Effects of temperature and microalgal diet on the fecundity, population growth and fatty acid composition of Pseudodiaptomus ishigakiensis (Calanoid, Copepoda)

Abstract

This study aims to investigate the optimal culture conditions of the marine calanoid copepod Pseudodiaptomus ishigakiensis, which is considered emerging live feed for marine larviculture. The effects of temperatures (20 °C, 25 °C, 30 °C and 35 °C) and microalgal diets Isochrysis galbana (ISO), Proteomonas sulcata (PRO), Chlorella sp. (CHL) and Tetraselmis chuii (TET) on the fecundity, population growth rate, composition of developmental stages and fatty acid composition of P. ishigakiensis were evaluated. The highest population growth rate (60.6 ± 4.9 ind./day) was found at 30 °C with the significantly-highest number of naupliar individuals (726.7 ± 30.6 ind.) and a high level of fecundity (14.4 ± 0.7 eggs/female). Whereas the lowest population growth was found at 35 °C (0.4 ± 0.2 ind./day). In the diet experiment, the population growth rate (73.8 ± 1.9 ind./day) was the highest in the PRO treatment with a great number of naupliar individuals (912.50 ± 24.7 ind.) and fecundity (13.4 ± 0.6 eggs/female). Both TET and CHL treatments showed the lowest population growth (0.5 ± 0.1 ind./day and 0.2 ± 0.1 ind./day, respectively) and absence of ovigerous female at the end of experiment, which indicated their unsuitability as feeds for P. ishigakiensis. Fatty acid compositions of copepods were affected by the fatty acid content of their microalgal diets. The copepods fed on ISO and PRO contained higher levels of eicosapentaenoic acid (EPA, C20:5 n-3; 4.51 ± 1.29–5.42 ± 0.64%) and docosahexaenoic acid (DHA, C22:6 n-3; 4.00 ± 0.34–5.92 ± 1.28%) composition compared to CHL and TET (EPA: 0.48 ± 0.15–2.65 ± 1.27%; DHA: 1.68 ± 0.26–1.89 ± 0.14%). This study revealed the optimal culture conditions and nutritional value of the copepod P. ishigakiensis, which provides implications for the managements of their mass culture, and utilization in marine larviculture.