Anders Alfjorden: Morphological and molecular studies of bivalves to assess the hidden diversity of protistan parasites: Investigations of cryptic diseases in shellfish

Abstract

This thesis investigates the host - parasitic relationships in mussel, started by investigating unexplained massmortalities in freshwater mussels, Margaritifera margaritifera. By compiling geodata with symptoms and histopathology (Paper 1). In Paper 2, I continued on these investigations, describing a parasitic gregarines in host. Using in situ hybridization (ISH) and ultrastructural analysis, we linked this gregarine to host detected lesions. To investigate fixed sampled, we used CARD-FISH demonstrating new patterns of parasitic infiltration of gonads. (Paper 3). In marine environments, protist parasites have been throughly documented, though several lesions remain unexplained. Using cell culture, we isolated Hexamita nelsoni linking this protist with blue mussels lesions in muscle & gonads, using CARD-FISH (Paper 4). The largest threat towards marine mussel aquaculture are Ascetosporean parasites, not culturable, requiring alternative methods for genomic studies. We used, density gradient filtration to concentrate Marteilia pararefringens and Bonamia ostreae from infected tissues, enabling these studies, Paper 5.