Healy, J.M. and Jamieson, B.G.M.
1993m.
Euspermatozoa, paraspermatozoa and spermatozeugmata of Littoraria
(Palustorina) articulata (Prosobranchia:
Caenogastropoda) with special reference to the Pseudotrich. Acta
Zoologica (Stockholm) 74, 321-330.
Paraspermatozoa and euspermatozoa of the
littorinid gastropod Littoraria
(Palustorina) articulala are examined
using
transmission electron microscopy and light microscopy. In the seminal
vesicle,
both sperm types occur, either as free cells or organized into
spermatozeugmata. It is shown that the elongate (120-140 mu-m),
flagellum-like
component of the paraspermatozoon is in fact a tubular extension of the
plasma
membrane which encloses granular material but no axonemes or
microtubules. This
structure. here termed the pseudotrich, shows no evidence of motility
and its
function remains obscure. The main body region of the paraspermatozoon
(length
32-36 mu-m) contains numerous spherical vesicles, scattered
mitochondria, one or
two large, rod-shaped bodies (length 20-24 mu-m) and a fusiform,
granular body
(containing DNA; probably a modified nucleus). The rod-shaped bodies,
granular
body and surrounding matrix are contained by a common membrane, and are
therefore separated from other contents of the paraspermatozoon. In
each
spermatozeugma, euspermatozoa are attached via the tips of their
acrosomes to
the paraspermatozoan body at the opposite end to the pseudotrich.
Euspernatozoa
exhibit a conical acrosomal complex (with axial rod and basal plate), a
tubular
nucleus sheathing the axoneme, a midpiece (5-6 helical mitochondrial
elements
sheathing the axoneme), an annulus (with two rings), a glycogen piece
and an
end piece (total sperm length 268-272 mu-m). The euspermatozoa of L.
articulata
are similar to those of most littorinids and many other
caenogastropods. The
presence of a pseudotrich in the paraspermatozoon appears to be
restricted to
the subgenus Palustorina.