Hi,

Almost animal is aerobic organism. Only three species of the animal phylum Loricifera (Spinoloricus nov. sp., Rugiloricus nov. sp. and Pliciloricus nov. sp.) can live under anaerobic condition. If you want to compare protein sequence between aerobic and anaerobic organisms, you should look for protozoa or prokaryote (not animal). However, I think that the difference between ana and aerobic organism may come from the pathway and not sure about protein sequence make sense or not. Anyway, animal is not organism for your study.