Why does Cyclestheria skip the usual larval stages?

The spinicaudate branchiopod Cyclestheria skips the usual larval stages because it develops its eggs within the space between its trunk and carapace, where they grow rapidly into miniatures of the adult form.1

While many crustaceans, including most branchiopods, typically emerge from the egg as a nauplius larva—a simple, unsegmented form with three pairs of appendages—this direct development allows Cyclestheria to bypass the free-living larval phase entirely. This mode of reproduction, which results in the hatching of fully formed juvenile miniatures, is also observed in other branchiopod groups such as ctenopods, anomopods, and onychopods.21