Journal of the Marine Biological Association of the UK

Research Article

Immunocompetence and heterozygosity in the mussel Mytilus edulis

Florence M.M.  Carissan-Lloyd a1, Richard K.  Pipe a2 and Andy R.  Beaumont a1c1
a1 School of Ocean Sciences, University of Wales, Bangor, Menai Bridge, Gwynedd, LL59 5AB, Wales, UK
a2 Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth, PL1 2PB, Devon, UK

Article author query
carissan-lloyd fmm   [PubMed][Google Scholar] 
pipe rk   [PubMed][Google Scholar] 
beaumont ar   [PubMed][Google Scholar] 


Multiple locus allozyme heterozygosity has been shown to be weakly, but significantly correlated with certain fitness parameters in bivalves. Immune function of individual Mytilus edulis from the Menai Strait, Wales, UK was assessed monthly over one year (1997–1998) by measuring total blood cell (haemocyte) counts, differential haemocyte counts (% basophils and eosinophils), phagocytic capability (by zymozan uptake) and intracellular superoxide generation. Sampled mussels were also scored at 9 allozyme loci. Mussels were then grouped into multiple locus heterozygosity (MLH) classes and plotted separately against the different measures of immunocompetence. No significant association was present between MLH and total haemocyte count, phagocytic capability or intracellular superoxide generation. However, there was a significant association between MLH and the character (basophilic or eosinophilic) of circulating haemocytes (r2=0·057, P=0·002). Highly heterozygous individuals tended to have significantly more eosinophilic haemocytes circulating in the blood than highly homozygous individuals. Eosinophilic haemocytes are known to have a high capacity for phagocytosis of invading organisms and these results may therefore be interpreted as increased health (=fitness) in more highly heterozygous individuals.

(Received July 22 2003)
(Accepted February 9 2004)

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