Leptostracans: Phyllocarida

Adult males sometimes swim long distances in search of mates using the first four pairs of pleopods. Young individuals and adult females rest on the bottom for hours. Their leaflike limbs beat rhythmically to move oxygen-carrying water through the carapace. In captivity leptostracans burrow in mud and often remain motionless. Inactivity and slow heartbeat allow them to live in environments with very little oxygen.

The eggs of most leptostracans are thought to be carried in a special chamber located beneath the carapace. The young develop within the eggs. They hatch resembling adults, but are distinguished by having a small fourth pair of pleopods. Water temperature has a tremendous influence on growth rates of immature leptostracans. Males develop gradually as they molt, or shed their external skeletons. Females continue to resemble immature leptostracans until they are ready to reproduce.