Natural variability and potential use of melanomacrophage centres as indicators of pollution in fish species from the NW Mediterranean Sea.

The present study provides a baseline assessment of the prevalence and densities of splenic melanomacrophage centres (MMCs) in 18 fish species from the NW Mediterranean Sea related to spatiotemporal and environmental factors and fish traits. Their correlation with other established health indicators, such as body condition indices (condition factor, hepatosomatic and gonadosomatic indices), parasite community descriptors and histological assessment of target organs (gills, liver and spleen) is also assessed. Despite MMCs variability is mainly attributed to the species identity and fish size, their potential use as generic biomarkers of health condition is pointed out for certain species (e.g. Spicara maena and Micromesistius poutassou) in which an increased response was identified, and whose potential drivers are discussed. Most importantly, present results provide a comprehensive assessment of MMCs in the fish community for future studies in the area.