Larval rearing of the giant Azorean barnacle, Megabalanus azoricus (Pilsbry, 1916): feeding trials, larval development and settlement on artificial substrata

A series of experiments were conducted to obtain an efficient larval rearing protocol for Megabalanus azoricus. The first part of this study investigates the effect of microalgae-based diets on survival and larval development. Mono and mixed-diets were tested at 20 +/- 1 degrees C, in a sequence of 11-day feeding experiments. The second part presents a preliminary study on the influence of a biofilm on recruitment and use of oyster spat collectors in a mass rearing system. A photographic record of larval development and a brief reference to the diagnostic features that enable quick larval staging are also presented, along with morphometric measurements. Of the microalgae tested (Chaetoceros sp., Chloromonas sp., Dunaliella sp., T-Isochrysis sp. and Skeletonema sp.) the mixed-diet Skeletonema sp. with T-Isocrysis sp. showed the highest survival percentages: total survival ranged from 79.7 to 85.7% and 69.7-80.0% of nauplii were in stage VI after 11 days of rearing. Cypris were also present, but only represented 5.3% of the survivors at most. In the mass rearing system juveniles were found settled in the collectors after 25 days, at 20 +/- 1 degrees C. However recruitment was less than 1%. Preliminary results showed no settlement preference towards collectors with biofilm. Nevertheless, this study provides the first record of M. azoricus settlement under laboratorial conditions and represent a starting point for future larval rearing studies.