Gecko lizards can walk on water


This video says about itself:

Geckos can run across water

Geckos (Hemidactylus platyurus) have the ability to exceed the speed limits of conventional surface swimming, running across water at up to almost a meter a second using a unique mix of surface tension and slapping.

Credits: UC Berkeley/Roxanne Makasdjian/Stephen McNally/Pauline Jennings, Jasmine A. Nirody, Judy Jinn, Thomas Libby, Timothy J. Lee, Ardian Jusufi, David L. Hu, Robert J. Full.

Music: Horses to Water by Topher Mohr and Alex Elena courtesy of YouTube Audio Library

From the University of California – Berkeley in the USA:

Acrobatic geckos, highly maneuverable on land and in the air, can also race on water

Geckos combine surface tension with foot slapping to stay above water surface

December 6, 2018

Summary: Asian geckos were observed running over water at nearly a meter per second, as fast as on land. Lab experiments show how. They get support from surface tension but also slap the water rapidly with their feet. They also semi-plane over the surface and use their tail for stabilization and propulsion. They thus sit between insects, which use only surface tension, and larger animals, which run upright via foot slapping alone.

Geckos are renowned for their acrobatic feats on land and in the air, but a new discovery that they can also run on water puts them in the superhero category, says a University of California, Berkeley, biologist.

“They can run up a wall at a meter per second, they can glide, they can right themselves in midair with a twist of their tail and rapidly invert under a leaf running at full speed. And now they can run at a meter per second over water. Nothing else can do that; geckos are superheroes,” said Robert Full, a UC Berkeley professor of integrative biology.

Full is the senior author of a paper that will appear this week in the journal Current Biology describing four separate strategies that geckos use to skitter across the surface of water. First author Jasmine Nirody, a biophysicist at the University of Oxford and Rockefeller University, conducted much of the research with Judy Jinn, both as Ph.D. students at Berkeley.

According to Full, who discovered many of the unique maneuvers and strategies geckos employ, including how their toe hairs help them climb smooth vertical surfaces and hang from the ceiling, the findings could help improve the design of robots that run on water.

Nirody first became intrigued by geckos’ water-running behavior after co-author Ardian Jusufi, now a biophysicist at Max Planck Institute for Intelligent Systems and another former UC Berkeley Ph.D. student, noticed that geckos in the forests of southeast Asia could skitter across puddles to escape predators.

In fact, they are able to run at nearly a meter, or three feet, per second over water and easily transition to speeding across solid ground or climbing up a vertical surface. Geckos sprinting on the water’s surface exceed the absolute swimming speeds of many larger, aquatic specialists including ducks, minks, muskrats, marine iguanas and juvenile alligators, and are faster in relative speed than any recorded surface swimmer, other than whirligig beetles.

How, she wondered, do they do that?

Smaller animals like insects — spiders, beetles and water striders, for example — are light enough to be kept afloat by surface tension, which allows them to easily glide across the surface. Larger animals, such as swans during takeoff or the basilisk lizard, and even dolphins rising up on their tails, rapidly slap and stroke the water to keep above the waves.

“Bigger animals can’t use surface tension, so they end up pushing and slapping the surface, which produces a force if you do it hard enough,” Full said.

But the gecko is of intermediate size: at about 6 grams (one-fifth of an ounce, or the weight of a sheet of paper), they are too large to float above the surface, but too light to keep their bodies above water by slapping forces only.

“The gecko’s size places them in an intermediate regime, a middle ground,” Nirody said. “They can’t generate enough force to run along the surface without sinking, so the fact they can race across water is really surprising.”

In experiments with flat-tailed house geckos (Hemidactylus platyurus), common in south and southeast Asia, she discovered that they actually use at least two and perhaps four distinct strategies to run atop the water surface.

Surface tension is essential, she found, because when she applied a surfactant or soap to eliminate surface tension, the geckos were much less efficient: their speed dropped by half.

Even without surface tension, however, they can move using slapping, paddling movements with their four legs like larger animals. Leg slapping created air pockets that helped keep their bodies from being completely submerged, allowing them to trot across the water in much the same way they run on land.

