Location of micropyles and early embryonic development of the two-spotted cricket Gryllus bimaculatus (Insecta, Orthoptera)
Article first published online: 15 MAR 2005
Development, Growth & Differentiation
Volume 47, Issue 2, pages 99–108, February 2005
How to Cite
Sarashina, I., Mito, T., Saito, M., Uneme, H., Miyawaki, K., Shinmyo, Y., Ohuchi, H. and Noji, S. (2005), Location of micropyles and early embryonic development of the two-spotted cricket Gryllus bimaculatus (Insecta, Orthoptera). Development, Growth & Differentiation, 47: 99–108. doi: 10.1111/j.1440-169x.2005.00786.x
- Issue published online: 15 MAR 2005
- Article first published online: 15 MAR 2005
- Received 29 July 2004; revised 8 December 2004; accepted 23 December 2004.
- germ primordium;
- Gryllus bimaculatus;
Early embryogenesis of the two-spotted cricket Gryllus bimaculatus was examined by scanning electron microscopy and several fluorescence staining methods, with special reference to these four issues: (i) the location of micropyles; (ii) the transfer of the female pronucleus following meiosis; (iii) the timing of cellularization; and (iv) the process of the germ primordium formation. Between two and four micropyles lie in the mid-ventral region of the egg. The egg nucleus is at the mid-dorsal periphery of the new laid egg, and meiosis resumes and is completed there. The female pronucleus moves to the mid-ventral side, and fertilization occurs there. Energid starts to proliferate and migrates to the periphery of the egg, initiating blastoderm formation. Actin caps surround each superficial nucleus. Cellularization occurs during the blastoderm stage. At a late blastoderm stage, nuclei aggregate in both the posterolateral patch-like regions of the egg to form a germ primordium. The germ primordium looks like a pair of dumbbells. Both the patches shift towards the ventral side and fuse into a germ primordium. The germ primordium contracts to produce a clearly delineated germ band. Observations on distribution patterns of F-actin indicate that, all through the process, the germ primordium retains that unity, and is not separated into two parts.