Ephemera (Ephemera) sachalinensis Matsumura, 1911

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) sachalinensis Matsumura, 1911

Figures 9–15

Material examined. Russia: Primorsky Krai, Khasansky District, Barabashevka River, below Fish Hatchery , 03.08.2007, 2♀ adults, T. Tiunova; Ryazanovka River , below Okhotbaza, 11.06.2003, 2♀ adults, T. Tiunova; Sakhalinskaya Oblast , Sakhalin Island, Lake Vavayskoye, eastern part, 18.07.2002, 3♀ adults, V. Teslenko; Amurskaya Oblast , Amur River basin, Bureya River, below Kulikovka village , 3♀ adults, T. Tiunova .

Distribution. East Siberia, Far East Russia, Mongolia, Korea, China, Kazakhstan (Irtysh River basin).

The egg has an oval shape close to quadrangular with rounded corners ( Fig. 9 ). Dimensions: 204.0–230.0 µm in length (213.5 µm) and 118.0–132.0 µm in width (125.8 µm). The thickness of the extrachorion-adhesive layer is 1.9–3.0 µm ( Fig. 15 ). The surface of the adhesive layer is shagreen or roughened ( Fig. 9 ). There are one or two micropyles per egg in the equatorial area ( Figs 9 , 13 ). Micropyles are “tagenoform-type” ( Figs 9–10 ), sperm guide weakly expressed (6.4–9.7 µm long, 3.0–5.0 µm wide), almost rectangular, elongated, distal margin not closed ( Figs 10–11 ). The micropylar canal, about 5 μm long, does not protrude above the adhesive layer ( Figs 9–10 ). Chorionic sculpturing consists of interrupted broken ridges, whose distribution and arrangement extend regularly over the whole chorion surface ( Figs 12–13 ). The proximal part of the micropylar opening (MO) does not elevate above the chorion ( Figs 13–14 ).

Figures

FIGURES 9–11. Egg morphology of Ephemera (Ephemera) sachalinensis: 9, general shape; 10–11, micropyle in the complex extrachorion-adhesive layer. AL-Ex—complex adhesive-extrachorion layer; MO—micropylar opening; mp—micropyle; CM—canal micropylar; SG— sperm guide.

FIGURES 12–15. Egg morphology of Ephemera (Ephemera) sachalinensis: 12–13, egg surface without complex extrachorionadhesive layer; 14, proximal part of micropylar canal on chorion surface; 15, thickness on the layer forming the eggshell. AL-Ex—complex adhesive-extrachorion layer; CS—chorion surface; MO—micropylar opening; mp—micropyle.