Oligoneuriella tuberculata Godunko & Staniczek

Sroka, Pavel, Bojkova, Jindriska, Godunko, Roman J., Soldan, Tomas, Namin, Javid Imanpour, Nejat, Farshad, Abdoli, Ashgar & Staniczek, Arnold H., 2019, New Oligoneuriidae (Insecta, Ephemeroptera) from Iran, ZooKeys 872, pp. 101-126 : 101

Oligoneuriella tuberculata Godunko & Staniczek sp. nov. Figures 1 , 2 , 3 , 4 , Table 2

Etymology.

The name of the new species refers to the presence of protuberances posteromedially on terga, which is a character unknown for any other species of Oligoneuriella . A tuberculum is the Latin expression for protuberance.

Type material.

Holotype: Male larva, IRAN, Kohgiluyeh and Boyer-Ahmad Province, Kata, Marbor River, 31°10.71'N, 51°15.78'E, 1562 m a.s.l., 04.05.2017, leg. Staniczek A.H., Godunko R.J., Pallmann M. & Nejat, F. The holotype is deposited at SMNS under inventory number SMNS_EPH_7574_B_3.

Paratypes: 165 larvae, same locality as holotype (40 larvae deposited in SMNS under inventory numbers SMNS_EPH_7574_B_1 and SMNS_EPH_7574_B_2, including DNA voucher specimens with inventory numbers specified in Table 1, 20 larvae deposited in IECA, 100 larvae deposited in SNHM, and 5 larvae deposited in MMTT_DOE).

Localities and biology.

The single known locality of O. tuberculata sp. nov. in Marbor River is situated in the southeastern part of the Zagros Mountains within the Khersaan River basin ( Fig. 9 ), in close proximity to the Dena Protected Area. The majority of the drainage area is used as pasturage for a small amount of livestock, in nearer surroundings the land use is mainly for farming and rural, residential purposes.

Marbor River at the type locality is a small, premontane river, 15-22 m wide, with depths up to 1.5-1.7 m ( Fig. 10A ). The river bed is braided and formed of coarse and fine gravel, with sparse cobbles. At the type locality the river formed two approximately equal branches with fast, turbulent flow (0.4-0.9 m/s), and a wide alluvium. The larvae inhabited the gravel substratum in the fast flow of the streamline, but were also found in the littoral zone.

Water quality at Marbor River was good, with conductivity 264 µS.cm, salinity 0.1 ‰, and temperature 15 °C.

The emergence of the species can be expected approximately between July and August, as all larvae collected here in May were small and only half-grown with small wing pads. Together with O. tuberculata sp. nov., only three other mayfly taxa were collected: Baetis (Rhodobaetis) sp. ( Baetidae ), Rhithrogena sp. ( Heptageniidae ) and Epeorus sp. ( Heptageniidae ).

Diagnosis.

According to the combination of following diagnostic characters, O. tuberculata sp. nov. can be distinguished from all other representatives of the genus Oligoneuriella worldwide:

• Body pale, abdominal terga with inconspicuous, pale maculae laterally ( Fig. 1A );

• eyes of male laterally not exceeding head margin ( Fig. 1A, E );

• dorsal side of foretibia with 3-4 setae arranged into irregular row subapically ( Fig. 2G );

• dense rows of long, hair-like setae on posterior margin of proximal 1/3-1/2 of middle- and hind femora ( Fig. 2B, C );

• posterolateral processes of abdominal segments relatively narrow ( Fig. 3G );

• terga II–IX with unpaired protuberance posteromedially ( Fig. 3A, B );

• posteromedial flattened setae on sterna III–IV up to 10 –15× longer than wide ( Fig. 3D, E );

• first gill plate significantly larger than remaining gill plates, without ridge near outer margin dorsally ( Fig. 4C, D );

• sparse setation on dorsal and ventral surfaces of gill plates II–VII ( Fig. 4A, B, E–H );

• ventral surface of gill plates II–VII with setae sparsely scattered only along outer margin of ventral cavity ( Fig. 4B, F, H );

• paracercus vestigial, approximately 5-segmented.

Description.

Larva. Submature larvae: body length 9-12 mm (female), 8-9 mm (male), length of cerci approximately 0.70 –0.85× body length, paracercus vestigial, 5-segmented.

Colouration ( Fig. 1 A–C ). General colour pale, yellowish-white, light brown to light dirty olivaceous; dorsal side darker than ventral one; pronotum with 2-3 small, pale, diffuse spots centrally; pro- and mesosternum whitish-yellow; abdominal terga with inconspicuous, pale maculae laterally; sterna uniformly yellowish.

