Scientists claim that about 95% of the world's oceans have not yet been studied by humans. This intriguing fact suggests that we generally know little about life on Earth, since it is in the ocean that most organisms live.
And the new discovery of biologists from the Museum of Natural History of Denmark only confirms this idea: the researchers discovered mushroom-like marine animals, which could not be attributed to any of the known categories of the tree of life.
The find belongs to the zoologist Jean Just and his colleagues. Scientists discovered 18 strange invertebrates while sorting materials collected in the Tasman Sea in 1986. During that expedition, scientists used special equipment that allowed them to collect small marine animals from the bottom of the sea.
In their article, published in the journal PLOS ONE, the researchers describe 14 individuals collected at depths of 400 and 1000 meters, and not belonging to any known animal or other life form. Distinctive features of "sea mushrooms" are asymmetry, multicellularity and the presence of a gel-like layer between the inner and outer "body".
The researchers realized that all individuals can be attributed to two species. Each was given a name (Dendrogramma enigmatica and Dendrogramma discoides) and attributed to the general genus.
Mysterious specimens of a new branch on the tree of life were immersed in formaldehyde and brought to the laboratory, where they were stored for some time in an alcohol solution. Because of this, subsequent DNA analysis to determine the relationship of "fungi" with other organisms became impossible.
However, under a microscope, the samples showed morphological similarities with two existing types - jellyfish and ctenophores. This suggests that they may be associated with one of these types, although at present this cannot be said with complete certainty.
In the near future, scientists plan to carry out a complete genetic analysis of the material of animals of the genus Dendrogramma (photo by Jorgen Olesen).
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Just also found similarities between the new genus Dendrogramma and the ancient extinct jellyfish that lived on Earth 600 million years ago, during the Ediacaran period.
This may indicate that the coastal waters of Australia have preserved the descendants of Ediacaran organisms, which are considered extinct in all other regions of the oceans. The pedigrees of animals that have survived more than one stage of mass extinction carry important information that helps researchers to reconstruct the course of evolution.
The next stage in the study of mysterious marine mushrooms will be the search for genetic samples. Some scientists are sure that it is necessary to organize a new expedition to find living individuals and deliver them to the laboratory for subsequent DNA analysis, but Just and his colleagues argue that the already available material may be sufficient for a full analysis with modern methods. Be that as it may, it will still take a long time.
