Effect of microalgae diets on population performance and fatty acids composition of Apocyclops panamensis (Marsh, 1913) (Cyclopoida, Copepoda)

Abstract

The microalgae effect on population performance and fatty acid composition of Apocyclops panamensis was studied in two independent experiments (E), with starting densities of 4,000 (E1) and 8,000 nauplii L-1 (E2). In both experiments, copepods were fed once a day for 20 days in 0.4 L triplicates with a single-species diet containing Isochrysis galbana at 1 105 cells mL-1 day-1 (ISO), a two-species diet containing Nannochloropsis sp. at 1 105 cells mL-1 day-1 and I. galbana at 0.5 105 cells mL-1 day-1 (N + I), and a single-species diet containing Nannochloropsis sp. at 2 105 cells mL-1 day-1 (NAN). In E1, the highest final total animal density was reached with diet ISO (11,000 ind. L-1) and N + I (14,000 ind. L-1). In E2, the highest final densities were also found with ISO (8,000 ind. L-1) and N + I (6,000 ind. L-1). At day 20, 90 % of the copepods belonged to nauplii and copepodite stages, except for NAN in E2. In E1, the number of eggs per females was higher when the diet included I. galbana in both experiments. Thus, copepods fed with diets containing I. galbana had the best performance. Exclusive feeding with Nannochloropsis sp. yielded copepods with higher omega-6 fatty acids (n-6) percentage, while those fed with I. galbana had a higher omega 3 (n-3)/n-6 ratio. The docosahexaenoic acid (DHA) content and the DHA/EPA ratio were higher in copepods fed exclusively I. galbana. Our data indicate that I. galbana provides a suitable nutritional profile for A. panamensis with 0.5–1.0 105I. galbana cells mL-1 day-1, reaching high densities of 6,000–14,000 copepods L-1, a 1.8–2.6 % of DHA and a DHA/EPA ratio of 1.6–2.9. We conclude that A. panamensis has the potential for intensive cultivation and therefore is suitable as live feed for finfish larviculture requiring a fatty acid profile rich diet in omega-3 fatty acids and DHA.