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Photo illustration by Laura Bagge; dragonfish by Sönke Johnsen; Cystisoma by Karen Osborn
Photo illustration by Laura Bagge; dragonfish by Sönke Johnsen; Cystisoma by Karen Osborn

Crustaceans Fake Out Predators With Glare-Resistant Coating

Photo illustration by Laura Bagge; dragonfish by Sönke Johnsen; Cystisoma by Karen Osborn
Photo illustration by Laura Bagge; dragonfish by Sönke Johnsen; Cystisoma by Karen Osborn

Today in "You Guys, The Ocean Is So Weird": Scientists say some crustaceans wear mattifying living layers to hide from predators. A report on the sea critters’ clever camo was published in the journal Current Biology.

Amphipods are a group of shrimplike crustaceans that make their homes in a variety of venues, from freshwater to beaches and deep into the sea. They’re not particularly charismatic creatures, but charisma doesn’t count for much in the darkness of the ocean. What counts is adaptability.

Some species have developed glowing fishing poles; others, sparkling arms. Some creatures light up in order to be seen, while others use illumination to hide. Others, like these amphipods, would prefer to avoid light altogether.

This is harder for them than it would be for you or me. Why? Because they’re naturally transparent—and reflective.

Scientists put seven specimens of mid-water amphipod species under high-powered microscopes and looked closely at their shells. When they zoomed way in, they discovered that all the amphipods were sporting little coats of what looked like beads on their bodies and legs. The beads themselves are microscopic, ranging from 50 to 300 nanometers in diameter depending on the species. This makes them just the right size and shape for absorbing undersea light.

Coating on the leg of a Cystisoma amphipod. Image Credit: Laura Bagge, Duke University

 
Biologist Laura Bagge is lead author on the study and a Ph.D. candidate at Duke University. Speaking in a press statement, she said the coating reduces reflections “the same way putting a shag carpet on the walls of a recording studio would soften echoes.” Some species’ coatings could cut down on glare by as much as 250-fold, rendering them effectively invisible to wide-eyed predators.

The coats are certainly effective. But what are they?

We're not totally sure. “They have all the features of bacteria,” Bagge said, “but to be 100 percent sure, we’re going to have to perform an in-depth sequencing project.”

Crustaceans shed their shells on a regular basis. For carefully camouflaged amphipods, this could mean becoming shiny again—unless they take their special coats with them. If the mattifying layers are indeed made of bacteria, they could easily be transferred to a new shell as the amphipod tugs its way out of the old one.

Mama Phronima with offspring inside a salp nest. Image Credit: Laura Bagge, Duke University

 
They could also share them with their kids. Phronima amphipods raise their babies in the hollowed-out bodies of a translucent creature called a salp. The researchers say it would be pretty simple for a mama amphipod to pass her coating materials on to little ones in the nest.
 
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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."

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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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