At the other extreme, the electrogenic elephantnose fish, an African freshwater fish, has one of the largest brain-to-body weight ratios of all known vertebrates (slightly higher than humans) and the highest brain-to-body oxygen consumption ratio of all known vertebrates (three times that for humans).
Di sisi lain, ikan belalai-gajah, ikan air tawar Afrika, memiliki salah satu rasio terbesar dari semua vertebrata (sedikit lebih tinggi daripada manusia) dan rasio konsumsi otak terhadap oksigen yang tertinggi dari semua vertebrata (tiga kali lebih besar daripada manusia).