Development of oral and branchial muscles in lancelet larvae of Branchiostoma japonicum

Cover illustration . Four larval stages of Branchiostoma japonicum in phase contrast microscopy. In this issue of the Journal of Morphology, Yasui and coauthors (pp. 465–477 ) analyze the dynamic remodeling of pharynx of Branchiostoma japonicum during metamorphosis. They show that the lancelet orobranchial musculature is apparently a larval adaptation to prevent harmful intake. However, vestigial muscles appeared transiently with the secondary gill formation suggesting a bilateral ancestral state of muscular gills, and a segmental pattern of developing branchial muscles without neural crest and placodal contributions is suggestive of a precursor of vertebrate branchiomeric pattern.