Head. Pale, yellowish-brown to dirty olive, slightly darker centrally; ocellar area brown. Antennae unicoloured, yellow. Head width/length 1: 1.1-1.3 in submature larvae ( Fig. 1 D–G ). Eyes black, relatively elongated, not exceeding contour of head in dorsal view in male submature larvae ( Fig. 1E ); distance between eyes 0.5 × narrower than eye width in male and about 1.2 × than eye width in female. Foremargin of head pale yellow, bordered by dense fringe of long bristle-like setae. Labium ventrally with short, flattened setae maximally 6.5 –7.0× longer than wide, irregularly distributed along proximal margin of paraglossae ( Fig. 1I ). Dorsal side of first segment of labial palp with a group of more than 30 long pointed and short bluntly pointed setae; group of short setae not distinctly separated from long setae situated more proximally on first segment of labial palp ( Fig. 1H ).

Thorax. Yellowish-brown to light dirty olive; base of wing pads with diffuse whitish maculation; two unclear whitish spots on mesonotum laterally; indistinct elongated maculae centrally. Pleural and ventral side paler than dorsal. Legs pale, whitish-yellow to yellow or slightly olivaceous, without any distinct ornamentation. Coxae and trochanters of same colour as other leg segments. Surface of legs covered with elongated bristles, spatulate and hair-like setae and small setae with star-like distal end (up to 15 μm long). Forecoxae with at least 30 long bristle-like setae distally and at least 20 long stout setae on inner margin. Foretrochanters with tuft of dense, long bristle-like setae distally. Femora unicoloured, occasionally with small diffuse spot distally. Forefemora length 2.0 –2.1× of their width; dorsal surface covered with few flattened setae of various length, arranged in irregular sparse rows near filtering setae centrally; sparse row of stout bristle-like setae extends along 1/3-1/4 of length of outer margin, and 13-17 short bluntly pointed setae in submarginal area ( Fig. 2A ). Filtering setae of femora and tibiae brown, unicoloured. Foretibiae with sparse setae along distal third of ventral side of foretibia ( Fig. 2F ); dorsal side with 3-4 setae arranged in irregular row in subapical part ( Fig. 2G ). Foretarsi with 2-3 bluntly pointed setae distally. Foreclaws moderately sclerotised at apex, with 4-5 denticles. Middle and hind coxae and trochanters with sparse setae of different size irregularly on surface. Femora of middle and hind legs with dense rows of long (longer than half of femur width) hair-like setae along 1/3-1/2 of posterior margin of femora; numerous thicker flattened and spine-like setae along posterior margin of proximal half of femora; small sparse spatulate setae scattered on dorsal surface of femora, forming irregular rows centrally; distal margin with setae of same shape, concentrated proximally and centrally, alternating with few elongated hair-like setae ( Fig. 2 B–E ). Tibiae of middle and hind legs with few short hair-like and spatulate setae irregularly grouped subapically and apically. Tarsi of middle and hind legs with 4-5 elongated bluntly pointed or rounded setae apically, 6-7 hair-like setae along inner margin (as long as tarsi or shorter), alternating with 2-3 shorter stout setae subapically. Claws of middle and hind legs with 5-7 denticles.

Abdomen ( Fig. 3 ). Yellowish-brown to dirty olive; indistinct diffuse pale maculae laterally; terga darker than sterna. Posterolateral processes relatively narrow, present on abdominal segments II–IX; processes on segment II indistinct. Apices of posterolateral processes well sclerotised. Posterolateral processes on segments IV–IX prominent, with outer margins nearly straight, slightly diverging from body axis; posterolateral processes of segment IX largest, with axes nearly parallel to body axis ( Fig. 3G ). Terga II–IX with unpaired posteromedial protuberance, rounded apically ( Fig. 3A, B ). Surface of terga covered evenly by very short spatulate setae rounded apically ( Fig. 3F ); number of setae on surface of terga gradually decreases from tergum II to IV; few flattened spatulate setae rounded apically (8-12 μm long; 9-10 μm wide) cover also posterolateral processes and terga I, V–X. Sterna covered with posteromedial groups of flattened setae, rounded apically ( Fig. 3D, E ). Length of these setae varies from 15-75 μm on sterna II and III; up to 100 μm on sterna IV–VIII; size of flattened setae gradually increases from sterna II to VII; individual setae are up to 10 –15× longer than wide. Large group of setae assembled predominantly posteromedially on sterna II–VIII. Sternum IX covered only with sparse spatulate setae (up to 12 μm long), few elongated flattened setae up to 20 μm long, and numerous hair-like setae. Sternum IX with deep U-shaped incision posteriorly between two pointed, strongly sclerotised processes.

