Males: Anterior part similar to females. Testis single, reflexed. Spicules paired and strongly curved with blunt tips (FIG.SEM). Spicule length/width about 4.2 (3.8-4.5) (Nguyen & Smart, 1997). Spicule head short, truncate anteriorly (Fig. SEM). Shaft present but short. Blade with anterior part well curved, posterior part slightly curved or almost straight. Velum large not covering spicule tip. Gubernaculum boat-shape in lateral view, in ventral view, gubernaculum tapering anteriorly to a slightly enlarged head. Gubernaculum large. Cuneus large needle-shaped, pointed posteriorly (Fig. SEM). Posterior region with twenty three genital papillae (eleven pairs and a single ventral preanal), variable in position. Three pairs are consistently found on the tail tip, three pairs in spicular region, five pairs subventral anterior to spicular region, and a single ventral papillae that is usually quite consistent in its position. The ventral portion of the tail is usually concave. This character seems to be fairly consistent although the degree of concavity varies somewhat. A thin flap of sclerotized cuticle occurs over the cloaca and serves to close the cloacal opening when the spicules are in a resting position. The cloacal opening is slit-like and on both sides are a pair of small lateral papillae-like structures. Whether these are innervated could not be determined but if so they could function as sensory organs to locate the vulva. No mucron was observed.
Measurements (n=10): Length=2400 micrometers (um) (1600-3000), width=168 um (113-207), stoma length=6.8 um (4.8-8.0), stoma width=8 um (6.4-9.6), anterior end to excretory pore=137 um (114-155), to nerve ring=146 um (120-168), esophagus length=190 um (155-209), testis reflexion=625 um (283-1008), tail=54 um (45-59), body width at cloaca=77 um (53-88), spicule length=93 um (80-106), spicule width=19 um (13-26), gubernaculum length=62 um (48-96), gubernaculum width=11 um (8-17), D%=72 (67-80). (After Poinar, 1985).
Infective juveniles (third stage enclosed in second stage cuticle) : These are narrower than the corresponding parasitic juveniles. Mouth and anus closed and esophagus and intestine collapsed. Tail usually constricted on the dorsal side. Lateral field with six to eight incisures depending on region of body observed. A bacterial pouch present in anterior portion of intestine containing symbiotic bacteria Xenorhabdus nematophilus. There was no retractile spine in the tail of the infective.
Measurements (n=25): Length of the infective stages = 680 micrometers (um) 608-800, greatest width = 28 um (25-32); distance from the head to the excretory pore = 65 um (61-69); distance from head to nerve ring = 92 um (85-96); distance from head to base of esophagus = 121 um (110- 131); length of the tail = 64 um (53-72); width at anus = 16 um (13-18),length of bacterial pouch= (27-48 um). (After Poinar , 1985)
Bacterial associates: Infective stages of S. intermedium carry cells of Xenorhabdus nematophilus in their intestine and liberate these in the insect host soon after penetration. The bacteria have been isolated using the blood drop method (Poinar, 1966) and cultured on nutrient and Tergitol-7 agar plates. The bacteria produce a brownish cream color on nutrient agar and a greenish blue color on Tergitol-7 agar.
Type locality: Charleston, South Carolina, USA; no type host: recovered from soil using wax moth larvae as bait.
Type specimens: Holotype (male) and allotype (female) deposited in the Nernatology collection at the University of California, Davis, California. Paratypes deposited at the Laboratoire des Vers, Museum national d'Histoire naturelle, Paris.
Dianosis:Steinernema intermedium can be separated from S. carpocapsae, S feltiae and S. glaseri by several characters. One of these is the length of the infective juveniles which range from 600-800 um. The lower end of this range does overlap with the upper end of S. carpocapsae (438-650 um) and the upper end of the range overlaps with the lower range of S. feltiae (700-1 000 um), yet on the average, the infectives are larger than those of S. carpocapsae and smaller than those of S. feltiae. This range is smaller than that of infectives of S. glaseri (864-1448) um. Also, the tail of the infective stage of S. intermedium is usually constricted, especially on the dorsal side. A constriction is lacking in infectives of S. feltiae and if present occurs on the ventral surface in S. carpocapsae and S. glaseri. The male tail of S. intermedium lacks a projection or spine of any type which separates it from both S. carpocapsae and S. feltiae. The spicules are generally more curved than those of S. carpocapsae, S. feltiae and S. glaseri. Blunt tips of spicules separate them from the hooked tip spicules of S. glaseri and the pointed spicules of S. carpocapsae. The gubernaculum of S. intermedium is unusual since the distal portion is bent upwards and encloses the distal portion of the spicules. The male tail of S. intermedium has a ventral concavity which is not present or as distinct in the other three neoaplectanids.
REFERENCE
Poinar, G. O. 1985. Neoaplectana intermedia n. sp. (Steinernematidae: Nematoda) from South Carolina. Revue de Nematology 8:321-327.
This document was constructed and is maintained by KHUONG
B. NGUYEN
Entomology & Nematology Department
University of Florida