Biotechnology and aquaculture of rotifers

Biotechnology can be defined as any technology that involves living organisms or their derivatives. In applying this definition to rotifers, we focus on their contribution in culturing of early larval stages of marine fish. After almost four decades of marine fish culture in captivity, the success of this worldwide industry is still quite dependent on mass culture of the species Brachionus plicatilis and B. rotundiformis. In mass culture, the rotifers are continuously driven to reproduce at high rates, in relatively extreme environmental conditions of high population density and high loads of organic matter. Therefore, the success of mass cultures and future improvements in these systems relies on a close interaction between basic and applied studies of rotifers. In the present review, we will attempt to analyze why rotifers are suitable for early life stages of fish and to describe, in general, methodologies that have been devised for reliable supply of rotifers in large quantities. Problems associated with rotifer production, nutritional quality and effect on fish health and nutrition, will be discussed. Research on B. plicatilis and B. rotundiformis has increased enormously during the past three decades and these two species are the best-studied rotifers so far. While much of the research on these species is directed or devoted to the needs of aquaculture industry, they are also used as models for addressing basic biological questions, due to the relative ease of culture and their availability. Studies on feeding, pheromones, speciation in rotifers, the occurrence and putative hormones involved in sexual and asexual reproduction and production of resting eggs, are few examples of such studies. Rotifers will probably maintain their role as food organism for fish larvae, in spite of attempts to replace them with more accessible formulated food. Development of new culture methods that will improve the nutritional quality and production efficiency of rotifers may result in more diversified and flexible tasks for these organisms in aquaculture.