Helicotylenchus dihystera ( Cobb, 1893 ) Sher, 1961

Daramola, Fisayo Y., Orisajo, Samuel B., Malan, Antoinette P. & Marais, Mariette, 2020, Molecular characterization of Helicotylenchus multicinctus and H. dihystera (Tylenchida: Hoplolaimidae) from Theobroma cacao in Nigeria, Zootaxa 4778 (2), pp. 343-356 : 347-348

Helicotylenchus dihystera ( Cobb, 1893) Sher, 1961

= Tylenchus dihystera Cobb, 1893

= Tylenchus olaae Cobb, 1906

= Tylenchorhynchus olaae ( Cobb, 1906) Micoletzky, 1922

= Helicotylenchus olaae ( Cobb, 1906) Sher, 1961

= Aphelenchus dubius var. peruensis Steiner, 1920

= Tylenchus spiralis Cassidy, 1930

= Helicotylenchus spiralis ( Cassidy, 1930) Sher, 1961

= Helicotylenchus nannus Steiner, 1945

= Helicotylenchus crenatus Das, 1960

= Helicotylenchus dihysteroides Siddiqi, 1972

= Helicotylenchus flatus Román, 1965

= Helicotylenchus glissus Thorne & Malek, 1968

= Helicotylenchus rotundicauda Sher, 1966

= Helicotylenchus punicae Swarup & Sethi, 1968

= Helicotylenchus teleductus Anderson, 1974

= Helicotylenchus paraconcavus Rashid & Khan, 1974

= Helicotylenchus membranatus Hui & Zhixin, 1993

Description. Female (n = 10): Habitus spiral. Lip 4 ± 0.6 (4–5) µm high and 7 ± 0.8 (6–9) µm wide; rounded anteriorly, with five to six annuli. Outer margins of labial framework extend 4 ±1.9 (3–6) µm posterior from basal plate. Cephalids not seen. Stylet knobs 2 ± 0.7 (2–4) µm high and 5 ± 0.5 (4–5) µm wide, rounded posteriorly, anterior faces indented. Position of DGO 12 ± 1.6 (9–14) µm behind stylet knobs. Median bulb oval, 12 ± 1.3 (10–14) µm long and 9 ± 0.9 (8–10) µm wide; valve 3 µm long and 3 µm wide. Excretory pore 98 ± 4.1 (93–1047) µm from front, i.e. at 15 ± 1.0 (13–16) % of body length. Hemizonid two annuli long, located one annule anterior to excretory pore (n =1). Hemizonion and fasciculi not observed. Width of annuli at midbody 1.3 ± 0.2 (1.0–1.7) µm. Body width at excretory pore 19 ± 2.8 (15–23) µm, at midbody 25 ± 3.5 (21–30) µm and at anus 16 ± 2.8 (12–20) µm. Epiptygma folded into vagina. Lateral field 6 ± 1.1 (6–8) µm wide; areolated anterior to excretory pore; inner two lines end on tail in a y-shaped pattern. Caudalid one annulus long located one annulus posterior to anus (n=1). Phasmid located from three eleven annuli anterior to anus. Tail 16 ± 1.8 (13–18) µm long, with 10 to 13 ventral annuli; tail asymmetrically rounded, and dorsally curved, with or without ventral projection, if present with rounded end.

Male: Not found.

Remarks. Our specimens were identified as H. dihystera because of spiral habitus, stylet length (mean value: 27 µm), body length (mean value: 641 µm), position of vulva (mean V value: 63 %), phasmids anterior to anus, inner lines of lateral field end on tail mostly in y-shaped pattern, tail asymmetrically rounded, with or without terminal projection (if present with rounded end), empty spermatheca, and absence of males ( Fortuner et al. 1981). The present specimens agree with the amended descriptions of Fortuner et al. (1981) and Fortuner (1991). The stylet length for the current specimens exceeds that of the 24–25 µm reported for Nigerian specimens by Ali et al. (1973), but still falls in the range for H. dihystera (20–31 µm) as reported by Marais (2001).