Dimorphic sperm formation by Sex-lethal

Significance Sperm exhibit dramatic evolutionarily divergent morphologies in almost all taxa. Some sexually reproductive species show polymorphisms in the sperm produced by single males. Here, we focused on Sex-lethal ( Sxl ), which is the master sex-determination gene in Drosophila melanogaster , and investigated its function in the lepidopteran insect Bombyx mori . Our genetic analyses revealed that Sxl is essential for the formation of anucleate nonfertile parasperm. It is not expected that Sxl would be involved in sperm polymorphisms. Yet, whereas many morphological observations and ecological surveys have been conducted on sperm polymorphisms, this paper identifies the gene involved in sperm polymorphisms. Moreover, we clearly demonstrate that parasperm of B. mori is necessary for sperm migration in female organs.