You’ve heard of sea stars and brittle stars. But have you heard about feather stars?
At first glance, feather stars look like plants. They have branching appendages that billow out from a central point, almost like a potted fern. But don’t be fooled! They are animals known as echinoderms. That means they are part of Phylum Echinodermata, along with sea urchins, sea stars, brittle stars and sea cucumbers. Echinoderms are invertebrates that are only found in the ocean and are known for their five-point radial symmetry and unique water vascular system.
Feather stars are in the class Crinoidea, which is a group of echinoderms that includes sea lilies and feather stars. There are about 550 species of crinoid alive today, but crinoids have been around for a long time. They first appeared in the fossil record about 300 million years before the dinosaurs during the Middle Cambrian period. Today, geologists use crinoid fossils to learn more about the areas where they are found, as they provide evidence of when land masses were underwater.
Crinoids get their name from the Greek word “krinon”, which means lily. That’s because their structure generally resembles that of the flower: they have branching appendages and attach themselves to a surface. Crinoids that have a “stalk” that connects them to that surface are called sea lilies, but crinoids that don’t have a stalk are feather stars.
Let’s get back to feather stars: they have feathery arms that typically appear in multiples of five, allowing them to keep the radial symmetry echinoderms are known for. Some species can have up to 150 arms! They use these plumy arms to capture plankton and other small bits of food that drift by them in the water column. And if they lose an arm to predation, they can regrow it, just like sea stars.
They have a few options to move around the sea floor. For short distances, they can use tiny leg-like appendages called cirri to inch along the substrate. They also use cirri to trap food particles they come across along the way. To move further, they can use their arms to swim in the water column. Check out the video below if you’ve never seen it—it’s absolutely hypnotizing.
Early research suggests that these charismatic echinoderms might be able to withstand warming ocean temperatures fairly well. According to crinoid researchers, feather stars are able to grow their limbs back more quickly in warmer temperatures, so we will hopefully continue to see these invertebrates despite warming oceans.
Although feather stars might not be as well-known as other echinoderms like sea stars and sea urchins, we think they are pretty fantastic. Next time you’re in the water or at an aquarium, keep an eye out for these beauties!