© 2005 International Council for the Exploration of the Sea
Host–parasite interaction of a muscle-infecting didymozoid in the Atlantic mackerel Scomber scombrus L.
a Instituto de Investigaciones Marinas (CSIC), ECOBIOMAR Eduardo Cabello 6, 36208, Vigo, Spain
b Centro de Investigacións Mariñas, CIMA Pedras do Corón s/n., 36620 Vilanova de Arousa, Pontevedra, Spain
c Department of Cell Biology, Institute of Biomedical Sciences and CIIMAR, University of Oporto Largo Prof. Abel Salazar, 4099-003 Porto, Portugal
*Correspondence to S. Pascual: tel: +34 986 23 1930, ext 183; fax: +34 986 29 2762. e-mail: spascual{at}iim.csic.es.
Numerous 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.
Keywords: didymozoid, infected muscle, mackerel, trematode
Received 17 June 2005; accepted 28 August 2005.