Iguana Awareness Day video


This National Geographic video says about itself:

8 September 2018

There are 43 different kinds of iguanas. From the green to the marine, and everything in between – today we celebrate Iguana Awareness Day.

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Salamanders better than lizards at regrowing tails


This May 2017 video says about itself:

Lizard Regenerates Tail; Time Lapse!

In this video you see footage of a [leopard] gecko who regenerates his tail. This is pretty cool to see so we thought we would put together a compilation of some of the best photos and images.

However, some animals are even better at regenerating tails.

By Leah Rosenbaum, 12:30pm, August 17, 2018:

How salamanders can regrow nearly complete tails but lizards can’t

Neural stem cells in the spinal cord prevent the reptiles from regenerating nerve cells

Salamanders and lizards can both regrow their tails, but not to equal perfection.

While a regenerated salamander tail closely mimics the original, bone and all, a lizard’s replacement is filled with cartilage and lacks nerve cells. That contrast is due to differences between stem cells in the animals’ spinal cords, researchers report online August 13 in Proceedings of the National Academy of Sciences.

When a salamander loses its tail, neural stem cells in the creature’s spinal cord can develop into any type of nervous system cell, including nerve cells, or neurons. But through evolution, lizard neural stem cells “have lost this ability”, says study coauthor Thomas Lozito, a biologist at the University of Pittsburgh. Lizards, while they can regrow cartilage and skin, cannot regenerate neurons, the researchers found.

Lozito and colleagues studied neural stem cells from the axolotl salamander (Ambystoma mexicanum) and from two lizard species — the green anole (Anolis carolinensis) and the mourning gecko (Lepidodactylus lugubris). The team also wondered if the lizard stem cells themselves weren’t capable of developing into neurons or if there was something about the environment of the lizard tail that prevented their regrowth. So the researchers implanted salamander neural stem cells into five gecko tail stumps. Some of the cells became neurons in the regrown tails, showing that the lizard stem cells were the problem.

The finding suggests that scientists would have to alter only the lizard stem cells instead of other parts of the tail to regrow a more complete appendage.

How lizards lost their ability to regenerate neurons and salamanders didn’t remains a mystery (SN: 11/28/15, p. 12). Scientists know that species’ places on the evolutionary tree have something to do with organisms’ ability to regrow body parts. “The more complex the species are, the less they can regenerate”, says developmental biologist Katharina Lust of the Research Institute of Molecular Pathology in Vienna, who was not involved in the study. Reptiles such as lizards are more complex organisms than amphibians like salamanders.

The researchers plan to use CRISPR/Cas9 gene editing to see if lizard neural stem cells can be modified to regenerate a perfect tail. Ultimately, the team hopes to one day coax stem cells in mammals to regenerate body parts.

“My goal is to make the first mouse that can regenerate its tail”, Lozito says. “We’re kind of using lizards as a stepping-stone.”

Caribbean lizards, victims and survivors of hurricanes


This 2014 video says about itself:

The Phylogenetic Tree of Anole Lizards

Biologist Jonathan Losos describes the traits that enable anole lizard species to live in their various habitats. In this educational video, join Dr. Losos on his quest to understand evolution by natural selection.

Explore the evolutionary path of the green anole lizards found in the Caribbean. Discover how the different species have evolved traits adapted to their environments and developed into distinct species.

From Nature magazine, 25 July 2018:

Hurricane-induced selection on the morphology of an island lizard

Hurricanes are catastrophically destructive. Beyond their toll on human life and livelihoods, hurricanes have tremendous and often long-lasting effects on ecological systems.

Despite many examples of mass mortality events following hurricanes, hurricane-induced natural selection has not previously been demonstrated. Immediately after we finished a survey of Anolis scriptus—a common, small-bodied lizard found throughout the Turks and Caicos archipelago—our study populations were battered by Hurricanes Irma and Maria.

Shortly thereafter, we revisited the populations to determine whether morphological traits related to clinging capacity had shifted in the intervening six weeks and found that populations of surviving lizards differed in body size, relative limb length and toepad size [which may help clinging to trees, thus surviving hurricanes] from those present before the storm.

Our serendipitous study, which to our knowledge is the first to use an immediately before and after comparison to investigate selection caused by hurricanes, demonstrates that hurricanes can induce phenotypic change in a population and strongly implicates natural selection as the cause.

In the decades ahead, as extreme climate events are predicted to become more intense and prevalent, our understanding of evolutionary dynamics needs to incorporate the effects of these potentially severe selective episodes.

Biologists have published a first-of-its-kind look at the physical characteristics of lizards that seem to make the difference between life and death in a hurricane: here.

See also here.

Global warming will increase the severity of hurricanes: here.

Australian lizards scare predators with ultra-violet light


This February 2018 video from Australia says about itself:

On this episode of Breaking Trail, Coyote catches a Blue Tongue Skink! While exploring the Australian outback just outside the town of Meandarra the team stumbles upon this large snake-like lizard!

Infamous for their large blue tongue defensive display, this species is well known in pet trades around the world. Get ready to meet Australia’s favorite skink!

