During spermatogenesis, unnecessary organelles and cytoplasmic components are shed from developing sperm in order to streamline them for optimal motility. These components are partitioned into structures known as ‘residual bodies’, which subsequently separate from the sperm and are lost. In the nematode worm C. elegans, this partitioning occurs immediately after the meiotic divisions, thus accelerating the process of sperm production. On p. 3253, Diane Shakes and colleagues exploit the interspecies diversity in spermatogenesis among nematodes to reveal how cellular components become partitioned. Focussing on the role of microtubules and actin, they characterise the process in C. elegans and in another nematode species, Rhabditis sp. SB347, and find important mechanistic variations between the two. In Rhabditis, which produces small spermatocytes, two rather than four sperm are generated during meiosis; the rest of the genetic material is partitioned into residual bodies. Interestingly, this mirrors oocyte production and resulting polar-body formation in females. These results provide insight into both the conserved and divergent mechanisms that underpin partitioning during spermatogenesis, and reveal how these segregation mechanisms can be modulated to achieve differences between species.
