[Feature] Get the axolotl region abbreviations checked and improved by an anatomist

[alessandrofelder]

Is your feature request related to a problem? Please describe.

The axolotl atlas "main structures" (higher level regions) are currently abbreviated by the first three letters of the region name.

Describe the solution you'd like
We should ask an anatomist about conventions and whether this can be improved.

Describe alternatives you've considered

If there's no good convention because the axolotl regions are too different from other species, we can leave as is.

Additional context

Sub-issue of #270