According to a team of scientists from the University of Copenhagen in Denmark, two species of sea-dwelling, mushroom-shaped organisms discovered off Australia cannot at present be placed in an existing phylum (primary subdivision of a taxonomic kingdom).
Specimens of Dendrogramma enigmatica and Dendrogramma discoides (with *). Image credit: Just J et al.
In 1986, Copenhagen University researcher Dr Jørgen Olesen and his colleagues collected these unusual organisms at 400 and 1,000 m deep on the Australian continental slope off eastern Bass Strait and Tasmania, and only just now described them as two species in a new genus, Dendrogramma, in the new family, Dendrogrammatidae.
The two species, named Dendrogramma enigmatica and Dendrogramma discoides, are multicellular and mostly non-symmetrical, with a dense layer of gelatinous material between the outer skin cell and inner stomach cell layers.
“The animals are composed of a body divided into a stalk with a mouth opening terminally, and a flattened disc,” the scientists wrote in a paper published in the journal PLoS ONE.
Dendrogramma enigmatica. Image credit: Just J et al.
“The mouth is set in a specialised, lobed epidermis field, leading into a gastrodermis-lined gastrovascular canal in the stalk which aborally branches dichotomously into numerous radiating canals in the disc.”
“While the animals are certainly multicellular, the precise structural identity of the epithelia lining the gastrovascular canal and the external remain to be studied and compared to that of other metazoans.”
“Dendrogramma shares a number of similarities in general body organisation with the two phyla, Ctenophora (comb jellies) and Cnidaria (jellyfish, hydra, sea anemones, corals), but cannot be placed inside any of these as they are recognised currently.”
Dendrogramma enigmatica. Image credit: Just J et al.
The scientists also found similarities to 600 million year-old Pre-Cambrian extinct life forms, suggested by some to be early but failed attempts at multi-cellular life.
“Current evidence suggests that they represent an early branch on the tree of life, with similarities to the 600-million-year-old extinct Ediacara fauna,” Dr Olesen said.
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Just J et al. 2014. Dendrogramma, New Genus, with Two New Non-Bilaterian Species from the Marine Bathyal of Southeastern Australia (Animalia, Metazoa incertae sedis) – with Similarities to Some Medusoids from the Precambrian Ediacara. PLoS ONE 9 (9): e102976; doi: 10.1371/journal.pone.0102976
