Isoperla asiatica Rauser 1968

Isoperla asiatica Raušer, 1968 Figs. 10–17 Material examined. Russia, Far East, Khabarovsk Krai: 1♂, Anyuisky National Park, Gassi Lake, Anyui River basin, Amur R. basin, 4.06.2019, N. Yavorskaya; 1♀, same locality, Anyui R., Adzhu Channel, 4.06.2019, coll. N. Yavorskaya; 2♀, same locality, Solomi R., Anyui R. basin, 3.06.2019, coll. N. Yavorskaya; Amurskaya Oblast: 6♂ 3♀, Bol’shiye Simichi River, Bureya R. basin, Amur R. basin, 9.06.2013, coll. V. Teslenko; 1♀, Zeya River, Ovsyanka settlement, Amur R. basin, 7.07.2015, coll. T. Tiunova; 1♂ 1♀, Dikan River, near the auto bridge, 27.07.2015, coll. V. Teslenko; Primorsky Krai: 1♀, Lazovsky Nature Reserve, Proselochnaya River, Proselochnaya cordon, Partizanskaya R. basin, 22.05.2007, coll. O. Zorina; 2♀, same locality, Staro-Kamensky stream, near Staraya Kamenka settlement, 28.05.2004, coll. Eu. Makarchenko; 1♂ 1♀, Bolshaya Ussurka River, Ussuri R. basin, Amur R. basin, settlement Zvenigorodka, 06.08.2004, coll. V. Teslenko; 1♂ 2 ♀, Ussuri River, Kamenka village, 07.05.1993, coll. V. Teslenko; 8♂ 8 ♀, Barabashevka River, near fish factory, 30.04.2003, coll. V. Teslenko. Egg. Shape oval, symmetrical, with anterior and posterior poles broadly rounded and a concave cross-section (Figs. 10‒11, 14); chorion thickness 2.9‒5.3 µm. Length 314–346 µm, width at the equator 237–261 µm (n=6). Collar well developed, with irregular longitudinal ridges; rim deeply serrated and curved outward; collar surrounded by slightly pronounced shoulder without ring (Figs. 11, 13, 15). Anchor mushroom-shaped, with small grouped globular bodies placed along a peripheral area of the anchor edge (Figs. 10, 12). Chorion surface is rough, covered with hexagonal follicle cell impressions with thick, slightly elevated ridges (Figs. 10‒11, 14, 16–17); floors with numerous (9–11) deep groove-like pits (Figs. 16‒17). Eclosion line absent. Micropyles located along ridges, FCI in the anterior ¼, and faintly noticeable (Figs. 10, 14). Micropylar canals straight or slightly sloping, tunnel-shaped, and relatively long; canals raised slightly above the surface (Fig. 17). Orifices the same size as FCI pits. Distribution. East Palaearctic species. Russia, Siberia: Altai, East Sayan, Baikal Lake basin, Transbaikalia; Far East: Amurskaya Oblast, Jewish Autonomous Region, Khabarovsk Krai, Primorsky Krai, Sakhalin Island. East Kazakhstan. Mongolia. China, Inner Mongolia Autonomous Region (Huo et al. 2020). Remarks. The shape, size, and chorion structure of the egg as a whole correspond to the first description by Zwick & Surenkhorloo (2005). Egg bears a specific collar with a serrated rim; the chorion structure appears as FCI’s with thick elevated ridges, their floors covered with numerous (9–11) deep groove-like pits.