Steinernema loci
Phan, Nguyen & Moens, 2001

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.



updated 16 November 2002