ironmental factors such as temperature, salinity or pollutants, elements of such microbiota may invade and colonize the host and eventually lead to disease out breaks and mortality, especially in larvae, spat and juve niles of natural and farmed bivalves. Compared than to oyster and clams, no apparent mortality and fewer pathologies have been reported in mussels. It is more likely that Mytilus spp. are a reservoir of infective agents for aquatic organisms and humans, since, for instance, they tolerate significant amounts of V. alginoly ticus, V. parahemolyticus and other vibrios. In fact, comparative and advanced understanding of the early induced host responses may sustain and improve the aquaculture production in many coastal regions world wide.

Immunocompetent mollusc cells, at least the circulat ing hemocytes, and a variety of molecular effectors pro vide a rapid and robust line of defence against potential pathogens. Once activated by the interaction between pathogen associated molecular patterns and pathogen recognition receptors, such cells display chemotactic and chemokinetic reactions, participate in encapsulation and melanization, carry out phagocytic or lytic killing. These events are made possible by the con certed action of transmembrane and soluble lectins, Toll like and virus sensing receptors, hydrolytic enzymes and proteolytic reaction cascades, short lived cytotoxic by products and antimicrobial peptides.

According to morphological observations and flow cyto metry, bivalve hemocytes are heterogeneous and very dynamic cells of 7 10 um size which can be classified into large granulocytes most active in pha gocytosis and ROS production, large hyalinocytes with intermediate activity, small non phagocytic semigranular cells and the less abundant blast like hyali nocytes. As Mytilus hemocytes respond to inter leukin 1, tumour necrosis factor and to opioid peptides they may be part of an ancient monokine like network. Also rele vant to the use of mussels as biosensors of coastal pollu tion the interdependence of cell processes modulated by chemical contaminants and infective agents requires additional study. The sequence data available for bivalve species are slowly but steadily growing, especially through EST col lections. A set of 1,714 cDNA probes of M.

gal loprovincialis was arranged to investigate the transcriptional signatures of pollutants but more work has subsequently been devoted to EST sequencing, also using technologies which provide very large amounts of short reads more difficult to annotate. Carfilzomib A double set of 5 and 3 ESTs of M. californianus, 42,354 in total, was used to investigate the influence of the tidal cycle on mussel physiology. As a result of laboratory treatments performed with environmental pollutants, bacterial antigens and viral like polynucleo tides, 18,788 high quality ESTs of M. galloprovincialis are now organized in a structured collection of 7,112 transcript sequences, named sellckchem Mytibase and includ ing most of the