Fine structure of the spermatozoon of an onychophoran, Peripatopsis.
The spermatozoon of the Onychophoran Peripatopsis moseleyi is described. This cell is characterized by the general filiform shape, the absence of an acrosome, the presence of mitochondrial derivatives, of an annulus and of nine accessory tubules and a manchette of microtubules around the axoneme. All of these characters are typical of highly evolved sperm models, like those of insects and mammals, and suggest a long evolutionary history. Only the position of the mitochondria, inserted between nucelus and axoneme, is reminiscent of annelid features.
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