TABLE CONTENTS

Sperm Development in the Free-living Marine Nematode Leptosomatides
marinae (Enoplida, Leptosomatidae)
Afanasiev-Grigoriev, A.G. & V.V. Yushin
Institute of Marine Biology FEB RAS, Vladivostok 690041, Russia
The leptosomatid Deontostoma californicum was the first free-living marine nematode
which spermatozoa have been studied by electron microscope (Proc. Helminthol. Soc.
Wash. 1973. 40: 30-36.). Recently we started a new study of male gametes in the
leptosomatids using Leptosomatides marinae as the representative. The reconstitution of
the nuclear envelope during the nuclear collapse of the spermatids and spermatozoa in L.
marinae confirmed the unity of the enoplids by this plesiomorphic character (Russ. J.
Nematol. 2006. 14: 119-125). The cytoplasmic events observed in spermatogenous cells of
L. marinae are also of special interest. In the early spermatids the proliferation of rough
endoplasmic reticulum (RER) and dictiosomes occurs. Two types of cytoplasm inclusions
appear: fibrous vesicles bounded by double membrane and dense vesicles with internal
system by microvillus-like projections. The latter are easily identified as ‘membranous
organelles’ or MO, unique component of nematode sperm. In the late spermatids the
fibrous vesicles were no longer detected; the numerous MO tend to be in close association
with the nucleus and its nuclear envelope. Periphery of the cell is occupied by
mitochondria and extensive synthetic apparatus (RER, dictiosomes). The immature
spermatozoon has the central elongated nucleus surrounded by the electron-light halo. The
periphery of the cell is occupied by numerous dense MO interspersed by occasional
mitochondria. The surface of the cell is arranged as numerous parallel ridges filled with
microtubule-like fibres. The spermatozoon development of L. marinae has the general
enoplid character: absence of MO-FB complexes. Moreover, the FB (fibrous bodies, one
more unique component of the nematode sperm) have not been detected as it was observed
also in Anticomidae, Anoplostomatidae, and Tripyloididae. The alternative pattern of
cytoplasmic events in the enoplids, separate development of FB and MO (Enoplidae,
Oxystominidae, Oncholaimidae) is also unique for nematodes. The enoplid spermatozoa
provide nematode phylogeny by distinct differential characters.
5 th International Congress of Nematology, 2008 194