Insect Navigation: Dung Beetles and the Starry, Starry Night

Panoramic image of the Milky Way.
European Southern Observatory/S. Brunier. Creative Commons.

Just as sailors once followed the stars to distant lands, dung beetles can use starry skies to navigate, according to an article published in the January 23 issue of Current Biology.

A research team led by Marie Dacke, a biologist at Sweden’s Lund University, conducted their experiments in the Johannesburg planetarium, which was fully darkened as well as illuminated with projections of the Milky Way and other stars.

As reported here in ScienceNews,

Dung-rolling insects are excellent for studying navigation because they collect their prized food source and single-mindedly roll it as directly as possible away from competitors and predators. Putting the beetles in weird get-ups during experiments doesn’t deter them. “They are so attached to their dung balls,” Dacke says, “that under all circumstances they just want to roll the ball in a straight line.”

via Dung beetles steer by the Milky Way | Zoology | Science News.

Dung beetle (Circellium bacchus.) There are thousands of species of dung beetles. Scarabaeus satyrus was the species used in the starlight experiment.
By Kay-Africa. Wikipedia Commons.

Infestation: Biopesticide Shows Promise for Bed Bug Sufferers

Discarded mattress. By Jamie Drummond. CC BY-NC-ND 2.0.

I wanted the journalism experience. That’s why I took an unpaid internship in Washington, D.C., before my senior year of college. As an added bonus that summer, I picked up a case of head-to-toe “bird lice” from the well-traveled futon in the apartment I was subletting. (Not sure where the bird ever was.) Ever since, I have suffered a mild case of what I’ll call FTTCM—fear of tiny things crawling on me. Considering my personal history, it may not have been the best idea for me to get in touch with bedbug expert Nina Jenkins last month. But for the sake of science, I had to give her a call.

Jenkins, senior research associate in entomology, and her colleagues at Pennsylvania State University (Alexis Barbarin, formerly a postgraduate student and now a post-doc at the University of Pennsylvania, and entomology professors Edwin Rajotte and Matthew Thomas), have found a natural fungal biopesticide to deal with these pests. The results of their study on the effectiveness of Beauveria bassiana appear in the Journal of Invertebrate Pathology.

Because of bed bugs’ growing resistance to chemical pesticides, it has become very difficult to get rid of them, Jenkins tells me. “They’ve become a huge problem in city areas: Philadelphia, New York City, and Cincinnati are all in the news for having a high prevalence of bed bugs in hotels and private housing.” (Gulp. I lived in Philadelphia not too long ago. And so did my bed.)

The bites of bloodthirsty bed bugs itch like mosquito bites do. And though there is no evidence that these bugs transmit diseases, they are very inconvenient to have around. “I think a lot of psychological damage goes with that,” Jenkins says. (Not that I would know anything about this.)

“The key to really addressing a bed bug infestation is getting to the harborage (where they bed down), which is otherwise inaccessible to chemicals,” Jenkins explains. “There are so many little cracks and crevices where the populations can hide out. Unless you can physically get them with a chemical, they remain unaffected.”

But bed bugs walk on bent tarsi (tiny “hooks” that make it easy for them to climb up soft furniture and frolic on your futon), so very little of their body makes contact with a surface that’s been sprayed with traditional pesticides. What this means is that little pesticide residue makes it back to the harborage.

The Penn State researchers conducted their tests using an oil spray containing B. bassiana on paper and on cloth. Though the spray is invisible when dry, it distributes enough fungal spores throughout the treated material to make it highly effective against bed bugs.

Once these spores come into contact with the cuticle of the bed bug, they germinate and bore through the epidermis, gradually reaching the hemocoel (body cavity containing the digestive and blood centers), where they do their damage. In the meantime, the insects carry the spores back to their nesting sites, infecting others.

In the Penn State experiment, three groups of ten bed bugs were placed on one of the two treated surfaces or on an untreated (control) surface for one hour. All of the exposed bed bugs died within five days. (As little as a minute of exposure appears to be fatal to the bed bugs, Jenkins says.)

Since their data has been released, Jenkins says they’ve been inundated with calls from long-term care facilities and home-renters who are desperate for a natural and effective way to control bed bugs. (They’ll have to wait while Jenkins and her colleagues do more tests and look for the best ways to bring the fungicide to the marketplace.)

Don’t expect treated sheets, however. Instead, Jenkins expects that a commercially available spray would go around light switches and on baseboards and bedskirts. “This will form a barrier over which bed bugs will have to crawl to find a blood meal.”

Trying to control my own urge to itch, I ask Jenkins if the work ever bugs her. She admits that she does get that skin-crawling feeling at times when she’s working in the lab. That’s because mixed bed-bug populations are hard to spot and keep track of: The adults resemble flattened apple pits, whereas the youngest “first instar” bed bugs are “tiny little dots.”

