Host–parasite interaction of a muscle-infecting didymozoid in the Atlantic mackerel Scomber scombrus L.

Abstract

AbstractNumerous ribbon-like aggregations of eggs of a trematode didymozoid were found embedded in the connective tissue, mostly between the epoxial skeletal muscle fibres, of mature mackerel Scomber scombrus collected from post-recruits of the eastern stock. Egg masses contained numerous developmental stages, including pre-vitellogenous oocytes to fully embryonated eggs. Genomic DNA isolation, PCR amplification, cloning, and sequencing strongly supported the view that the eggs belong to a yet unidentified didymozoid. There was minor muscular damage to the host, namely focal distortion of host fibre architecture to accommodate the parasite, and the mild host response consisted of different stages of encapsulation. Concurrent heavy infection makes the mackerel flesh unappealing to eat, although the quality of the fish is not significantly affected and there is no public health danger.