This study describes spermatogenesis in a
majid crab (Maja brachydactyla) using electron microscopy
and reports the origin of the different organelles
present in the spermatozoa. Spermatogenesis in M. brachydactyla
follows the general pattern observed in other
brachyuran species but with several peculiarities. Annulate
lamellae have been reported in brachyuran spermatogenesis
during the diplotene stage of first spermatocytes,
the early and mid-spermatids. Unlike previous
observations, a Golgi complex has been found in midspermatids
and is involved in the development of the
acrosome. The Golgi complex produces two types of
vesicles: light vesicles and electron-dense vesicles. The
light vesicles merge into the cytoplasm, giving rise to
the proacrosomal vesicle. The electron-dense vesicles are
implicated in the formation of an electron-dense granule,
which later merges with the proacrosomal vesicle. In the
late spermatid, the endoplasmic reticulum and the Golgi
complex degenerate and form the structures–organelles
complex found in the spermatozoa. At the end of spermatogenesis,
the materials in the proacrosomal vesicle
aggregate in a two-step process, forming the characteristic
concentric three-layered structure of the spermatozoon
acrosome. The newly formed spermatozoa from testis
show the typical brachyuran morphology