Larval development of a warm-water immigrant barnacle, Solidobalanus fallax (Cirripedia : Archaeobalanidae) reared in the laboratory

In 1994 a warm-water barnacle Solidobalanus fallax was recorded for the fir st time in the UK (Southward, 1995). The naupliar development of this immig rant species is now described, from larvae reared in the laboratory. The pl anktotrophic nauplii of S. fallax reached the cyprid stage 8d after hatchin g, at 25 degrees C. Larval development includes six naupliar and one cyprid stage, following the typical pattern of the thoracican Cirripedia. Nauplia r stages have a broad rounded convex cephalic shield without dorsal and mar ginal spines. Nauplii have a trilobed labrum with the small teeth found in other warm-water species. The abdominal process becomes nearly equal to the dorsal thoracic spine in stage VI. The arrangement of abdominal spines and larval setation are in the usual balanoid pattern. The significant differe nce of the S.fallax larvae from those of the related temperate-water archae obalanid species Hesperibalanus hesperius supports the classification of th ese species into separate genera.