Is it ok to kill animals which do not possess consciousness?
If it turns out that a certain animal species, such as starfish, do not possess consciousness, then from an ethical perspective I believe that this would imply that they fall into the same category as plants.

In some cases, we may wish to refrain from killing such animals for environmental and ecological reasons, just as we may wish to refrain from killing certain plants for these same concerns.

However, I see nothing wrong in principle with killing an animal for food if the animal possesses no more consciousness than does a plant or a brain dead human.