This Bug Only Warns You Not to Attack It After You Attack It

Rile up a cat and it might arch its back, raise its fur, bare its teeth and start hissing at you. Kitty’s little tantrum is what’s known as a deimatic or startle display, a way of scaring or distracting a threat and buying some time to escape. Lots of animals have their own displays like this. Some are honest warnings about the animals’ defenses (like toxins), while others are just bluffs. Either way, the display only benefits an animal if it scares or stops a predator before an attack. There’s not much use in telling a predator how dangerous you are or trying to scare it off when it’s already chewing on your leg. It would make sense, then, for a startle display to be obvious and come before an attack.

And that’s usually how it works. But not for Australia’s mountain katydid (Acripeza reticulata).

These thumb-sized cricket cousins are slow and clumsy, and defend themselves by secreting bitter chemicals from their abdomens. These chemicals not only taste bad, but are toxic to birds and mammals (but are, oddly, aphrodisiacs for some insects). The katydids scare potential predators and advertise their toxins with a startle display that involves vomiting and flashing the vivid red, blue, and black stripes hidden beneath their dull brown wings. It’s impressive, but to zoologist Kate Umbers, the display seemed to be too little, too late, because it came after the bugs were attacked. 

In the field, Umbers found she could pick the bugs up no problem, and only after she grabbed them did they try to deter her or give any indication that they had other defenses. In this case, that was fine. Umbers wasn’t going to hurt the bugs, after all. But flashing a warning or startle display so late wouldn’t help them if they’d been snatched up in some animal's claws instead of a scientist’s hands. 

Umbers was puzzled, and teamed up with Johanna Mappes (who has done some cool work with snakes that I’ve covered here before) to test the defensive reactions of 40 more katydids in the lab. Almost none of them reacted when the scientists blew on them, waved a book over their heads to look like a passing bird or tapped a pen near them. They only flashed their colors and puked when they were prodded or grabbed. 

As counterintuitive as a post-attack startle display is, Umbers and Mappes say it starts to make sense when you think about the katydid’s other characteristics. While most animals would startle a predator and then flee while it was distracted, the katydids can’t really do that. In addition to being slow and clumsy, the bugs can’t jump very far, and only the males can fly. What they do have going for them, though, is their chemical defenses and a set of tough, leathery brown wings that both shield their abdomen and blend in with leaves and stones on the ground. 

The researchers now think that the bug’s display isn’t too late, but just sits in a chain of defenses in a place that breaks with the way nature usually does things. They think the katydid relies on camouflage as much as possible to avoid predators. If it is spotted and attacked, its tough wings help it survive the initial attack and the combination of toxins and startle display deters a second attack. Holding off on the startle display instead of using it earlier like most animals would helps the bug avoid revealing itself to a predator that might not have actually noticed it. 

Umbers and Mappes would like to test their hypothesis and see how the katydid’s defense suite fares against real predators, but there’s another problem they’ll have to solve first. No one seems to know what eats these katydids. Umbers did notice lots of ravens and magpies in the areas where the bugs are found, so they’re likely candidates. Both these birds tend to investigate prey with their beaks before chowing down, which would give the bug a chance to flash its colors after initial contact but before it’s really in danger of becoming lunch. 

Andreas Trepte via Wikimedia Commons // CC BY-SA 2.5
Climate Change Has Forced Mussels to Toughen Up
Andreas Trepte via Wikimedia Commons // CC BY-SA 2.5
Andreas Trepte via Wikimedia Commons // CC BY-SA 2.5

Researchers writing in the journal Science Advances say blue mussels are rapidly evolving stronger shells to protect themselves against rising acid levels in sea water.

Bivalves like mussels, clams, and oysters aren’t good swimmers, and they don’t have teeth. Their hard shells are often the only things standing between themselves and a sea of dangers.

But even those shells have been threatened lately, as pollution and climate change push the ocean's carbon dioxide to dangerous levels. Too much carbon dioxide interferes with a bivalve’s ability to calcify (or harden) its shell, leaving it completely vulnerable.

A team of German scientists wondered what, if anything, the bivalves were doing to cope. They studied two populations of blue mussels (Mytilus edulis): one in the Baltic Sea, and another in the brackish waters of the North Sea.

The researchers collected water samples and monitored the mussel colonies for three years. They analyzed the chemical content of the water and the mussels’ life cycles—tracking their growth, survival, and death.

The red line across this mussel larva shows the limits of its shell growth. Image credit: Thomsen et al. Sci. Adv. 2017

Analysis of all that data showed that the two groups were living very different lives. The Baltic was rapidly acidifying—but rather than rolling over and dying, Baltic mussels were armoring up. Over several generations, their shells grew harder.

Their cousins living in the relatively stable waters of the North Sea enjoyed a cushier existence. Their shells stayed pretty much the same. That may be the case for now, the researchers say, but it definitely leaves them vulnerable to higher carbon dioxide levels in the future.

Inspiring as the Baltic mussels’ defiance might be, the researchers note that it’s not a short-term solution. Tougher shells didn’t increase the mussels’ survival rate in acidified waters—at least, not yet.

"Future experiments need to be performed over multiple generations," the authors write, "to obtain a detailed understanding of the rate of adaptation and the underlying mechanisms to predict whether adaptation will enable marine organisms to overcome the constraints of ocean acidification."

University of Adelaide
Scientists Find Potential Diabetes Drug in Platypus Venom
University of Adelaide
University of Adelaide

The future of diabetes medicine may be duck-billed and web-footed. Australian researchers have found a compound in platypus venom (yes, venom) that balances blood sugar. The team published their results in the journal Scientific Reports.

So, about that venom. The platypus (Ornithorhynchus anatinus) may look placid and, frankly, kind of goofy, but come mating season, the weaponry comes out. Male platypuses competing for female attention wrestle their opponents to the ground and kick-stab them with the venom-tipped, talon-like spurs on their back legs. It’s not a pretty sight. But it is an interesting one, especially to researchers.

Animal venoms are incredible compounds with remarkable properties—and many of them make excellent medicine. Many people with diabetes are already familiar with one of them; the drug exenatide was originally found in the spit of the venomous gila monster. Exenatide works by mimicking the behavior of an insulin-producing natural compound called Glucagon-like peptide 1 (GLP-1). The fact that the lizard has both venom and insulin-making genes is not a coincidence; many animal venoms, including the gila monster’s, induce low blood sugar in their prey in order to immobilize them.

It’s a good strategy with one flaw: GLP-1 and compounds like it break down and stop working very quickly, and people who have trouble making insulin really need their drug to keep working.

With this issue in mind, Australian researchers turned their attention to our duck-billed friends. They knew that platypuses, like people, made GLP-1 in their guts, and that platypuses, like gila monsters, make venom. The real question was how these two compounds interacted within a platypus’s body.

The researchers used chemical and genetic analysis to identify the chemical compounds in the guts and spurs of platypuses and in the guts of their cousins, the echidnas.

They found something entirely new: a tougher, more resilient GLP-1, one that breaks down differently—and more slowly—than the compounds in gila monster spit. The authors say this uber-compound is the result of a "tug of war" between GLP-1’s two uses in the gut and in venom.

"This is an amazing example of how millions of years of evolution can shape molecules and optimise their function," co-lead author Frank Gutzner of the University of Adelaide said in a statement.

"These findings have the potential to inform diabetes treatment, one of our greatest health challenges, although exactly how we can convert this finding into a treatment will need to be the subject of future research."


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