The Voracious Fish That Looks Like a Pug and Stings Like a Bee

The only way a stargazer could turn its frown upside down is if you rotated this picture 180 degrees.

We’ve all had that moment. You get a half hour away from the house and realize, I left the stove on, didn’t I. Or in the case of two particularly irresponsible parents in the early ‘90s, I left Macaulay Culkin in the house, didn’t I. You freeze, you go wide-eyed, and your jaw drops a little.

It’s a kind of terror a fish known as the stargazer embodies its entire life. It may not be worrying about a visit from Child Protective Services, but it does have to worry about eating. The bulging eyes and frowny mouth that make it look like an aquatic pug are brilliant adaptations for an ambush predator. And even beyond its … singular looks, this is one of the sea’s most remarkable fishes—it’s venomous and it shocks like an electric eel.

Unless you’ve got a coral reef to duck into, the bottom of the ocean is a place of constant peril. Death comes from above, sideways, and, with the strategy of the 50 or so species of stargazer thrown in the mix, from below. To get a jump on their prey, the fish burrow into the sand, exposing only their mouths and bug-eyes. This has an added bonus of hiding the stargazers from their own enemies swimming above.

So the stargazer is buried there, biding its time, probably thinking about eating and stuff. Some species even utilize a specially-shaped piece of flesh on the inside of their mouths, which acts like a lure to fish and crustaceans hunting on the seafloor. “They’re able to stick this out of the mouth when they’re burrowed, resembling a segmented worm to draw the attention of other fish,” says systemicist Martin Gomon of Australia’s Museum Victoria. (The anglerfishes utilize a similar ruse, only their lures are actually modified dorsal spines. Also, their sex is kinky.)

Curious fish expecting an easy meal instead get a healthy dose of death. All the stargazer has to do is rapidly open its gaping maw, and the resulting vacuum drags the prey to its doom. It’s so effective, the predator has no need for nasty, big, pointy teeth to snag its prey—its chompers are relatively tiny.

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 But this lifestyle comes with unique challenges. For one, the stargazer has to worry about the water flowing out of its buried gills kicking up sand. If potential prey see the substrate bubbling up around the predator, the ruse is up. So the stargazer has a clever adaptation: Its gill covers are fringed with finger-like projections that may better disperse the water coming out, as opposed to firing it out as a solid jet.

Its mouth, too, has frills around the edges to keep sand from falling in as the fish gulps water. And it’s not just that the stargazer wants to avoid choking to death here. Sand is, of course, super abrasive. “What you want to do is minimize the amount of sand that damages the gills over time,” says Gomon.

While the stargazer’s camouflage may be top-notch, it isn’t perfect. So the fish deploys additional countermeasures in the event of an oh-bother-I’m-in-another-animal’s-mouth kind of situation. First, it has a venomous spine just above the base of its pectoral fins (those would be the ones on the fish’s sides). While its venom is still poorly studied, it’s apparently got some kick, considering stargazers have dropped a handful of humans dead.

Some stargazer species also deploy a second countermeasure: a specialized organ behind their eyes that fires out a blast of electricity. Like an electric eel, stargazers can zap their enemies, though they use it for defense, not hunting. And the stargazers’ blast is far weaker than an electric eel’s—50 volts compared to 600—but the jolt may just be enough to startle a predator into turning the fish loose.

With any luck, that fake worm will attract a fish to its doom. So when a stargazer does the worm, it’s a bit more literal than for humans.

Really, though, the stargazers’ strategy is to go unseen. Which makes one species, Pleuroscopus pseudodorsalis, particularly strange. Other stargazers will swim around as juveniles and settle into the sand once they reach about 2 inches long. But this species’ larva spends an inordinate chunk of its life braving a zone even more dangerous than the seafloor, the open ocean, only settling once it’s reached a foot long.

The juvenile’s body is uniquely suited for this lifestyle. Its eyes and mouth, for instance, aren’t angled as far back on the head, allowing it to better tackle prey straight ahead. “We thought it was a different species entirely,” says Gomon, “but the form of the body changes quite dramatically” between the juvenile and adult stages. Considering boats have brought the young up on baited lines, the fish appear to be active predators as juveniles.

But even though it’s removed from the relative safety of the seafloor, the juvenile is far from conspicuous, having evolved its own form of clever camouflage. The top half of its body is a dark blue, while its underside is paler—the same kind of countershading, as it’s known, that the great white shark deploys. Predators watching from above will have a harder time picking the stargazer out from the dark background of the water below, while predators watching from below will have a harder time picking it out from the sunlight trickling down from the surface.

Read more at Wired Science