Development of sperm cells of Volvox carteri f. weismannia (Chlorophyceae)

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Abstract
A high yield of male colonies of Volvox carteri f. weismannia can be attained in culture within 70–90 hr after inoculation of fresh Volvox medium to a concentration of 15–20 colonies/ml. The development and morphology of the sperm bundles in the male colonies were studied by light and electron microscopy. The nuclei of the mature sperm cells are characterized by osmiophilic material along the inner membrane and within the nucleus. Discrete spherical areas of fine fibrillar nuclear material are also observed. A tripartite layer of sheath material surrounds each sperm cell and the whole sperm bundle at maturity. Prominent eyespots are present in the reduced chloroplast; the cells contain rough endoplasmic reticulum, Golgi bodies, two contractile vacuoles, a microbody and a complex mitochondrial system near the flagellar bases. When the sperm cell is freed from the sheath and swims independently, the flagella are directed posteriorly from the apex. It is able to change its shape rapidly and can form an anterior extension or beak.