From ScienceDaily:

Australian lizard scares away predators with ultra-violet tongue

Researchers investigate how the blue-tongued skink uses a full-tongue display to deter attacking predators

June 7, 2018

When attacked, bluetongue skinks open their mouth suddenly and as wide as possible to reveal their conspicuously coloured tongues. This surprise action serves as their last line of defence to save themselves from becoming prey says Martin Whiting, of Macquarie University in Australia, who conceived the study just published in Springer’s journal Behavioral Ecology and Sociobiology. The research revealed that the back of the northern bluetongue skink‘s tongue is much more UV-intense and luminous than the front, and that this section is only revealed in the final stages of an imminent attack.

Bluetongued skinks of the genus Tiliqua are medium-large sized lizards widely found throughout Australia, eastern Indonesia and Papua New Guinea. They are well camouflaged but their strikingly blue tongues are distinct and are UV-reflective in species in which this has been measured. When attacked, they open their mouths wide to reveal their tongues.

The research team set out to investigate the tactics that bluetongue skinks use to ward off attackers, and focused on the largest of the bluetongue skinks, the northern bluetongue skink (Tiliqua scincoides intermedia). This omnivorous, ground-dwelling lizard of northern Australia is well camouflaged thanks to the broad brown bands across its back. However, birds, snakes, monitor lizards — all animals thought to have UV vision — are among its main predators.

First the researchers gathered information about the colour and intensity of different parts of the lizard’s tongue using a portable spectrophotometer to measure the tongues of thirteen skinks. The first exciting finding was that the blue tongue is actually a UV-blue tongue. The researchers then established that the rear of the skinks’ tongues was almost twice as bright as the tips. When a predator approached, the skinks would remain camouflaged until the very last moment, before opening their mouths widely and revealing their highly conspicuous UV-blue tongues.

The next part of the study involved simulating ‘attacks’ on these lizards using model (fake) predators. The team used a snake, a bird, a goanna (monitor lizard), a fox and a piece of wood as a control. The model predator attacks were simulated within a controlled environment.

“The lizards restrict the use of full-tongue displays to the final stages of a predation sequence when they are most at risk, and do so in concert with aggressive defensive behaviours that amplify the display, such as hissing or inflating their bodies,” explains lead author Arnaud Badiane. “This type of display might be particularly effective against aerial predators, for which an interrupted attack would not be easily resumed due to loss of inertia.”

The more intense the attack and the risk they were experiencing, the more full-tongue displays the animals were seen to use, and the greater section of their tongues they would reveal. Such displays were also most often triggered by attacking birds and foxes, rather than by snakes or monitor lizards.

“The timing of their tongue display is crucial,” adds Badiane. “If performed too early, a display may break the lizard’s camouflage and attract unwanted attention by predators and increase predation risk. If performed too late, it may not deter predators.”

World’s oldest lizard fossil discovery


This video says about itself:

Megachirella – The mother of all lizards

19 May 2018

In this video the authors talk about the significance of the discovery and take us behind the scenes of the research project.

From the University of Bristol in England:

World’s oldest lizard fossil discovered

May 30, 2018

An international team of paleontologists, which includes the University of Bristol, have identified the world’s oldest lizard, providing key insight into the evolution of modern lizards and snakes.

The 240-million-year-old fossil, Megachirella wachtleri, is the most ancient ancestor of all modern lizards and snakes, known as squamates, the new study, published today in the journal Nature, shows.

The fossil, along with data from both living and extinct reptiles — which involved anatomical data drawn from CT scans and DNA — suggests the origin of squamates is even older, taking place in the late Permian period, more than 250 million years ago.

Tiago Simões, lead author and PhD student from the University of Alberta in Canada, said: “The specimen is 75 million years older than what we thought were the oldest fossil lizards in the entire world and provides valuable information for understanding the evolution of both living and extinct squamates.”

Currently, there are 10,000 species of lizards and snakes around the world — twice as many different species as mammals. Despite this modern diversity, scientists did not know much about the early stages of their evolution.

Tiago Simões added: “It is extraordinary when you realize you are answering long-standing questions about the origin of one of the largest groups of vertebrates on Earth.”

Co-author, Dr Michael Caldwell, also from the University of Alberta, added: “Fossils are our only accurate window into the ancient past. Our new understanding of Megachirella is but a point in ancient time, but it tells us things about the evolution of lizards that we simply cannot learn from any of the 9000 or so species of lizards and snakes alive today.”

Originally found in the early 2000s in the Dolomites Mountains of Northern Italy, researchers considered it an enigmatic lizard-like reptile but could not reach conclusive placement, and it ramained nearly unnoticed by the international community.

In order to better understand both the anatomy of Megachirella and the earliest evolution of lizards and snakes the authors assembled the largest reptile dataset ever created.

The authors combined it with several new anatomical information from Megachirella obtained from high-resolution CT scans.

All this new information was analysed using state of the art methods to assess relationships across species, revealing that the once enigmatic reptile was actually the oldest known squamate.

