Abstract Eukaryotes have evolved towards one of two extremes along a spectrum of strategies for remodelling the nuclear envelope (NE) during cell division: disassembling the NE in an open mitosis or constructing an intranuclear spindle in a closed mitosis. Both classes of mitotic remodelling involve key differences in the core division machinery, but the evolutionary reasons for adopting a specific mechanism are unclear. Here, we use an integrated comparative genomics and ultrastructural imaging approach to investigate mitotic strategies in Ichthyosporea, close relatives of animals and fungi. We show that species within this clade have diverged towards either a fungal-like closed or an animal-like open mitosis, most likely to support distinct multi- or uninucleated states. Our results suggest that multinucleated life cycles favour the evolution of closed mitosis. One-Sentence Summary Mitotic specialization in animal relatives reveal that multinucleated life cycles favor the evolution of closed mitosis

Life cycle-coupled evolution of mitosis in close relatives of animals