This week, we have…

• A fun fact inspired by Metazooa

• Answers to last week's games

• Reader survey

Sea lions sleep with one brain open

Ever have that feeling where you’re half-asleep, but also half scanning the horizon for sharks? That’s exactly what sea lions (Metazooa animal #712) do thanks to a trick called unihemispheric slow-wave sleep (USWS)—they power-down one hemisphere of the brain while the other stays on lookout for predators and keeps the body surfacing for air. Electro-encephalogram tags show that in open water these pinnipeds string together dozens of micro-naps under ten minutes each, adding up to roughly five–eight hours of shut-eye per day, yet never missing a breath or a beat.

The awake hemisphere shows a burst of the alertness chemical acetylcholine (a pattern first measured in their close cousins, northern fur seals), while the drowsy side stays chemically quiet—evidence that sea-lion brains literally flip a biochemical “awake” switch from left to right and back again.

Sleep posture matters, too. At the surface a sea lion “rafts,” floating horizontally with flippers splayed for balance; in shallows it may sprawl on the seabed and bob up for air every few minutes. REM sleep—the vivid-dream stage we enjoy—vanishes almost entirely at sea and returns only when the animals haul out on land, proving you don’t need dreams to wake up refreshed when half your brain is always on guard.

Learn more: Science.org, NCBI

Trivia

Answers to last week's games

Monday, July 7 to Sunday, July 13.

Linxicon

The following are the shortest paths from last week:

• #510 pay → amount → approximately → roughly

• #511 perhaps → positive → pleasant → chilly → ice

• #512 computer → mainframe → main → mainly → largely

• #513 league → win → happy → thank

• #514 contrast → competition → candidates → candidate

• #515 just → simply → physically → physical → external

• #516 civil → civilization → theory → possibility

• #517 Play now!

Elemingle

• #166 Lanthanum

• #167 Lead

• #168 Fermium

• #169 Promethium

• #170 Seaborgium

• #171 Copper

• #172 Calcium

• #173 Play now!

Forgeous

Play Forgeous for July 14