Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, 1985

Figures 1 −48

Ecdyonurus russevi Braasch & Soldán, 1985: Entomol. Nachr. Berichte, 29 (2): 67−68, figs 1−2, 5−6 [description]; Buffagni et al. 2009: Distr. Ecol. Pref. Europ. Fresh. Organ. Ephemeroptera, 3: 68 [distribution, biology]; Kazancı & Türkmen 2012: Review of Hydrobiology, 5 (2): 149 [faunistics]

? Ecdyonurus russevi Braasch: Kazancı 2001: Türk. Suları Arast. Dizisi, Series VI: 51 [faunistics, adults] russevi Braasch & Soldán 1985 [E]: Kluge 2004: The Phylogenetic System of Ephemeroptera: 176 [in Ecdyonurus /fg2] Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, 1985: Bauernfeind & Soldán 2012: The Mayflies of Europe ( Ephemeroptera): 266, 587, fig. 152 [taxonomy, distribution, biology]

Diagnosis. Ecdyonurus russevi can be distinguished from other representatives of the subgenus Ecdyonurus by the following combination of characters: the colour pattern of abdominal terga, consisting of a tripartite spot dorsally and a conspicuously bent, wavy, oblique stripe laterally; presence of one dark band at the base of male compound eyes; cross veins not bordered with dark maculation in subimagines; comparatively short, broadly trapezoidal penis lobes with prominent apical sclerite; presence of symmetrical rounded protuberances on styliger near gonostylus segment I [in adults]; relatively short and slender lateral projections of pronotum, slightly bent inwards; tarsi distally darkened; a ring with sharply delineated margins; slender, tongue-shaped gill I, in combination with a symmetrical, relatively narrow gill IV [in larvae]; exochorion densely and regularly covered with macrogranula, relatively few KCT’s scattered over all the chorionic surface, with concentration of only a few of them on one pole [in eggs].

Male imago. Measurements: body length 10.5−12.0 mm; fore wing length 11.0−13.0 mm; cerci length 24.0−28.0 mm (approximately 2.0−2.2 times longer than body). General colour of body pale yellowish to yellowish brown; thorax only slightly darker than other body parts (based on the material preserved in ethanol for more than 35 years) (Figs 1−5).

Head. Colour yellowish-brown to brown; clypeus unicoloured light brown or dirty yellow. No stripes or bands on the head. Compound eyes nearly contiguous along a short segment on inner margin; eyes distinctly bicoloured laterally, with dirty grey upper 2/3, and black lower 1/3 of eyes length (Figs 2, 3). Ocelli greyish-black to black at the base, whitish to dirty grey apically. Antennae light brown, paler basally.

Thorax. Prothorax light brown to brown; diffused deep brown smudges centrally or near posterior margin on pronotum (Fig. 2). Mesothorax light brown to brown dorsally; the area around anterolateral scutal costa [ALSc; all abbreviations according to Kluge 2004] slightly darker; brownish spot on posterior scutal protuberance [PSp] anteriorly; dark violet stripe along prelateroscutum [PLS], well visible also from lateral side (Figs 2, 3). Lateral side of mesothotax light brown; distinctly dark violet longitudinal spots on katepimeron [KEM], anterior paracoxal suture [PCxsA], posterior arc of prealar bridge [PAB:PA] and partly KES [katepisternum]; ventral side unicoloured, brown. Metathorax brown, with darker spots centrally.

Fore legs distinctly darker than middle and hind legs. Fore femora yellowish-brown proximally to dark brown distally; fore tibia the same colour as the tip of fore femora (or slightly paler), except paler distal end; segment I and II of fore tarsi occasionally darker than other ones, or all tarsal segments unicoloured brown (same colour than tibia or slightly paler). Middle and hind legs yellowish-brown to light brown; femoral tip and base of tibia darker; tarsal segments unicoloured yellowish-brown, occasionally with slightly darker segments IV and V. All tarsal claws brown.

