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Title: Sperm Morphology and Development in Two Acoel Turbellarians from the Philippines 
Author: Boyer, Barbara Conta; Smith, George W.
Date: 1982-07
Publisher: University of Hawai'i Press
Citation: Boyer BC, Smith GW. 1982. Sperm morphology and development in two acoel Turbellarians from the Philippines. Pac Sci 36(3): 365-380.
Abstract: In this study we compare spermiogenesis and ultrastructure of the
mature sperm in two species of acoel Turbellaria from the Philippines. Sperm
development is divided into five stages: (1) the early undifferentiated state, with a
large nucleus, sparse cytoplasm containing few organelles, and no inclusions;
(2) spermiogenesis I, in which Golgi activity is prominent, dense bodies appear in
the cytoplasm, and peripheral centrioles migrate toward the nucleus; (3) spermiogenesis
II, in which a manchette of microrods forms around the nucleus,
refractile bodies are produced by the Golgi, and free 9+0 flagella are seen
between the cells; (4) spermiogenesis III, which is characterized by marked cell
elongation, nuclear condensation, and flagellar elongation and incorporation
into the developing spermatid shaft; and (5) the mature sperm, which has a
proximal nucleus, a middle shaft region containing a central keel of microrods,
laterally incorporated axonemes, and many inclusions such as refractile bodies,
dense bodies, open vesicles, mitochondria, and a distal flagellar region containing
the two 9+0 axonemes tapering to terminal basal bodies. We propose that
the refractile bodies may function as acrosomes, that the central keel provides
support, that the biflagellate condition is important in providing the motile force
that moves the sperm through intercellular spaces, and that the 9+0 axonemes
may contain some central structure. The microrods of the keel appear to be a
previously undescribed cellular component. The peculiar morphology of these
spermatozoa is probably an adaptation associated with locomotion through the
interdigitated acoel parenchyma where an extremely elongate cell, propelled
flagellar tip first by undulations, is particularly efficient.
ISSN: 0030-8870

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