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26 July 2022 Developmental Staging of Sexual Egg Formation in Daphnia pulex: Unmated Females Resorb Meiotic Oocytes to Resist Starvation
Yugo Takahata, Hitoshi Miyakawa
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Abstract

Under favorable conditions, daphnids produce only female neonates by parthenogenesis, while they produce male neonates and start sexual reproduction when they detect cues signaling a deteriorating environment. Identifying the regulatory mechanisms of such cyclical parthenogenesis is important for understanding how organisms adapt to environments and expand their habitats. However, most previous studies using the model species Daphnia magna and Daphnia pulex have focused on production of male offspring (sex determination), whereas the process of meiosis induction in females has not been investigated. Here, we report a simple experimental method to induce meiosis effectively in D. pulex females. Through observations using the new method, we describe the process of sexual reproduction along an individual developmental time course. Meiotic oocytes are oviposited only when females mate within a certain time window, and failure to mate within that window results in subsequent resorption of oocytes, a measure that may increase resistance to starvation. These results further our understanding of regulatory mechanisms and evolutionary processes in the complicated life-history of Daphnia.

© 2022 Zoological Society of Japan 1
Yugo Takahata and Hitoshi Miyakawa "Developmental Staging of Sexual Egg Formation in Daphnia pulex: Unmated Females Resorb Meiotic Oocytes to Resist Starvation," Zoological Science 39(5), 407-412, (26 July 2022). https://doi.org/10.2108/zs220010
Received: 31 January 2022; Accepted: 18 May 2022; Published: 26 July 2022
KEYWORDS
alteration of reproductive strategies
Cyclical parthenogenesis
Daphnia
post-copulatory oviposition
resistance to starvation
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