Female: Very small, slender. Body tapering uniformly
from above vulva to a finely rounded tail tip. Cuticle marked by
distinct transverse striae, interrupted in the lateral fields by 3 incisures
that appear as 2 bright lines with a fainter one between. Lip region
continuous with body contour, with distinct, rounded lips. When head
observed from a face view, 4 small, round lips appearing slightly more
elevated than the two broader lateral lips. Labial papillae appearing
as 4 minute dots.
Spear flexible, very long and slender. Spear slightly curved when specimens relaxed by gentle heat. Small muscles visible around basal spear knobs in live specimens. Dorsal esophageal gland opening into esophageal lumen about 5u behind spear knobs. Conspicuous excretory pore on ventral side in region of median esophageal bulb. Esophagus consisting of a long, narrow precorpus which widens into the valvated median bulb and a small posterior esophageal bulb distinctly separated from intestine. Cells throughout the intestine not uniformly filled with granules, giving vacuolated effect. Vulva inconspicuous, without lateral membrane. Vagina extending directly inward less than half the diameter of the body. Numerous small sperm in uterus. Ovary outstretched. No postuterine sac. Obscure anus visible in live specimens.
Male: Males rare. Body about the same size as that of female, with similarly shaped lips. Lateral field marked by e incisures. Stylet and esophagus lacking. Large vacuoles in body cavity. The ventrally curved spicula surrounded by an anal sheath, which has a short dorsal extension. Gubernaculum simple. Tail slightly concave, narrowing to a finely rounded tip.
Larva: Larva with a well-developed spear, 34u long, and distinct esophagus. Body forming a loose coil when in normal relaxed position.
Type specimens: Holotype, female, collected in September, 1955, Collection No. 261; allotype, male, same data as holotype; 46 paratypes; all in Canadian Collection of Nematodes.
Type habitat: Soil about roots of fowl blue-grass (Poa palustris L.).
Type locality: Three miles south of Blackburn, Ontario.
Distribution: This species was also collected from meadow sod near Nesbitt, Manitoba.
Diagnosis: The females of P. aciculus differ from all other species of Paratylenchus in having a longer spear (67u). Other species with spears nearly comparable in size are P. aculentus n. sp. (58u), P. goodeyi Oostenbrink, 1953 (51u), P. audriellus n. sp. (51u), and P. anceps Cobb, 1923 (45u). The spear length of P. anceps was misinterpreted as 67u in Oostenbrink (1953).
The presence of 3 lateral lines and the anterior position of the vulva distinguish P. aciculus from all others of the same genus except P. aculentus n. sp., from which it differs in having conspicuous lips and in having a more tapering tail.
Males of P. aciculus do not have a spear.
(Description- Brown, 1958)