The Immune System of Shrimp

Introduction Penaeid shrimp aquaculture is an important economic activity worldwide. Nevertheless, shrimp production has been seriously affected by diseases, mostly those caused by viruses (Flegel, 2006) and Vibrio bacteria (Bachère, 2000). Shrimp resistance to invading organisms is strongly influenced by its immune status. The defense mechanisms of crustaceans is less developed than that in finfish and other vertebrates (Figure 1). More specifically, crustaceans have no adaptive memory. In other words, they do not have the ability of producing immunoglobulins, so that they apparently depend only on innate defense systems (Roch, 1999). Understanding shrimp defense mechanisms in combination with different strategies can contribute to improve disease management. In fact, several different methods exist to learn about the health/disease status of these animals, including the evaluation of immune/physiological parameters such as hemolymph protein concentration, total hemocyte counts, phenoloxidase activity, free radical production, phagocytic activity, and field variables including stress tests, survival, and growth rates, which can be used as shrimp health status indicators (Rodríguez y Le Moullac, 2000). The purpose of this bulletin is to review some major defense mechanisms of shrimp.