Culturing Brachionus rotundiformis Tschugunoff (Rotifera) using dried foods: application of gamma-aminobutyric acid (GABA)

Abstract

This study investigated the population growth of the rotifer Brachionus rotundiformis (Stype) in batch cultures using dried Nannochloropsis oculata and Chlorella vulgaris with gamma-aminobutyric acid (GABA) supplementation. The effectiveness of GABA (50 mg l-1) was tested during the lag phase of rotifer growth and every 2 days in small cultures, at an initial density of 50 ind ml-1. In large cultures, 200 rotifers ml-1 were exposed to GABA for 24 and 48 h before upscaling to 20 l cultures. GABA enhanced rotifer population density and egg/female ratio in both foods compared to the control. Pre-GABA exposure for 48 h caused higher rotifer population densities on days 5 and 6 (with both foods) and 8 and 10 (with C. vulgaris), than their respective controls. Ammonia concentration increased equally in all of the treatments. Production of B. rotundiformis using dried N. oculata and C. vulgaris can be significantly enhanced by 48 h of pre-GABA exposure to reach maximum density within 6 and 8 days, respectively, despite high ammonia concentrations. These findings provide insight into mechanisms for maintaining continuous reproduction of rotifers in natural habitats by using GABA as a chemical signal to regulate their life cycle and overcome the potential effects of physiological stresses such as high ammonia.