Are eating raw oysters a violation of the first Precept?

The first Precept is to abstain from Killing a "living being". Is there a consistent definition of Living Being that we should not kill to avoid violating the first Precept? I have heard of a definition such as a Living Being means they have the Five Aggregates, so that Plants / Germs do not count as they do not have all Five and cannot be reincarnated into.... etc. But I don't know if this definition is widely accepted in either Theravada or Mahayana. If this definition is accepted, how do we know what beings do not have all Five Aggregates? If not, is there any other definitions that we can use? Would also want to know if Clams, Oysters, Corals...etc... are considered as having all of the Five Aggregates too. Five Aggregates: 1. form (or matter or body) (rupa), 2. sensations (or feelings, received from form) (vedana), 3. perceptions (samjna), 4. mental activity or formations (sankhara), and 5. consciousness (vijnana)