Measurements (n = 50): L': 600-755 (675) um; neck length: 100-131 (119) um; B: 450-550 (520) um; L'/B ratio: 1.1-1.5 (1.3); fenestral length: 35-50 (42) um; fenestral width: 17-28 (24) um; fenestral L/B: 1.5-2.1 (1.8).
Mature cysts spheroidal with small, obtuse vulval cone and well-developed neck. Colour varies from pale yellowish to dark brown, the vast majority examined being light creamy brown. When dried they become characteristically wrinkled and partially collapsed, assuming a prune-like appearance. Wall pattern consists of irregular zig-zag lines and punctations. Subcrystalline layer thin and matt-white. Egg-sac small and empty. Fenestration of the bifenestrate type with a less clearly defined outline than those of H. avenae or H. mani. Vulval slit 8-15 (11) um long. Distance between semifenestrae 6-9 (7) um. Bullae conspicuous, rounded and located near the top of the vulval cone. Underbridge bifurcate, sclerotized and much stronger than that of H. mani. Anus 43-56 (48) um from the vulval slit. The anus is frequently displaced from the continuation of the fenestral axis.
Measurements (n = 60): L: 105-140 (126) um; B: 46-57 (50) um; L/B ratio: 2.1-2.9 (2.5).
Cylindrical with rounded ends. Egg-shell hyaline. Enclosed larvae folded four times into five more-or-less equal parts.
Measurements (n = 100): L: 573-694 (638) um; B: 19-32 (23) um; stylet length 23-28 (25) um; true-tail length: 83-103 (94) um; clear-tail length: 51-75 (62) um; anal body width: 17-18 um; a ratio: 22-34 (29); c ratio: 5.9-7.6 (6.9); clear-tail/stylet length: 1.9-3.1 (2.5).
Body elongate, cylindrical, tapering slightly anteriorly but markedly in the tail region. Head slightly offset from the body and measuring 3-6 (5) um long by 8-11 (10) um wide. Head annulation inconspicuous. Cephalic framework strongly sclerotized. Stylet very strong with basal knobs whose anterior faces are concave. Anterior cephalids indistinct, usually occurring two annules behind the head constriction; posterior ones at the seventh annule (about mid-stylet level). Dorsal oesophageal gland orifice 8-10 (9) um behind the stylet knobs. Valvate median bulb, nerve ring and oesophageal gland aas shown in Fig. 5B. Excretory pore located 116-136 (129) um behind the head. Hemizonid about 8 um in front of the excretory pore, hemizonion not seen. Lateral field consists of four lines forming three equally broad bands. The outer lines are crenate; outer bands regularly areolate.
Measurements (n = 100): L: 1060-1450 (1292) um; B: 33-40 (38) um; stylet length: 28-33 (30) um; spicule length: 36-43 (39) um; gubernaculum length: 11-14 (12) um; ratio a: 35-40 (37).
Males are very numerous, occasionally occurring in large clusters of up to 100 individuals. The body is cylindrical and when killed assumes an open C-shape. The posterior region (1/3 body) is sharply twisted through 90O. Head 7 um long by 12 um wide with five indistinct annules and a labial disc. The head-constriction clearly differentiates the head from the rest of the body. Cephalic framework sclerotized. Anterior cephalids inconspicuous, occurring two annules posterior to the head constriction; posterior cephalids at the seventh annule. Stylet strong with well-developed rounded basal knobs. Dorsal oesophageal gland orifice 6-10 (8) um behind the stylet knobs. Oesophagus indistinct, with poorly developed median bulb; valve plates small, located 106-119 (114) um from the anterior extremity. Hemizonid about 9 annules in front of the excretory pore which is located 178-202 (191) um from the anterior end. Hemizonion inconspicuous, occurring about 4 annules behind the excretory pore. Spicules bidentate, twisted. Gubernaculum simple. Phasmids inconspicuous, slightly preanal at about the level of the inner tip of the gubernaculum. Lateral field consists of four equally spaced lines forming three bands; outer lines crenate, outer bands areolate.
H. iri is similar to H. avenae and H. mani but differs from them in many respects. Mature cysts are much lighter in colour than those of H. avenae or H. mani and when dried they become characteristically wrinkled and partially collapsed, giving them a prune-like appearance. The "a" ratio of males averages 37 compared with 49 in H. mani and 40 in H. avenae. The larvae have a much longer tail and the ratio of clear-tail to stylet length is much greater than in H. avenae or H. mani (2.5 in H. iri compared with 1.6 in H. mani and 1.5 in H. avenae). The larval lateral field of H. iri consists of three equally broad bands, like that of H. mani while that of H. avenae consists of a single slender band (Franklin, 1969). Gravid females are generally larger.
The host range of H. iri does not include wheat, oats or barley.
The name iri is derived from Ir, the name of a legendary prince, which is the origin of most of the names of Ireland.
Type host: Brown top (Agrostis tenuis). No other hosts
so far known.
Type locality: Grass field, Irish Grid reference H8047 9307, Draperstown, Northern Ireland.
(Description- Mathews, 1971)
DNA Sequences Obtained
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