Ephemera (Ephemera) transbajkalica Tshernova, 1973

Tiunova, Tatiana M., 2024, Egg morphology of six East Palaearctic species of the genus Ephemera Linnaeus (Ephemeroptera: Ephemeridae), Zootaxa 5497 (3), pp. 381-399 : 387

Ephemera (Ephemera) transbajkalica Tshernova, 1973

Figures 16–23

Material examined. Russia: Amur Oblast, Selemdzha River basin, Burunda River, mouth, tributary of Nora River , 16.06.2004, 2♀ adults, T. Tiunova; Republic of Sakha (Yakutia), Aldan River basin, Ungra River, base of Ungrinsky reserve “Yukhta,” 01.08.2006, 2♀ adults (reared), T. Tiunova .

Distribution. East Siberia, Far East Russia, Mongolia.

The egg is oval-shaped ( Figs 16–17 ). Dimensions: 220.0–226.0 µm in length (220.8 µm) and 123.0–129.0 µm in width (124.6 µm). The thickness of the extrachorion-adhesive layer is 1.3–1.7 µm ( Figs 21, 23 ). The surface of the adhesive layer is slightly roughened; almost smooth ( Figs 16, 18 ). There are one or two micropyles in the equatorial area ( Figs16–17 ); micropyles are “tagenoform-type”; sperm guide well expressed (10.0–19.6 µm long, 4.2–7.2 µm wide), elongated, oval, with pointed distal margin, not deep ( Figs 18–19 ). Micropylar canal: 4.0–6.0 µm long and 2.3–7.1 µm wide; weakly protrudes above the adhesive layer ( Figs 16, 18 ). The chorionic surface is covered by the regular mesh unit’s penta- or hexagonal cells, each with a flat, almost smooth bottom and a convex protuberance in the middle ( Fig. 23 ). The proximal part of the micropylar opening elevates above the chorion ( Figs 20, 22 ).

Figures

FIGURES 16–19. Egg morphology of Ephemera (Ephemera) transbajkalica: 16–17, general shape; 18–19, micropyle in the complex extrachorion-adhesive layer. AL-Ex—complex adhesive-extrachorion layer; CM—canal micropylar; mp—micropyle; SG—sperm guide.

FIGURES 20–23. Egg morphology of Ephemera (Ephemera) transbajkalica: 20, egg surface without complex extrachorionadhesive layer; 21, thickness on the layer forming the eggshell; 22, proximal part of micropylar canal on chorion surface; 23, chorionic sculpturing. AL-Ex—complex adhesive-extrachorion layer; CS—chorion surface; MO—micropylar opening; mp—micropyle.