Feather Star
A 480-million-year-old animal that can walk, swim, or anchor itself — and has been filtering food the same way since before fish existed
No photo available for Feather Star
Superpower
Crinoids can alternate between three completely different lifestyles: anchored to the seafloor using a stalk (like a plant), free-swimming by rippling their arms in coordinated waves, or walking across the seafloor using claw-like appendages (cirri). They feed by extending arms (up to 200 in some species) into the current and using tube feet coated in sticky mucus to intercept drifting food particles — a mechanism essentially unchanged from their Cambrian ancestors 480 million years ago.
Overview
Crinoids (class Crinoidea) are echinoderms — relatives of sea urchins and starfish — and one of the oldest animal groups still living in something close to their original form. Fossil crinoids constitute enormous quantities of Paleozoic limestone. The 600+ living species are remnants of a group that once dominated shallow seas. Stalked crinoids (sea lilies) live attached to the deep seafloor; feather stars (the majority) shed their stalk early in life and become mobile, spectacularly colored animals visible on tropical coral reefs.
Found in
All oceans worldwide from shallow tropical reefs (feather stars) to deep ocean floors (sea lilies) at depths to 9,000m. Feather stars are particularly diverse and colorful in the Indo-Pacific and are often visible to divers on coral reefs.
Things worth knowing
- 1
Crinoids can shed and regrow arms — a detached arm continues to writhe for hours after separation, potentially distracting a predator while the crinoid escapes. The arm regrows completely within weeks.
- 2
Some crinoid species can move surprisingly fast when threatened — swimming by rapidly beating their arms in coordinated waves, covering significant distances to reach shelter.
- 3
Crinoid fossils are so abundant in some Paleozoic limestone deposits that the rock is almost entirely composed of their skeletal fragments — entire cliff faces in some parts of the US Midwest are primarily crinoid remains.
- 4
Some small fish and shrimp species live exclusively inside the arms of specific crinoids — feeding on captured food particles, camouflaged to match the crinoid's colors, and never leaving their host.
- 5
Crinoids face upward into currents to feed — unlike most sessile filter feeders, they actively reposition their arms and body to maximize capture efficiency as current direction changes throughout the day.