Wings hyaline, transparent, with yellowish-brown to light brown venation; costal and subcostal field of fore wings yellowish-milk distally (more translucent proximally), pterostigma with 5−10 simple cross veins, 2−4 cross veins are furcated; venation of fore and hind wings typical for Heptageniidae .

Abdomen. Terga light brown to brown; tergum I brown in the posterior half, darker than others; terga II −VII yellow to light brown centrally; a narrow dark brown to reddish brown border near posterior margin of terga II −VII dorsally, prolonged into a characteristically bent, wavy, oblique stripe laterally (Figs 1, 5, see also Braasch & Soldán 1985: 68, figs 1, 2); triangular-like spots on surface of terga III −V (VI) centrally and brownish-violet smudges near anterior margin of segment (Fig. 4); terga II, VII and VIII only with brownish-violet smudges anteriorly; terga IX and X unicoloured light brown. Sterna unicoloured yellowish-brown; violet to blackish nerve ganglia visible on sterna II (III), IV −VII. Cerci dark brown to brown proximally, yellowish to whitish in distal half; segment joints blackish.

Genitalia. Styliger pale, yellowish, gonostyli slightly darker; two small symmetrical and rounded protuberances near gonostylus segment I; small hump on inner margin of gonostylus segment II (Fig. 10). Penis lobes yellowish, moderately expanded; lobes comparatively short and little stretched laterally, with rounded outline distally, broadly trapezoidal (Figs 10, 11). Basal sclerite relatively massive, with few very small pointed setae along posterior margin; lateral sclerite broad, nearly parallel sided centrally, slightly wider distally (Figs 9, 10; see also Bauernfeind & Soldán 2012: 587, fig. 152). Apical sclerite relatively slender; the tip distinctly projecting above the lobes, covered with very small pointed setae on inner margin and slightly bent outwards (Figs 8, 10, 11). Titillators light brown, narrow, with 1−2 small subapical teeth.

Female imago. Measurements: body length 10.0−13.0 mm; fore wing length 10.5−12.5 mm; cerci length 16.0−19.0 mm (approximately 1.5 times longer than body). General colour of body yellowish-brown to light brown.

Head light brown, with diffused smudges on clypeus; vertex posteriorly with narrow dirty violet transversal stripe. Eyes and basal part of ocelli unicoloured greyish-black; antennae yellowish-brown (Figs 13, 14).

Thorax colour and spots arrangement on dorsal and lateral sides similar to those in male imago. Fore legs light brown proximally; brown to dark brown distally; fore tibia intensively brown proximally, paler towards distal end; fore tarsi the same colour than distal part of tibia. Middle and hind legs yellowish-brown, generally unicoloured, occasionally femora slightly darker than tibia and tarsi. Wings the same colour than in male imago. Pterostigmatic area with numerous furcate and simple cross veins.

Abdomen yellowish-brown, with generally similar colour pattern as in male imago (Fig. 15). Violet-blackish nerve ganglia on sterna III (II)−VII. Subgenital and subanal plates rounded apically; subgenital plate not broad, occasionally reaching segment VIII −IX articulation; subanal plate nearly triangular, smoothly concave laterally (Fig. 12). Cerci brown basally, yellow to whitish distally.

Female subimago. Measurements: body length 8.7 mm; fore wing length 9.5 mm; cerci length 10.0 mm (approximately 1.14 times longer than body). General colour of body similar to female imago, but more grey tinted.

Head and antennae yellowish-brown. Thorax yellowish-brown to light brown. Prothorax yellowish-brown; mesothorax with darker areas around lateroparapsidal suture [LPs], prelateroscutum [PLS] and anteronotal protuberance [ANp] (see Kluge 2004), other arrangement of spots on lateral sides of mesothorax similar to imagos of both sexes; metathorax light brown.

Legs the same colour patterns as in female imago. Wings uniformly yellowish-grey, relatively transparent; venation yellowish-brown without dark maculation around cross veins.

