Champion of the Week: A Glass-Headed Fish, a Blood-Squirting Lizard, a Sparrow-Sized Bug, a Blushing Sand Swimmer, and the Mouthless Worm That Ate Them All

It is Saturday, which in this house means the five champions who survived the week get dragged back into the arena to fight each other, and me, and the concept of dignity. Here is the bracket I have assembled from Monday through Friday: a deep-sea fish with a see-through head, a lizard that squirts blood out of its own eyeballs, a New Zealand bug that weighs as much as a bird, an Argentine armadillo the size of a dinner roll that swims through sand and blushes when it is warm, and a worm with no mouth that dissolves whale skeletons for a living. Cross-taxa, cross-hemisphere, cross-any-line-of-good-taste. Exactly how I like it. I judge on three things and three things only: how cool, how weird, and how gross. Let's crown a Critter of the Week.

The bracket, and why nobody is safe

Five winners. One crown. No refunds. I researched each of these little freaks until I had at least two real sources swearing the facts were true, because unlike my opinions, my facts have to hold up.

Barreleye: the fish that watches you through its own forehead

The barreleye (Macropinna microstoma) has a transparent, fluid-filled dome over the top of its skull, and its actual eyes are two glowing green tubes sitting inside that dome. Those green lenses may filter out the sunlight coming straight down so the fish can pick out the faint bioluminescent glow of prey against the dark. The eyes rotate: they point straight up to spot the silhouettes of food drifting overhead, then swivel forward when it is time to eat. And the two dark spots on the front of its face that look exactly like eyes? Those are its nostrils. The real eyes are in the aquarium of its own head.

It lives around 600 to 800 meters down and tops out at about 15 cm. For decades everyone assumed its gaze was locked upward until MBARI filmed a living one and watched the eyes swing around like security cameras. Cool rating: absurd. Weird rating: it has a windshield.

Texas horned lizard: the state reptile with a blood cannon

The Texas horned lizard (Phrynosoma cornutum) is the official state reptile of Texas, which means Texas looked at a spiky toad that shoots blood out of its face and said yes, that one, put it on the seal. When a canid predator - a coyote, a fox, your labrador - gets too close, the lizard ruptures tiny vessels around its eyes and fires an aimed stream of its own blood up to five feet. The blood is diet-derived nasty and tastes foul specifically to dogs and their relatives; it does basically nothing to birds, so the lizard saves the trick for the right audience.

What funds this blood budget? Ants. Up to about 70 percent of its diet is harvester ants, picked off a trail one at a time, which is why it has an oversized stomach: ants are terrible calories. It can also puff its body up so its scales stick out and it becomes a mouthful of spikes. Gross rating: it weaponized anemia. Cool rating: undeniable.

Wetapunga: the bug that shows up to a fight weighing as much as a sparrow

The wetapunga (Deinacrida heteracantha) is a New Zealand giant weta and one of the heaviest insects on Earth. A gravid female can hit about 35 grams, heavier than an average house sparrow, and captive record-holders have reached around 70. The name roughly translates to god of ugly things, which is the single greatest thing any culture has ever named an animal.

It is flightless, nocturnal, eats leaves, and its body plan has barely changed in about 190 million years, making it older than the tuatara it shares an island with. It survives naturally on exactly one place, Hauturu (Little Barrier Island). When bothered it hisses by rubbing its legs against its abdomen and waves its spiny back legs at you. Cool rating: it is a living fossil the size of your palm. Weird rating: it breathes through holes in its shell and molts eleven times to get this big.

Pink fairy armadillo: a dinner roll that swims through dirt and is embarrassed about it

The pink fairy armadillo (Chlamyphorus truncatus) is the smallest armadillo alive, roughly 10 to 12 cm and about 120 grams, endemic to the sandy plains of central Argentina. It is a sand swimmer that spends nearly its whole life underground and is so rarely seen that scientists list it as Data Deficient. Here is the detail that broke me: its pink shell is not fused to its body. It is attached only by a thin membrane along the spine, like a saddle draped over the animal.

And it is pink for a reason. Blood flows into that thin shell to dump heat, which makes it flush pinker when the animal is warm, and drains out to conserve heat, which makes it go pale. It is a mammal that changes color with its mood ring of a back. It also has a flattened rear plate it uses to tamp down soil behind itself as it tunnels, and it almost never survives in captivity. Cool rating: it blushes to thermoregulate. Weird rating: detachable outerwear.

Osedax: the boneworm with no mouth and 600 husbands

And then there is the zombie worm (genus Osedax). It has no mouth. No gut. No stomach. No anus. What it has is a root system that it drills into the bones of dead whales that fall to the seafloor, secreting acid through a proton pump to dissolve the bone and release the fats and collagen trapped inside. It cannot digest that on its own, so it farms symbiotic bacteria in its roots to do the eating for it. A mouthless animal that acid-melts a whale skeleton and lets bacteria absorb the soup.

It gets worse, and by worse I mean better. The Osedax you can see are all females. The males are microscopic and live by the dozens to the hundreds inside her tube - MBARI has found large females carrying harems of more than 600 dwarf males. She is a mouthless bone-dissolving acid worm and she is also running a studio apartment packed with 600 tiny husbands. A whale skeleton can be stripped clean in as little as a decade. Gross rating: off the chart. Weird rating: also off the chart.

Tale of the tape

• Coolest: the barreleye and the wetapunga split this. A glass head versus a 190-million-year-old palm-sized tank.
• Weirdest: the pink fairy armadillo with its detachable blushing saddle, closely stalked by the Osedax.
• Grossest: not close. The lizard squirts blood, but the worm has no mouth, melts bone with acid, and lives with hundreds of husbands.

You know what they say: coolness gets you into the bracket, but grossness wins the belt.