An anonymous reader writes "Researchers at Case Western Reserve University have successfully managed to turn a cockroach into a battery. The research relies on a Cockroach’s diet. As a cockroach eats, it produces trehalose, a complex sugar. An anode is introduced into the cockroach’s gut, coated in an enzyme that breaks the trehalose down into two simpler sugars. These are then broken down again by another enzyme so that the electrons bound up in the sugars are set free, which then rush toward the cathode, completing the circuit.
The amount of energy being generated by the process is still exceedingly small; only 100 microwatts of energy at .3 volts were produced..."Link to Original Source