Inside the mouths of beroid ctenophores, macrocilia are present and essential for feeding.

Each macrocillium contains multiple axonemes that are surrounded by a common membrane with a distinct capping structure at the distal tip.

The cap structure consists of extensions of axonemal microtubules that are embedded in an electron dense matrix to form pointed projections or "teeth".

During the beat cycle of macrocilia, these teeth shift from a straight to hooked configuration which is thought to aid ingestion and break up prey.

These macrocilia are diverse amongst Beroe families and can be used to identify ctenophores by way of morphological differences.