Development time of male and female rotifers with sexual size dimorphism
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Dwarfism in males is a common phenomenon in planktonic monogonont rotifers. Considering the small body size of males, some studies suggested that the development time of male rotifers is faster than that of females. However, empirical studies associated with such a speculation are scarce. In this study, we used two common rotifer species, Brachionus calyciflorus and Brachionus plicatilis (each with two geographical populations), to test the hypothesis that the development time of dwarf males is significantly shorter than that of females. Results showed that male eggs (embryos) were deposited much faster than female eggs (embryos) in both Brachionus species. However, the embryonic development time of these small male eggs (embryos) was longer than that of large female eggs (embryos). As a result, males needed significantly longer total development time than females. The total development time of males was 2–3 h longer than that of females in both Brachionus species. Male-producing and female-producing females in the two Brachionus species did not show any difference in development time. Because sexual reproduction begins at high population densities in both species, postponement of development in males will be advantageous by decreasing mating costs in male rotifers.
KeywordsCost of sex Dwarf male Haploid Mictic female Sexual reproduction
We thank several anonymous reviewers for constructive comments that improve our manuscript greatly. We also thank Booth M.J. for linguistic improvements. This study was supported by the National Natural Science Foundation of China (31000218; 41206110), the Program for Liaoning Excellent Talents in University (LR2015009), and the Natural Science Foundation of Dalian (2012J21DW013).
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