“Our best joke,” she says, is to announce, “‘Three or four of them escaped! And we’re not sure where they are!’ Everyone freaks out.” I know how they feel.

Estrogenic: Consumption of Certain Plants May Be Linked to Aggression in Monkeys

Red colobus monkeys in Uganda.
Image by Duncan (Wellington, NZ). CC By-S.A. 2.0.

Munching on large amounts of phytoestrogen-rich leaves from the Milletia dura tree appears to alter hormone levels and behavior among red colobus monkeys, according to a study published in the journal Hormones and Behavior.

Studying a group of male red colobus monkeys in Uganda, scientists from the University of California-Berkeley found that levels of estradiol and cortisol rose with seasonally higher consumption of estrogen-like compounds. In addition, the monkeys fought and mated more, and indulged less in the social-bonding activity of grooming.

“It’s one of the first studies done in a natural setting providing evidence that plant chemicals can directly affect a wild primate’s physiology and behavior by acting on the endocrine system,” said study lead author Michael Wasserman, who conducted the research as a graduate student at UC Berkeley’s Department of Environmental Science, Policy and Management. “By altering hormone levels and social behaviors important to reproduction and health, plants may have played a large role in the evolution of primate — including human — biology in ways that have been underappreciated.”

via Eating estrogenic plants alters hormones in monkeys, may increase aggression and sex.

Researchers warned against assigning too much influence to phytoestrogens, however, explaining that diet is just one factor in behavior. Others include the hormones already produced inside the body as well as the amount of competition for food and mates.

Eavesdropping: A Peek at the Snooping Skills of Beetles, Bats, Canaries (and a Few Humans)

The Eavesdropper by Eugene de Blaas (1843-1932).
Image in the Public Domain due to age.

Human history is full of examples of eavesdropping, from neighbors snooping on the party line to the FBI scouring the Gmail account of Gen. David Petraeus. In a post on her blog Brain Pickings, Maria Popova takes a peek at John L. Locke’s book Eavesdropping: An Intimate History (Oxford University Press, 2010) for some explanation of its causes. Animals do plenty of eavesdropping, too, to avoid predators, defend their territories, and assess the fitness of their mates. Here are some ways that beetles, bats, and canaries snoop for information. (But don’t tell anybody you heard this from me.):

Beetles

Margaridisa sp. Flea beetles normally like to chomp away on leaves from the pink flowering Cordobán tree (Conostegia xalapensis). But the presence of aggressive ants seems to put a damper on their appetite.

To test if these beetles eavesdrop on the communication pheromones of ants in order to avoid them, David Gonthier, an environmental sciences researcher at the University of Toledo, coated the underside of some leaves with “crushed ant liquids” from the species A. instabilis and dotted others with only water. His results appear in the open-access journal PLOS One.

The control leaves sustained 3.8 times more damage and had three times more beetles on them than the ant-marked leaves. In addition, two experiments comparing control leaves with leaves that had previously been “patrolled” by A. instabilis and another ant species, C. textor, found about twice as much damage among the control leaves.

The researcher found no significant differences in leaves that had been patrolled by a third ant species, S. geminata, but more experiments may be needed to understand those results.

Bats

Bats use echolocation, releasing short wavelength signals that bounce off other objects, in order to find food and orient themselves, as well as to socialize. By eavesdropping on these signals, bats can glean information from others. One study in Proceedings of the Royal Society Bby scientists from Germany’s University of Ulm and other institutions looks at the extent to which bats can gather social information, such as the sex of the caller, from these vocal signatures.

Greater sac-winged bat (S. bilineata).
Felineora. Creative Commons.

Their study involved the greater sac-winged bat (Saccopteryx bilineata). Even though they mate only during a brief time in December, males of this species defend their daytime roosting space from other males and try to attract females to it throughout the year.

After capturing bats with mist nets, researchers banded individuals and released them one at a time in order to record their distinctive echolocation calls. Then they recorded the responses of roosting males as individual bats were released, one by one, near the colony’s roosting site. All of the roosting males crooned courtship songs to approaching females and warned off approaching males with territorial vocalizations.

Due to the distance and darkness, it is unlikely that scent or visual information helped these males tell the difference between male and female bats, the study concludes. “Through passive information transfer and eavesdropping, echolocation calls play a crucial and hitherto underestimated role for social communication in a highly mobile and gregarious nocturnal mammal.”

Canaries

Eavesdropping doesn’t always generate reliable information, however—especially when the subject knows they’re being watched.

Domestic canary (Serinus canaria).
L.E. MacDonald. Creative Commons.

