1063-0740/03/2904- $25.00 © 2003
Russian Journal of Marine Biology, Vol. 29, No. 4, 2003, pp. 224–229.
Original Russian Text Copyright © 2003 by Biologiya Morya, Maiorova, Adrianov.
Sipunculan coelom is a capacious body cavity con-
sisting of two major compartments: the anterior tentac-
ular coelom and the posterior trunk coelom [6, 10, 21].
The anterior coelom comprises the tentacular canals,
the ring canal located at the base of the tentacle crown,
and the contractile (or Polian) vessel lying on the dorsal
wall of the esophagus. No connection exists between
the two coelomic compartments; however, the contrac-
tile vesicle extends deeply into the trunk coelom.
Through the wall of the contractile vessel, the coelomic
ﬂuid is ﬁltered from the anterior tentacular coelom to
the posterior trunk coelom . The tentacular coelom is
completely separated from the environment, whereas
the trunk compartment is open to the exterior via a pair
of nephridia. The body cavity of sipunculan worms is
lined by a coelothelium, which consists of multiciliated
cells and podocytes with their processes, and by a thick
layer of an extracellular matrix [2–4, 20–23].
Suspended in the coelomic ﬂuid of both compart-
ments are various free-ﬂoating coelomocytes differing
in their structure and functions . Erythrocytes con-
stitute the vast majority (over 90%) of coelomocytes.
Since hemerythrin (an iron-containing respiratory pig-
ment) was found in sipunculid erythrocytes, they are
termed hemerythrocytes [11, 26, 28]. It is the presence
of this pigment to which the coelomic ﬂuid owes its
pinkish color. There are several schemes of classiﬁca-
tion of sipunculan coelomic cells [11, 13, 16, 18, 21].
There have been a number of biochemical and cytolog-
ical studies on the coelomocyte structure; however,
they predominantly deal with the cells of the extensive
trunk coelom (erythrocytes, amoebocytes, granulo-
cytes, urns, and granular clusters of several specialized
cells) [5, 8, 9, 12, 14–16, 18, 19, 24, 26, 27].
In contrast to the trunk coelom, only two types of
free-ﬂoating cells were found in the tentacular coelo-
mic compartment: pigment cells (erythrocytes) and
granulocytes serving a defensive function . In his
paper of 1960, Manwell  was the ﬁrst to report the
difference in size between the corresponding types of
coelomocytes in the two coelomic compartments of
, the erythrocytes in the tentacular
coelom being signiﬁcantly smaller than those in the
trunk coelom. These conclusions were supported by
, who studied another
Our paper provides the ﬁrst data on the ultrastruc-
ture (using both transmission (TEM) and scanning
electron microscopy (SEM) techniques) of all coelo-
mocyte types in the tentacular coelom of
These data will be used in a comparative morphofunc-
tional analysis of coelomocytes from coelomic cavities
of sipunculid worms.
MATERIALS AND METHODS
were collected among the
at a depth of 3 to 4 m in
Vostok Bay (Sea of Japan) in summer 2000 and sum-
mer 2001. Coelomic ﬂuid was taken from the coelomic
cavities of individuals of both sexes. Coelomocytes
were obtained by sedimentation and ﬁxed for electron
microscopy. The cells from the tentacular and trunk
coelomic compartments were ﬁxed separately. Living
cells and cells ﬁxed in 10% formalin were examined
and photographed with Olympus and Polyvar light
microscopes using Nomarski optics. For electron
microscopy, the specimens were ﬁxed in 2.5% glutaral-
Ultrastructure of the Coelomocytes in the Tentacular Coelom
Ikeda, 1904 (Sipuncula)
A. S. Maiorova and A. V. Adrianov
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received February 10, 2003
—Free-ﬂoating coelomocytes in the tentacular coelomic cavity of the sipunculan
Ikeda, 1904, were studied using light interference contrast microscopy and scanning and transmission electron
microscopy. The following coelomocyte types were distinguished: hemerythrocytes, amoebocytes, and two morpho-
logical types of granular cells. No clusters of specialized cells that had been reported to occur in the trunk coelom of
were found in the tentacular coelom. The corresponding types of coelomocytes from the tentacular and
trunk coelomic cavities were shown to differ in size. These two coeloms are completely separated in sipunculans.
coelom, coelomocyte, erythrocyte, hemerythrocyte, amoebocyte, granulocyte, sipunculan,