Crustaceans: Microbes and Defense Mechanisms

Abstract

Crustaceans are one of the most diverse arthropods that have successfully inhabited the aquatic ecosystems including freshwater, estuarine and marine. They have enormous benefits for the economy and human health and are of great significance to the aquaculture industry. Crustaceans are a rich source of protein and hence contribute to more than 70% of the world’s economy through aquaculture. These animals are prone to many pathogenic species of microbes, especially bacteria. Most of the bacterial diseases in crustaceans are due to pathogenic strains belonging to Vibrio spp. Pseudomonas spp. and Aeromonas spp. that are known to cause blackspot diseases, necrosis and other shell diseases. To combat such infectious pathogens, crustaceans have developed simple but strong innate defense strategies. These innate immune mechanisms are activated upon specific recognition of molecules such as lipopolysaccharides, glycoproteins, glycolipids and peptidoglycans present in the invading microbes. An array of immune components both cellular and humoral are involved in the crustacean effector defense processes including phagocytosis, antibacterial activity, encapsulation and agglutination. This chapter presents an overview of the microbes infecting the crustaceans, especially the decapods and focuses on the various defense mechanisms adopted by them.