Saharan silver ants, short-legged but world’s fastest


This 29 October 2019 video says about itself:

Watch Saharan silver ants run | Science News

Slowed-down videos of silver ants on a portable runway in the Sahara sun show how the synchronized movements of three legs at a time let the ants achieve high speeds. As an ant runs, a trio of legs (the right front, right rear and left middle circled) touch down only briefly (white circles, ground phase) and then swing forward rapidly (black circles, swing phase). The final video clip shows an ant rushing by in real-time.

By Susan Milius in Science News, October 29, 2019 at 12:26 pm:

Saharan silver ants are the world’s fastest despite relatively short legs

At top speeds, these scavengers basically gallop, with all six legs in the air at once

The world’s newly crowned fastest known ants don’t look as if they’ve got the legs to be champs.

Saharan silver ants (Cataglyphis bombycina) have merely runner-up proportions, with legs about 18 percent shorter than those of a related desert ant (C. fortis). Yet adjusting for body length, video shows silver ants rushing along about twice as fast as their leggier cousins.

Sarah Pfeffer of the University of Ulm in Germany and colleagues took a high-speed video camera to Tunisia to get that video of the shorter ants in their hot and sandy home. At an oasis on the northern edge of the great dunes, the researchers searched for glimpses of silver.

Tiny silver hairs coat the ants, reflecting some of the sun’s glare and shedding heat (SN: 6/22/15). When Pfeffer, an applied neuroethologist, digs out a nest to study, several thousand ants seething in her transport box look “like quicksilver,” she says.

That silvery protection comes in handy because the ants stay in their nests at night and scavenge for food in the furnace of midday. “The sun really burns down,” Pfeffer says. Surface sand temperatures can soar over 60° Celsius (about 140° Fahrenheit). Even at ant heights, the air is still brutal.

Silver ants, however, get two bonuses for foraging in the worst of the heat. It’s a great time to find fresh carcasses of creatures that the sun fried but that heat-averse scavengers haven’t found yet. Also, ant-hungry predators often take shelter from the heat, so silver ants are less likely to become lunch themselves.

To see how those shortish legs can run through hell, Pfeffer set up an outdoor open-topped metal runway dusted with sand. She then offered a free lunch for ants. “They love mealworms,” she says. As ants rushed along the runway, Pfeffer got high-speed film of the step details. The shorter legs compensate by packing more strides into each second, up to 47 for the silver ants running at top speed versus 36 for their taller relatives, the team reports October 16 in the Journal of Experimental Biology.

Pfeffer clocked speeds as high as 855 millimeters per second. That’s 108 times a silver ant’s body length in a second.

The camera picked up six legs moving in two groups of triplets, like alternating tripods. At higher speeds, an ant gets airborne for just an instant with no legs touching the ground. In horses, that’s galloping. Pfeffer describes it as gliding, since the ants zoom forward smoothly instead of galumphing.

That glide is fast enough to crown the dune dwellers as the fastest ant known so far, though not the fastest insect. They’re beaten, in terms of body lengths per second, by tiny mites in southern California. Young Paratarsotomus macropalpis can zoom across concrete around three times as fast (SN: 6/12/14).

Migrants drown off Tunisia


This 23 July 2019 video says about itself:

Tunisia struggling to bury drowned migrants

The port city of Zarzis in Southern Tunisia is struggling to find a resting place for migrants who drowned at sea trying to reach Europe.

Zarzis is overwhelmed in its efforts to bury drowned migrants.

“Why only Zarzis? Because in Zarzis culture we can’t leave bodies. It’s sad, but these people could be our sister, our mother, our father, our children. And in Zarzis, we have young people who have been shipwrecked at sea. And we know how it feels to have someone drowned at sea”, said Deputy Zarzis Mayor, Faouzi Khenissi.

The Gabès hospital receives these bodies and is the only one in the region with the capacity to take DNA samples.

“For the Gabès Regional Hospital there are fears that this number and this situation will recur at the hospital and in the Gabès region. Our fear is that there is no plan. We need a plan. A group is needed to deal with these disasters that may happen again in the future”, said Hospital Director, Hechmi Lakhrech.

The port city of Zarzis is appealing for international support.

“An international appeal. Help us. The municipality of Zarzis is at its limits. We have limited means. We cannot afford to do better than this”, he added.

On July 1, more than 80 bodies were recovered on the Tunisian coast between the port city of Zarzis and Djerba in the south of the country.

On July 12, 45 more bodies were retrieved in a day. The Red Crescent said the country is struggling to support rescued migrants and even more so those who died.

Tunisians protest against bloody Saudi crown prince


This 27 November 2018 video says about itself:

🇹🇳’No to the murderer‘: More protests in Tunisia against MBS visit | Al Jazeera English

Hundreds of Tunisians protested against Saudi Crown Prince Mohammed bin Salman‘s arrival to Tunis, in the latest leg of his visit of Middle Eastern nations.

This is his first trip outside of Saudi [Arabia] since the murder of journalist Jamal Khashoggi in the kingdom’s consulate in Istanbul, on October 2. Al Jazeera’s Jamal Elshayyal reports from Tunis.

