. pseudoligactis will produce hursts when appropriately stimulated. Effective stimuli include: (1) increased suction of the hydra in the recording electrode; (2) intermittant light stimulation of the whole preparation; and (3) exposure to stimuli inducing a feeding reaction in the animal. When H. pseudoligactis is induced to give bursts of CP's, their temporal patterns are similar to those pre- viously noted for preparations of H. pirardi. (1 ) The effect of increased electrode suction. In the course of long-term recordings of the spontaneous activity of several species of Hydra, it was observed that animals damaged during placement in the electrode produced many RP's. McCullough (1965) also noted an increased RP frequency in hydra placed in stressful recording situations. For animals such as H. pirardi, which normally produce many bursts of CP's, the initial effect is an elongation of the inter-CP burst interval accompanied by more pulses per burst and longer burst lengths. On the other hand, for hydra usually giving single CP's, such as H. pseudoligactis, the effect is to change the CP pattern to one primarly of burst of f " ' fl (l \ L 1 1 i \l [ L I ' ' ' 1 \5OO>uv it Tttr nrr IBI- IBI- r IB, TIT Imv IBI- IOSECS. FIGURE 8. Electrical record of H. pseudoligactis under high electrode suction (20 cm of water). In order to study the induction of bursts in H. pseudoligactis more syste- matically preparations were exposed to three different levels of suction in the recording electrode (0, 10, 20 cm of water). It was found that either inter- mediate (10 cm) or high (20 cm) pressure induced bursts of CP's accompanied by enhanced RP frequencies during inter-CP burst intervals. An example of an electrical record of a preparation at the higher pressure is given in
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
