In Java, the for loop index is explicitly declared as a part of the loop structure. For example, for (int i = 0; i < 10; i++), where int i is the explicit declaration of the index. In Python, the for loop doesn't require explicit declaration of the loop index; it's directly inferred from the iterable object being looped over. Ruby and JavaScript also handle the loop index differently, where the loop variable may be initialized automatically or inferred from an iterable.