Little is known about the development of the atypical protonymphon larva. The adults are free living, while the larvae and the juveniles are living on or inside temporary hosts such as polychaetes and clams. When the attaching larva hatches it still looks like an embryo, and immediately attaches itself to the ous legs of the father, where it will stay until it has turned into a small and young juvenile with two or three pairs of walking legs ready for a free-living existence.