Ephemera

Tiunova, Tatiana M., 2024, Egg morphology of six East Palaearctic species of the genus Ephemera Linnaeus (Ephemeroptera: Ephemeridae), Zootaxa 5497 (3), pp. 381-399 : 395

Key to six Ephemera species upon eggs

1. The egg size is 250 µm or more, and the surface of the chorion is smooth without or with a weakly expressed very fine reticulation ( Figs 27–28 ).................................................................... E. (S.) japonica

- The egg size is less than 250 µm; surface of the chorion with reticulation ( Figs 6 , 12 , 23 , 36 , 45 )...................... 2

2. Sperm guide well expressed ( Figs 2 , 9 , 16 , 27 , 39 )........................................................... 3

- Sperm guide absent ( Fig. 31–32 ).............................................................. E. (E.) shengmi

3. Sperm guide relatively deep ( Figs 2 , 9 , 16 )................................................................. 4

- Sperm guide is shallow and almost flat ( Figs 38–39 ).............................................. E. (E.) strigata

4. Sperm guide is relatively oval and short; the micropylar canal is 12–18 µm ( Figs 3–4 )................... E. (E.) orientalis

- Sperm guide an elongated, micropylar canal less than 10 µm ( Figs 10–11 , 18–19 ).................................. 5

5. Sperm guide is almost rectangular; the distal margin is weakly defined and almost open; the surface of the chorion is intermittently fractured ( Figs 10, 11 , 13 )............................................................... E. (E.) sachalinensis

- Sperm guide oval, with pointed, close distal margin; surface of the chorion with small-mesh reticulation ( Figs 18, 19 , 23 )...................................................................................... E. (E.) transbajkalica

Figures

FIGURES 27–30. Egg morphology of Ephemera (Sinephemera) japonica: 27–28, egg shapes; 29, micropyle in the complex extrachorion-adhesive layer; 30, proximal part of micropylar canal on chorion surface. AL—adhesive layer; CM—canal micropylar; MO—micropylar opening; CS—chorion surface; mp—micropyle; SG—sperm guide.

FIGURES 5–8. Egg morphology of Ephemera (Ephemera) orientalis: 5–6, egg surface without complex extrachorion-adhesive layer; 7, proximal part of micropylar canal on chorion surface; 8, thickness of the layer forming the eggshell. AL-Ex—complex adhesive-extrachorion layer; CS—chorion surface; MO—micropylar opening; mp—micropyle.

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.

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.

FIGURES 35–37. Egg morphology of Ephemera (Sinephemera) shengmi: 35–36, egg surface without complex extrachorionadhesive layer; 37, proximal part of micropylar canal on chorion surface. AL-Ex—complex adhesive-extrachorion layer; CS—chorion surface; MO—micropylar opening; mp—micropyle.

FIGURES 42–45. Egg morphology of Ephemera (Sinephemera) strigata: 42, remains of the adhesive layer on the egg surface; 43–44, proximal part of micropylar canal on chorion surface; 45, chorionic sculpturing. AL-Ex—complex adhesive-extrachorion layer; CS—chorion surface; CM—canal micropylar; MO—micropylar opening.

FIGURES 1–4. Egg morphology of Ephemera (Ephemera) orientalis: 1–2, general shape; 3–4, micropyle of the complex extrachorion-adhesive layer. CM—canal micropylar; MO—micropylar opening; mp—micropyle; SG—sperm guide.

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 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 38–41. Egg morphology of Ephemera (Sinephemera) strigata: 38–39, general shape and arrangement of the micropyles; 40, micropyle in the complex extrachorion-adhesive layer; 41, chorion thickness. AL-Ex—complex adhesive-extrachorion layer; C—chorion; CM—canal micropylar; MO—micropylar opening; SG—sperm guide.

FIGURES 31–34. Egg morphology of Ephemera (Sinephemera) shengmi: 31–32, general shape and arrangement of the micropyles; 33, proximal part of micropylar canal on chorion surface; 34, thickness on the layers forming the eggshell and chorion. AL-Ex—complex adhesive-extrachorion layer; AL—adhesive layer; C—chorion; MO—micropylar opening; mp—micropyle.