Co-author Dr Randall Nydam of the Midwestern University in Arizona, said: “At first I did not think Megachirella was a true lizard, but the empirical evidence uncovered in this study is substantial and can lead to no other conclusion.”

Co-author Dr Massimo Bernardi from MUSE — Science Museum, Italy and University of Bristol’s School of Earth Sciences, added: “This is the story of the re-discovery of a specimen and highlights the importance of preserving naturalistic specimens in well maintained, publicly accessible collections.

“New observations, that could arise from the use of new techniques — as for the mCT data we have obtained here, could provide a completely new understanding even of long-known specimens.”

Buffalo saves lizard from lion


This video from South Africa says about itself:

Buffalo Launches Lion into Air to Save Lizard

29 May 2018

Have you ever seen a lion being thrown into the air by a buffalo, do 3 flips and then land on its feet? Now you have.

Business System Manager, Sune Eloff (32), was out for a drive on the H4-1, just west of Lower Sabie, in the Kruger National Park, when she came upon an almost funny interaction between a buffalo and a young lion who was trying to catch a monitor lizard. Interesting events soon started to unfold…

Sune tells Latestsightings.com: “We spent some time at Sunset dam watching impala coming down for a drink. We decided to move on and saw some lions sleeping in the riverbed. They were so calm and peaceful and then suddenly we saw all of them get up and move into the reeds. At this point I took out my camera as they were watching something that we could not see. Suddenly a young lion came out of the reeds with a water monitor lizard that he had just caught. This is when the entire scene started to unfold…

Some buffalo in the vicinity had noticed that the lion had captured a lizard and one of them came storming in as if he knew this lizard needed protecting. To our absolute astonishment, the buffalo proceeded to get his head right under the puzzled lion and somersault him through the air.

It was crazy! I had mixed feelings… the excitement of everything happening was overwhelming. I felt bad for the young lion, but luckily he had enough brains to know that he needed to get out of there, and fast, so off he ran. The three dagga boys (male buffaloes) still charged into the reeds every now and again but the lions scampered off.

I have never seen anything like this in my life and I’ve been a Kruger visitor since the age of 2, definitely a first for me!”

Green-blooded lizards, new research


This new family tree suggests green blood coloring may have arisen four times independently among some members of the skink family of lizards in New Guinea. Each tip at the wide end of the diagram represents a different modern species in New Guinea, Australia or surrounding islands. Photos show green-blooded Prasinohaema species from different origins: 1) P. virens; 2) new, unnamed species; 3) P. semoni; 4) P. prehensicauda

This new family tree suggests green blood coloring may have arisen four times independently among some members of the skink family of lizards in New Guinea. Each tip at the wide end of the diagram represents a different modern species in New Guinea, Australia or surrounding islands. Photos show green-blooded Prasinohaema species from different origins: 1) P. virens; 2) new, unnamed species; 3) P. semoni; 4) P. prehensicauda.

By Susan Milius, 2:10pm, May 16, 2018:

Green blood in lizards probably evolved four times

Studying the bizarre color might someday offer insights into human jaundice

Green blood is weird enough. But now the first genealogical tree tracing green blood in New Guinea’s Prasinohaema lizards is suggesting something even odder.

These skinks have been lumped into one genus just because of blood color, says biologist Christopher Austin of Louisiana State University in Baton Rouge. Yet they don’t all turn out to be close relatives. Green blood looks as if it arose four separate times in the island’s lizards, he and colleagues propose May 16 in Science Advances.

These lizards do have crimson red blood cells, but that color is overwhelmed by extreme buildups of a green pigment called biliverdin at levels that could kill other animals. Biliverdin forms as the oxygen-carrying hemoglobin molecules break down in dead red blood cells. In humans, biliverdin is converted into the bile that, in excess, causes yellow jaundice. An excess of the biliverdin itself can cause green jaundice. In one case study, levels reaching nearly 50 micromoles of biliverdin per liter of blood were deadly in humans. Yet Austin has found lizards thriving with 714 to 1,020 micromoles per liter (SN: 8/20/16, p. 4).

To figure out how such a peculiar trait evolved, he and colleagues compared segments of DNA and reconstructed the evolutionary history of green-blooded lizards and some close relatives. The greens did not emerge as a single cluster, but were scattered among the reds. The most probable explanation is that green blood, though rare, evolved independently multiple times, he says. The team is now working out the full sequences of lizards’ DNA building blocks and hoping to spot clearer evolutionary clues, such as particular mutations that helped red turn green. He hopes this research eventually will yield insights into human bile disorders.

High but harmless biliverdin hasn’t turned up in the blood of other reptiles, or in mammal and bird blood. Older papers, however, argue for high circulating biliverdin in some sculpins and other fishes in at least two more families, two frogs and insects such as tobacco hornworm caterpillars.

Whether the pigment offers any advantage is still a mystery. When Austin started studying lizards, he wondered if green blood would deter predators. “I tested the hypothesis by eating a few lizards myself and also feeding lizards to native birds and snakes”, he says. “No ill effects.” Now he’s musing that biliverdin might discourage blood parasites such as malaria pathogens.