Basket stars are the starfish relatives you’re least likely to see in their full glory. Key basket star fact: They do their work of unfolding their tangled arms and capturing passing prey in the dead of night.
Another: If you come across one during a night dive and stop to look at it – shining a light on it, of course – it’s going to fold right up and not quite disappear in front of your eyes. A beam of light is its cue to compress itself in a little ball that resembles a large, knotted tangle of cord.
IN THE UNIVERSE OF ECHINODERMS, BASKET STARS ARE FIRST COUSINS TO THE MUCH-MORE-FAMILIAR BRITTLESTARS. The two groups share membership in Class Ophiuroidea, which makes them close relatives. Except that look like brittlestars the same way that Danny DeVito looked like Arnold Schwarzenegger’s twin in their movie together.
With their complex arrays of arms and branching smaller arms spread out, they prosper by creating a “net” facing into the current and snagging shrimps and other small prey that come their way. By the time daylight arrives, they’re gone and hidden away.
Their aversion to light extends even to folding themselves up under repeated flashes of a photographer’s strobes, as I’ve found out the hard way myself.
BASKET STAR FACTS 1: WORLDWIDE DISTRIBUTION
They’re found in the oceans worldwide, from deep arctic depths to warm shallow reefs. There are an estimated 175 species, but many are deep sea creatures you’re unlikely to see in person.
Overall, they’re among the largest echinoderms. The largest of the largest is Gorgonocephalus stimpsoni, which can sport a disc as much as six inches across and arms more than two feet long. The species you’re likely to see on Caribbean dives is the Giant Basket Star (Astrophyton muricatum), with arms growing to some 18 inches. As usual, diversity of species is greater in the Indo-Pacific than in the Atlantic/Caribbean. It’s estimated that basket stars can live as long as 35 years.
BASKET STAR FACTS 2: ANATOMY
The architecture of a basket star does begin with a five-pointed disc-shaped body at its base and five arms, like any good echinoderm. But once the arms begin extending from each point, they branch and sub-branch so that stretched out the effect is one of a loose, tangled wicker basket.
As complicated as their “baskets” may seem, the animals share the echinoderm support system of ossicles – calcium carbonate plates under their skin – and a water vascular system for operating their arms. Their guts are contained in the disc; their mouths are on the underside.
Like their brittlestar cousins, they can drop an arm as a diversion in a pinch and eventually regenerate it. Most species reproduce by broadcast spawning but some can simply spit in two and regrow the other half.
Like all echinoderms, they feature an abundance of water-operated tube feet, but not for locomotion. Located on the underside of the arms, the tube feet help them in passing food along.
BASKET STAR FACTS 3: MODIS OPERANDI
Basket stars are suspension feeders, which means that as darkness comes on they unfold their net-like arms, positioning themselves to maximize access to the current and sieve edibles as they pass by. Unlike planktivores that specialize in microscopic food particles, basket stars go for small mollusks, jellyfishes, crustaceans like shrimps and copepods, and similar prey.
Their arms are lined with hooks and spines that constantly wave and coil to snag prey, wrapping around a krill or other victim, encasing it in threads of mucus and passing it along its tube feet to the animal’s mouth for consumption.
Species like the Northern Basket star (Gorgonocephalus arcticus), found from Cape Cod north to the Arctic, are known to sometimes work in pairs, connecting to each other to form a larger basket surface.
BASKET STAR FACTS 4: LOCATION, LOCATION, LOCATION
Averse to light, these echinoderms hide out during the day, often in nooks in crannies. But when it comes to positioning themselves for access to plankton-laden currents, location is everything. That means situating themselves facing into the passing waters atop a perch of rocks, corals or, often, on the reef, sea rods or sea plumes. They climb there using their arms.
On the reef, many save themselves the trouble of climbing. Often, as daylight comes on, they simply fold their arms into tangled balls enmeshed in a sea plume’s branches. They look more like a knot of cord all balled up than like two-feet wide animals.
BASKET STAR FACTS 5: THE GOLDILOCKS RULE
Some species, especially in deep arctic waters, spend their time working the currents from a station on the sediment of the sea bottom.
Wherever, when you’re a basket star, the current has to be just right – strong enough to sweep copious copepods along, not so strong that it blows away the broadside array of arms and sub-arms.
PRINCIPAL SOURCES: Marine Life, Caribbean, Bahamas, Florida, Marty Snyderman & Clay Wiseman; Reef Creature Identification, Florida, Caribbean, Bahamas, Reef Creature Identification, Tropical Pacific, Paul Humann, Ned DeLoach; Marine Life of the North Atlantic, Andrew Martinez; Gorgonocephalus!!, The Echinoblog; Basket Stars, Science and the Sea; ARE BASKET STARS, SEA STARS?, Seattle Aquarium; Brittle And Basket Stars: Ophiuroidea, Encyclopedia.com; Basket Star, Memorial University of Newfoundland; Death by basket star is silently terrifying (VIDEO), EarthTouch News Network; Basket star, Wikipedia.