Abdominal segments pale, yellowish brown; oblique dirty violet stripes well visible on lateral sides of terga II −VIII and connected by distinct transversal stripe near posterior margin of segment dorsally; the shape of these stripes and intensity of the colour of its parts as in fig. 2, in Braasch & Soldán (1985: 68). Shape of subgenital and subanal plates as in female imago. Cerci dirty brown, slightly paler distally.

Male subimago. Unknown.

Mature larva (Figs 20–43). Measurements: body length 7.5−9.5 mm; cerci length 8.0− 9.5 mm; paracercus length 9.0−10.0 mm. General body colour yellowish-brown to brown, occasionally to brownish-olive; ventral side distinctly paler than dorsal side.

Head. Colour yellowish-brown, light brown to brownish-olive; a few small whitish spots near ocelli bases and posteriorly on vertex. Head nearly rectangular, widest part at eyes level. Antennae yellowish-brown to brown, darker proximally.

Mouthparts. Labrum not wide; a single oblique row of 7−10 strong bristles in median half ventrally (Figs 20, 21). Mandibles (n = 20) with 7–12 prosthecal bristles. Maxillae (n = 20) (for more information see Haybach 1999): number of comb-shaped bristles (N_CBS) = 15–23 (mainly 16−19) (+ 2–3 small pointed bristles); number of teeth on 5th comb-shaped bristle (N_TCB5) = 9–15 (mainly 10–12); number of hair-like setae on dorsal upper side (N_DOR) = 4–9 (mainly 4–8); outer margin of maxillae without hair-like setae (N_OUT) = 0 (as in most taxa of the subgenus Ecdyonurus; regularly present only in E. macani Thomas & Sowa, 1970, E. starmachi Sowa, 1971, E. torrentis Kimmins, 1942 according to Haybach 1999); number of hair-like setae on ventral basal part of maxillae (N_VEN) = 6–14 (mainly 8–11); number of hair-like setae at the base of maxillary palps (N_PLBas) = 2–8 (mainly 4−6); number of setae on the outer margin of the first segment of maxillary palps (N_PLS) = 21–42; number of setae on the inner side of the first segment of maxillary palps (N_PLP) = 28–50 (mainly 30–40). Labial palps covered with numerous hair-like setae on the dorsal side of the first segment (N_LPH) = 20–38 arranged in 1–2 rows. Glossae nearly square, with rounded outer margin (Fig. 22).

Thorax. Pronotum yellow to brownish-olive; several pale spots centrally and laterally near pronotum projections. Pronotum moderately expanded laterally; lateral projections light yellow to yellowish-olive, relatively short and slender, asymmetrical, bent inwards; apex of lateral projections bluntly pointed or nearly rounded; the width/length ratio of semipronotum to caudal projection (cf. Bauernfeind & Humpesch 2001) is 3.0– 3.6 in mature and 3.2−3.9 in younger larvae (Figs 16, 17). Meso- and metathorax yellowish-brown to brown; several longitudinal and transversal pale spots centrally. Thorax unicoloured whitish-yellow ventrally; a few small maculation near legs base.

Legs yellowish-brown to brown, with yellow pattern similar to "broken" cross on femora dorsally (cf. e.g. Martynov & Godunko 2013; Kłonowska-Olejnik et al. 2007). Tibiae light brown, slightly paler distally. The length/width ratio of hind femora is 2.5–2.8. Tarsi yellowish brown to brown; darkened distally. Tarsal claws brown, with 2–3 teeth; occasionally claws without any teeth (Fig. 40).

Legs setation. Outer margin of femora with row of long bristles dorsally, and regular row of small pointed stout setae more posteriorly on ventral side; inner margin of femora with irregular row of bluntly pointed and spatulate stout setae, covered with sparse fine hair-like setae (Figs 25, 26). Inner margin of tibia and tarsi sparse row of spatula-like and pointed setae, alternating with fine hair-like setae; outer margin covered with slightly elongated hair-like setae and sparse pointed setae. Sparse bluntly and acutely pointed stout apically setae on trochanters (Fig. 29).

