
31-05-2012
Most literature still have all mantas under the name M. birostris but in 2009 (Marshall, Compagno and Bennett: Zootaxa 2301) it was established that there are at least two species: the smaller (up to 5.5 m in span) M. alfredi is almost entirely tropical, sometimes seen in relatively shallow coastal waters, and is found in the Indo-Pacific and east Atlantic. The larger (up to 7+ m in span) M. birostris can be seen both in tropical and warm temperate regions, tends to be found in deeper waters, and is found in the Indo-Pacific, east Pacific and Atlantic. In the Caribbean/W. Atlantic there is also a possible new manta species that is intermediate in size; its range only overlaps with M. birostris.
I haven't done a thorough check but I wonder what species really are kept at the different aquariums. The mantas in Okinawa Churaumi Aquarium are M. alfredi. The one in Georgia Aquarium that came from South Africa is M. alfredi and the three that came from Florida are the possible new species. I haven't seen good photos of them but based on their origin I guess the manta at Lisbon Oceanarium was M. birostris, the mantas at Atlantis Aquarium are the possible new species or M. birostris, and the mantas at Osaka Kaiyukan Aquarium are M. birostris or M. alfredi.
I have attached three photomontages and a preliminary map from Marshall, Compagno and Bennett (2009). The first two montages illustrate the primary differences between typical M. birostris (A) and typical M. alfredi (B). I have not included the physiological differences (e.g. denticles) because they are of limited use to us. Both species also occur in rarer dark (with less white than typical) and light (with less black) morphs. Explanation to first two photomontages, each number representing a difference: (1) presence, colour and shape of supra-branchial shoulder patches (2) ventral spot distribution and colouration (3) presence or absence of caudal spine (5) colour of mouth.
The final photomontage (with labels A, B, C, D) shows some examples of the possible new species from the Caribbean/W. Atlantic.
Last edited by condor; 31-05-2012 at 06:15 AM..
Reason: added photos
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