Megaperlodes tiunovi Te

Teslenko, Valentina A., 2015, A new species of Megaperlodes Yo k o y a m a et al. 1990 (Plecoptera, Perlodidae) from the South of the Russian Far East, Zootaxa 3904 (4), pp. 553-562 : 554-561

Megaperlodes tiunovi Te sl e nk o s p. n.

( Figs. 1–19 )

Description. Adult habitus. Sexually dimorphic, female larger than male. Mean body length from tip of the head to the apex of abdomen, males, 17.0–17.3 mm; females 22.0–26.2 mm. Wings slightly shortened. Forewing length, males, 15.2–16.0 mm; females, 19.8–21.8 mm; wingspan, males, 32.3–34.1 mm; females 42.8–46.8 mm. The front wing of male and female ( Fig. 1 ) black, fumose, veins dark, in the middle with a contrastive white frosted spot, occupying about ⅓ of the wing length. The spot extends from R1 to the posterior wing edge, lateral margins of the spot are indistinct, and veins in the spot paler. Wing venation includes an irregular net near the apex sometimes consisting of four rows of cells. Seven to ten cross veins between C and Sc; five apical veins between Sc and R1 ( Fig. 1 ). Rs with five apical branches. Nine to thirteen veins between М and Cu2; four anal veins branching into six. Hindwing black fumose, slightly paler in the cord area, in males especially. Anal area enlarged and pleated, A2–A5 forked; A5 with dark small spot at base.

General body colour black with yellow spots; membranous ventral portions also yellow ( Figs. 2, 3 ). Head and pronotum matt black, with sharply delimited bright yellow marks. Head with compound eyes wider than the pronotum; M-line smooth and distinct ( Fig. 4 ). Interocellar area with a small tear-shaped bright-yellow spot, widest anteriorly. A small yellow triangle extends along the epicranial stem on the occiput ( Fig. 4 ). A posterolateral reticulate callosity behind each compound eye. Antennae shorter than cerci, black; palpi dark brown. Head ventrally yellow brown ( Fig. 3 ). Submentum almost square, with slightly rounded lateral margins, the submental gills very small to almost absent in both sexes. The pronotum rectangular, same width as the head width under the compound eyes, with narrow longitudinal thread-like median yellow band widened triangularly at the anterior pronotal margin as well as before the posterior pronotal furrow ( Fig. 4 ). Pronotal rugosites smooth, the lateral fields matt. The arms of the mesosternal ridge meet the posterior corners of the furcal pits; suture between basisternum and furcasternum indistinct ( Fig. 3 ).

Abdominal tergites black, strongly sclerotized and covered by short colourless clothing hairs, only tergum 1 with X-shaped white spot medially, with a rounded inside black spot. Abdominal segments 1–5 divided laterally by yellow pleural folds, more distinct in females; posterior segments ring-shaped, entire, fully sclerotized ( Fig. 3 ). Legs black except bright yellow joints ( Fig. 2 ).

Male. Abdominal tergum 8 black, slightly impressed dorsomedially; two submedial rounded swellings covered by short colourless hairs close to the posterior margin, especially apparent in lateral view ( Figs. 5, 8 ). Posterior margin of tergum 9 with a medial triangular notch, which extends ½ of the length of tergum 9, two posterolateral rounded swellings covered by short fine colourless hairs ( Fig. 7 ); in repose tergum 9 hidden by tergum 8 and noticeable as narrow band with a triangular posteromedial notch ( Fig. 5 ). Sternum 9 bears a scoopshaped subgenital plate extending backward and curved upward ( Figs. 5, 6 ). Sternum 10 narrow, pale medially with two black lateral bands hidden by the subgenital plate in ventral view ( Fig. 6 ). Tergum 10 entire, black, with median diamond-shaped yellow spot, covered by short fine colourless hairs ( Fig. 7 ). In repose, tergum10 tapers backward and caudally triangular, the paraprocts touch in contact dorsomedially, pressed against the lower face of tergum10. In everted condition, a yellow membranous strip with rounded posterolateral edges protrudes from under the edge of tergum10 and supported by a small medial conical peg located between the paraproct lobes and concealed by them in repose ( Figs. 7, 8 ). The paraproct sclerite wide, heavily sclerotized basally, narrowed and bluntly rounded distally ( Figs. 5, 6, 8 ). Eversible paraproct with lobe (EPL) arises from the base of the paraproct sclerite ( Fig. 8 ). EPL large, inflated, ball-shaped basally, yellow and bears a long fingerlike projection, extended at the base and pointed towards the top ( Figs. 6–8 ); ventral face of the projection membranous, the dorsal face covered by long thin brown-red sclerotized setae, more densely in the distal ⅓ of the projection ( Figs. 8, 9 ). Both projections closely appressed, directed obliquely backward and upward ( Figs. 6–8 ).

