Body Size Influence on Respiration Rate and Mitochondrial Metrics in Mytilus edulis L. Gill Tissue

Metabolic rate is a crucial trait shaping organismal physiology,adaptability, and ecological roles, with extensive studies on itsallometric relationship with body size. Larger organisms have lowermass-specific metabolic rates, a pattern observed across taxa andontogeny. Despite numerous hypotheses, no universally accepted theoryexists on the biological mechanisms of metabolic allometry, particularlyfor suborganism-level. We investigated the relationship betweenbody size and metabolic rate as well as mitochondrial characteristicsin isolated gill tissue of the marine mussel Mytilus edulis. Results indicated that metabolic allometry patternsobserved at the organismal level did not manifest at the tissue level.Our study also revealed that while the density of mitochondria ingill tissue did not differ significantly between large and smallindividuals, area and perimeter of mitochondrial cross-sections increasedsignificantly with body mass. This finding contrasts with mammaliandata, suggesting potential phylogenetic differences. Larger musselsexhibited higher mitochondrial activity, supporting a link betweenmitochondrial morphology, activity, and growth rates. Our resultshighlight the importance of mitochondria in mollusk metabolism andgrowth, warranting further exploration into the mechanisms translatingmitochondrial characteristics into growth rates.