Life Cycle Characteristics of the Deep-Burrowing Mud Shrimp Upogebia Major (Thalassinidea: Upogebiidae) on a Tidal Flat Along the Northern Coast of Tokyo Bay

Life cycle characteristics of the thalassinidean mud shrimp Upogebia major (de Haan), which is the deepest burrower among intertidal benthic animals in central Japan, were studied on a tidal flat along the northern coast of Tokyo Bay. Ovigerous females were observed from December to May. Females deposited eggs only once per breeding season, and eggs started hatching in March. Occurrence of the first zoea was observed in March and April, followed by benthic settlement in May. Growth over the first year was rapid, and females deposited their first eggs in the third breeding season, 31 months after their settlement. The data indicate that U. major has one of the longer immature periods among upogebiid shrimps. Adult shrimps live at least several years after maturation. Depth of the burrow increases with body length. The deep burrows of U. major provide refuge from predators and physical stress, allowing the shrimps to survive for a long time. The data from this study suggest that this species thus allocates more energy to rapid growth and adult survival than to quick reproduction.