Effect of culture density and antioxidants on naupliar production and gene expression of the cyclopoid copepod, Paracyclopina nana

Abstract

Although attempts have been made to use mass cultures of marine copepods as live foods in marine aquaculture, some limitations such as low density culture still exist. In the intensive culturing of copepods, crowding stress by increases in culture density can negatively affect their fecundity and development. The brackish water cyclopoid copepod, Paracyclopina nana has the potential for mass culturing as livefeed. The objective of present study was firstly to investigate the effect of culture density on naupliar production, and also to analyze the expression of several antioxidant-, stress-, and vitellogenesis-related genes in P. nana to assess the stress of crowding in high density cultures. Secondly, we investigated the effect on four widely known antioxidants at crowding stress of the copepod P. nana kept at high culture density.To investigate the effect of culture density, 200 adult females of P. nana with first egg sac were cultured at four densities of 1, 5, 10 and 20 individuals/mL. In addition, the effects of four antioxidants such as vitamin C (VC), vitamin E (VE), β-carotene (BC), and sodium selenite (SS) on P. nana were investigated in this study. Total RNA was isolated from the copepod and real time RT-PCR were carried out to find gene expression profiles in P. nana.The naupliar production of the copepod decreased with increasing culture density. The expression of gluta