1063-0740/04/3005- © 2004
Russian Journal of Marine Biology, Vol. 30, No. 5, 2004, pp. 323–327.
Original Russian Text Copyright © 2004 by Biologiya Morya, Preobrazhenskaya, Tarasova.
The distribution patterns of benthic foraminiferans,
their population density, and their assemblage struc-
ture, as affected by environmental factors, were studied
in Peter the Great Bay (Sea of Japan) at Furugelm
Island and in Vityaz Bay in July and August 1999 .
The study of the taxonomic composition of the total
foraminiferan assemblage revealed four specimens of
(d’Orbigny) ﬁlled with
offspring (two specimens in Severnaya Bay of
Furugelm Island and two specimens in Vityaz Bay).
Interestingly, offspring-containing foraminiferan tests
have been recorded from a natural habitat, but not in an
experiment. There are no published reports of such a
It is well known that the life cycle of foraminiferans
comprises an alternation of sexual and asexual genera-
tions. The ﬁrst investigations into the life cycle of fora-
miniferans were undertaken as early as the end of the
nineteenth century. Munier-Chalmas  discovered
dimorphism in foraminiferans and Lister  and
Schaudinn  revealed the true cause of this phenom-
enon. These investigators found that sexual and asexual
generations alternate in the life cycle of
and that individuals which are repro-
duced sexually have a microspherical test and those
formed asexually have a macrospherical test. During
the ﬁrst half of the twentieth century, the life cycles of
other foraminiferans were studied more thoroughly
[16, 18, 22, and others]. Grell and his students [14, 15,
and others] made an important contribution to the study
of sexual reproduction and nuclear dualism in some
genera and species of the family Rotaliidae. Voronova
and her adherents [1–3] performed deep investigations
into the life cycle of
phometric studies of the nuclei of this foraminiferan.
Nuclear dualism has long been known only for the aga-
monts. M.N. Voronova was the ﬁrst to ﬁnd it in the
. Later, Goldstein
[12, 13] studied in detail the reproductive cycle,
particularly gametogenesis, in
To date, about
10000 species of foraminiferans have been described;
however, the full life cycle has been studied, exclu-
sively experimentally, in only 30 species .
Aspects of the morphology, taxonomy, systematics,
phylogeny, and evolution of foraminiferans connected
with the reproduction process have been successfully
worked out by foreign and Russian investigators [4–6,
10, 11, 17, 23–25, and others].
The aim of the present research is to elucidate, based
on previous studies of foraminiferan life cycles,
whether the offspring of
is produced in a
sexual or asexual way.
MATERIALS AND METHODS
The material for the study was four adult specimens
tests, numerous juvenile forms (up to 10 ind./cm
plastogamous pairs (up to 12 ind./cm
) encountered in
sand samples. Two offspring-ﬁlled foraminiferan tests
were found in samples 1 and 2 collected near Furugelm
Island at 12 and 7 m depths at a bottom water tempera-
ture of 15 and 17
C and the other two in samples 3 and
Sexual Reproduction of the Foraminiferan
(d’Orbigny, 1839) in Nature
T. V. Preobrazhenskaya and T. S. Tarasova
Institute of Marine Biology, Far East Division, Russian Academy of Sciences,
Vladivostok, 690041 Russia
Received February 4, 2004
—The taxonomic composition of the entire foraminiferan assemblage in the southern part of Peter the
Great Bay (Sea of Japan) was studied during the summer 1999 expedition. Along with other foraminiferans,
several offspring-ﬁlled tests of
(d’Orbigny, 1839) were found in surface sediment
samples. Based on the extensive literature on the reproductive cycle of foraminiferans and indirect evidence, it
was found that each of the parent individuals of this species was a partner in a plastogamous pair, thus being a
gamont, while their offspring were agamonts. The gamogony stage, contrary to the generally accepted opinion,
took place under natural conditions in summer (not in fall or winter) at a bottom water temperature of 15–18
The results of this research may be important in paleogeographical and paleoecological reconstructions.
Foraminifera, progeny, life cycle, plastogamous pair, gamogony, gamont, agamont.