But they also seem to use their smooth, water-repellent skin to plane across the surface, similar to hydroplaning but referred to as semi-planing, a technique used by muskrats.

Finally, they also use their tail to swish the water like an alligator, providing propulsion as well as lift and stabilization.

“All are important to some extent, and geckos are unique in combining all these,” Full said.

“Even knowing the extensive list of locomotive capabilities that geckos have in their arsenal, we were still very surprised at the speed at which they could dart across the water’s surface,” Nirody said. “The way that they combine several modalities to perform this feat is really remarkable.”

In the lab, she and her colleagues built a long water tank, placed the geckos on a plank and startled them by touching their tails. Using high-speed video, they were able to closely study the geckos’ techniques and estimate the forces involved.

This research was funded by the National Science Foundation and the Swiss National Science Foundation. Other co-authors of the paper are Thomas Libby and Timothy Lee of UC Berkeley and David Hu from Georgia Tech.

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Australian lizards and parasites, new study


This 2017 video says about itself:

Australian Common Garden Skink or Pale-Flecked Garden Sunskink

From the University of Colorado at Boulder in the USA:

Forest fragmentation disrupts parasite infection in Australian lizards

November 29, 2018

In a study with implications for biodiversity and the spread of infectious diseases, CU Boulder ecologists have demonstrated that deforestation and habitat fragmentation can decrease transmission of a parasitic nematode in a particular species of Australian lizard, the pale-flecked garden sunskink.

The new experimental research, published today in the journal Ecology, found that specimens of the blue and brown-colored, index finger-length skinks who live in isolated forest plots were 75 percent less likely to be infected with parasitic worms than their counterparts living in untouched, continuous forests — an indication that the parasite’s life cycle had been disrupted.

A decrease in parasite prevalence isn’t necessarily good or bad for an ecosystem, the researchers said, but it can result in dramatic changes.

“Parasites are a massive unseen component of an ecosystem and there so many that we don’t see,” said Associate Professor Kendi Davies of CU Boulder’s Department of Ecology and Evolutionary Biology (EBIO). “Parasites regulate populations and influence multiple hosts. It’s largely unknown how these complex interdependencies respond to changes.”

Habitat fragmentation in the form of deforestation remains a major threat worldwide. Scientists estimate that nearly one-third of global forests have disappeared, leaving behind a patchwork of ecological “islands” that can threaten food chains and alter long-standing species interactions

“Fragmentation is a big deal because it leads to loss of biodiversity and ecosystem functions” said Julian Resasco, lead author of the study and a postdoctoral researcher in EBIO. “It can also change the way diseases spread, with the potential to impact human health.”

The new study was conducted at the long-running Wog Wog Habitat Fragmentation Experiment, a 33-year-old continuously-run experiment in the eucalyptus forests of New South Wales, Australia. The site allows researchers to compare uninterrupted forestland to forest fragments that have been isolated by clear-cutting and burning.

Resasco zeroed in on skinks after a chance observation. While examining the gut contents of many historical specimens preserved in a museum, he noticed that the commonly-found lizards had been infected with a particular parasitic nematode. After consulting with Australian colleagues, he learned that it was, in fact, a brand new species.

“I wanted to quantify infections by these nematodes to see if fragmentation had an effect on parasitism,” Resasco said.

The nematodes use a small amphipod crustacean species as an intermediate host, which is in turn eaten by the skink, resulting in infection. But forest fragmentation significantly reduces the moist leaf litter habitat that these amphipods require, depriving the skinks of a meal and the parasites of a transmission pathway.

The study found that among skinks living in continuous forest, 55 percent contained nematodes compared to just 11 percent of skinks living in the fragments.

“We see the consequences of messing with key players in the landscape,” said Resasco.

The next step, the researchers said, is to think in even longer timescales. Now more than thirty years in at Wog Wog, parts of the landscape there have gradually changed from clear-cut to pine plantation forest, which could prompt a rebound.

“Pine forests are a pretty desirable place for the amphipods to live,” said Matthew Bitters, a doctoral researcher in EBIO and a co-author of the study. “So if they do recover, will that mean a rise in skink infections again? Or has something else emerged to disrupt the transmission?”

