Ref ID : 6458
Marco Ferraguti and Barrie G.M. Jamieson; Spermiogenesis in Bythonomus lemani and the phylogenetic position of the Lumbriculidae (Oligochaeta, Annelida). Hydrobiologia 155:123-134, 1987
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Spermiohistogenesis and spermatozoal morphology of the lumbriculid Bythonomus lemani have been investigated by means of electron microscopy. Though spermiohistogenetic events follow the general microdrile pattern, some features are peculiar; chromatin is clumped in the first stages and tis condensation is very irregular, as in Eisenia. Manchette geometry is similar to that of hirudineans, as the microtubules are helically arranged from the very early stages. A number of mitochondria are always present in the collar region. The mature sperm also departs from the microdrile model and is more similar to the megadrile one in (1) the strong withdrawal of the base of the acrosome vesicle into the acrosome tube; (2) the apparent development of rudimentary connectives. On the other hand, some features seem to be unique among oligochaetes, including the inclined longitudinal axis of the axial rod and tilted anterior end of the nucleus. Spermatologically, lumbriculids may be interpreted as advanced microdriles which may be descended from a stock which also gave rise to Haplotaxidae, Moniligastridae, and the true Opisthopores.