Full text loading...
Zoological Science
Abstract
The freshwater crustacean genus Daphnia has been used extensively in ecological, developmental and ecotoxicological studies. Daphnids produce only female offspring by parthenogenesis under favorable conditions, but in response to various unfavorable conditions and external stimuli, they produce male offspring. Although we reported that exogenous exposure to juvenile hormones and their analogs can induce male offspring even under female-producing conditions, we recently established a male induction system in the Daphnia pulex WTN6 strain simply by changing day-length. This male and female induction system is suitable for understanding the innate mechanisms of sexual dimorphic development in daphnids. Embryogenesis has been described as a normal plate (developmental staging) in various daphnid species; however, all studies have mainly focused on female development. Here, we describe the developmental staging of both sexes during embryogenesis in two representative daphnids, D. pulex and D. magna, based on microscopic time-course observations. Our findings provide the first detailed insights into male embryogenesis in both species, and contribute to the elucidation of the mechanisms underlying sexual differentiation in daphnids.
We would like to thank Dr. Eiji Watanabe, Department of Neurobiology, Laboratory of Neurophysiology, National Institute for Basic Biology, Aichi, Japan, for providing an incubator. We thank members of the iguchi laboratory for helpful advice and discussion. This work was supported by a JSPS Research Fellowship for Young Scientists to KT (No. 12J05579), CH (No. 12J04065), JSPS KAKENHI Grant Number 26840115 to CH, 24370029, 24657022 and 15H04396 to TI, the Ministry of the Environment of Japan (TI), Collaborative Research Project organized by the Interuniversity Bio-Backup Project (IBBP) to TI, and a grant from the National Institute for Basic Biology (TI). Our work benefits from, and contributes to, the Daphnia Genomics Consortium.
Data & Media loading...