Tudge, C.C., Jamieson, B.G.M.,
Sandberg, L. and
Erseus, C. 1998b. Ultrastructure of the mature spermatozoon of the King
Crab Lithodes maja (Lithodidae, Anomala, Decapoda): further
confirmation of a lithodid-pagurid relationship. Invertebrate
Biology 117, 57-66.
Ultrastructure of the spermatophore
and
spermatozoon of the king crab Lithodes
maja is described and illustrated. The
spermatophore is a pedunculate structure of which the major components
are the
sperm-filled ampulla, stalk, pedestal, and a smaller accessory ampulla
at the
base of the main ampulla. Each spermatozoon features a subspherical,
concentrically zoned acrosomal vesicle, capped by a centrally perforate
operculum and posteriorly embedded in the cytoplasm, and a large
globular
nucleus. Three microtubular arms emerge from the cytoplasm below the
acrosomal
vesicle. The spermatophores and spermatozoa share many features with
those of
their nearest postulated relatives-members of the Paguridae (the genus Pagurus
in particular). Spermatophore characters that link L. maja with pagurids are
the presence of the accessory ampulla (synapomorphy, also with the
parapagurids) and the homogeneous granular nature of the spermatophore
wall.
Sperm characters include the simple concentric zonation of the
acrosomal
vesicle, the shape and differentiation of the operculum (synapomorphic
with
Paguridae), the electron-dense plume in the base of the acrosomal
chamber
(synapomorphy with Pagurus),
and absence of microvillar projections in this
chamber. Several features in which L.
maja differs from species in the genus
Pagurus include the central
perforation in the operculum, the absence of
reticulated acrosome zones, and indications of an irregular flange in
some
planes of the acrosomal vesicle (possible autapomorphy).