(Szczygiel, 1970) Brzeski, 1982
||Tylenchus facultativus Szczygiel, 1970
||Ottolenchus facultativus (Szczygiel, 1970)
Siddiqi & Hawksworth, 1982
||Malenchus piahyuensis Monteiro, 1974
||Ottolenchus piahyuensis (Monteiro, 1974) Siddiqi,
Females (n = 38): L = 0.48 (0.42-0.55)mm; a = 30 (25-36);
b = 6.1 ( 5.0-6.7); c = 4.6 (3.7-5.5); c' = 10 (7-14);
T/VA = 1.8 (1.2-2.5); V = 65 (60-70); V' = 84 ( 78-86); MB
= 42 (39-48); stylet = 68um.
Males (n = 5): L = 0.45 (0.40-0.53) mm; a = 33 (30-36);
= 5.8 (5.5-6.0); c = 4.1 (3.5-4.8); MB = 43 (39-45); stylet = 6
um; spicules = 16 (15-18) um; gubernaculum = 3-5 um.
Annule width 1.7-2.3 um. Head not demarcatd
or slightly narrower than neck, with two (seldom three) annules.
Stylet 6-7 um in European populations, and 7-8 in Australian ones.
Median bulb ovate, posterior bulb short, occasionally slightly elongated.
Length of oesophagus 77 um (70-89). Excretory pore 40 (35-45)
annules posterior to head end.
Vagina more than half of body width. Spermatheca
up to 34 um long. Sperm in spermatheca rounded, 1.5-2.0um
in diameter. Posterior uterine sac shorter than body width.
Between vulva and anus there are 28 (23-35) annules.
Tail variable, mostly rounded at the end.
Tail length 108 um (79-133); often no annulation on posterior portion
Males rare. Bursa delicately crenated, small,
begins near anterior end of spicules.
The above description is based on specimens from
several collections in Poland, Ischia island in Italy, several places in
south-western part of New South Wales, and from South Australia.
The measurements are combined from all these populations.
Malenchus piahyuensis is synonimized with
facultativis because studies of the holotype and the paratype as well
as the comparison with the description did not show any differences.
The type specimens of M. piahyuensis are preserved in such a state
that many characters are not visible.
O. facultativis can be differentiated from
parvus by its annulated head and shorter female genital tract that
does not reach the oesophagus. It differs from O. vesiculosus
by a shorter stylet. However, further studies of morphological variability
of single female progenies may demonstrate that these differences are not
significant at specific level.
(Description- Brzeski, 1982)
L = 0.42-0.55; a = 25-36; b = 5.0-6.7; c = 3.7-5.5;
= 7-14; V = 60-70; stylet = 6-8um; (Brzeski, 1982)
Diagnosis (emended): Ottolenchus facultativus is distinguished
by its: 1) total length 380-630 um range as reported for all populations
studied (Brzeski, 1982 and this study); 2) coarse body annuli ranging from
1.3-2.6 um; 3) tail shape narrowly cylindroid with bluntly rounded
terminus, with variations narrowly conoid ending in finely rounded tip;
4) prominent postuterine sac reniform, broadly rounded, less than one vulval
body diameter in length; 5) position of excretory pore; 6) short V-a distance,
tail/V-a 1.2-2.7; 7) head with rectangular labial plate, longer laterally
than dorso-ventrally, sinuous amphidial openings from near oral disc through
2-3 body annuli.
(Description- Raski & Geraert, 1986)