MANATEE CEREBRAL-CORTEX - CYTOARCHITECTURE OF THE CAUDAL REGION IN TRIHECHUS-MANATUS-LATIROSTRIS

In several brains of the Florida manatee, Trichechus manatus latirostr is, the architecture of caudal regions of cerebral cortex was examined in order to complete a map of cortical areas in the brain of this uni que herbivore. Through observation of sections stained for Nissl subst ance, myelinated axons, acetylcholinesterase and cytochrome oxidase, w e have identified 11 new cortical areas based on qualitative cytoarchi tectural appearance and measurements of laminar thicknesses, for a tot al of 24 such cortical areas in manatee cerebral cortex. Some areas ex hibit poorly differentiated laminae while in others there are 6 clearl y demarcated layers, often with sublaminar organization. Some previous ly identified areas were found to extend into the region caudal to the vertically oriented lateral fissure. As in other mammalian brains, co rtical areas in manatees are organized in concentric rings of allocort ex, mesocortex, and isocortex. Putative functional roles have been ass igned to most of the identified areas based on location, architecture, behavioral and anatomical considerations, and extrapolation from othe r taxa in which functional mapping has been done.