. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0 00 0 25 0 50 0 75 1 00 1 25 1 50 1 75 2 00 120 100 80 60 40 20 0 -20 •40 60. 0 00 0 25 0 50 0 75 1 00 1 25 1 50 1 75 2 00 Figure 2. Electromyograms recorded from electrodes embedded in central anaerobic circular muscle of a brief squid ( cm dorsal mantle length) while swimming at 6, 15, and 24 cm s"'. Mantle diameter and acceleration are plotted underneath each recording. There are no obvious waveforms at 6 cm s~'. occasional waveforms at 15 cm s~', and frequent waveforms at high speeds (24 cm s '). At high speeds,
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0 00 0 25 0 50 0 75 1 00 1 25 1 50 1 75 2 00 120 100 80 60 40 20 0 -20 •40 60. 0 00 0 25 0 50 0 75 1 00 1 25 1 50 1 75 2 00 Figure 2. Electromyograms recorded from electrodes embedded in central anaerobic circular muscle of a brief squid ( cm dorsal mantle length) while swimming at 6, 15, and 24 cm s"'. Mantle diameter and acceleration are plotted underneath each recording. There are no obvious waveforms at 6 cm s~'. occasional waveforms at 15 cm s~', and frequent waveforms at high speeds (24 cm s '). At high speeds, high-amplitude electrical activity occurs during each mantle contraction, and lower amplitude electrical activity sometimes occurs during mantle expansion. Furthermore, mantle contractions are more erratic at 24 cm s"1 than at 6 cm s~'. significant proportion of the noise might have been removed with a 60-Hz notch filter (Loeb and Guns. 1986), but un- fortunately the electromyographic system used could not be configured with a notch filter. Considering the high level of background noise, it is possible that some low-level EMG activity was undetected. However, it is unlikely that anaer- obic EMG activity was absent at low speeds because it was concealed in the noise. EMG activity from the thin periph- eral (aerobic) muscle zones was easily distinguishable and consistently recorded at low speeds when muscular activity was lowest in spite of the electrical noise, and thus EMG activity from the thick, powerful central (anaerobic) muscle zone should have been visible if those fibers were active. Although electrical noise probably did not mask circular muscle activity, which was the focus of this study, it inter- fered with detection of EMG activity from the smaller radial muscles. Dissections revealed that electrodes crossed radial muscle bands, which are active during mantle expansion and hyperinflation (, a sharp increase in mantle diameter just prior to contraction) (
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