Female. Sternum 8 black with a small pale spot anteromedially, a short transversal subgenital plate extending slightly beyond the edge of sternum 8 ( Fig. 10 ), posterior margin of the plate with a weak medial notch separating two lateral lobes, slightly rounded posteriorly, covered by small setae ( Fig. 10 ). Lateral margins of subgenital plate rounded. Abdominal sternum 9 black with pale spot medially, a pair of dark posterolateral sclerites looks like oblique bands directed to anterior margin. Abdominal sternum 10 and the blunt paraprocts unmodified and back.

Egg. Trilateral ( Fig. 11 ), 614 X 345 µm with narrow anterior pole. The longitudinal ridges (maximal width 65 Μm) delimiting the three faces of the egg, densely covered by globular bodies ( Figs. 11, 12 ). Each face additionally with a transverse ridge close to the posterior pole, also covered by globular bodies smaller and less dense, than on the longitudinal ridges ( Fig. 11 ). A row of 3–7 micropyles near transverse ridge ( Figs. 11, 13 ) on each of the three faces. Micropyle openings elevated above the chorion surface, rostral with rounded margins ( Figs. 13, 14 ). Collar short, formed by medially projecting extensions of the three longitudinal ridges, each top of extension flaky, and petal-shaped, smooth on inner surface ( Fig. 15 ). Collar delimited by rim on outer side basally ( Figs. 15, 16 ). Anchor mushroom-shaped with short pedicel ( Fig. 16 ); external surface pleated with globular bodies ( Fig. 16 ). Internal surface of anchor as Fig. 15 . The margin of the anchor covers the pedicel, not reaching the collar’s rim ( Fig. 16 ). The chorion surface smooth ( Fig. 14 ).

Larvae. Mature female larvae 20.5–21.5 mm long (n=2). General colour grey-brown with a pale pattern. Body covered by short brown clothing hairs. Antennae, cerci and ventral body side pale grey. Head wider than the pronotum with a large, triangular, pale spot in front of the anterior ocellus extending onto the clypeus, labrum pale ( Fig. 17 ). M-line pale, distinct; interocellar area brown with tear-shaped central pale spot ( Fig. 17 ). A small triangular pale spot laterally from each posterior ocellus and the tentorial callosities pale. Occiput with a large triangular pale spot around the epicranial stem, two pairs of pale spots bordered by sinuate brownish rims behind each eye. No postocular spinule row. Lacinia unidentate ( Fig. 18 ), narrow apically, pointed and well sclerotized, basal ½ expanded. Submarginal setae absent. Galea reaches more than ½ of the lacinia length. Mandible ( Fig. 19 ) simple, not deeply cleft, with medial setae; mandibular teeth without serrations; a small patch of acanthae basally from the last tooth. Submentum square with almost straight lateral margins; submental gills very short or almost absent. Pronotum trapeziform, transverse with rounded angles; anterior margin wider than posterior one; median, dorsal stripe pale, narrow, slightly wider posteriorly, a pale reticulate stripe presents on each lateral field of pronotum; pronotal margins without fringe of bristles ( Fig. 17 ). Legs pale-grey, femur ventrally in distal ½ with elongate brownish mark. Outer margins of femur, tibia and tarsus with a fringe of colourless silky hairs.

Abdominal segments 1–5 divided by hairless pleural membranes. Terga with a few colourless long hairs posteriomedially, more pronounced on the last terga; the bristles at posterior tergal margins not detected. Terga brown with irregular yellow median band, the brown edge in front of it with three prominent dark spots; the distinct caudal setae present on terga 8 and 9; the pattern on terga 9 and 10 diffuse ( Fig. 17 ). All abdominal terga covered by brown clothing hairs. Paraprocts normal length, apex rounded. Cerci pale greyish with dorsal fringe of fine, silky, colourless hairs ( Fig. 17 ) increasing in length towards apical cercal segments, each cercal segment with an apical whorl of short brown setae.

Material examined. Holotype, male. Russian Far East, Primorsky Region, the Brus’ya River under road bridge, near Bamburovo Settlement, 42.56.480'N 131.19.120'E, 12.05.2014, coll. Teslenko V. Paratypes: 1 male, 6 females, 7 exuviae, the same locality and data as holotype, coll. Teslenko V.; 2 males (dissected in vial), 10 females (one dissected in vial).

