ISSN 10630740, Russian Journal of Marine Biology, 2011, Vol. 37, No. 5, pp. 366–370. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © Nguyen Vu Thanh, V.G. Gagarin, 2011, published in Biologiya Morya.
The fauna of freeliving nematodes of Vietnam is
still poorly studied. Nematode biodiversity attracts
significant attention in the context of the creation of a
new database for the biomonitoring of water quality in
the basin and wetland ecosystems of Vietnam. This
project is a part of the Vietnamese State National
NAFOSTED Project, which deals with investigations
of biodiversity and fauna of freeliving nematodes in
Vietnamese coastal waters for the period of 2007–
MATERIALS AND METHODS
The material for our study was collected in Novem
ber 2008 in the South China Sea, in coastal waters of
E). Ground samples were collected using a
Ponartype grab sampler. For statistical and quantita
tive analysis of nematodes three samples were taken at
each the station. The samples were fixed with a 10%
hot formaldehyde solution. To extract nematodes
from ground samples we used LudoxTM 50, a colloid
solution, which is utilized for the extraction of free
living nematodes instead of centrifuging. Ludox was
added to the samples, the obtained solution was settled
for 45 min, and then the upper layer of liquid contain
ing nematodes was transferred into another dish. This
procedure was repeated twice, each time adding an
additional portion of Ludox to the sediment. Mea
surements and identification of nematodes were per
formed under an MBB1A dissection microscope
using permanent paraffinglycerol preparations.
In differential diagnoses and in tables we used the
standard indices of De Man as follows: (L) body
length; (a) body length to maximum body diameter
ratio; (b) body length to esophagus length ratio;
(c) body length to tail length ratio; (c') tail length to
body diameter (at the area of anus or cloaca) ratio;
(V) distance between the anterior body end and vulva
to total body length ratio expressed as a percentage.
Order Plectida Malakhov, 1982
Family Cyartonematidae Tchesunov, 1990
These are comparatively small nema
todes. The cuticle is smooth as seen under a light
microscope. Somatic setae are absent. Head end is
tapered and conically pointed. Lips are absent; mouth
opening is small and narrow. There are four short sub
lateral cephalic setae. Cephalic capsule is fused, well
developed, embraces circularly the anterior end of the
nematode. Amphideal fovea are large, circular, located
on cephalic capsule. Pharynx consists of three parts:
an anterior cylindrical part; a middle narrow one con
stituted of ducts of pharyngeal glands and a pearlike
posterior one constructed of pharyngeal gland cell
bodies. Intestine is blindended, neither rectum nor
anus are present. A renette gland is located at the level
with the anterior part of midgut. Two or one phago
cytic cells are located along the anterior part of mid
gut. Female gonad is paired; ovaries are reflexed, of
cyartonematid type. Testes are paired, opposed. Spi
cules are relatively short, arcuate, with a capitulum.
A New Genus and Two New Species of Marine FreeLiving
Nematodes from the Coastal Waters of Southern Vietnam
Nguyen Vu Thanh
and V. G. Gagarin
Institute of Ecology and Biological Resources, Vietnamese Academy of Science and Technology, 10000 Hanoi, Vietnam
Institute of Inland Water Biology, Russian Academy of Sciences, Borok, 152742 Russia
email: email@example.com; firstname.lastname@example.org
Received March 24, 2011
—A new genus and two new species of freeliving marine nematodes from sediments in the coastal
zone of the South China Sea (Vietnam) are described.
gen. n. morphologically resembles
Cobb, 1920, but differs from it in having a welldeveloped cephalic capsule.
gen. n., sp. n. is the type and the only species of the genus.
sp. n. differs from all
species of the genus
Cobb, 1920 by the shape of the amphidial fovea and shorter lateral fields.
freeliving marine nematodes, new taxa,
gen. n. et sp. n.,
sp. n., South China Sea, coast of Vietnam.