Is there any kind of adaptive immunity in invertebrates?

A time-course study on the resistance of Penaeus japonicus induced by artificial infection with white spot syndrome virus

“…However, it remains to be clarified if these results can be explained by the existence of an adaptive secondary immune response in invertebrates homologous to that observed in vertebrates or to a distinct type of immunoprotective pathway [27]. It is generally accepted that enhanced protection against bacterial pathogens is induced not through specific immune response by antigens but through non-specific immune responses by bacterin as an immunostimulant [28].…”

Fenneropenaeus indicus is protected from white spot disease by oral administration of inactivated white spot syndrome virus

“…has been reported (Itami et al 1989, Teunissen et al 1998. The mechanism of protection remains unexplained and may be an adaptive secondary immune response, homologous to that observed in vertebrates, or a distinct crustacean type of immunoprotective pathway (Arala-Chaves & Sequeira 2000). The presence of bactericidins in P. monodon hemolymph after exposure to heat-killed V. alginolyticus has been reported (Adams 1991) and would seem to demonstrate some type of immune memory (Teunissen et al 1998).…”

A syntenin-like protein with postsynaptic density protein (PDZ) domains produced by black tiger shrimp Penaeus monodon in response to white spot syndrome virus infection

“…Despite the importance of these viral diseases, there is little knowledge of the nature of the interaction between shrimp, or crustaceans in general, and viral pathogens (Flegel 2001). To address this lack of knowledge, there is increasing interest in the cellular and humoral responses of shrimp, especially with respect to identification and characterization of immune effectors (Söderhäll & Cerenius 1992, 2000, Holmblad et al 1999, Roch 1999, Arala-Chaves & Sequeira 2000, Johanson et al 2000, Vargas-Albores & Yepiz-Plascencia 2000. It is expected that basic research on immune processes will lead to a better understanding of the immune response and provide for improved strategies of disease prevention, including genetic selection of disease-resistant animals from domesticated stocks.…”