Sea Star and Worm Swarm Explained

We assume that spineless sea critters like sea stars, worms, and urchins are loafers, idly existing while the real action happens around them. This time-lapse video from the BBC shows us just how wrong we are.

An unlikely army of harmless-looking creatures swarms over the corpse of a leopard seal, and what happens next isn't pretty. A bounty like this comes about once in a decade for these animals, and they'll feast for months.

The BBC does a pretty good job of explaining the basics of what's going on here. But let's learn a little more about the featured creatures' hunting habits. Sea stars, ribbon worms, sea urchins, and their cousins may be spineless, eyeless, and even toothless, but that doesn’t stop them from getting their meal on.

Ninja Stars

For all their beauty, sea stars (the preferred term for starfish, since they're echinoderms, not fish) are pretty ruthless hunters. Instead of eyes, a sea star has an eye spot at the end of each arm, which can sense light and dark. The sea star creeps over the ocean floor, groping for its next victim. Most of the time, these are of the crunchy outside/gooey inside variety: snails, barnacles, clams, and mussels. If a shellfish refuses to cooperate, the sea star will wrap its arms around the bivalve, then use its sticky tube feet to pry the shell open.

Once its prey is near, the sea star will eject its stomach, which oozes over the prey and digests it on the spot. After the prey has been liquefied, the sea star just sucks its stomach back in. Watch this sunflower star nonchalantly sidle up to a juicy-looking (and apparently slow-witted) wolf eel. Just, you know, being friendly.

Worm of Nightmares

Ribbon worms made headlines twice recently, first when a purple specimen spewed its branched proboscis on a man's hand, and again when a shamrock-green beast showed up in Taiwan. It may look silly on land, but in the water, the ribbon worm (phylum Nemertea) is not to be trifled with. They’re enormous, for one thing. The green species, Lineus fuscoviridis, can reach up to 6 feet long. But that’s nothing compared to the rest of its family. Scientists believe that Lineus longissimus may grow to nearly 200 feet. That’s longer than a blue whale, and a whole lot slimier.

Then there’s that proboscis. When a ribbon worm finds something worth eating, it lashes out like a chameleon with its extendable, sticky proboscis. And no morsel is too large; like pythons, ribbon worms can swallow creatures three to four times their own size. For even larger meals, like the seal in the video up top, some species make a hole (or find one), then slither in and eat their prey from the inside out.

Raccoons of the Sea

It’s no surprise that sea urchins turned up at the dead-seal party. They’re notorious trash-eaters, subsisting on algae, dead fish, and other sea garbage. Just as the urchin’s body is bristling with spines, its mouth, located on the underside of its body, bristles with big, sharp teeth. When they’re not gnawing on rotting flesh, urchins use their teeth to scrape algae off of rocks, which can apparently be pretty noisy.

Bonus! Other Unexpected Attackers

They might not have made an appearance in this video, but sea anemones are plenty gross in their own right. These relatives of urchins and sea stars look like beautiful, delicate flowers, but their tentacles are covered with neurotoxins, and they will eat anything they can grab. The giant green anemone pictured below is in the process of devouring an entire baby cormorant:

Image Credit: Lisa Habecker

Even clams, mussels, and oysters are not as defenseless as we long thought. Natural history accounts reaching back to the 19th century tell of birds felled by the very shellfish they intended to eat. After a 1996 storm on the Jersey Shore, huge numbers of surf clams washed up on the beach. Scientists combing the beach found almost 40 birds with their bills or feet snapped tight inside the shells of defiant clams. Some of these birds were able to shake their captors; others fell into the sea and drowned. So let’s not underestimate the little beasts! 

How Bats Protect Rare Books at This Portuguese Library

Visit the Joanina Library at the University of Coimbra in Portugal at night and you might think the building has a bat problem. It's true that common pipistrelle bats live there, occupying the space behind the bookshelves by day and swooping beneath the arched ceilings and in and out of windows once the sun goes down, but they're not a problem. As Smithsonian reports, the bats play a vital role in preserving the institution's manuscripts, so librarians are in no hurry to get rid of them.

The bats that live in the library don't damage the books and, because they're nocturnal, they usually don't bother the human guests. The much bigger danger to the collection is the insect population. Many bug species are known to gnaw on paper, which could be disastrous for the library's rare items that date from before the 19th century. The bats act as a natural form of pest control: At night, they feast on the insects that would otherwise feast on library books.

The Joanina Library is famous for being one of the most architecturally stunning libraries on earth. It was constructed before 1725, but when exactly the bats arrived is unknown. Librarians can say for sure they've been flapping around the halls since at least the 1800s.

Though bats have no reason to go after the materials, there is one threat they pose to the interior: falling feces. Librarians protect against this by covering their 18th-century tables with fabric made from animal skin at night and cleaning the floors of guano every morning.

[h/t Smithsonian]

Honey Bees Can Understand the Concept of Zero

The concept of zero—less than one, nothing, nada—is deceptively complex. The first placeholder zero dates back to around 300 BCE, and the notion didn’t make its way to Western Europe until the 12th century. It takes children until preschool to wrap their brains around the concept. But scientists in Australia recently discovered a new animal capable of understanding zero: the honey bee. According to Vox, a new study finds that the insects can be taught the concept of nothing.

A few other animals can understand zero, according to current research. Dolphins, parrots, and monkeys can all understand the difference between something and nothing, but honey bees are the first insects proven to be able to do it.

The new study, published in the journal Science, finds that honey bees can rank quantities based on “greater than” and “less than,” and can understand that nothing is less than one.

Left: A photo of a bee choosing between images with black dots on them. Right: an illustration of a bee choosing the image with fewer dots
© Scarlett Howard & Aurore Avarguès-Weber

The researchers trained bees to identify images in the lab that showed the fewest number of elements (in this case, dots). If they chose the image with the fewest circles from a set, they received sweetened water, whereas if they chose another image, they received bitter quinine.

Once the insects got that concept down, the researchers introduced another challenge: The bees had to choose between a blank image and one with dots on it. More than 60 percent of the time, the insects were successfully able to extrapolate that if they needed to choose the fewest dots between an image with a few dots and an image with no dots at all, no dots was the correct answer. They could grasp the concept that nothing can still be a numerical quantity.

It’s not entirely surprising that bees are capable of such feats of intelligence. We already know that they can count, teach each other skills, communicate via the “waggle dance,” and think abstractly. This is just more evidence that bees are strikingly intelligent creatures, despite the fact that their insect brains look nothing like our own.

Considering how far apart bees and primates are on the evolutionary tree, and how different their brains are from ours—they have fewer than 1 million neurons, while we have about 86 billion—this finding raises a lot of new questions about the neural basis of understanding numbers, and will no doubt lead to further research on how the brain processes concepts like zero.

[h/t Vox]


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