Healy, J.M. and Jamieson, B.G.M.
1989e. An ultrastructural study of spermatozoa of Helix aspersa
and Helix pomatia (Gastropoda, Pulmonata). Journal of
Molluscan Studies 55, 389-404.
Spermatozoa of the pulmonates Helix aspersa
Muller and H. pomatia Linnaeus
are examined in detail using
transmission
electron microscopy (TEM). Important features such as the acrosome,
perinuclear
sheath, nucleus and terminal region of the midpiece are described for
the first
time. Also presented are the first ultrastuctural observations on
spermatozoa
from spermatopheres in any pulmonate gastropod (H. aspersa). No
morphological
differences could be found between sperm taken from spermatophores and
those
within the hermaphrodite duct in H.
aspersa. Spermatozoa of H.
aspersa
and H. pomatia show all the
characteristics of euthyneuran spermatozoa,
namely: a
helically-keeled nucleus; distinctive arrangement of acrosomal
components
(apical vesicle, acrosomal pedestal), and extremely elongated midpiece
(axoneme
and glycogen helix enclosed by matrix and paracrystalline layers). The
sperm
nucleus of both species is short, and the midpiece also forms the
terminal
portion of the spermatozoon (glycogen piece absent). The extraordinary
positioning of the acrosome in H.
aspersa-reflected backwards
from the
nuclear
apex-is not observed in H. pomatia,
though a perinuclear sheath
(possibly
another acrosomal component) is present in sperm of both species. Helix
spermatozoa are compared with other euthyneuran sperm and
briefly
discussed
from the systematic viewpoint.