Changes in carotenoid composition in different developmental stages of copepods: Pseudocalanus acuspes Giesbrecht and Acartia spp.

Abstract

Carotenoid contents and composition were studied in three successive developmental groups of copepod populations from the southern Baltic Sea. Samples were collected with >80% prevalence of any one of three developmental groups: (i) nauplii, (ii) copepodids I-III and (iii) copepodids IV-V and also adults of Pseudocalanus acuspes Giesbrecht and Acartia spp. (Copepoda: Calanoida). Samples were collected over the years 1991-1999 from May to September at six sampling sites in the southern Baltic Sea. The carotenoids were analysed by means of reverse-phase high-performance liquid chromatography (RP-HPLC). The mean total carotenoid concentrations (astaxanthin, astaxanthin esters, canthaxanthin and other carotenoid unidentified and derived from the diet) found in three groups of developmental stages for P. acuspes were 556 μg g -1 dry weight (d.w.) in naupliar stages, 791 μg g -1 in copepodids I-III, and 868 μg g -1 in copepodids IV-V and adults. The average carotenoid concentrations in Acartia spp. were 619, 764 and 872 μg g -1 d.w., respectively. Significant changes were observed in the proportion of carotenoids of separate developmental groups. Astaxanthin and canthaxanthin occurred in all developmental groups, with the evident dominance of astaxanthin. However, copepodid groups I-III and especially IV-V including adults, showed an increased proportion of astaxanthin esters. This suggests that astaxanthin is the main active carotenoid in copepod metabolism. It acts most probably as an efficient free radical quencher and may be involved in rapid metabolism of stored lipids in mostly unfeeding young nauplii. The feeding stages (late nauplii and copepodids I-III and IV-V) are evidently able to metabolize this pigment by esterfication and further degradation.