Aquaculture Reports (Nov 2021)
A bioenergetic approach for a novel aquaculture species, the giant barnacle Austromegabalanus psittacus (Molina, 1788): Effects of microalgal diets on larval development and metabolism
Abstract
Acorn barnacle aquaculture is a new activity based on species that possess potential due to several production advantages (e.g., no selective filters and rapid growth at very high densities). Extensive cultures have been developed in Chile and Portugal, but its settler (early juvenile) supply shows a high seasonal variability, which promotes the development of settler supplies from hatchery production. The effect of culture conditions on naupliar stages, cyprid and newly metamorphosed juvenile are key for hatchery production. Using the giant barnacle Austromegabalanus psittacus as model, we examined the effects of microalgae diets (Isochrysis galbana, Chaetoceros gracilis and a Mix 1:1 ratio) and concentration (2 × 105, 4 × 105 and 6 × 105 cells mL−1) on developmental time, mortality and metabolism (oxygen consumption, ammonia excretion and O:N ratio) from naupliar stages (NII-NVI) to cyprid stage. A bioenergetic approach was suggested to quantify how culture conditions influenced net growth efficiency for naupliar stages, as well as energy losses from cyprid and to newly metamorphosed juvenile. Nauplii fed with I. galbana did not fully complete naupliar stages, reaching a 100 % mortality at NIV stage. Overall, the shortest larval development time was observed at C. gracilis/2 × 105 cells mL−1 treatment along naupliar stages. The highest cyprid mortality was found in larvae fed during their development as nauplius with mixed diet at 2 × 105 cells mL−1. No differences in respiration and ammonia excretion rates between the treatments of each larval stage were found, with exception of cyprid from mix/2 × 105 cells mL−1. The highest dry weight of the cyprid and highest lipid content was obtained in C. gracilis/6 × 105 cells mL−1. The energy content provided by lipids and proteins for cyprid was significantly affected by diet and concentration. Outcomes from this study demonstrated that microalgae type and concentration have an important influence on larval development, survival and energy accumulation in A. psittacus.
