Fig. 1. Larvae are a common feature of Metazoa.

(A) A phylogeny of animals shows the widespread presence of ciliated larvae, especially among the superphylum Lophotrochozoa (Loph.). Black dots, character presence; white dots, absence; gray dots, unconfirmed. (B and C) Schematics of larvae presented in this study, (B) in blue box the trochophore larva of the Pacific oyster Crassostrea gigas, represented as both ventral (V) and lateral (L) views. C. gigas larvae at the trochophore stage lack an apical tuft of sensory cilia and paired protonephridia. (C) In yellow, schematics of the Müller’s larva of the polyclad flatworm Prostheceraeus crozieri depicted as ventral and lateral views.