Oligoneuriopsis jessicae Agnew, 1973

Barber-James, Helen M., Zrelli, Sonia, Yanai, Zohar & Sartori, Michel, 2020, A reassessment of the genus Oligoneuriopsis Crass, 1947 (Ephemeroptera, Oligoneuriidae, Oligoneuriellini), ZooKeys 985, pp. 15-47 : 15

Oligoneuriopsis jessicae Agnew, 1973 Figure 7

Oligoneuriopsis jessicae Agnew, 1973: 116, fig. 1A, B (nymph).

Material examined.

Eswatini (former Swaziland) • 14N; Malolotja stream, Nkomati River system; 26.1167°S, 31.1144°E; alt. 1227 m a.s.l.; 3 Mar. 2003; R. Bills leg.; AMGS; GEN 1733E • 7N; Jubukweni stream near Mbuluzi, Nkomati River system; 26.2028°S, 31.1944°E; alt. 1044 m a.s.l.; 29 Mar. 2003; R. Bills leg.; AMGS; GEN 1734B • 4N; Lubuyane stream near Mnyokane, Nkomati River system; 26.1572°S, 31.2081°E; alt. 1435 m a.s.l.; 4 Apr. 2003; R. Bills leg.; AMGS; GEN 1738B.

Comments.

Agnew (1973) examined material from the National Institute for Water Research (NIWR), Pretoria, and stated it would be housed in the Transvaal Museum (now known as Ditsong Museum). However, Agnew (pers. comm., 1983) indicated that when he moved from the university where he had been based, the technicians in his former laboratory discarded all of the material that he had left in his office, including all of the Oligoneuriidae material he had examined. Examination of mayfly material in Ditsong Museum (February 2019), and discussions with the late Curator Dr Martin Kruger† (pers. comm., 22 February 2019) confirmed that this material was not in this museum. As no material has since been collected from or near to the type locality (Queen River, 35 km from Barberton, 25.8200°S, 30.8100°E), no neotype has been designated.

Male and female imagos.

Unknown.

Nymph.

Lengths. Body up to 20 mm and 22 mm in male and female nymphs respectively; cerci (and caudal filament) up to 14 mm (4.5 mm) and 15.8 mm (6.9 mm) in male and female nymphs respectively. General colouration pale to hazelnut brown, with small, paired paler spots in the middle of each tergum of mature nymphs in some individuals; head pale to dark brown, without markings, darker between eyes, becoming paler brown towards distal margin of head (Fig. 7A ). Ventrally, head chestnut brown, gills at base of maxillae forming a pale cream coloured “beard” ventrally at base of head. Pro- and mesonotum dark brown, with pale brown marking on mesonotum, forming a distinct M-shape in mature nymphs. Legs light brown, femoro-tibial articulation darker; setae of forelegs light brown, same colour as the legs. Femur and tibia of foreleg shorter than those of mid or hind leg; in all cases, femora longer than tibiae. Coxal-femoral articulation of mid and hind legs with dark brown stripe ventrally. Setae on the outer margin of mid and hind femora well developed, tapering off slightly in length towards the apex, scattered spatulate setae over entire surface but more concentrated along margins; mid and hind tibae and tarsi with strong fringe of fine, even setae along the outer margin. Distal end of tibiae of mid legs with three stout spines on inner side.

Abdominal tergites darker than sternites, no distinctive markings except for dorsal paired paler brown spots on each side of the midline of the tergites in mature specimens; sharply pointed dorsal tubercles present on tergites I-VII, gradually decreasing in size posteriorly (Fig. 7A ); sternites uniform pale brown, with no markings. Dense patch of posteriorly orientated setae ventromedially on abdominal segments II-V, much reduced patch on segment VI. Gills II-VII almost subequal in size, gill I smaller. On all gills except for gill I, fibrillae slightly shorter than lamella length. Lamella of gill I less than half the length of the fibrillar portion. Lamellae II-VII with long and thin setae on their distal inner margin. Posterolateral spines of the abdomen increasing in size posteriorly. Cerci and caudal filament uniformly medium brown.

Whole nymph (dorsal aspect) and gills as illustrated by Agnew (1980) and Fig. 7A . Lateral view of anterior of nymph (Fig. 7B ), shows dorsal abdominal spines in profile.

Affinities.

Nymphs of O. jessicae mainly differ from those of O. lawrencei by the presence of sharply pointed dorsal tubercles on tergites I-VII. The dorsal setae along the hind femur are long in O. lawrencei , O. dobbsi and O. elisabethae , extending to the apex of the femur, while in O. jessicae the setae are shorter and taper off, not reaching the apex. Gills in O. jessicae are shorter than the half length of the corresponding tergite, as in O. elisabethae , while in O. lawrencei , the gills reach approximately half length of the corresponding tergite, even longer in O. dobbsi . Adult material is needed for comparison with other species.

Habitat preference.

Moss-covered stones in current. Nymphs mature in April (autumn).

Known distribution.

Eswatini; South Africa: Mpumalanga near Barberton.

Figures

Figure 7. Oligoneuriopsis jessicae A whole nymph, dorsal view B lateral profile, showing dorsal abdominal tubercles. Scale bar: 5 mm (A).