Protests erupt in Tunisia after self-immolation of journalist Abderrazak Zorgui: here.

Tunisians protest against Saudi Arabian crown prince


This 24 November 2018 video says about itself:

Tunisia protesters call for cancellation of MBS visit

Protesters in Tunisia are pressuring the government to cancel a planned visit by the Saudi crown prince, because of his suspected involvement in the murder of Jamal Khashoggi.

Activists and demonstrators are pointing to Tunisia’s role in the 2011 Arab Spring revolutions

strongly opposed by the Saudi absolute monarchy, which bloodily suppressed them in their own country and in Bahrain. The dictator of Tunisia then fled to Saudi Arabia.

and the juxtaposition of Mohammed bin Salman’s suspected role in the murder of the journalist, as well as the arrests of dozens of Saudi civil and political activists. But the cash-strapped Tunisian government is warning the protests could stop much-needed financial aid from the kingdom. Al Jazeera’s Hashem Ahelbarra reports.

African desert ants smell very well


This video says about itself:

BBC Silver Desert Ant, Cataglyphis, Sahara Desert

Clip from BBC’s Africa, episode 5, Sahara, 2013, narrated by Sir David Attenborough. Includes behind the scenes footage.

From the Max Planck Institute for Chemical Ecology in Germany:

Desert ants have an amazing odor memory

The insects can learn many food odors and remember them all their lives

September 24, 2018

Scientists at the Max Planck Institute for Chemical Ecology used behavioral experiments to show that desert ants are able to quickly learn many different food odors and remember them for the rest of their lives. However, their memory for nest odors seems to differ from their food odor memory: Whereas food odors are learned and kept after a single contact, ants need several trials to memorize nest odors. Moreover, ants forget a nest-associated odor very quickly after it has been removed from the nest. Hence, ants process food and nest odors differently in their brains.

The desert ant Cataglyphis fortis has amazing abilities to trace food and to return to its nest in the North African desert. Its sense of smell has a central function for orientation. The ant is not only a master navigator, it is also a memory artist. Behavioral scientists Markus Knaden from the Max Planck Institute for Chemical Ecology has been studying the navigational skills of this ant species for years. Until now, he was particularly interested in how the small insects find their way back to their nest after an extensive search for food in the vast salt pans of the Tunisian Sahara. After all, the nest entrance is only a small inconspicuous hole in the desert surface. He and his team found that — apart from other factors — the specific nest odor plays a crucial role. However, during their experiments, the researchers had noticed that ants learned food odors much faster than nest odors. “Our central question was whether different types of memory exist for food and nest search. The idea to compare both learning processes popped up when we observed that the ants were able to learn food odors so incredibly fast in comparison to nest odors which need to be trained much longer”, first author Roman Huber explains.

The scientists developed a simple experiment to test the response of ants to more than 30 different food odors. They held the end of a stick which had been scented with an odor about two meters away from a foraging ant on the ground so that the wind blew the odor to the ant. At first, most odors were ignored by the ants and did not evoke any response. “After we had offered a food crumb to the ants which had been scented with one of these odors, however, the ants were almost always attracted by this odor afterwards”, Markus Knaden says. “We were amazed how quickly the ants learned food-associated odors and how long they could remember them. Even ants that had learned an odor more than 25 days ago were able to remember it.” In nature, most ants have a short life and are usually killed by a predator within six days. Therefore it is particularly astonishing that ants that have reached more than four times the average age could still remember what they had learned.

On the other hand, ants were not able to learn nest-associated odors as quickly as food odors. When the researchers attached a scent to the nest entrance, the ants needed five to ten trials to learn the odor as a nest cue. Only after several trainings did they concentrate their nest search on this odor. When the odor was removed from the nest and after the ants had returned to the nest a few times, they completely stopped responding to the former nest cue. In ants, odors are obviously processed differently in the brain depending on whether they are food or nest cues.

Markus Knaden provides an explanation: “The two different odor memories make sense. During its entire life, an ant encounters many different pieces of food while foraging. Since the insect finds its food mainly through olfactory cues, it is important for an ant to learn the odor of good food in order to specifically search for it later. The nest, in contrast, should always smell the same during an ant’s short life. Therefore no extraordinary memory is needed to locate the nest entrance by following olfactory cues. It is sufficient if an ant knows how the nest smelled when it left to search for food, to find it on its way home. It is unlikely that the nest odor changes while an ant is away foraging.”

The scientists now want to design lab studies to underpin the results of the behavioral experiments in the natural habitat of the desert ants. Their goal is to employ imaging techniques, like calcium imaging, to locate and visualize the different memories in the ant brain and to compare brain activities during food and nest search. “We already use similar techniques for the visualization of brain activity in flies and moths. It would be great to establish these techniques for ants as well, because ants exhibit a particularly complex behavior”, Markus Knaden says.

New research describes the behavioral and chemical strategies of a Florida ant, Formica archboldi, that decorates its nest with the dismembered body parts of other ant species: here.