Over 95% of animal species are invertebrates, whose immune systems are extremely diverse and have evolved to be very efficient in protecting the animals from pathogens. Unlike vertebrates that arm themselves with both innate and adaptive immune systems, invertebrates have to rely on innate immunity that, although well developed, is also well developed and sophisticated. Humoral and cellular responses of immune systems are broadly classified into broad ways of detecting and eliminating pathogens. Immune mechanisms in invertebrates are very important in the recognition of pathogens and the initiation of appropriate responses and mainly consist of the detection of pathogen-associated molecular patterns (PAMPs). Pattern recognition receptors (PRRs) such as these PAMPs will trigger immune signaling pathways and set in motion various defense mechanisms (Imler & Bulet, 2005; Medzhitov, 2007). Invertebrate immune response plays an important role in their survival in different environments and reveals a more comprehensive understanding of the evolution of immune systems among animals.