Electromyography and analyses
Electromyograms were recorded simultaneously with the
video experiments described above to document the sequence of
muscle activation relative to kinematic events. Electromyograms
were recorded using bipolar electrodes, each of which was
constructed from 1.8 m lengths of 0.0057 cm diameter insulated
alloy wire. Approximately 1 mm at the end of each wire was
stripped of insulation and bent backwards to form a hook. A third
piece of hooked insulated wire 3 cm long was placed alongside
each bipolar electrode to allow verification of electrode
placement in case the electrode was inadvertently pulled out.
The electrodes were implanted in nine cranial muscles using 26
gauge hypodermic needles. The guitarfish were anesthetized
during surgery using 0.065 g l−1 tricaine methanesulfonate (MS-
222). The guitarfish were intubated and maintained on this
dosage of anesthetic during surgery using the recirculated
seawater/anesthetic solution. Following electrode implantation,
all the electrode wires were glued together to form a cable and
sutured to the skin just posterior to the synarcual (fused cervical
vertebrae). The surgical procedure took approximately 30 min,
after which the guitarfish was returned to the experimental tank
and intubated with fresh sea water until it had recovered enough