Larval development of Capitulum mitella (Cirripedia: Pedunculata) reared in the laboratory

Abstract

Larval development of Capitulum mitella (Cirripedia: Pedunculata) comprises six nauplius stages and a cyprid. Unilobed labrum, a larval trait of pedunculate and chthamalid barnacles, bears two groups of slender hairs and two pairs of strong teeth on the distal labral margin, and a pair of teeth on the lateral labral margin. Frontolateral horns extended under the anterior cephalic shield margin are diagnostic features through all nauplius stages. The posterior border of the cephalic shield bears a pair of distal cephalic shield spines in nauplius stages II and III, and a pair of long posterior shield spines in nauplius stages IV, V and VI. A hispid seta is consistently found at the fourth group of the antennal endopodite through stages II–VI. The dorsal thoracic spine, abdominal process and the paired posterior shield spines have numerous small spines. Morphological features such as the cephalic shield, labrum, abdominal process, antennules, antennae and mandibles in all nauplius and cyprid stages are illustrated and described. In this species, the numerical setations of the antennule are found to be beneficial for intra-specific identification of barnacle nauplius stages without the need for dissection.