Morphology of the nervous system of the barnacle cypris larva (Balanus amphitrite Darwin) revealed by light and electron microscopy

The central nervous system of the cypris larva of Balanus amphitrite consis ts of a brain and posterior ganglion. The neuropil of the brain includes pr otocerebral and deutocerebral divisions, with nerve roots from the protocer ebrum extending to the eyes and frontal filaments, and nerve roots from the deutocerebrum extending to the first antennae (antennules) and cement glan ds. The neuropil of the posterior ganglion includes subesophageal and thora cic divisions, with nerve roots from subesophageal divisions extending to t he gut, and nerve roots from each of the six thoracic divisions extending t o their corresponding thoracic appendage. The antennular nerve is the major peripheral extension of the nervous system and is composed in part by effe rent fibers that innervate setae on the antennules. The cyprid nervous syst em is small, containing fewer than 2000 neurons, but is well organized for coordinating a response to settlement cues.