On a recent tour of the Dallas World Aquarium, we had to opportunity to see a very unusual colony of Mycedium, together with two other recognizable species in the genus. All three colonies of these chalice corals were imported as Mycedium corals, with one colony looking like a perfect Mycedium elephantotus, and the other colony being a good card-carrying member of the Mycedium robokaki complex
The third colony of Mycedium pictured above with the brown tissue, large pink oral discs and light red edge is unlike anything we have seen before. The contrast between the oddball Mycedium is even more pronounced when all three colonies are brought together to contrast their corallite size, shape, features, and the general texture of each beautiful coral.
There is a point where Mycedium and Pectinia become increasingly similar to each other, we don’t know where that point is, but flattened colonies of Pectinia sure do bear a lot of similarities with Mycedium. The only potential way to tell one from the other is to watch for the extension of sweeper tentacles at night which we believe to be a more frequent trait in Pectinia corals, which are known to set off the stinging cell fireworks at night.
Despite the extreme flatness of the unusual pink eyed chalice, our running theory is that this particular coral is indeed a Mycedium with unique features, but which was also collected in an area of really calm water flow and moderate lighting, muting the skeletal features which would otherwise more easily peg it into the genus within which it belongs. With so many colonies of unrecognizable or otherwise, unidentifiable “species” of these large polyped Mycedium and flattened Pectinia corals, there’s a handful of new species here just itching to be giving a close look by coral taxonomists, and several probably new species waiting to be formally described.