Gills ( Fig. 4 ). Gill I significantly larger than following gills, rounded and symmetric, without ridge near outer margin; gills II–VII circular. Size ratios between gills I and IV approximately 1: 0.7 (length) and 1: 0.6 (width). All gill pairs equipped with bundle of whitish filaments, usually shorter than respective gill plate. Dorsal surface of gill I with sparse flattened setae concentrated mainly proximally ( Fig. 4C ). On lateral margins of gill plates, setae relatively short; setae bordering inner part of distal margin slightly longer (up to 25-30 μm long). Ventral surface of gill I with few isolated submarginal setae distally (up to 25 μm long, Fig. 4D ); these setae strongly plumose, similar to setae occurring on ventral surface of following gill pairs. Sparse setation on dorsal and ventral surfaces of gills II–VII; dorsal surface covered with short spatulate setae ( Fig. 4A, E, G ); ventral surface with relatively short plumose setae sparsely scattered centrally along outer margin of ventral cavity ( Fig. 4B, F, H ).

Cerci whitish, unicoloured, with inner marginal fringe of fine, hair-like setae. Paracercus vestigial, 5-segmented ( Fig. 3H ).

Egg, imago, and subimago. Unknown.

Affinities.

Among the Palaearctic genera of Oligoneuriidae , attribution of O. tuberculata sp. nov. to the genus Oligoneuriella is obvious, based on the shape of head, legs, and gills (see Bauernfeind and Soldán 2012). In the worldwide key to Oligoneuriidae genera published by Edmunds (1961), O. tuberculata sp. nov. erroneously would key out to the Nearctic and Neotropical genus Lachlania Hagen, 1868 due to the presence of a highly reduced paracercus. Edmunds (1961) at that time had not been aware of any Oligoneuriella species with reduced paracercus, since such species were only described later ( Al-Zubaidi et al. 1987, Sroka et al. 2015). Despite the superficial resemblance of O. tuberculata sp. nov. to Lachlania , they differ in their setation on the anterior head margin. In O. tuberculata sp. nov., there are long, bristle-like setae (as in all Oligoneuriella ). In Lachlania these setae are short and spatulate, which represents a crucial larval apomorphy of Lachlania (see Kluge 2004). In fact, Lachlania phylogenetically represents a quite distant lineage from Oligoneuriella and Oligoneuriopsis (Massariol et al. 2017). Relatively long setae medially on sterna II–V in O. tuberculata sp. nov. suggest a closer relationship with Oligoneuriopsis , but a large lamella of gill I and a short row of setae on the posterior margin of femora excludes this attribution (see the discussion on O. villosus sp. nov. below).

Within Oligoneuriella , the most closely related species to O. tuberculata sp. nov. are O. bicaudata Al-Zubaidi et al. 1987 from Iraq and O. pectinata Bojková & Soldán, 2015 from Turkey. Both species share with O. tuberculata sp. nov. the reduction of the paracercus to only a few segments, large lamella of gill I compared to other gill pairs, and the extent of setation on the posterior margin of middle and hind femora forming long and dense fringe. Nevertheless, O. tuberculata sp. nov. can be differentiated from both species by several characters:

(i) The first gill plate is markedly larger than gill pairs II–VII, nearly circular and symmetric, without a ridge near the outer margin in O. tuberculata sp. nov. In contrast, O. pectinata has an oval gill I, only slightly larger than the remaining gill pairs, with an indistinct ridge close to the outer margin (see Fig. 4C, D ; Sroka et al. 2015: 341, fig. 46a, b). In O. bicaudata , the size ratio of gill I and remaining gill pairs is similar to O. tuberculata sp. nov., although the shape of gill plates is slightly different. In O. tuberculata sp. nov., the gill plate I is more circular ( Fig. 4C, D ), whereas in O. bicaudata it is rather elongated, narrowing proximally ( Al-Zubaidi et al. 1987: fig. 5).

