Description of the naupliar stages of Megabalanus tintinnabulum (Cirripedia: Balanidae)

Abstract

Larval development of Megabalanus tintinnabulum was studied in the laboratory. At 26 ± 1°C the development from nauplius I-VI required about 4 days, when the diatom Chaetoceros wighami was used as food. Detailed morphological drawings and setation formulae of appendages of all 6 naupliar stages are presented for the first time. Notable features of the nauplii include the presence of a spinulated lateral margin, a trilobed labrum with teeth, long dorsal and posterior shield spines, a single tooth on the inner prong of the antennal gnathobase, comb-shaped cuspidate setae on the antennae, and spines and simple denticulate setae on the mandibular endopodite in naupliar stage II. The present description of the nauplii is not in lull agreement with the previous description of this species from this coast by Daniel (1958). Differences in stage sizes, naupliar morphology, and setation of appendages are used to distinguish this species from other megabalanines and the nauplii of megabalanines from those of balanines in the Balanus amphitrite group.