Oligoneuriopsis dobbsi (Eaton, 1912)

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 dobbsi (Eaton, 1912) Figures 5 , 6

Oligoneuria dobbsi Eaton, 1912: 243, fig. 1 (female imago).

Oligoneuriella dobbsi : Ulmer, 1924: 32.

Oligoneuria sp.: Vayssière, 1936: 130 (nymph).

Oligoneuriopsis dobbsi : Kimmins, 1960: 276, figs 9, 10 (female and male imagos).

Oligoneuriopsis grandaeva ( Navás, 1936: 125, fig. 21) (female imago).

Material examined.

Kenya • 28N; Mount Elgon, Teremi upstream; 0.8973°N, 34.5973°E; alt. 2456 m a.s.l.; 13 Oct. 2019; W. Graf leg. • 23N; Mount Elgon, Teremi; 0.9094°N, 34.5994°E; alt. 2407 m a.s.l.; 13 Oct. 2019; W. Graf leg. • 13N; Mount Elgon, Kimurio upstream; 0.8913°N, 34.5892°E, alt. 2239 m a.s.l.; 11 Oct. 2019; W. Graf leg. • 46N (among them 1N - GBIFCH00890747 - sequenced); Mount Elgon, Kimurio tributary 2; 0.8956°N, 34.5878°E; alt. 2347 m a.s.l.; 8 Nov. 2019; W. Graf leg. • 15N; Mount Elgon, Kibisi upstream; 0.9028°N, 34.6175°E; alt. 2298 m a.s.l.; 9 Nov. 2019; W. Graf leg. • 8N; Mount Elgon, Kapkateny upstream; 0.8959°N, 34.5990°E; alt. 2293 m a.s.l.; 11 Oct. 2019; W. Graf leg. • 7N; Mount Elgon, Kapkateny midstream; 0.8325°N, 34.6234°E; alt. 1896 m a.s.l.; 12 Oct. 2019; W. Graf leg. • 2N; Mount Elgon, Kapkateny downstream; 0.8144°N, 34.6243°E; alt. 1660 m a.s.l.; 14 Oct. 2019; W. Graf leg.; all MZL.

Male imago.

As redescribed by Kimmins (1960), with the following complement extracted from mature male nymphs: penis lobes with characteristic sclerotized proximal process ending in a simple projection; apex of the lateral longitudinal lobe of penis in a small club-shaped sclerite ca. 1.5 × larger than the lateral lobe (Fig. 5B ).

Nymph.

Lengths. Body up to 17 mm and 25 mm in male and female nymphs respectively; cerci (and caudal filament) up to 10 mm and 11 mm in male and female nymphs, respectively.

General colouration medium to dark brown, in general darker in mature nymphs than in immature ones (Fig. 6A ). Head dark brown, with four lighter maculations between the compound eyes, and a black marking present on the frons between the ocelli; generally also with a rounded light maculation between antennae. Ventrally, head a uniform light brown colour. Gills at base of maxillae forming a “beard” ventrally at base of head, much paler in colour relative to head capsule (Fig. 6B ). Pro- and mesonotum dark brown, with lighter maculae laterally and medially. Legs light to medium brown, femoro-tibial articulation with a blackish spot. Femur and tibia of foreleg shorter than those of mid or hind leg, fore tibia longer than fore femur; on mid- and hind legs, femora and tibiae subequal in length. Setae on the outer margin of mid and hind femora well developed, slightly decreasing in size and reaching the apex (Fig. 5A ). Tibiae and tarsi with long, even fringe of setae along entire dorsal margin. Abdominal tergites uniformly dark brown, each with a pair of light spots in the middle, except tergite X which bears four light spots in proximal part. Sternites medium brown, laterally dark brown, with two small pale median markings, especially visible on sternites IV to VIII. Dense patch of posteriorly orientated setae ventromedially moderately developed on abdominal sternite II, well-developed on sternites III-V, absent from other segments. Gills III-VII almost subequal in size, more than ¾ of the corresponding segment, gill II smaller, ca. 1/2 the size. On all gills except for gill I, fibrillae shorter than lamella length. Lamella of gill I a little bit shorter than the length of the fibrillar portion. Lamellae II-VII with long and thin setae on their distal inner margin. Posterolateral spines of the abdomen absent of segments I and II, then increasing in size from segment III to IX, those of this last one being ca. ¼ the length of the segment.

Cerci uniformly medium brown, caudal filament paler brown towards apex.

Affinities.

Oligoneuriopsis dobbsi male imago seems to be closely related to O. lawrencei from which it differs by the presence of crossveins in the proximal part of the subcostal area (see Kimmins 1960, fig. 9), as well as by the shape of the proximal process of the penis sclerite which is shorter and less pointed than in O. lawrencei . The supposed nymph of O. dobbsi presents also similarities with the one of O. lawrencei , but differs in several respects, namely, the absence of a slight carina on the head, the general colouration of the body, the size of gill II, smaller than the following ones in O. dobbsi , whereas subequal to the following ones in O. lawrencei , the patch of setae on sternites (II) III-V in O. dobbsi compared to sternites II-IV (V-VI) in O. lawrencei , and finally the size of gill I lamella, much shorter in the latter than in O. dobbsi .

Remarks.

The association of the nymphs from Mount Elgon with the adults described by Eaton (1912) as Oligoneuriopsis dobbsi is putative at the moment, because we have no rearing of the nymphs and no COI sequences from Eaton’s material. However, we think this association is realistic, for the following reasons. First, male genitalia extracted from a mature nymph are compatible with those drawn by Kimmins (1960), especially the proximal process which is thick and shorter than in the other species, and the apex of the lateral longitudinal lobe of penis which is slightly clavate distally. Secondly, localities for the nymphs and adults are only distant from ca. 100 km, whereas no other Oligoneuriopsis populations are known in a radius of thousands of kilometres. Additional nymphal material has been collected by Laban Njoroge, National Museums of Kenya, Nairobi, from the Aberdare range of mountains in Central Kenya and one specimen from Mount Kenya. Images of these nymphs correspond completely with the nymphs of O. dobbsi described here. The Aberdare range is ca. 200 km east of the type locality, Kericho, while Mount Elgon is around 150 km north. It is reasonable to assume that a single species is represented in this area.

Known distribution.

Kenya.

Figures

Figure 5. Oligoneuriopsis dobbsi, male nymph A hind leg B genitalia (sternite IX removed). Black arrows: Apex of the lateral longitudinal lobe of penis. White arrows: Proximal process of penis. Scale bar: 1 mm.

Figure 6. Oligoneuriopsis dobbsi, male nymph A in dorsal view B in ventral view. Scale bar: 5 mm.