Measurements (n = 23): Length= 8600 (5200-11500) micrometers (um); width= 252.2 (210-300) um; length of stoma =9.5 (7-13) um; width of stoma=9 (6-12) um; distance from anterior end, to base of oesophagus = 196 (130-232) um; to excretory pore = 74.5 (40-135) um; to nerve ring = 141.4 (108-187) um; V = 51 (44-56); length of tail = 27.6 (19-36) um; width at anus = 66 (45-95) um.
Males, first generation : Cuticle, lip region and pharyngeal region similar to those of females. Testis single, reflexed. Spicules paired, arcuate, symmetrical, with ribs and thin velum. Capitulum rounded. Distal tips of spicule sharply pointed with a ventral concavity giving them a hooked appearance. Gubernaculum rounded anteriorly in first generation, with a small straight or recurved projection in the second generation. Genital papillae twenty-three, including six ventrolateral preanal pairs, one adanal, two postanal; two lateral and one single preanal. Mucron absent. Tail terminus bluntly conical in the second generation.
Measurements (n = 30): Length = 1480 (1200-1900) um; width = 130 (110-176) um; length of stoma = 2.9 (1.5-5) um; width of stoma = 4.40 (3.5-5) um;distance from anterior end, to base of oesophagus = 137 (121-155) um, to excretory pore = 65.5 (53-78) um, to nerve ring = 105 (92.5-124) um; length of tail = 26.5 (21-32) um; width at anus = 44 (37-32) um; length of spicules = 69 (58-75) um; width of spicules = 12 (10-15) um; length of gubernaculum = 43.5 (33-50) um.
Infective juveniles : Body slender, tapering to both ends, usually with sheath. Cuticle with fine striae. Lateral fields with six ridges. Lip region smooth, generally continuous. Mouth closed. Esophagus long and narrow, distinctly narrower at level of nerve ring, terminating in a valvated basal bulb. Cardia present. Anterior portion of intestine with dorsally displaced pouch containing symbiotic bacteria. Lumen of intestine narrow, rectum long, narrow; anus distinct. Excretory pore at about middle of esophagus. Nerve ring distinct, immediately anterior to basal bulb. Hemizonid located at level of basal bulb. Genital primordium evident. Tail conical with pointed terminus.
Measurements (n = 20): Length = 510 (470-590) um; width = 21.5 (19-24) um; distance from anterior end, to base of oesophagus = 91.5 (85-95) um, to excretory pore = 43 (40-46) um, to nerve ring = 73 (68-85) um, to hemizonid = 80 (75-85) um; length of tail = 49 (44-54) um; width at anus = 14 (12-17) um; a = 24.1 (19.5-30.9); b = 5.5 (4.9-6.3); c = 10.6 (9.2-13. 1); D = 0.46 (0.44-0.50); E = 0.88 (0.79-0.97).
Type specimens : Holotype: female deposited in the Museum national d'Histoire naturelle, Paris, France. Paratypes: four females and seven males of the first generation, ten females and ten males of the second generation and fourteen free living infective juveniles in the mentioned institution and in the University of California, Davis, U.S.A. Eighteen females and twenty-three males of the first generation, twenty-one females and sixteen males of the second generation and six free living infective juveniles in the Centro de Zoologia Aplicada, Universidad Nacional de Cordoba.
Type habitat and locality : Soil from Estancia Sol de Mayo, Rio Cuarto, Cordoba, Argentina.
Diagnosis and relationships
: Females of both generations of S. ritteri differ
from the rest of the species of the genus, except S. feltiae Bovien,
1937 and S. scapterisci Nguyen & Smart, 1990 in having a well
developed epiptygma. In S. feltiae it is less developed whereas
in S. scapterisci it is more developed than in S. ritteri
. The latter differs from S. feltiae by the absence of a mucron
on the tail tip of males and first generation females, and by characters
of the infective juveniles (L=0.47-0.59 mm vs 0.70-1.00 mm; anterior end
to excretory pore distance = 44-54 um vs 53-67 um; esophagus length = 85-95
um vs 115-150 um; tail length = 44-54 um vs 70-92 um). S. ritteri
differs from S. scapterisci by the absence of a mucron on the tail
tip in first generation adults and by mean values of most measurements
in all stages, except for a few measurements that have greater values:
body width at anus level (males of both generations and first generation
females), tail length (first generation males), body length and greatest
width (first generation females), distance from anterior end to excretory
pore (infective juveniles) the rest of them have lower values in S.
ritteri. This new species if most similar to S. carpocapsae, S.
rarum and S. kushidai in general morphology of the infective
stage, in males and females. It differs from the first two species by the
absence of a mucron in adults of the first generation and by greater values
of ratios D and E of the infective juvenile (D= 0.4 0.50 vs 0.23-0.28 and
0.34-0.41; E = 0.79-0.97 vs 0.54-0.66 and 0.70-0.86 respectively). It differs
from the latter by the round-shaped tail in adults of the first generation
and by the measurements of all morphometrics being mostly lower in all
stages.
REFERENCE
Doucet, M. M. A., and M. E. Doucet. 1990. Steinernema
ritteri n. sp. (Nematoda:
Steinernematidae)
with a key to the species of the genus. Nematologica 36:257-265.
This document was constructed and is maintained by KHUONG
B. NGUYEN
Entomology & Nematology Department
University of Florida