“Fragmentation research has a long history of studying species interactions such as pollination, seed dispersal and predation,” said Resasco. “Parasitism has received less attention but such research is important for understanding how landscape changes affect biodiversity and disease transmission.”

Tegu lizard DNA sequenced


This November 2018 video shows a tegu lizard.

From GigaScience:

The warm and loving tegu lizard becomes a genetic resource

The tegu, a South American lizard with its own heating system, has had its genome sequenced to an unprecedented level of quality

November 27, 2018

Summary: Researchers have sequenced the genome of the tegu, Salvator merianae: a lizard that has taken an evolutionary step toward warm-bloodedness. It is also a highly desired pet, that can often be house-trained; unfortunately, as part of the exotic pet trade, it has been released in new environments and become a threat to local species. This extremely high-quality tegu genome sequence will be of use to researchers in the fields of evolution, physiology and ecology.

Published today in the open-access journal GigaScience is an article that presents the genome of the tegu lizard, which has mastered a trick that is highly unusual in the reptile world: it can turn on its own heating system.

Most reptiles are not able to control their body temperature like mammals do and instead must rely on its environment, such as available sun and shade, to attain an optimal body temperature. The tegu, Salvator merianae, however, has taken a step towards being full-blown warm-blooded: It can raise its own body temperature by up to 10°C above its surroundings. Another, but more negative, aspect of the tegu is that is an invasive species and poses a serious threat to endangered species. Although it is a native of South American rain forests and savannas, the charismatic nature of the tegu — and that it can even achieve some level of house training, makes it an extremely charming pet that is much beloved by reptile aficionados. Unfortunately, international trade in exotic pets are one of the primary reasons that species enter new environments where they can become a menace to the native species. Given the tegu’s unique biological characteristics and its potential peril to the environment, the availability of an extremely high-quality genome sequence of this large lizard serves as a rich resource for identifying and analyzing the underlying molecular basis of these aspects.

The tegu genome sequence, provided by a team of researchers led by Michael Hiller at the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden (Germany), is of unprecedented quality. To accomplish this the researchers used state-of-the-art technology to read the tegu’s DNA and assemble its genome sequence. The newly released genome sequence of S. merianae is more than two billion DNA letters long and contains more than 22,000 genes. It is the most complete assembly of any reptile genome so far and will also aid scientists to study other lizards and snakes.

By using so called “long read” (Pacific Biosciences) sequencing technology, the researchers were able to overcome some of the challenges of assembling reptile genomes. Hiller and first author Juliana Roscito explain: “Similar to other reptiles, a large portion of the tegu genomes consists of repetitive sequences, which occur many times in the genome. Repeats are a main problem when assembling a genome, especially when repeats are longer than the length of the sequenced DNA fragments, which results in gaps (breaks) in the assembly.”

The tegu is emerging as an interesting model species in its own right. One of the motivations for the authors to sequence the tegu genome actually related to their interest in another group of reptiles: snakes. The authors explain what they had in mind: “We were interested in studying limb loss in snakes and other reptiles. Since limbless reptiles had ancestors with fully developed limbs, we needed a well-assembled genome of a lizard with fully developed limbs as a reference.” Given that there are few reptiles with sequenced genomes, the authors decided to produce this themselves.

Another component of the article, especially given that reptiles are under-represented among. the vertebrates with sequenced genomes, the authors also provide a whole-genome alignment between the tegu and 16 other species. “We hope that these resources facilitate comparative reptile genomics to understand how unique morphological features evolved in this group of species and how vertebrate genomes evolve in general,” Michael Hiller and Juliana Roscito conclude.

Prehistoric giant Australian Megalania lizards


This 11 November 2018 video says about itself:

When Giant Lizards Ruled Australia – Megalania

Monitor Lizards are a fantastic group of animals, as they include the largest lizards alive today, but at one point in time they got even bigger

Galapagos iguanas’, sea lions’ small animal friends


This 8 November 2018 video says about itself:

Iguanas and Sea Lions Have Surprising Animal Allies | BBC Earth

In Galapagos, crabs and smaller lizards have a special relationship with iguanas and sea lions that benefits all involved. Narrated by Tilda Swinton.