In planktotrophic species, the larvae develop from small eggs with a limited
yolk reserve, and therefore must supplement their nutrition by feeding on
phytoplankton during their planktonic stage in order to reach metamorphosis
into the adult form.

Lecithotrophic species have large eggs with a yolk supply sufficient to
nourish the larva through its metamorphisis, so the larval forms do not have
to feed.

Paul M.