A study published in PLOS One on socially-monogamous domestic canaries looked at the effect of having an audience on males’ behavior. Researchers from Paris West University Nanterre la Défense paired up 21 male canaries and 21 female canaries in cages, allowing them to mate. Later they placed those same male canaries in cages with different, but familiar, females, with whom they could interact. These interactions either took place in front of another empty cage or a cage containing a familiar female or their own mate. When there was no audience, the male canaries courted the most. They courted the least in front of their own mates.

“These results show that male domestic canaries can adjust their behaviour according to the social bond they share with the audience,” the study states. “Indeed, subjects courted less in the presence of their mate than in the presence of a familiar female. This suggests that males suffer costs while engaging in extra-pair behaviours in the presence of their mate.”

A second eavesdropping experiment found that male canaries competed more aggressively against other males for food when they had an audience. The presence of a mate or a familiar female led to more attacks on the competing male.

The study concluded: “One could assume that males losing a contest would suffer a decrease in their reproductive success in both situations: eavesdropping familiar females would not choose them as sexual partners … while eavesdropping mates would engage more in extra-pair copulations … ”

Elephants: Around the Waterhole with Field Biologist Caitlin O’Connell-Rodwell

Caitlin O’Connell-Rodwell in Etosha National Park.
Photograph by Tim Rodwell.

 
When it’s time to leave the waterhole, African elephant family groups have a special way of announcing their departure. “We call it the ‘let’s go’ rumble,” explains Caitlin O’Connell-Rodwell, a Stanford University scientist who has been studying elephants in Namibia’s Etosha National Park for 20 years. First comes the low-frequency call of the matriarch, followed by a series of close or overlapping rumbles from other high-ranking females. “What you get is a call that’s at least three times the size of the original call,” O’Connell-Rodwell says. “It’s as if they need the motivation of this call to action.” Her study of these departure vocalizations recently appeared in the journal Bioacoustics.

But the scope of O’Connell-Rodwell’s research is larger (one might say elephantine): Her interests extend from seismic communication to wildlife conservation to the effects of the environment on elephants’ social structure. “There are a lot of different questions we have, because elephants are long-lived social animals,” she says. “It takes years to find particular social patterns.” Hoping to learn as much as possible about the elephants without disturbing them, O’Connell-Rodwell and her colleagues have set up a solar-powered camp at Mushara waterhole. 

O’Connell-Rodwell is also co-founder of Utopia Scientific, a nonprofit research and education organization, as well as the author of three books, including The Elephant’s Secret Sense: The Hidden Life of the Wild Herds of Africa. Here are a few glimpses of her work among the elephants of southern Africa:

You Talking to Me?

The waterhole is a great place to see the social behavior of elephants, as shown in another recent study by O’Connell-Rodwell in Ethology, Ecology, and Evolution. In a dry year, male elephants appear to know their place in the social order, following a kind of water-hole etiquette. “A lower-ranking elephant will typically stick his trunk inside the dominant bull’s mouth, and then step away as if to say, ‘I’m just going to drink over here where it’s really salty,’” O’Connell-Rodwell says. (“Elephants use their trunks like people use handshakes–as a greeting, a sign of respect, or appeasement.”)

Studying waterhole behavior, O’Connell-Rodwell found that elephants form linear dominance hierarchies in years with low rainfall. “When there are minimal resources, you have to have more order to prevent chaos,” she says. “Everyone knows where they stand, so there is less fighting and less stress.” Acts of affiliation, like the trunk-in-mouth described above, are more common than aggression.

But during wet years, things can get a little surly. O’Connell found younger bulls to be more aggressive than affiliative. (Aggressive behaviors can include anything from charging another elephant to flaring the ears.) “You don’t need to kowtow to the dominant [bull] when you can drink anywhere,” she says. “There is a lot more aggression when there is uncertainty in the ranking.”

Bulls in a Rush

When male elephants break out of the protected borders of the Etosha National Park, they often wind up in places where they’re unwanted. This puts them at risk of getting shot by humans. Concerned about the conservation of this sensitive species, O’Connell-Rodwell has experimented with one promising way of getting bulls to return: broadcasting a recording of an estrus call.

Continue reading

Dolphins: While We Sleep, They Echolocate the Night Away

Bottlenose dolphin. Photo by Peter Asprey, Scotland. Creative Commons.

I got a touch of dolphin envy when I first saw a new study in the journal PLoS One that shows these marine mammals can stay partly awake for at least 15 days, keeping track of their environment. (I’m useless and cranky if I get less than 7 hours of shut-eye each night.)

