Nucleus has been around since about 1700, spawning nucleic, nuclear, nucleobranch and other words used in the sciences. I doubt that it will change. The ending is -ar, not ear, so it is like some of the others- granule, cellule, etc.

Have yet to meet with a perpendicule, but it has a nice sound to it. Hmmm, will have to find a use for it.

Nucule is a word used by botanists. It probably has appeared as the adjective, nucular in their writings.