The neuromuscular basis of swimming movements in embryos of the amphibian Xenopus laevis.

When removed from their egg membranes, Xenopus embryos can swim. High-speed cinematography shows that, in swimming, lateral undulations pass rostro-caudally down the body. The swimming rhythm period is 40-100 ms. In swimming, electrical activity in myotomal muscles alternates on opposite sides of a segment and sweeps rostro-caudally in ipsilateral myotomes. Myotome muscle physiology was examined. Muscle fibres are electrically coupled to each other, and the fibres are able to spike. The possible role of a myotomal conduction pathway in swimming is discussed.