[
International Worm Meeting,
2021]
C. inopinata is the closest species to C. elegans, but these two species have various morphological and ecological differences. Notably, C. inopinata is nearly twice as long as C. elegans, while its embryonic size is ~20% longer. In this study, we compared the cellular dynamics of C. inopinata and C. elegans zygotes. To visualize chromosomes and cell membrane, C. inopinata strains that express GFP::histone and GFP::PH (Pleckstrin-Homology) domain were constructed by the microparticle bombardment and cellular behaviors in zygotes of the two strains were analyzed by DIC and fluorescent live imaging. We found differences between the two species in 1) the position of the polar bodies and pronuclei formation, 2) the position of pronuclear meeting and metaphase plate formation, and 3) the mitotic spindle oscillation. While polar bodies in C. elegans almost always form in the anterior end of the embryo, those in C. inopinata appeared at random positions. In C. elegans zygotes, the female and male pronuclei formed in the anterior and posterior end, respectively, migrate to the center to meet; in C. inopinata zygotes, the pronuclei appeared at random positions, and the position of pronuclear meeting and metaphase plate formation was more posterior than in C. elegans. While the mitotic spindle of most Caenorhabditis nematodes, including C. elegans, oscillates during anaphase, that in C. inopinata did not. The mitotic spindle in C. inopinata was formed at a skewed angle, then gradually rotated to a horizontal position. Despite the differences in the location of the pronuclear meeting and metaphase plates, the relative position of the cleavage furrow was equivalent to each other. Thus, some microtubule-dependent aspects of cellular dynamics of C. inopinata zygotes were different from those in C. elegans.