do some neotenic salamanders not undergo metamorphosis

Yes, some neotenic salamanders do not undergo metamorphosis. Metamorphosis in amphibians typically involves a significant transformation from the larval stage to an adult form that is better adapted to terrestrial or semi-aquatic environments. However, neotenic salamanders retain their larval characteristics throughout their lives and thus do not undergo this transformation.

In neotenic salamanders like the Axolotl (Ambystoma mexicanum), the following aspects prevent them from undergoing typical metamorphosis:

1. External Gills: These salamanders retain their external gills, which are efficient for breathing underwater but not suitable for air breathing on land.
2. Aquatic Lifestyle: They remain aquatic throughout their life, lacking adaptations for terrestrial locomotion.
3. Diet: Neotenic salamanders often have a diet and foraging behavior suited to an aquatic environment.
4. Reproduction: They reproduce in water, laying eggs attached to underwater plants or structures.
5. Body Structure: The body structure of neotenic salamanders, with a slimy skin and large tail, is optimized for swimming rather than walking or climbing.

While neotenic salamanders do not undergo typical metamorphosis, it's worth mentioning that they still go through a process of growth and development, reaching sexual maturity and continuing to grow in size. However, this growth does not involve the dramatic changes in physical appearance and physiology seen in metamorphosing salamanders.

It is also important to note that while the Axolotl is a well-known example of a neotenic salamander, other salamander species may exhibit varying degrees of neoteny, with some undergoing partial metamorphosis while retaining certain larval features.