For a tiny marine worm found in the Bay of Naples and elsewhere, life ends in a frenzy. The worms lose a lot of their internal organs, their eyes get bigger, and they rise to the surface. There, as they paddle furiously, they release sperm and eggs, creating the next generation. And it’s all triggered by moonlight.

The worms are one of more than 10,000 species of marine bristle worm. They’re only about an inch long. Each body segment has a pair of paddle-like structures tipped with bristles. The worms live at the bottom of warm, shallow waters around the world. And they’re considered “living fossils”—they haven’t changed much in tens of millions of years.

The bristle worms are especially sensitive to changing light levels. They build tubes on the ocean floor. When a shadow passes across them, they pull back into the tubes to elude possible predators. And their end-of-life ballet is triggered by moonlight.

The body changes begin around the time of “new” Moon, when there’s little or no moonlight. The worms then rise to the surface not long after the full Moon.

Scientists recently studied how that happens. They found that some proteins react differently with different light levels. Under bright sunlight, they stay apart, in separate units. But under dimmer conditions, the units stick together. That allows the worms to not only distinguish between day and night, but between different phases of the Moon—a light-activated “trigger” for a big change.

Conditions in the Arctic Ocean may be about to switch gears. That could mean that Arctic waters would become more like those in the North Atlantic—a process known as “atlantification.” As a result, sea ice would disappear a lot faster than it has in recent years.

The rate of sea-ice loss peaked in 2007. The total amount of ice is still going down, but much more slowly than it was before. In December of 2023, in fact, the sea ice increased at a higher rate than in all but two other months in the past 45 years.

A recent study said the slowdown in ice loss may be a result of the Arctic dipole—a pattern in the way air circulates over the far north. Today, there’s high pressure over the Canadian arctic, and low pressure over Siberia.

That pattern reduces the flow of warmer water from the North Atlantic Ocean into the Arctic Ocean. There’s a thicker layer of colder, fresher water at the top of the Arctic. That keeps the ice from vanishing as fast as expected based on the higher air temperatures produced by our warming climate.

Scientists looked at decades of observations made from ships, airplanes, and satellites. They found that the dipole might be about to flip over—from “positive” to “negative.” If that happens, the changing circulation in the atmosphere would allow more water to flow in from the Atlantic. That would warm the upper layers of the Arctic, causing sea ice to disappear much faster—boosting the “atlantification” of the Arctic.

Some tiny sea snails may look like angels, but they act more like little devils. They rip their favorite prey from their shells. And the prey just happens to be a relative.

Sea angels are found around the world, from the arctic to the tropical waters near the equator. Most range from the surface to depths of a couple of thousand feet, although some have been seen more than a mile down.

Sea angels are born with shells, but they lose them as they become adults. They’re no more than a couple of inches long, and they have streamlined bodies. They’re mostly transparent, which helps them hide from predators. The Antarctic sea angel has extra protection: it produces a nasty chemical that keeps most predators away.

What gives sea angels their “angelic” appearance is a pair of wings. They’re adapted from the muscular foot of their land-based cousins. The creatures move through the water by flapping those wings. They can move twice as fast as their prey.

Their favorite treat is another sea snail—the sea butterfly. Some angels lie in wait, while others are more active hunters. They grab their prey with small tentacles that extend from the head. Hooks allow them to pull the butterfly from its shell in as little as two minutes.

Sea angels and their prey are jeopardized by climate change, which makes the oceans more acidic—a hazard for any creature that produces a shell. That’s an extra challenge for these angelic little devils flapping through the world’s oceans.