CYTOPLASMIC BRIDGES AND MUSCLE SYSTEMS IN SOME POLYMYARIAN NEMATODES

Abstract

The somatic musculature of nine genera of nematodes (Contracaecum, Toxascaris, Toxocara, Porrocaecum, Cyslidicola, Amplicaecum, Physaloptera, Thoracostoma, and Dermatoxys) was examined by means of serial sections and dissections examined with the light microscope, and, in one instance (Thoracostoma), by use of an electron microscope. Interconnections between muscle cells (cytoplasmic bridges) were demonstrated in the musculature of the polymyarian nematodes, but could not be seen in Dermatoxys, the only meromyarian nematode studied. Cytoplasmic bridges occur in greater frequency in the anterior end of the nematodes. Innervation processes of muscle cells frequently branch before they associate with the median chords. In the head end of Toxascaris, Toxocara, and Porrocaecum, muscle cells are doubly innervated, sending innervation processes to sublateral nerve cords as well as to the median hypodermal chords. Cytoplasmic bridges probably are the basis of the electrical pathways by which contraction impulses are spread from cell to cell. The complexly interconnected muscle cell systems demonstrated undoubtedly serve, along with the nematode's hydrostatic skeleton, as the mechanism by which coordinated muscular activity is achieved.