Ameletus khasanensis, Tiunova, Tatiana M., 2013

Tiunova, Tatiana M., 2013, New species of Ameletus Eaton, 1885 and redescription of Ameletus longulus Sinichenkova, 1981 from the Russian Far East (Ephemeroptera: Ameletidae), Zootaxa 3630 (3), pp. 519-533 : 520-524

Ameletus khasanensis sp. nov.

( Figs 1–21 , 24–26 )

Material examined. Holotype male imago (reared from larva), RUSSIA, Primorskiy Kray, Khasanskii region, Ryazanovka River, below the bridge of automobile line, 23.IV.2003, T.Tiunova. Paratypes: collected together with the holotype: 3 male and 5 female imagines (reared), 2 male and 4 female subimagines, 5 mature larvae and 8 larval exuvia.

Description. Male imago (in alcohol). Length (mm): body 13.8–14.2; forewings 12.7–13.4; cerci 17.3–17.8. Head: upper portion of eyes gray; lower portion dirty gray. Medial and lateral ocelli pale. Thorax: Medioscutum and submedioscutum brown; medial longitudinal suture narrow and dark brown. Sublateroscutum dark brown or dark; prelateroscutum pale. Medioparapsidal suture light brown. Scutellum light brown; scuto-scutellar impression dark brown. Posterior scutal protuberance brown ( Fig. 1 ). Femur and tibia of forelegs from brown to dark brown; tarsal segments from light brown to yellowish; joints dark brown; middle and hind legs from brownish to yellowish with brown joints; dorsal surface of the fore tibia without spinules.

Length (mm) of foreleg segments: femora 3.1; tibiae 2.2–2.4; tarsal segments 0.4–0.5, 1.3–1.9, 0.7–1.1, 0.7–0.9, and 0.5. Wings hyaline; crossveins of forewings between C and R veins dark brown and bordered by brown ( Fig. 2 ); other veins from yellowish to colorless. All veins of hind wings colorless ( Fig. 3 ). Abdomen: terga brownish, translucent; lateral margin whitish; tergum I dark brown; terga II–VI from brownish to whitish with a pair of wide brown medial stripes; terga VII–X dark brown with lighter anterior lateral corners. Sterna whitish, translucent; sternum IX with brown lateral margins. Styliger and forceps brownish; first segment of forceps darker then other segments ( Fig. 4 ). Penis lobes pale in the inner and brown in the external parts, tops covered with small spines; lateral penis lobes with pointed apices that bend medially ( Figs.6–7 ); each ventral plate bears a single long pointed denticle at an angle to the lateral lobe ( Figs. 5, 8 ); the distance between denticle base and lateral lobe is the maximum width of the denticle ( Fig. 8 ). Cerci brownish at base and yellowish distally.

Female imago. Length (mm): body 14.6–16.6; forewings 13.7–14.8; cerci 13.5–14.5. Overall color from light brown to brown. Thorax: Mesonotum brown. Forelegs brown; middle and hind legs light brown, joints darker. Color of wings as in the male. Abdomen: tergum I dark brown; terga II–X dirty brown without maculation (abdomen with eggs) or with diffuse maculation (without eggs). Sterna, as terga. Subgenital plate has a smooth and shallow depression ( Fig. 9 ). Cerci light brown and darker at the base.

Male subimago. Overall color dirty brown. Wings whitish and translucent. All crossveins of fore- and hind wings bordered by brown. Terga dirty brown with diffuse maculation. Sterna light brown; sternum IX whitish with brown lateral margins. Forelegs dirty brown; middle and hind legs lighter. Cerci brownish.

