Meningeal Lymphatic and Glymphatic Structures in a Pelagic Delphinid (Delphinus delphis).

The glymphatic system, an analog of the peripheral lymphatic system in the brain, and the meningeal lymphatic system are critical to central nervous system health. The glymphatic system functions to distribute cerebrospinal fluid and important compounds throughout the brain and to remove metabolic waste. The flow of cerebrospinal fluid through this system is affected by changes in cerebral blood flow, intracranial pressure, and vascular tone. Cetaceans experience profound cardiorespiratory alterations while diving that can directly affect cerebrospinal fluid and blood flow and, thus, glymphatic function. Our goal was to investigate glymphatic and lymphatic system structures, including perivascular spaces, aquaporin-4 water channels, meningeal lymphatic, and dural venous sinus vessels in the common dolphin (Delphinus delphis), using immunofluorescent labeling, histochemical staining, and postmortem computed tomography (CT) angiography. We highlight perivascular spaces and aquaporin-4 water channels surrounding blood vessels in the parenchyma and demonstrate evidence of meningeal lymphatic vessels and associated dural venous sinuses. These results demonstrate that common dolphins possess the key anatomical structures required for functional glymphatic and meningeal lymphatic systems. Future studies can build upon these anatomical discoveries to study the function and role of these systems in brain health in this species.