Spatial, Histochemical, and Ultrastructural Analysis of Melanomacrophages in the Liver of the Red-Eared Slider (Trachemys scripta elegans).

Melanomacrophages (MMs) are pigmented phagocytic cells observed in ectotherms. Investigating MMs is valuable for elucidating the evolutionary background of the vertebrate immune system. However, studies regarding the distribution and function of hepatic MMs remain limited. This study investigated the spatial distribution, histochemical, and ultrastructural characteristics of intracellular inclusions in hepatic MMs in red-eared sliders (Trachemys scripta elegans). MMs are distributed throughout the periphery of the hepatic portal system, with minimal presence elsewhere. MMs contained heterogeneous intracellular inclusions with variable staining characteristics on Masson's trichrome, periodic acid-Schiff, and Berlin blue stains. These findings provide an anatomical basis for comparative immunological investigations of MMs.