They are neither jellyfish, nor octopuses, nor starfish. These strange animals that seem to have come from another planet have been living on Earth for a long time! But what have scientists discovered in the icy waters bordering Antarctica?
Crinoids, whose name in Greek means lily, may look like sea plants with roots, stems and leaves reminiscent of them, but they are animals nonetheless! They are part of the phylum (or branch) of echinoderms and are therefore related to starfish, brittlestars, sea urchins, and sea cucumbers. Four new species of these strange creatures have been described in a recently published study. invertebrate systematics Which solves the mystery of their kinship.
a deep mystery solved
Most modern crinoids are winged stars, a group of mobile crinoids capable of crawling along the ocean floor due to cirrus, a type of organ they also use to cling to their substrate. The long arms that wing stars use to feed have numerous barbules to capture plankton, and sometimes allow them to swim! These dynamic species exist in a very wide range of marine environments, they are also found in the abyss and in the cold waters around Antarctica!
The study, which has just been published, has studied the winged stars of this species. promachocrinus kerguelensis, the only one of its kind, that lives around Antarctica. The researchers sequenced mitochondrial genes from a large number of samples. It turned out that it was eight different species of crinoids, four previously proposed and four entirely new, that were finally lumped together under this name! But how is this possible?
It happens that biologists have difficulty separating species that are morphologically very close, so these species are inadvertently grouped together under the same name. These are called cryptic species complexes, which scientists can mostly only identify through molecular analysis. With advances in the study of the genomes of invertebrates in the waters of the Antarctic region, marine biologists are discovering more and more mysterious species. The researchers therefore established new morphological criteria that make it possible to separate almost all newly described species of feather stars from the genus PromachocrinusWhich will henceforth facilitate studies aimed at assessing the true biodiversity of these extreme environments!
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