I agree that Gohma is just a multi-legged one eyed monster. She just takes a slightly different form in each game. A lot of reoccuring bosses do that. She takes the form of any existing creature with at least 8 legs, which include a spider, crab, and centipede. Other forms she could take in the future include a tick, lobster, millipede, and other various species of crab. Too bad scorpion was already taken.