Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, 1985

Godunko, Roman J., Vidinova, Yanka & Soldán, Tomáš, 2015, Redescription of Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, 1985 (Ephemeroptera: Heptageniidae), Zootaxa 3915 (4), pp. 551-568 : 552-564

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).

Figures

FIGURES 1 – 5. Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, male imagines, paratypes: 1, body, left side, lateral view; 2, head and thorax details, dorsal view; 3, head and thorax details, left side, lateral view; 4, abdominal segments details, dorsal view; 5, abdominal segments details, left side, lateral view.

FIGURES 10 − 12. Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, male imago, paratype (10, 11), female imago, topotype (12): 10, genitalia, ventral view; 11, penis lobes, dorsal view; 12, tip of abdomen, ventral view.

FIGURES 6 – 9. Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, male imago, paratype: 6, genitalia, dorsal view, scale bar = 100 Μm; 7, penis lobes, dorsal view, scale bar = 100 Μm; 8, details of apical sclerite of penis lobe, dorsal view, scale bar = 10 Μm; 9, details of lateral sclerite of penis lobe, dorsal view, scale bar = 10 Μm.

FIGURES 13 – 15. Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, female imago, topotype: 13, body, left side, lateral view; 14, head and thorax details, left side, lateral view; 15, abdominal segments details, left side, lateral view.

FIGURES 20 – 26. Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, mature larvae, topotypes: 20, labrum, ventral view, scale bar = 100 Μm; 21, bristles on the ventral side of labrum, scale bar = 100 Μm; 22, glossa and paraglossae, dorsal view, scale bar = 100 Μm; 23, setae on fore femur distally, dorsal view, scale bar = 10 Μm; 24, seta on fore femur centrally, dorsal view, details, scale bar = 10 Μm; 25, inner margin of fore femur centrally, dorsal view, scale bar = 10 Μm; 26, outer margin of fore femur centrally, dorsal view, scale bar = 10 Μm.

FIGURES 27 – 34. Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, mature larvae, topotypes: 27, 33, setae on middle femur centrally (general view and details), dorsal view; 28, 32, 34, setae on middle femur distally (general view and details), dorsal view; 29, setae on middle trochanter; 30, 31, setae on hind femur proximally (general view and details), dorsal view. Scale bars = 10 Μm.

FIGURES 35 – 40. Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, mature larvae, topotypes: 35, left gill I, scale bar = 100 Μm; 36, right gill IV, scale bar = 100 Μm; 37, right gill VII, scale bar = 100 Μm; 38, posterior margin of abdominal tergum IV centrally, scale bar = 10 Μm; 39, surface of terminal filament, details, scale bar = 10 Μm; 40, tarsal claw of hind leg, scale bar = 100 Μm.

FIGURES 41 – 43. Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, mature larva, topotype: 41, right gill I; 42, right gill IV; 43, left gill VII.

FIGURES 16 – 19. Ecdyonurus (Ecdyonurus) russevi Braasch & Soldán, larvae, Mladezhka River (May 2009): 16, body, dorsal view; 17, head and thorax details, dorsal view; 18, abdominal segments, ventral view; 19, abdominal segments, dorsal view.