A newly named species from the Antarctic Ocean represents the rich and strange diversity of those frigid waters, where scientists have found new and unexpected creatures in recent years. In this case, a small “flower star” named after a strawberry resembles an alien mop head, or the facehugger from the movie Alien. But not to worry – the strange creature eats tiny plankton and has no interest in human faces.
Between 2008 and 2017, scientists used boats to trawl the Antarctic Ocean, hitting such locales as the South Orkney Islands, Elephant Island, the Davis Sea, and the South Sandwich Islands, all while looking for new specimens. They came up with the dramatic new flower star and three other crinoids, a group that’s related to starfish and sea urchins.
The trawl caught the striking Promachocrinus fragarius at 2,600 feet, although members of the genus can live as deep as 6,500 feet.
What Is a Feather Star?
These adaptable creatures have lived in the world’s oceans since about 490 million years ago and dominated the sea floor during part of the Mississippian Period, which ran from 360 million years to 320 million years ago. They left behind a large amount of fossilized remains underwater and on what is now land, where their remains formed many of the limestone rocks.
The new species, Promachocrinus fragarius – from the Latin “fragum,” for strawberry – has 20 arms and many more thin cirri, along with the strawberry-shaped body that earned the species its name.
These organisms eat by positioning themselves in water currents and sticking out their arms, which are lined with “tube feet” that catch plankton in mucous. When the crinoid is ready to move on, it uses its arms to swim to a new perch.
Two of the other new species, P. unruhi and P. uskglassi, have similar anatomy, with 20 different arms each, although subtle distinctions set them apart. P. unruhi has large cirri that rival the size of its arms, and P. uskglassi has a large, conically-shaped body.
Evolution at a Glacial Pace
These strange animals illustrate how evolutionary forces have shaped the Antarctic Ocean, particularly during the Last Glacial Maximum, about 20,000 years ago. Then, during the last surge of the Last Ice Age, glaciers covered a large percentage of the Southern Ocean, which greatly affected evolution there.
According to the paper, many types of fauna went extinct, while other species lived on in areas of the continental shelf left uncovered by ice. Others dove to the deep sea or survived in polynyas, which are pockets of ocean surrounded by ice.
“These barriers isolated populations, creating bottlenecks and inhibiting gene flow between populations,” says the paper by three researchers from the Scripps Institution of Oceanography at the University of California at San Diego. “As ice later retreated, new areas of seafloor were exposed, creating new environmental niches and decreasing barriers between regions, potentially allowing populations to expand once again.”
As a result, the southernmost latitudes of the world have produced some of its most unusual animals and some of the most difficult to study. The Promachocrinus genus, the paper notes, verges on the “cryptic,” meaning some of its member species look alike but have major genetic differences and cannot reproduce with one another.