(ii) The setation on the surface of gills: in O. tuberculata sp. nov., dorsal and ventral surface of the gill I is equipped with very few flattened setae ( Fig. 4C, D ), whereas in O. pectinata relatively dense setation occurs, especially on the ventral surface ( Sroka et al. 2015: 341, fig. 46a, b). The setae on the ventral surface of gills are strongly plumose in both species. However, these setae are shorter (up to 25 μm long) in O. tuberculata sp. nov. than in O. pectinata (up to 32 μm long) ( Sroka et al. 2015: 344, fig. 66a). Lateral margins of the first gill are equipped with rich, long setae in O. pectinata , in contrast to O. tuberculata sp. nov. with relatively short setae along margins ( Fig. 4C, D ). Details of gill setation are unknown for O. bicaudata .

(iii) All three species can be separated by the shape of abdominal segments. Unpaired posteromedial protuberances on terga are characteristic for O. tuberculata sp. nov. ( Fig. 3A, B ), as they are lacking in O. pectinata and Al Zubaidi et al. (1987) did not mention any protuberances on the terga of O. bicaudata . Thus, given the conspicuousness of this character, we consider it plausible to assume that the protuberances are absent in this species. Moreover, the protuberances are missing in the material identified as O. bicaudata collected near the type locality of this species in Iraq (Al-Saffar, pers. comm). Furthermore, posterolateral processes of the abdominal segments II–VII are relatively narrow, slightly bent outwards in O. tuberculata sp. nov. ( Fig. 3G ), in contrast to relatively robust and straight processes in O. pectinata . In O. bicaudata , these processes are very thin, curved inward apically, especially on segment IX ( Al-Zubaidi et al. 1987, fig. 2).

(iv) All three species have a pale body colouration and an inconspicuous colour pattern on the abdominal terga. However, O. pectinata is slightly darker, with a pair of diffuse median spots on terga, whereas O. tuberculata sp. nov. is characterised by the presence of diffuse maculae laterally. Abdomen of O. bicaudata is pale brown, without any distinct pattern ( Al-Zubaidi et al. 1987).

An analysis of diagnostic characters based on adults is impossible at present, as adults are not known for O. tuberculata sp. nov. and O. bicaudata . The colouration pattern and size of eyes would slightly differ in fully mature larvae from the material described herein.

Figures

Figure 1. Oligoneuriella tuberculata sp. nov., larvae A habitus in dorsal view B habitus in ventral view C habitus in lateral view D head of male in lateral view (immature larva) E head of male in dorsal view (immature larva) F head of female in lateral view G head of female in dorsal view H detail of setae on distal part of labial palp segment I in dorsal view I detail of setae on proximal margin of paraglossae in ventral view. Scale bars: 2.0 mm (A-C); 0.5 mm (D-G); 0.1 mm (H); 0.2 mm (I). Same scale bar for D and E. Same scale bar for F and G.

Figure 2. Oligoneuriella tuberculata sp. nov., larvae, legs A forefemur in dorsal view B middle femur in dorsal view C hind femur in dorsal view D middle leg under SEM in dorsal view E micro sculpture of leg cuticula under SEM in dorsal view F apical part of foretibia with subapical setae in ventral view G shape of foretibia with subapical setae in dorsal view. Scale bars: 0.5 mm (A-D, F, G); 0.02 mm (E). Same scale bar for A-C. Same scale bar for F and G.

Figure 3. Oligoneuriella tuberculata sp. nov., larvae, abdomen A abdomen under SEM in dorsal view B detail of tergal protuberances under SEM C abdomen under SEM in ventral view D detail of setae on sternum III under SEM E detail of setae on sterna III and IV F detail of setae on surface of terga G outline of abdomen. H detail of abdomen tip under SEM with bases of cerci and vestigial paracercus. Scale bars: 0.5 mm (A-C, H); 0.2 mm (D-F); 1 mm (G).

Figure 4. Oligoneuriella tuberculata sp. nov., larvae, gills A gill IV under SEM in dorsal view B gill IV under SEM in ventral view C gill plate I in dorsal view D gill plate I in ventral view E gill plate IV in dorsal view F gill plate IV in ventral view G gill plate VII in dorsal view H gill plate VII in ventral view. Scale bars: 0.1 mm (A-H). Same scale bar for C-H.

Figure 9. Map of Iran with localities of Oligoneuriella tuberculata sp. nov. (star) and Oligoneuriopsis villosus sp. nov. (circles).

Figure 10. Photos of the localities with occurrence of Oligoneuriella tuberculata sp. nov. and Oligoneuriopsis villosus sp. nov. A Marbor River near Kata (type locality of O. tuberculata sp. nov.) B right tributary of Marun Rud River near Bagh Malek (type locality of O. villosus sp. nov.) C Balarud River near Andimeshk (locality of O. villosus sp. nov.) D Shamil River near Shamil (locality of O. villosus sp. nov.).