Meeting Abstract
The existing literature on the meninges in reptiles has an abundance of contradictory claims and nomenclatural revisions. In part this stems from the literature containing mainly single-species studies that were performed under either a developmental or mammalian perspective. There is still disagreement about the number of meningeal layers in reptiles, and the relative degree of vascularity associated with the individual layers. To explore this subject we examined post-embryonic specimens of four reptilian taxa: American alligator (Alligator mississippiensis), western diamondback rattlesnake (Crotalus atrox), Chinese pond turtle (Mauremys reevesii), and water monitor lizard (Varanus salvator). Specimens from each species were examined using three different techniques: paraffin histology, freeze fracturing prior to scanning electron microscopy, and high-resolution X-ray micro-CT analysis. The analysis centered on four anatomical regions: 1) the cervical spinal cord, 2) longitudinal (parasagittal) sections through the foramen magnum, 3) the structure of the tela choroidea over the 4th ventricle, and 4) the cerebral cortex. In all four species three meningeal layers, of varying distinctiveness, could be identified; these were identified as pia mater, arachnoid mater, and dura mater. In all four species there was considerable variation in the relative position of the arachnoid mater, meaning that the sizes of the subdural and subarachnoid spaces were variable. In general, the meninges of the examined reptiles are similar to those of the more studied mammals with three clear distinctions: there are no prominent septa or trabeculae; the meninges, and more specifically the dura mater, do not exhibit a marked transition at the foramen magnum; and the meninges over the 4th ventricle are more continuous or “closed” than in mammals.
