Simplify the following text for a Grade 8 native English-speaking person.
Original: It was originally thought that this parasite infected fish brains ( hence the specific epithet cerebralis ) , however it quickly became apparent that while it can be found in the nervous system , it primarily infects cartilage and skeletal tissue .
Simplified: At first , people thought that this parasite infected fish brains , so they named it cerebralis , which means brain-related . Then , people found out that it mostly infects cartilage and bones .