M.G. Black C.A. Edwards G.K. Walker 1996 <p><span>Adult zebra (</span><i>Dreissena polymorpha</i><span>) and quagga (</span><i>Dreissena bugensis</i><span>) mussels were induced to release large quantities of live spermatozoa by the administration of 5-hydroxytryptamine (serotonin). Sperm were photographed alive using phase-contrast microscopy and were fixed subsequently with glutaraldehyde followed by osmium tetroxide for eventual examination by transmission or scanning electron microscopy. The sperm of both genera are of the ect-aquasperm type. Their overall dimensions and shape allow for easy discrimination at the light and scanning electron microscopy level. Transmission electron microscopy of the cells reveals a barrel-shaped nucleus in zebra mussel sperm and an elongated nucleus in quagga mussel sperm. In both species, an acrosome is cradled in a nuclear fossa. The ultrastructure of the acrosome and axial body, however, is distinctive for each species. The structures of the midpiece are shown, including a unique mitochondrial "skirt" that includes densely packed parallel cristae and extends in a narrow sheet from the mitochondria.</span></p> application/pdf 10.1139/z96-093 en NRC Research Press Comparative morphology of zebra (<i>Dreissena polymorpha</i>) and quagga (<i>Dreissena bugensis</i>) mussel sperm: Light and electron microscopy article