Zombie Fungi, Full Bladders

David Hughes

Zombie spores: The stalk growing 
out of this worker ant’s head will infect her friends.

Zombie humans are all the rage on the big and small screens today. But in tropical rain forests across the globe, you’re more likely to bump into zombie ants infected by a parasitic fungus that has hijacked the bugs’ nervous systems. As part of a ZOMBIE FUNGUS WORLD TOUR, a group of biologists has recently discovered four new species in Brazil (PLoS One, DOI: 10.1371/journal.pone.0017024).

The life cycle of these Ophiocordyceps fungi reads like a science fiction screenplay. Once their spores infect an ant, the fungal cells replicate until they completely take over the ant’s body, killing it within three to nine days. But before the ant dies, the fungus makes it take one last trip outside its colony.

This zombie ant staggers into the forest in search of a leaf that hangs about 10 inches off the ground and sits in the perfect amount of sunlight for fungal growth. The ant then bites into the leaf and dies latched onto it. The fungus preserves and protects the ant’s exoskeleton, probably with an array of antimicrobial compounds, while a fungal stalk slowly grows from the ant’s head. After a couple of weeks, this stalk starts releasing spores to continue the cycle.

Each type of these newly discovered fungi targets a specific ant species, says study leader David P. Hughes, an entomologist at Pennsylvania State University. The fungi tailor the shape of their spores to their ant hosts’ travel habits. For example, to snag solitary ants that forage over great distances across the forest floor, some fungi produce linear spores that can fly out into the forest like “buckshot,” Hughes says.

As Hughes continues his world tour in Colombia and Ghana, he hopes to culture the fungi species he finds so researchers can study them in the lab. One question he wants to answer: What chemicals do the fungi deploy to brainwash the ants?

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Hold it: Bladder control leads to better choices.

Although humans don’t have to worry about fungal mind control, we’ve all made impulsive decisions that we’ve regretted. Now, Dutch psychologists report a way to avoid these rash choices: Fill your bladder.

Psychologists have known that when people are hungry or sexually aroused, they tend to make impulsive decisions, says Mirjam Tuk, a behavioral scientist at the University of Twente. The drive to immediately satiate a bodily need spills over into other parts of a person’s behavior, such as the desire to pick an immediate, but smaller, cash prize instead of waiting for a larger one. So Tuk wondered whether CONTROLLING BODILY NEEDS, such as holding one’s bladder, could lead to restraint in decision making.

She set up a ruse to fill her subjects’ bladders by telling them that they were participating in a taste test of bottled water. Half of the subjects had to drink five full glasses of different waters to judge their flavors, and others had to take only one sip from each.

Forty-five minutes after the tastings, the participants had to decide how they’d like to receive their compensation: $16 paid the next day or about $30 sent 35 days later. Those who drank the full glasses had a stronger urge to urinate and opted for the larger payout more often than the sippers, who had less full bladders, picked the short-term reward, Tuk and her colleagues report in the April issue of Psychological Science.

Tuk says that understanding how physical restraint spills over to other behaviors could allow psychologists to help people deal with impulsivity, especially those who make poor food choices. Until then, when faced with a big decision, bottoms up!

Chemical & Engineering News

ISSN 0009-2347

Copyright © 2011 American Chemical Society