Ultrastructural Characterization of Lipid-Rich and Vesicle-Like Structures in <em>Leishmania </em>(<em>L.</em>)<em> amazonensis</em>

Lipid-rich structures are frequently observed in Leishmania spp., yet their morphological diversity and stage-specific distribution remain insufficiently described. Here, we performed an ultrastructural and fluorescence-based characterization of Leishmania (L.) amazonensis promastigotes and intracellular amastigotes using transmission electron microscopy (TEM), scanning electron microscopy (SEM), BODIPY® lipid staining, and Nanoparticle Tracking Analysis (NTA). Promastigotes exhibited vesicle-like and membrane-derived compartments concentrated in the flagellar pocket, as well as electron-dense lipid bodies adjacent to the Golgi complex. Intracellular amastigotes displayed rounded morphology within parasitophorous vacuoles and contained distinct lipid-rich inclusions. BODIPY staining confirmed neutral lipid pools in promastigotes. NTA detected submicron particles in culture supernatants, with amastigotes showing higher particle abundance (3.1–5.9 × 10⁸ particles/mL) and smaller mean sizes (132–171 nm) compared with promastigotes. These observations provide a descriptive account of lipid-rich and vesicle-like structures in L. amazonensis and offer morphological context for future investigations into membrane dynamics, lipid metabolism, and parasite–host interactions. No inference of vesicle identity, biogenesis, or function is made, in accordance with MISEV2023 recommendations.