The manta rays are the largest ray in the world and among the largest planktivorous fish, growing up to 900 cm from one wing tip to the other. The species belong to the elasmobranch group that includes sharks, skates and other rays. Scientist argued for a long time on the classification of manta rays, at some point ten different species of manta rays were described. However, after much disagreement, all manta rays in the world were classified as one single species for many years: Manta birostris. Recently, a young scientist, Dr Andrea Marshall undertook a comprehensive study of these animals off the coast of Mozambique. Dr Marshall discovered and proved mainly via field observations that there are at least 2 different species of manta rays. Manta alfredi (same as we find in eastern Australia) and Manta birostris.
• Manta alfredi tend to grow up to 5m across and live in shallow coastal waters. This is the main species encountered in eastern Australia.
• Manta birostris can grow over 8m across and live in deeper water and open ocean.
Both species have a worldwide distribution in tropical and subtropical waters.
For your Interest: Marshall AD, Compagno LJV and Bennett MB (2009), Redescription of the genus Manta with resurrection of Manta alfredi (Krefft, 1868) (Chondrichthyes; Myliobatoidei; Mobulidae), Zootaxa, Vol 2301, 1-28pp
and Manta birostris can be differentiated by few morphological aspects:
The dorsal coloration: M. birostris has very distinctive white triangular shoulder bars while M.alfredi has more faded and rounder coloration mark in this area.
The size: M. birostris can grow up to 8 m while M.alfredi tend to grow up to 5m from one wing tip to the other
Ventral natural markings: M. birostris do not have any spot pattern present between the gill slits and has half moon-shaped markings on both of the last gill slits. M.alfredi can display spot and coloration patterns on most of its ventral surface.
Caudal spine: M. birostris has a vestigial caudal spine, mostly encased in calcified mass and skin, present on the dorsal surface of the tail just behind the dorsal fin. M.alfredi has no sign of this vestigial caudal spine.
Note: both species include black colored individuals with white patches on the belly surface. This is just a difference in skin pigmentation. Black mantas are not a different species.
Class: Chondrichthyes (cartilagenous fishes)
Subclass: Elasmobranchii : rays, sharks, and skates
Order: Mylibatiformes (devil rays, eagle rays and cow-tail rays)
Species: Manta alfredi