SATTERLIE, RA; PIRTLE, TJ; Arizona State University; Abilene Christian University: Organization of Parapodial Dorsoventral Muscles in the Pteropod Mollusc, Clione limacina

A great deal is known about swim control in Clione, including the neural basis of central pattern generation, modulation of swim activity during accelerations, and the architecture of swim muscle in the wing-like parapodia. One aspect of swimming, and particularly swim acceleration, that has yet to be investigated is the control of wing thickness. Dorsoventral muscle cells have been observed in light and electron microscopes, but their overall organization is unknown. A serendipitous result from an immunohistochemical investigation of hyperpolarization-activated cation channels has provided a description of the distribution of dorsoventral muscle cells in the wing of Clione. The antibody is specific since it also stains one of the three smooth muscle layers in Clione buccal cones, and it stains two pairs of central neurons in the cerebral ganglia. There is no evidence the antibody is binding to the cation channels. Dorsoventral cells are individually placed, but densely packed throughout the wing. Each has a soma in the central hemocoelic space of the wing, and provides a dorsal process and a ventral process, each of which branches several times as it runs between swim muscle bundles toward the respective epithelia of the wing. At the epithelium, each branch turns parallel to, and inserts on the basement membrane of the epithelium. Electron micrographic analysis confirms the dorsoventral muscle cells are of the smooth type.