Nematode may trick birds with berry-bellied ants

Comparison of normal worker ants (top) and ants infected with a nematode. When the ant Cephalotes atratus is infected with a parasitic nematode, its normally black abdomen turns red, resembling the many red berries in the tropical forest canopy. According to researchers, this is a strategy concocted by nematodes to entice birds to eat the normally unpalatable ant and spread the parasite in their droppings. (Credit: Steve Yanoviak/University of Arkansas)

Timeline, 2008: Host-parasite relationships can be some of the most interesting studies in biology. In some cases, a parasite requires more than one host to complete its life cycle, undergoing early development in one host, adult existence in another host, and egg-laying in still another. There’s the hairworm that turns grasshoppers into zombies as part of its life cycle, and the toxoplasma parasite, which may alter the behavior of humans and animals alike. Often, the infection ends with the host engaging in life-threatening behaviors that lead the parasite to the next step in the cycle.

A recent discovery of a most unusual host-parasite relationship, however, results in changes not only in host behavior but also in host appearance. The infected host, an ant living in the forest canopy in Panama and Peru, actually takes on the look of a luscious, ripe fruit.

Berry-butted ants

Researchers had traveled to the Peruvian forest on a quest to learn more about the airborne acrobatics of these ants, Cephalotes atratus. This ant is a true entomological artist, adjusting itself in midair if knocked from its perch. Re-orienting its body, it can glide back to the tree trunk, grabbing on and climbing to where it belongs, avoiding the dangers of the forest floor.

As the investigators monitored the colony, they became aware of some odd-looking members of the group. These ants had large red abdomens that shimmered and glowed and looked for all the world like one of the tropical berries dotting the forest around them. Curious about these odd ants, the scientists took some to the lab for further investigation. Ant researchers are an obsessive breed, and they had even placed a bet over whether or not these berry-bellied ants were a new species.

A belly full of another species’ eggs

When they sliced open one of the bellies under a microscope, what they found surprised them. Inside, a female nematode had packed the ant’s abdomen full of her eggs. The bright red belly was an incubator and, the researchers surmised, a way station on the nematode’s route to the next step in its life cycle. This was the same old C. atratus with a brand new look.

Tropical birds would normally ignore these ants, which are black, bitter, and well defended with a tough, crunchy armor. But any tropical bird would go for a bright, red, beautiful berry just waiting to be plucked. The scientists found that in addition to triggering changes to make the ant belly look like a berry, the nematode also, in the time-honored manner of parasites, altered its host’s behavior: the berry-bellied ants, perched on their trees, would hold their burgeoning abdomens aloft, a typical sign of alarm in ants. A bird would easily be tricked into thinking that the bug was a berry. One quick snap, and that belly full of nematode eggs would be inside the belly of a bird.

Poop: A life cycle completed

And then the eggs would exit the bird the usual way, ending up in the bird’s feces. The ants enter the picture again, this time collecting the feces and their contents as food for their colony’s larvae. The eggs hatch in the larvae and the new nematodes make their way to the ant belly to start the cycle anew.

The nematode itself is a new find, a new species dubbed Myrmeconema neotropicum. And it seems that earlier discoverers of the berry-bellied ants also thought they had a new species on their hands: the researchers turned up a few previous berry-bellied specimens in museums and other collections labeled with new species names. No one had thought that the difference in appearance might be the result of a parasitic infection: this relationship is the first known example of a parasite causing its host to mimic a fruit.

Birds remain the missing link

There is one hitch to the newly discovered nematode-ant-bird association: the researchers never actually saw a tropical bird snap up a juicy, fruit-mimicking ant. They report seeing different species of birds scan the bushes where such ants sheltered, but there were never any witnessed ant consumptions. Thus, this inferred piece of the puzzle—the involvement of birds and their droppings in the life cycle of this nematode—remains to be proven.

Advertisements

Ancient Peruvian beer breweries

Rich Peruvian women brewed beer

When it comes to drunken women, the Peruvians have always been different. In many societies, women are not supposed to drink at all. They certainly aren’t supposed to get knee-walking, rip-roaring drunk, matching shot for shot with a man. It’s generally considered unladylike, and these days, studies keep coming out indicating that overimbibing may have more adverse effects on women’s health than it does on men’s.

But the Peruvians of today, especially those living in the Andes, indulge in equal-opportunity carousing. It appears that they simply are following a tradition that may be more than 1000 years old.

What drove agriculture? Beer or bread, naturally

A few years ago, archaeologists discovered large broken vats on top of a 8000-foot-high mesa, Cerro Baul, in the Peruvian Andes. Among the vats were the remnants of smaller vessels and some shawl pins that belonged to noblewomen of the Wari people, a pre-Incan civilization that suddenly disappeared about 1000 years ago. From about 600 AD to 1000 AD, however, the civilization flourished around Cerro Baul. Nobles lived on the mountaintop, and farmers and middle-class artisans and technicians lived and worked in the valleys below.

The researchers felt that they must have stumbled across one of the world’s ancient breweries. Breweries attract anthropologists and historians because beer competes with bread as the driving force behind the development of agriculture. Every civilization appears to have brewed, usually using grains like wheat and barley. Some of the oldest suspected breweries date back as far as 3000 BC in Egypt, and suspected breweries have also been discovered in what is now Iraq.

But the equivocal “suspected” is what makes the Peruvian find so delicious. Ancient breweries defy clear identification because the beer was brewed from the same grains used to make bread; thus, it is difficult to distinguish the cereal-based residue on pot fragments as the result of brewing vs. baking. What the brewery-hunters of the world needed was a civilization that used some unusual ingredient in its beer, something that they didn’t also use in their bread. And they found it in the Wari people of ancient Peru.

Corn fermented, pepper-flavored beer

Even today, native Peruvian beer stands out among the world’s brews. It is fermented from corn and flavored with berries from the pepper tree. No other beer in the world has this combination, and the Peruvians apparently do not use the pepper tree to make bread. This concoction, called “chicha” today, is apparently very like what the Wari people brewed high on their mesa 1000 years ago.

The researchers latched onto pepper tree residues as the ingredient that would allow them to definitively identify an ancient brewery. The pepper berries contain a compound called oxalic acid that can adhere to ceramic pottery for centuries. Using techniques like liquid chromatography, they were able to confirm that this compound was indeed present in the large vats on Cerro Baul.

Wild, ancient Peruvian bacchanal

They had suspected as much. The vats themselves were huge and obviously designed to hold liquid. The surprise was that the brewery and the vats appeared to have been destroyed in a single night of carousing just before the Wari abandoned their mountaintop. Researchers surmise that the nobles of the town engaged in ritual drinking and drunkenness—the big guns got the larger Wari beer steins—and then, when the ceremony ended, they destroyed their ceramic vats and set the place on fire. After the building had burned to the ground, the nobles placed jewelry on top of the remains, possibly to identify it as a sacred place.

Interestingly, among the destruction, the archaeologists found the noblewomen’s shawl pins. They surmise that the women may have brewed the beer; in later Incan civilizations, upper-class women brewed beer, and only upper-class people drank chicha with the pepper-tree flavor added.

Of course, you have to taste test it

When it was active, the brewery may have produced hundreds of gallons of beer a week. In an effort to experience the flavor, some archaeologists recreated the ancient concoction and report that it is not quite as dark as a modern-day stout, and has sweet, peppery flavor with a bitter finish.

%d bloggers like this: