ANALISI ISTOPATOLOGICA E BIOMOLECOLARE DELLA WINTER DISEASE in SPARUS AURATA

Gilthead sea bream Sparus aurata is one of the most important fish reared in coastal lagoon with ”valliculture” in the Mediterranean area. During cold periods it is affected by a metabolic syndrome termed “Winter disease” which causes a mortality rate reaching, in some cases, 60% in the North of Italy.An experiment was conduct to analyse the adaptative response to low temperatures using three kind of analysis techniques. This experimental trial was based on a case-control scheme. Seabreams were divided into two main groups: seabreams in the “case” tank were exposed to low temperature, whereas for those in the “control” tank temperature was constantly warm. Tissue samplings were carried out through acute and chronic phase. A first analysis with Microarray technology was performed to reveal the differences of gene expression between fish reared at low temperature and controls. Secondly was performed Real-Time RT-PCR to validate Microarray results and evaluate the differences of gene expression during the experiment. Lastly were evaluate histological analysis of the skin and the cephalic kidney samples during the experimental protocol, and other tissues such as gill, liver, spleen and kidney were collected and analysed after a recovery phase at the end of the experiment. Biomolecular analysis demonstrates that there is an up-regulation of genes belonging to pathways such as energetic metabolism and lipid metabolism in liver and a down-regulation of genes belonging to immunitary response. In gills up-regulated genes belong to very different pathways involved in apoptosis, ROS scavenger and lipidic methabolism, moreover down-regulated genes belong to the immunitary response pathway. Histopatological analysis demonstrate a different distribution of melanomacrophage centres in cephalic kidney and a greater severity of lesions affecting fish exposed to low temperature. It is the first time that cold response was analysed with both biomolecular and histological techniques in Sparus aurata to understand the aetiopathogenesis of Winter Stress Syndrome.