REPRODUCTION

Barnacles must mate.  The long penis transfers sperm  from one individual to another.  Barnacles are both male and female therefore improving the chances for successful mating.  The fertilized eggs develop in a special cavity.  During the spring and summer, Balanus glandula produces two to six broods.  From 1000 to 30,000 nauplius larvae are produced in each brood.

LIFECYLE

Barnacles do not spend their entire lives as the shelled animal you see on rocks and pilings.  The microscopic nauplius larvae swim and drift through the water.   After a few weeks they change their form to look something like a miniature clam.  This cyprid larva attaches on or near adult barnacles and again changes its form to eventually look like the barnacles we recognize.

Copulating barnacles

Barnacle life cycle