The Fine Structure of Schistosoma mansoni Sperm (Trematoda: Digenea)

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Abstract
The sperm of the blood fluke S. mansoni consist of a bulbous head 8 .times. 2 .mu.m, with a rounded anterior tip and tapering posterior region, followed by a relatively short flagellum .apprx. 20 .mu.m long. Electron microscopy revealed that these sperm are devoid of an acrosome, while a few undifferentiated mitochondria accumulate at the anterior part of the head. The nucleus appears dense, except for some electron-lucent patches. The flagellum starts at the basal body, posterior and slightly lateral to the nucleus, and the axial complex is of the 9 + 0 type. A layer of microtubules runs longitudinally, just beneath the plasmalemma, from the anterior part of the head to the initial part of the flagellum where they overlap with the axial complex. This relatively rudimentary type of S. mansoni sperm is probably related to the low activity required for fertilization.