In addition to xenobiotic assaults, cultured bivalve mollusks (mussels and
oysters) and crustacean arthropods (Penaeid shrimps) are continuously confr
onted with infectious microorganisms. The deadly effect of infections are m
ost probably underestimated as the diseased animals rapidly vanish in natur
e, and only in aquacultural farms are mortalities reported as causing econo
mical breakdowns. To fight severe epizootic infections and to stabilize pro
duction, we have to simultaneously extend our knowledge on their immune def
ense systems and develop multiple strategies for promoting disease resistan
ce. The presence of macrophage-like phagocytes and several morphologically
distinguishable circulating hemocyte types have been reported as well as so
me humoral activities. More recently, activities related to vertebrate inna
te immunity have also been described, including inflammatory processes and
the generation of radical oxygen intermediates (ROIs) and nitric oxide (NO)
, cytotoxic proteins and several families of antimicrobial peptides. Concer
ning the strategies to increase disease resistance, immunodiagnostic techni
ques for early detection of the pathogens are under development using molec
ular probes and antibodies. As not all individuals within a species suffer
from certain diseases, programs of genetic selection have been instituted.
Finally, genetic engineering have been employed to characterize immune gene
regulation mechanisms that might be used for transgenesis or as selection
criteria. (C) 1999 Elsevier Science B.V. All rights reserved.