Gonadal macrophage aggregates in fish: A preliminary quantitative study in red mullet.

A histological study was conducted in red mullet, Mullus barbatus, collected from two sites characterized by different anthropogenic impacts. The aim of the study was to assess sex‐, size‐, season‐ and site‐related variation in gonadal macrophage aggregate (MA) size, number, and relative area. Gonadal MAs were most abundant in males than in females. The number of MA was significantly higher in males from the most impacted site in October, with larger individuals showing more MA than smaller ones. MAs were always found in ripe testes, whereas they occurred only in regressing ovaries. These preliminary findings suggest that the presence of ovarian MA in red mullet is most likely related to ovary regression after spawning, whereas the presence of testicular MA is not necessarily associated to gonad regression, and may vary with season, size, and water quality.