Stout setae on dorsal surface of femora of various types: (i) central part of fore femora with rounded apically parallel sided spatulate setae (much rarer proximally and distally) (Figs 23, 24); (ii) spatulate parallel sided setae accompanying with rounded apically setae with slightly convergent margins on middle femora centrally (the same types also proximally and distally) (Figs 27, 28); (iii) dominance of apically convergent setae rounded at the tip on the entire surface of hind femora (Figs 30−33) (occasional slender obtuse apically setae distally, see Fig. 34).

Abdomen. Contrasting pattern of terga well preserved only in recently collected material; topotypical material of mature larvae with diffused colour pattern, mostly unicoloured yellowish-brown to light brown due to long-term preservation in ethanol. Terga yellowish-brown to brownish-olive; general scheme of colour pattern is quite similar in mature and younger larvae (Figs 16, 17 and 19 based on young larvae): tergum I with broad light spot centrally, two light smudges laterally; terga II and III with two small spots centrally, two spots laterally near posterior margin of segment; terga VI and V with U- or V-shaped spot centrally, two spots laterally near posterior margin of segment; terga VI and VII with 2 or 3 spots of a different shape centrally (round, triangular or semilunar), additionally broad spots posterolaterally; terga VIII and IX with broad spot centrally (occasionally V-shaped); tergum X unicoloured brown (indistinct longitudinal maculation centrally only). Nymphs with distinct hypodermal markings (dark brown oblique stripes) on lateral sides of terga I −VI (VIII). Posterior margin of terga with large pointed teeth alternating with numerous irregularly scattered smaller teeth (Fig. 38). Surface of terga with numerous fine hair-like setae.

Sterna whitish-yellow to yellowish-brown (Fig. 18 based on young larvae); occasionally two brownish spots on sterna II −VII, and broad spot on sternum VIII (in some specimens V-shaped); sternum IX unicoloured yellowish-brown to light brown (in female), yellowish-brown with brown gonostyli buds (in male); posterolateral projections not elongated, nearly triangular (more stout in female). Nerve ganglia well visible on thoracic and abdominal segments (mainly abdominal sterna I −VII or VIII).

Gills yellowish to dirty violet coloured plate (more intensively centrally); tracheation pale, hardly visible. Gill I slender, tongue-shaped, rounded apically, with dense tuft of long tracheal filaments, as long as gill plate (Figs 35, 41). Gills IV leaf-shaped, symmetrical, relatively narrow and rounded at the tip (Figs 36, 43); gill VII slightly asymmetrical, without a tuft of tracheal filaments (Figs 37, 42).

Cerci and paracercus yellowish-brown to brown, paler distally; stout, acutely pointed stout setae around distal margin of each of segment (Fig. 39).

Egg. Measurements: length 150–170 Μm; width 100–115 Μm. Eggs broadly oval, somewhat barrel-shaped (Fig. 44). Chorionic surface densely covered by numerous small tubercles or macrogranula (diameter 0.4–0.7 Μm; spaced at a distance of 0.05–0.7 Μm), typical for the Ecdyonurus eggs (Figs 44−46; see e.g. Gaino & Rebora 2003; Kłonowska-Olejnik et al. 2007); only one type of knob-terminated coiled threads (KCT’s) on the surface of exochorion; KCT’s not numerous, more or less evenly distributed on exochorion surface (Figs 44, 45); insignificant concentration of not enlarged KCT’s (diameter 3.2–4.0 Μm) on one egg pole only (Figs 47, 48). Three to five micropyles visible in subequatorial area; sperm guide ovoidal, 7.5–10.0 Μm in length and 6.5–7.5 Μm in width; remarkable micropylar rim with dense row of tubercles (Fig. 46).