[vimeo width=”680″ height=”400″]http://vimeo.com/11416114[/vimeo]
Convolutriloba retrogemma, the dreaded red planaria flatworm, is a loathed aquarium pest which just moved up in the world. Although once grouped with the Platyhelminthes, the true flatworms, the Planaria which include the familiar pest have recently become reclassified as being more closely related to bilaterally symetrical worms, now placed closer on the tree of life to the echinoderms and sea squirts than the jellyfish. The Xenacoelomorph is the new phylum in the animal kingdom which was erected to house our new understanding of where the Planaria reside on the tree of life.
As a lifelong student of the finer points of invertebrate zoology, something seems quite unsettling about seeing a branch of ‘lowly flatworms’ being elevated into a new phylum so close to the more complex lifeforms. The simple body plan of planarians made them an easy link in the evolutionary tree but as genetic research points out, appearances are not what they seem. Even if flatworms are now considered a more evolved form of life, we still don’t want them in our tanks, neither the red flatworms in the video above nor the Acro-eating-flatworms that can devastate the plans of ambitious coral farmers.