在有利的条件下，大型溞会进行孤雌生殖，以在短时间内增加后代产量。然而，在不利的条件下，水蚤会进行有性繁殖并产生休眠卵。在这里，我们报告了对大型溞产卵过程的实时观察。我们观察到，在产卵过程中，细胞内容物不规则地流过狭窄的卵管。无定形卵巢卵在产卵后立即形成椭圆形，最终形成圆形。休眠卵的产卵以类似的方式发生。根据观察结果，我们提出，与果蝇卵不同，水蚤卵在产卵过程中无法保持细胞质的完整性。我们还确定孤雌卵在 20 分钟内被激活，如卵黄膜形成所证明的那样。因此，大型溞的卵可能在产卵过程中受到挤压压力而被激活，这是合理的。

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Live observation of the oviposition process in Daphnia magna

In favorable conditions, Daphnia magna undergoes parthenogenesis to increase progeny production in a short time. However, in unfavorable conditions, Daphnia undergoes sexual reproduction instead and produces resting eggs. Here, we report live observations of the oviposition process in Daphnia magna. We observed that the cellular contents flowed irregularly through the narrow egg canal during oviposition. Amorphous ovarian eggs developed an oval shape immediately after oviposition and, eventually, a round shape. Oviposition of resting eggs occurred in a similar way. Based on the observations, we propose that, unlike Drosophila eggs, Daphnia eggs cannot maintain cytoplasmic integrity during oviposition. We also determined that the parthenogenetic eggs were activated within 20 min, as demonstrated by vitelline envelope formation. Therefore, it is plausible that the eggs of Daphnia magna may be activated by squeezing pressure during oviposition.