Dendrogramma: two unclassifiable deep-sea animals discovered off the coast of Australia | Biology

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According to a team of scientists from the University of Copenhagen in Denmark, two species of mushroom-shaped marine organisms found off Australia cannot currently be placed in an existing phylum (primary subdivision of a taxonomic kingdom).

Specimens of Enigmatic dendrogram and Discoid dendrogram (with *). Image credit: Just J et al.

In 1986, University of Copenhagen researcher Dr Jørgen Olesen and his colleagues collected these unusual organisms at a depth of 400 and 1000 m on the Australian continental slope off the eastern Bass Strait and the Tasmania, and they just described them as two species of a new genus, Dendrogram, in the new family Dendrogrammatidae.

The two species, named Enigmatic dendrogram and Discoid dendrogram, are multicellular and mostly non-symmetrical, with a dense layer of gelatinous material between the outer skin cell and the inner cell layers of the stomach.

Animals are composed of a body divided into a rod with a terminally opening mouth and a flattened disc,” the scientists wrote in an article published in the journal. PLoS A.

Enigmatic dendrogramma.  Image credit: Just J et al.

Enigmatic dendrogram. Image credit: Just J et al.

“The mouth is located in a specialized, lobed epidermis field, leading to a gastroderm-lined gastro-vascular duct in the stem which dichotomously branches into numerous radiating ducts in the disc.”

“Although animals are certainly multicellular, the precise structural identity of the epithelium lining the gastro-vascular duct and the outer one remains to be studied and compared to that of other metazoa.”

Dendrogram shares a number of similarities in general body organization with the two phyla, Ctenophora (comb jellies) and Cnidaria (jellyfish, hydra, sea anemones, corals), but cannot be placed inside any of them as they are currently recognized.

Enigmatic dendrogramma.  Image credit: Just J et al.

Enigmatic dendrogram. Image credit: Just J et al.

Scientists have also found similarities to extinct Precambrian life forms that are 600 million years old, suggested by some to be early but unsuccessful attempts at multicellular life.

“Current evidence suggests that they represent an early branch of the tree of life, with similarities to the extinct Ediacara fauna that is 600 million years old,” said Dr Olesen.

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Just J et al. 2014. Dendrogram, New genus, with two new non-bilateral species of the marine bathyal of south-eastern Australia (Animalia, Metazoa uncertae sedis) – with similarities to some jellyfish from Precambrian Ediacara. PLoS A 9 (9): e102976; doi: 10.1371 / journal.pone.0102976


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