A group of researchers led by Brian Branstetter, of the National Marine Mammal Foundation, conducted the experiment on two bottlenose dolphins: a 30 year-old female (SAY) and a 26-year-old male (NAY) in a portable floating pen in the San Diego Bay.

Each dolphin was trained to monitor the pen for electronically simulated (“phantom”) targets in eight different locations and press a response paddle when they detected them.

Like bats, dolphins emit sounds (in their case, clicks) and listen to them bounce off objects through a process called echolocation. But bats typically snooze away the day. Dolphins stay more vigilant, 24/7. At night, one hemisphere of their brain remains alert while the cerebral cortex and thalamus on the other side goes to sleep, the article explains. (If only I could achieve unihemispheric sleep, I could get so much more accomplished.)

The experiment took place over three, five-day sessions. As the PLoS one article states, “The dolphins would have no knowledge of where or when a phantom target would occur and would have to continuously echolocate on the eight stations to detect a phantom target.” Trainers reinforced correct responses with fish.

SAY was 96 to 99 percent accurate in detecting echoes from the research project’s “phantom echo generator.” NAY was 75 to 86 percent accurate. Because of her “superior performance,” SAY was selected for another 15-day test. She continued to echolocate successfully during that time.

So why are dolphins peppier than the rest of us?

Previous research shows that unihemispheric sleep likely evolved in dolphins because of the need to remain close to the surface for breathing. It’s possible, the PLoS One article states, that it also serves to keep them alert to predators. (Sharks are a frequent threat.)

“From an anthropomorphic viewpoint, the ability of the dolphin to continuously monitor its environment for days without interruption seems extreme,” the article states. “However, the biological, sensory and cognitive ecology of these animals is relatively unique and demanding. If dolphins sleep like terrestrial animals, they might drown. If dolphins fail to maintain vigilance, they become susceptible to predation. As a result, the apparent extreme capabilities these animals possess are likely to be quite normal, unspectacular, and necessary for survival from the dolphin’s perspective.”

I think it’s time to set aside my jealousy. At least I can sleep well, knowing there are no sharks about.

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Botany Q & A: All Chris Martine is Saying … Is Give Plants a Chance

Whenever my four-year-old comes across a picture of a baby animal—any animal, even a beady-eyed, tongue-flicking rat snake breaking out of its shell—she responds with an Awwwww. She even wanted to make a home for the slug we encountered on the sidewalk the other day, proclaiming, “It’s so cute.” Like many kids, she’s obsessed with animals. Christopher Martine doesn’t mind people of any age fawning over fauna, but he thinks it’s time that his own field, botany, gets a little love, as well. That’s what has led the Bucknell University biology professor to create the video series, Plants are Cool, Too!

“One of the missions here is to sort of spread the word that the plant kingdom is a really important driver of all the processes that life on Earth depends on, but not do that in a way that’s sort of stale and people roll their eyes and say yeah yeah yeah,” Martine says. Instead, he’s using what he calls a “guerilla botany” approach to “draw people in with the coolest stories about plants [and] also to highlight the person or people doing the botanical research.”

In the second and most recent episode, which has been posted on YouTube, Martine travels to the fossil beds of Clarkia, Idaho, to look at 15 million-year-old leaves preserved between layers of rock. Then he interviews a group of University of Idaho scientists who have been studying the leaves and working to prove that it’s possible to extract DNA from them. (He also eats a baked potato, which hopefully wasn’t quite so old.)

“That’s kind of a controversial idea that the DNA from those specimens can actually be accessed and sequenced,” notes Martine. “Not every scientist actually believes it’s even possible to extract DNA that old. This would really set back the clock for how far back we’ve gone with DNA technology.”

Martine talked to me recently about his hopes for the video project: Continue reading

Arsenic and New Science: FIU scientist is trying to take the risk out of rice.

Let’s see what’s on this week’s dinner menu.

Monday: pasta and cheese sauce with broccoli

Tuesday: salmon burgers and asparagus over a bed of rice and arsenic

Wednesday—Wait a minute. Arsenic?

I was disturbed to read a Consumer Reports study about the prevalence of arsenic in rice, which is one of my favorite menu staples. According to an article in the November 2012 issue of the magazine, most of the 223 samples of rice products it analyzed—from baby cereal to basmati—contained detectable amounts of the toxic metal. In addition, arsenic levels were found to be higher in brown rice than in white rice.

Further analysis by Consumer Reports showed that rice eaters had 44 percent higher levels of arsenic in their urine than those with rice-free diets.

Those findings come as no surprise to Barry Rosen, a molecular biologist at Florida International University who’s been studying arsenic, a human carcinogen, for more than 30 years. Rosen and his collaborators are working to reduce arsenic levels by genetically engineering rice grains that will vaporize the toxin. Continue reading