Larval development and metamorphosis in Balanus amphitrite Darwin (Cirripedia; Thoracica): significance of food concentration, temperature and nucleic acids

The influence of food concentration (Chaetoceros calcitrans at 1 x 10(5) an d 2 x 10(5) cells ml(-1)) and temperature (20 degreesC and 30 degreesC) on the nucleic acid content of the nauplii and the cyprids of Balanus amphitri te, an acorn barnacle, was evaluated, Food concentration and temperature jo intly determined the naupliar instar duration. The total naupliar developme nt period lasted 9-11 days at 20 degreesC and was longer when compared to 5 -6 days observed at 30 degreesC. Increase in rearing temperature and food c oncentration positively influenced the size of the larvae. Food concentrati on influenced the DNA of III and VI naupliar instars and temperature influe nced the DNA of I-V and V instar nauplii. The RNA content of IV-VI naupliar instars was also influenced by the rearing temperature. Naupliar experienc e determined cyprid metamorphosis capability. The RNA content of larvae, th at had longer total naupliar duration at 20 degreesC, was considerably less than those raised at 30 degreesC. This difference in RNA content was refle cted in the capability of the cyprids to survive at 5 degreesC. The resulta nt cyprids at 20 degreesC could only successfully metamorphose over 2-4 day s, whereas, those at 30 degreesC could do so over 8-16 days. Such differenc es in the capability to metamorphose will be of critical importance to recr uitment and early post-settlement mortality. (C) 2001 Elsevier Science B.V. All rights reserved.