Other material. 5 egg masses, 7 exuviae, the same locality, 18.05.2014, coll. V. Teslenko; 2 nymphs, the same locality, 28.04.2013, coll. I. Tiunov.

Etymology. The species is named in honor of the ornithologist Ivan M. Tiunov, who also made significant contributions to the knowledge of the stonefly and mayfly fauna of the Russian Far East.

Distribution. The new species is known from the small foothill salmonid stream, the Brus’ya River. This stream is located in the South Russian Far East in the Primorsky Region near the border with China and Korea. The Brus’ya River flows out from the East Manchurian Mountains to the Peter the Great Bay of the Sea of Japan. The type locality is situated about 5 km from the mouth ( Fig. 20 ). Water temperature at the time of collection (12 of May 2014 at 12 am) was 3.8ºC.

Remarks. Megaperlodes tiunovi is smaller in size than M. niger and differs in number of the abdominal segments divided laterally by yellow pleural folds, segments 1–5 are divided in M. tiunovi , whereas segments 1–6 are divided laterally by pleural folds in M. niger . The front wing M. tiunovi is black with a contrasting white frosted spot medially ( Fig. 1 ), the front wing M. niger ( Fig. 21 ) lacks a spot. The male of M. niger lacks a median yellow spot on tergum 10. In everted condition, the posterior margin of tergum 10 of M. niger appears like a long transversal slightly sclerotized sclerite with rounded lateral margins ( Fig. 23 ). The paraproct sclerite of M. niger is larger than in M. tiunovi and completely heavily sclerotized, with the base hemispherical, the sclerite long, medially narrowed, and then widened and distally bluntly rounded ( Figs. 23, 25 ). The rectangular base of the EPL of M. niger has a long fingerlike projection, narrowed from base to the pointed tip ( Figs. 23, 25 ), and densely covered by short setae ( Fig. 24 ). The female subgenital plate of M. niger is caudally rounded and covered by short setae ( Fig. 26 ). The egg of M. niger has a wider anterior pole with an entire collar ( Figs. 27, 28 ). Each egg face has medially an additional hemispherical swelling ( Fig. 27 ); the micropyles are shorter than in M. tiunovi , slightly elevated above the chorion surface, openings with rounded margins ( Figs. 29, 30 ). The larvae differ in color, shape of submentum and pronotum ( Fig. 3 E in Inada et al. 1998).

Figures

FIGURE 20. Type locality on the Brus’ya River (Photo by I. Tiunov).

FIGURES 1 – 3. Megaperlodes tiunovi sp. n.: 1. Wings of female. 2. Habitus, female, dorsal. 3. Habitus, female, ventral. Scale (mm): 1 = 5.0.

FIGURES 4 – 10. Megaperlodes tiunovi sp. n.: 4. Head and pronotum, dorsal. 5. Male abdominal tip in repose, posterior. 6. Same, everted, ventral. 7. Same, everted, dorsal. 8. Same, everted lateral. 9. Tip of the fingerlike projection, of the everted paraproctal lobe, lateral. 10. Female, subgenital plate, cleared, ventral.

FIGURES 11 – 16. Megaperlodes tiunovi sp. n., egg: 11. Habitus: anchor, longitudinal ridges, anterior pole, row of micropyles, dorsal. 12. Globular bodies on longitudinal ridge. 13. Row of micropyles, dorso-lateral. 14. Chorion structure and micropyles lateral. 15. Internal surface of anchor, pedicel, collar, dorsal. 16. External surface of anchor, collar, dorsal.

FIGURES 17 – 19. Megaperlodes tiunovi sp. n., larvae: 17. Habitus, female. 18. Right lacinia, ventral. 19. Right mandibular, ventral.

FIGURES 21 – 26. Megaperlodes niger: 21. Wings of female. 22. Head and pronotum of male. 23. Male abdominal tip with everted paraproctal lobes, dorsal. 24. Tip of the fingerlike projection of the everted paraproctal lobe, lateral. 25. Male abdominal tip with everted paraproctal lobes, lateral. 26. Female abdominal tip, ventral. Scale (mm): 21 = 5.0.

FIGURES 27 – 30. Megaperlodes niger, egg: 27. Habitus: anchor, longitudinal ridges, median semispherical swellings, row of micropyles, dorsal. 28. Anchor and collar, dorsal. 29. Row of micropyles, dorso-lateral. 30. Chorion structure and micropyles lateral.