Meet the First Gene-Edited Reptile: An Albino Lizard
By Malavika Vyawahare
Think of a reptile that's been genetically mutated, and Godzilla springs to mind. Or maybe ninja turtles.
But the real thing is here, and it's neither hell-bent on destroying Tokyo nor eating pizza in the sewers. Instead, it's a pale, finger-sized lizard — the world's first gene-edited reptile, researchers at the University of Georgia reported this week.
In a paper published in the journal Cell Reports, Douglas B. Menke and his colleagues described how they made an albino version of the brown anole (Anolis sagrei), a species of lizard native to Cuba and the Bahamas.
"Instead of performing gene-editing on fertilized eggs or single-cell embryos, we performed gene-editing on unfertilized eggs while they are still physically attached to the ovary of adult female lizards," said Menke, a geneticist and developmental biologist.
The first genetically modified animal was a transgenic mouse, created in 1974. But it was only seven years later that researchers could edit genes that were passed on to future generations. In the case of the albino lizard, the changes are inheritable.
Though gene editing has been around for decades and the advent of CRISPR technology makes it easier and is more efficient to carry out, doing so in reptilian zygotes is particularly challenging. Researchers consider it best to make an edit when the embryo is newly formed. For animals that reproduce sexually, the target is usually a single cell at this stage.
In reptiles, it's difficult to pin down when fertilization actually happens, in large part due to internal fertilization and sperm storage, where females can store sperm for extended periods. In A. sagrei lizards, the females can store sperm for more than two months.
The Anolis genus, which includes more than 400 species, is native to Central and South America and the Caribbean islands. Brown anole lizards are widely distributed beyond their native Cuba and Bahamas because they're a highly invasive species. The lizards used in the experiment were caught from the wild in Orlando, Florida.
The scientists performed surgery to insert gene-editing reagents into 146 unfertilized eggs of 21 adult female lizards. The females were then mated with adult males. A fraction of the resulting offspring carried the mutation, which manifested as albinism. The edit is unlikely to be lethal to the animals.
The downside of manipulating the egg and not the embryo is that it doesn't host the paternal DNA, reducing the chances that the edit will manifest in the offspring. For their study, the authors had to wait for three months for the lizard eggs to hatch to verify whether their editing method had induced the desired mutation.
Only about 6 to 9 percent of the eggs in which the edit was introduced produced mutant lizards. This is low when compared to other methods that report efficiencies of 80 percent or more. However, being able to produce the change in those few individuals is itself a breakthrough. The authors say the efficiency can be boosted by targeting larger eggs (more than 0.75 mm in diameter), which had the highest success rate in this experiment.
Editing genes is one of the key ways to deduce what role they play and which traits they're associated with. The University of Georgia researchers are already exploring different gene functions in Anolis lizards and say they hope this will aid in the study of genetic defects in humans. For example, people with albinism are also likely to have poor eyesight due to defects in a part of the eye called the fovea. Mice that are widely used for genetic studies don't have a fovea and so studying in albinism in mice may not shed light on the link between albinism and impaired vision.
Gene editing can also be used to curb invasive species populations. Its most widely known application is to control mosquito populations, but with advances in gene editing this could be extended to invasive reptiles as well.
"There are over 10,000 described species of reptile, and the genome of each species contains around 25,000 protein-coding genes. There is a whole universe of unstudied biology in these animals," Menke said. "We hope that other research groups will adapt our gene-editing method to investigate gene function in additional reptile species."
Reposted with permission from our media associate Mongabay.
The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.
"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."
The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.
They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.
They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.
But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.
"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.
What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.
It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.
To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.
First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.
Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.
University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.
"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."
Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.
"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.
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