ISSN 10630740, Russian Journal of Marine Biology, 2011, Vol. 37, No. 1, pp. 73–75. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.V. Chernyshev, 2011, published in Biologiya Morya.
Pilidia from the “
described as early as 1858 . Since then, they have
been found in various coastal areas of Europe, North
America, and at the Pacific coasts of Asia and Austra
lia [1, 3–5, 7]. Dawydoff  has described three forms
(“species”) of pilidia of this group, viz.,
p. galeatum, p.
, from the coastal
waters of Vietnam. There is no doubt that
are actually larvae of nemerteans of the
family Hubrechtellidae [2, 3].
During surveys of the meroplankton in the South
China Sea, I found a pilidium from the “
group, which appeared to be a new form. A description
of this form is presented here. The pilidium was stud
ied in vivo and fixed in 4% formaldehyde with prelim
inary magnesium chloride anesthesia. DAPI staining
was used to reveal the distribution of nuclei with the
use of fluorescent microscopy: 2
l of DAPI stock
solution were added to 100 ml of phosphate buffer; the
pilidium was placed for 1 min into a droplet of the
solution obtained, then washed in the phosphate
buffer and examined under a Leica MZ75 microscope.
Single specimen. Collected on June 3,
2007 in the South China Sea, Van Phong Bay,
E, subsurface catch.
The pilidium is at a late stage of devel
opment. The larva is 430
m long and 495
the lateral lobes are 167
m long, the maximum width
m. The anterior and posterior surfaces of the
helmet are convex; the anterior surface of the live pil
idium is more convex than the posterior one. The
anterior lobe is wider than the posterior part of the pil
idium. The lateral lobe is narrow, curved, and directed
downwards; the anterior and the posterior lobes do not
protrude. The helmet consists of large pentagonal–
septagonal cells, reaching to 90
m in diameter. In live
pilidia, the ciliary band in front of the lateral lobes and
on the lower end of the lobes is pigmented light yellow.
The apical organ is 40
m in diameter, not pigmented,
its tuft about 160
m long. Any retractor muscle that is
connected with the apical organ has not been yet
detected. The juvenile larva is connected with a thick
and short (43
m) strand to the posterior wall of the
helmet (Fig. 1c). The helmet wall is thickened in the
site of the connection; nuclei in the thickening form
two adjacent groups (Fig. 1f). The anterior–posterior
axis of the pilidium and the anteriorposterior axis of
the juvenile form an angle of approximately 15
juvenile larva is about 320
m long; its posterior part
was drawn and curled up to form, very probably, the
caudal cirrus. The anterior end bears an accumulation
of lightyellow pigment. The proboscis of the juvenile
was partly turned inside out upon fixation.
The pilidium described is undoubt
edly similar in its form to typical
however, it differs from them by having a higher hel
met and the presence of one short and thick strand
(the typical pilidia have two long and thin strands,
which connects the juvenile specimen with the poste
rior part of the helmet.
The description of
notes two distinctly separate strands of muscle fibers
that connect the embryo with thickenings on the pos
terior wall of the helmet . I have observed similar
pairs of strands in
from the Sea of
Japan; the sites of their connections stand widely
apart, with accumulations of cells there; their nuclei
A New Form of Larvae of the
(Nemertea) from the Coastal Waters of Vietnam
A. V. Chernyshev
Institute of Marine Biology, Far East Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia;
Far East State University, Vladivostok, 690600 Russia
Received May 20, 2010
—A new form of
from the coastal waters of Vietnam (Van Phong Bay) is
described. One distinguishing feature of this form is the presence of a short unpaired strand connecting the
juvenile larva to the posterior wall of the helmet.
: nemerteans, pilidia.