Seems there are now 5 species of Arapaima......
1. A. gigas
2. A. agassizi
3. A. mapae
these 3 are known only from the preserved holotypes,
and have 18 or fewer caudal fin rays.
4. an undescribed species endemic to the protected Mamiraua reserve
5. Arapaima arapaima 31 caudal fin rays
All captive Arapaima are likely to be A. arapaima
http://www.practicalfishkeeping.co.uk/content.php?sid=95
1. A. gigas
2. A. agassizi
3. A. mapae
these 3 are known only from the preserved holotypes,
and have 18 or fewer caudal fin rays.
4. an undescribed species endemic to the protected Mamiraua reserve
5. Arapaima arapaima 31 caudal fin rays
All captive Arapaima are likely to be A. arapaima
http://www.practicalfishkeeping.co.uk/content.php?sid=95