Larval development of Balanus reticulatus Utinomi, 1967 (Cirripedia, Thoracica) and a comparison with other barnacle larvae

Abstract. The morphological features of the cephalic shield, labrum, abdominal process, antennules, antennae and mandibles of Balanus reticulatus are described and illustrated. The size and setation formulae of the larvae are given at each stage. The trilobed labrum and lateral margin of the cephalic shield with numerous small spines are diagnostic features for all the subsequent nauplius stages. Numerous small denticulate processes on the surface of the cyprid carapace are major morphological characteristics not found in other balanomorph species. We have constructed keys from stage II to stage VI for the predominant barnacle nauplii of Korean coastal waters, based on morphological traits such as total length, shield width, labrum shape, the presence or absence of posterior shield spines and dorsal shield spines in stages IV, V and VI, the specific setal type in the fourth segment of the antennal endopodite, and setation formulae of Pollicipes mitella, Chthamalus challengeri, Megabal-