Cocatre-Zilgien J.H. & Delcomyn F. (1990). Fast axon activity and the
motor pattern in cockroach legs during swimming. Physiol. Entomol.
Abstract. Electromyographic recordings were made from muscles that extend the
trochanter/femur of each of the six legs of American cockroaches, Periplaneta
americana (L.), while the insects swam in water. The recordings showed two novel
features. (1) During swimming, muscle activity in different legs was coordinated
in the alternating tripod pattern commonly seen during free walking on land, not
in the pattern of synchronous leg pairs common to other large terrestrial
insects in water. (2) Fast axons were usually recruited along with slow axons,
even when the insect swam at a moderate pace. Fast axon activity always started
after the middle of the slow axon burst in intact insects, but vanished from
most bursts in the stump of the leg after amputation of the femur. The
alternating tripod pattern was maintained even after amputation. Possible causes
of fast axon recruitment are discussed.
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