KHUONG
B. NGUYEN
Entomology & Nematology Department
University of Florida
DESCRIPTION
Male
(first generation). Body curved ventrally or C-shaped when heat-killed.
Cuticle smooth. Head rounded, slightly offset from the body. SEM face view
with six pointed labial papillae and four cephalic papillae. Amphids in-conspicuous.
Mouth opening funnel-shaped or cup-shaped. Stoma shallow. Pharynx muscular:
procorpus cylindrical; metacorpus slightly swollen, non-valvate; isth-mus
indistinct; basal bulb pyriform. valve not observed. Nerve ring surrounding
isthmus or just above basal bulb. Cardia prominent and protruding into
intestine lumen. Excretory pore between nerve ring and middle of pharynx.
Excretory duct cuticularised: excretory gland swollen and elongated. Monorchic
gonad reflexed. Spicule paired, yellow-brownish in colour and ventrally
curved (SEM1) ; spicule head (manubrium)
ca 33% spicule length and longer than wide. Velum thin. Gubernaculum ca
65% of spicule length, boat-shäped. swollen at middle and proximal
end with knob ventrally curved. A single ventral precloacal papilla and
eleven pairs of genital papillae present and arranged as follows: five
pairs subventrally preanal; one pair subdorsal at the same level of the
single ventral pre-cloacal papillae; two pairs subventral in cloacal region;
two pairs caudal (SEM2) , subventral
and one pair caudal, subdor-sal. Tail conoid without mucron. Phasmids in-conspicuous.
Measurements, in micrometers (n=20). L=1397
± 83(1128-1500), W=85±10(60-100), EP=121±6(106-133),
NR=138±7(124-148), ES=165±6(152-175), testis reflexion=249±82(80-384),
tail length=27±3(24-33), ABW=38±2(32-42), spicule length=71±4(60-80),
gubernaculum length=46±3(40-52), D%=73±5(61-80), SW=1.9±0.1(1.7-2.1),
GS=0.7±0.1(0.5-0.8).
Female (first generation). Body
robust, spiral-shaped or C-shaped when heat-killed. Cuticle smooth. Head
broadly rounded. SEM face view with six pointed labial papillae and four
cephalic papillae. Amphids inconspicuous. Mouth opening funnel-shaped or
cup-shaped. Stoma shal-low. Pharynx with cylindrical procorpus; metacorpus
slightly swollen and non-valvate: isthmus indistinct; basal bulb pyriform,
valve not observed. Excretory pore between nerve ring and middle of pharynx.
Excretory duct cuticularised and excretory gland swollen. Cardia prominent
protruding into intestine lumen. Didel-
phic. amphidelphic gonad reflexed and tightly filled with eggs. Vulva
a transverse slit on a protuber-ance without epiptygma and near middle
of body . Vagina short, oblique with muscular walls. Tail shorter than
anal body width with terminal peg (SEM3)
.
lnfective juveniles. Often enclosed in cuticle of second-stage.
Body long, slender. Anterior end rounded, broad; lip region smooth, slightly
offset from the body. Mouth and anus closed. On SEM face view, labial papillae
not observed; pore-like amphids situated below labial disc just above cephalic
papillae. Pharynx long and narrow, isthmus distinct and surrounded by nerve
ring, basal bulb elongated with valve. Cardia prominent. Excretory pore
between nerve ring and middle of pharynx. Hemizonid distinct and located
at isthmus level.
Bacterial pouch rarely seen and tightly crowded with bacteria. Lateral
field with eight ridges (SEM4) (nine
lines) distinct (at mid-body). Tail conoid without mucron. Hyaline portion
well pronounced about 46% of tail length. Phasmids distinct and located
in anterior half of tail.
Measurements, in micrometers
(n=20). L=986±45(896-1072), W=37±3(30-45), EP=80±3(71-86),
NR-102±5(89-111), ES=141±6(126-155), tail length=75±4(66-83),
ABW=21±2(18-27), a=27±2(24-30), b=7±1(6-8), c=13±1(11-15),
D%=57±3((52-63), E%=107±7(94-120). H%=46±3(40-52).
Diagnosis
and relationships. Steinerneina loci is distinguished
fro others by the following characters. The infective juveniles (IJ) have
a rounded and broad anterior end. The lip region is smooth, slightly offset
from the body. The lateral field at mid-body has eight ridges (nine distinct
lines). The spicule head (manubrium) is longer than wide. Steinernerna
loci is morphologically similar to S. arenarium and S.
glaseri but can be distinguished from S. glaseri by a shorter
IJ body length [985 (896-1072) vs 1130 (864-1448) um] and a more an-terior
position of the IJ excretory pore [80 (71-86) vs 102 (87-110) um]; from
S.
arenarium by a shorter IJ body length [985 (896-1072) vs 1034 (724-1408)
um] and a more anterior position of the IJ excretory pore [80 (71-86) vs
83 (76-86) um]. The morphometrics of S. loci are close to those
of S. longicacidum. S. oregonense, S. kraussei
and
S. karii but the new species can be separated from
S. longicaudum
by a shorter body length [885 (896-1072) vs 1063 um], and a shorter tail
length [75 (66-83) vs 95 um] from S. oregonense by a more posterior
position of the excretory pore (80 (71-86) vs 66 (60-72) u m), a longer
esophagus [141 (126-155) vs 132 (116-148) um], and a longer tail [75 (66-83)
vs 70(64-78) um]; from S. kraussei by a more posterior position
of the excretory pore [80 (71-86) rs 60 (56-66) um]; and from
S. karii
by a more posterior position of the excretory pore [80 (71-86) rs 74 (68-80)
um.
Type host: unknown
Type locality: sandy soil on the sea beach
in Thachkhe, Thachha, Hatinh, Vietnam.
Type specimens: Holotype: Gent University,
Institute of Zoology, K.L. Ledeganckstraat 35, 9000, Belgium.
Reference
Phan, K. L, N. C. Nguyen, and M. Moens, 2001.Steinernema loci sp. n. and Steinernema thanhi sp. n. (Rhabditida:Steinernematidae) from Vietnam. Nematology 3:503-514.