Mature larva. Length (mm): body 12.2–15.5; cerci 5.0–6.8. Head: light brown tinged with grayish. Labrum (length 0.8 of width) with a shallow apical incision; distal and lateral margins brown; middle part of labrum with light triangular spot; lateral side lighter than margins ( Fig. 10 ). Incisor of the left mandible with four denticles; first largest, the fourth smallest; the third slightly smaller than the second ( Fig. 11 ). Incisor of the right mandible with three denticles; first nearly equal to the third ( Fig. 12 ). Labium whitish; paraglossae length does not exceed glossae length ( Fig. 13 ). First comb-shaped seta of maxilla with wide and rounded denticles, their number less than ten ( Fig. 21 ). Thorax: pronotum and mesonotum light brown. Legs brownish; femur of forelegs brownish, darker than middle and hind legs; tarsus with claw brown; joints brown; setae on dorsal surface of base of fore femora not forming a group ( Fig. 14 ). Lengths (mm) of leg segments as follows. Foreleg: 1.6–2.0; tibia 0.7–1.1; and tarsus 1.2–1.6. Middle leg: femur 1.6–1.8; tibia 0.8–1.0; and tarsus 1.0–1.3. Hind leg: femur 1.7–2.1; tibia 0.7–1.0; and tarsus 1.0–1.3. Abdomen: terga brownish tinged with whitish; maculation on terga II–IX diffuse in the form of paired elongated strokes; all terga with alternating large and small spines. Sterna brownish or whitish. Gills white; gills I and II small, rounded in distal part; gill I without anal ribs, width 0.61 of length ( Fig. 15 ); gill II with small anal ribs, width 0.68 of length ( Fig. 16 ); gills III–VI with anal rib far from anal margin; width 0.54 of length ( Figs. 17–19 ); gill VII with truncated inner distal margin, width 0.54 of length ( Fig. 20 ). Cerci light brown, darker on the proximal portion, with yellowish tips.

Eggs. General form of egg flattened ellipse with a length of 198–218 μm and a width of 102–121 μm ( Fig. 24 ). The chorionic surface is covered by large-mesh regular penta- or hexagonal cells; each cell with a flat, almost smooth bottom and a convex protuberance in the middle; borders of cells solid, relatively high; every four or five cells united by one small round knob, terminating in coiled threads similar in appearance to a flower ( Fig. 25 ), which cover the whole egg evenly; large and round knobs arranged on one pole ( Fig. 26 ). Micropyles in subequatorial area; sperm guide round ( Fig. 24 ).

Etymology. The name refers to the type locality, the Khasanskii region, where the types were collected.

Distribution and biology. Known only from the type habitat in southern Primorskyi Kray. Mature larvae and adults were collected during the flight period in a small foothill river. The temperature during the day (April 23) ranged from 4.1 to 8.3°C. The subimagos emerged on a warm sunny day. The mature larvae crawled, halfsubmerged to stones protruding from the water and molted to subimago.

Figures

FIGURES 1 – 9. Ameletus khasanensis sp. nov., male imago: 1. Mesonotum, dorsal view. 2. Fore wing. 3. Hind wing. 4. Sternum IX, styliger and gonostyli. 5. Genitalia, lateral view. 6. Penis, ventral view. 7. Penis, dorsal view. 8. Penis, lateral view. 9. Subgenital plate, female, dorsal view. Scale (mm): 4 – 9 = 0.5; 1, 3 = 1.0; 2 = 2.0.

FIGURES 10 – 20. Ameletus khasanensis sp. nov., larva: 10. Labrum, dorsal view. 11 – 12. Apices of mandibles, dorsal view: 11 – left mandible, 12 right mandible. 13. Labium, dorsal view. 14. Femur of foreleg. 15 – 20. Gills: 15. Gill I, 16. Gill II, 17. Gill III, 18. Gill IV, 19 Gill VI, 20. Gill VII. Scale (mm): 10, 13, 15 – 20 = 0.5; 11 – 12 = 0.2. The arrow shows the group of setae.

FIGURES 21 – 23. Comb-shaped setae of maxilla: 21. Ameletus khasanensis sp. nov., 22. Ameletus longulus, 23. Ameletus costalis. The arrow shows the first seta.

FIGURES 24 – 26. Ameletus khasanensis sp. nov., egg: 24. General view. 25. Structure of chorion and small knob-terminated coiled threads. 26. Large knobs. The arrow shows the micropiles (mp).