Necturus alabamensis
The Alabama waterdog (Necturus alabamensis) is a medium-sized perennibranch salamander inhabiting rivers and streams of the Southeastern United States and is listed as endangered in most states where it occurs. It is currently found eastern Mississippi, Alabama, the Florida panhandle and western Georgia. It is completely aquatic and gilled throughout life. All mudpuppies and waterdogs have bushy external gills, two gill slits, a laterally compressed tail, and four toes on front and hind feet. Adult Alabama waterdogs measure 10-13 cm snout to vent length (15-22 cm total length). The dorusm is reddish brown to nearly black and some populations have spots on the dorsum. The venter lacks spots in all age classes. The tips of its toes are light colored and the body and head are flattened. Sexually mature males can be distinguished by the swollen cloaca and pair of enlarged cloacal papillae that project posteriorly. Hatchlings are mottled dorsally with a few light spots. In some populations, juveniles have light stripes on the head and back. Juveniles have a dark eye stripe running from the nostril, through the eye to the gills while the stripe is retained in adults.
Characteristics of a Nervous System in N. alabamensis
This particular organism does have a nervous system and it is almost diagrammatically simple in anatomy The generalized brain is rather small. The relatively large cerebrum (collectively, the two large anterior lobes of the brain) is associated with the large and important olfactory and vomeronasal organs, both of which are used for smelling. The surprisingly complex social organization of these organisms is largely based on olfaction. The eyes, usually large and well developed, are reduced and nearly lost in some cave-dwelling species. Vision is especially important in terrestrial foraging, because the projection of the tongue is guided visually.
Certain parts of the inner ear are large and well developed. Hearing mechanisms of the this salamander are not fully understood. There is no middle ear cavity and no external ear. One middle ear bone rests in the structure known as the vestibular fenestra. The other bone of the middle ear rests in the posterior part of the fenestra and is joined by muscles to the pectoral girdle. In most species these bones are variously fused or lost, so that only one survives. The spinal cord and the peripheral nervous system, in example the paired cranial and spinal nerves, are generalized in their structure, and there are distinct brachial and sacral plexuses, both of which are important nerve networks that supply the limbs.
Certain parts of the inner ear are large and well developed. Hearing mechanisms of the this salamander are not fully understood. There is no middle ear cavity and no external ear. One middle ear bone rests in the structure known as the vestibular fenestra. The other bone of the middle ear rests in the posterior part of the fenestra and is joined by muscles to the pectoral girdle. In most species these bones are variously fused or lost, so that only one survives. The spinal cord and the peripheral nervous system, in example the paired cranial and spinal nerves, are generalized in their structure, and there are distinct brachial and sacral plexuses, both of which are important nerve networks that supply the limbs.