Author: Jonathan Losos Page 43 of 129

Husak Lab member Erik Sathe putting a lizard through its paces. Photo by Jerry Husak

AA contributor Jerry Husak has just published a great paper in The Journal of Experimental Biology on the effect of training (=practice) on the sprinting and endurance capabilities of green anoles. The Inkfish blog on Discover magazine’s website has written a brilliant description of the study:

Athletes don’t normally need to be chased down the track to get their training mileage in. But a green anole lizard is not a normal athlete.

Scientists wanted to know whether it’s possible to train a lizard at all. Human athletes and other mammals perform better with consistent exercise, but is this universal? Can a reptile increase its stamina? What about its sprint speed? So the scientists became lizard athletic trainers, which really means lizard harassers. Results were mixed.

The green anole lizard, or Carolina anole (Anolis carolinensis), is a common laboratory species. Basic rules of its biology—for example, how it responds to exercise—ought to apply to other vertebrates, such as humans. In the past, scientists have successfully used exercise to increase endurance in frogs, birds, alligators and crocodiles. But the same efforts with lizards have been inconclusive.

Jerry Husak, a biologist at the University of St. Thomas in Minnesota, studies lizards with the help of undergraduate researchers. He and his students decided to try creating “Olympic lizards.” They would train their subjects for two kinds of athletic ability, neither of which was totally foreign to the reptiles. Some lizards would become endurance athletes; this long-distance locomotion would mimic the slow patrolling and foraging anoles do in nature. And other lizards would become sprinters; in nature, they use bursts of speed to escape predators.

Thirty lizards were divided into sprinters, distance runners, and a control group. The sprinting track was a dowel two meters long and five centimeters wide, propped at a 45-degree angle. The researchers chased the lizards up the dowel and used infrared beams to measure their fastest speed. Sprinters “trained” three days a week for eight weeks. Gradually, the researchers increased the training intensity by making the lizards do more runs per day.

Meanwhile, the distance runners did their training on a treadmill. The researchers set the treadmill to a low speed and gently prodded the lizards with a paintbrush to keep them moving. These athletes had to stay on the treadmill for 30 minutes at a time, or until they were exhausted. (How do you know anoles are exhausted? “When we flip them over onto their backs and they can no longer flip themselves back onto their feet,” Husak explains. Glad he’s not my trainer.) These lizards, too, exercised three times a week for eight weeks, while the steepness of the treadmill gradually increased.

At the end of the training regimen, the researchers tested all their lizards a final time. The distance runners had clearly improved. On a fast treadmill, the endurance-trained lizards could run for almost three times as long as they had initially. Blood samples showed that their hematocrit levels—a measure of red blood cells, which carry oxygen—had also increased. And dissecting the limbs of dead lizards revealed that their muscle fibers had grown, just as they do in exercising mammals.

The sprinting lizards were a little more disappointing. In their final trials, they didn’t run any faster than they had before training. But their muscle fibers had also grown. Husak suspects that these athletes had actually improved—they just didn’t feel like performing.

“I definitely think the sprint-trained ones increased their sprinting abilities,” Husak says. But after the lizards had spent so much time being handled by humans, he says, “We just couldn’t motivate (i.e., scare) them enough…to run as fast as they could.”

There’s not likely to be a lizard Olympics anytime soon. Creating athletic anoles isn’t the only goal of Husak’s research, though. He’s ultimately interested in the tradeoffs that come with being a good athlete. Animals that spend more energy on reproduction, for example, may have to sacrifice life expectancy or immunity. Do the same tradeoffs happen when animals spend their resources to build beefy muscles?

Husak has gotten closer to answering that question by showing that lizards can be trained. Now he just has to figure out how to scare them into performing their best—because even if the biology of exercise is the same across vertebrates, the power of a “Just Do It” poster isn’t.

The post doesn’t say much, but it’s nice for this lovely anole to get the attention it deserves!

If you search for photos of A. lividus online, there aren’t all that many. Several more nice ones have appeared previously on AA, such as this one:

Photo by Jim Hewlett

and here’s one from Calphoto:

If you want to read more on this not-well-studied species from an island recently ravaged by volcanoes, AA is the place [1,2].

Photo by Dick Bartlett.

Dick Bartlett found this lizard a week ago, deep in the rainforest along the Rio Mazon, Dpto Loredo, Peru. He says “The blue irises initially indicated transversalis but the more I’ve thought about it, the more unsure I have become.” Anyone able to identify it?

Phelsuma guimbeaui from Mauritius.

Despite the brilliant colors, the natrual history of day geckos (Phelsuma) is little known. The most recent issue of Herpetological Conservation and Biology includes a very nice study on the habitat use of two Mauritian species, showing that they are most abundant in native forest and pointing out that, thanks to their pollinating services, they are keystone species. An interesting point is that even though day geckos are essentially Old World anole doppelgängers, in their habitat use they differ in rarely leaving the trunks of trees. One of the authors is legendary ornithological conservationist Carl Jones, almost single-handedly responsible for preventing the extinction of several Mauritian bird species.

Here’s the abstract:

Many fragile ecosystems across the globe are islands with high numbers of endemic species. Most tropical islands have been subject to significant landscape alteration since human colonisation, with a consequent loss of both habitat and those specialist species unable to adapt or disperse in the face of rapid change. Day geckos (genus Phelsuma) are thought to be keystone species in their habitats and are, in part, responsible for pollination of several endangered endemic plant species. However, little is known about key drivers of habitat use which may have conservation implications for the genus. We assessed the habitat use of two species of Phelsuma (Phelsuma ornata and Phelsuma guimbeaui) in Mauritius. Both species showed a strong affinity with tree trunks, specific tree architecture and are both restricted to native forest. Tree hollows or cavities are also important for both species and are a rarely documented microhabitat for arboreal reptiles. Both P. ornata and P. guimbeaui avoid areas of high disturbance. Our data suggest that active conservation of Phelsuma requires not only the protection and restoration of native forest, but also implementation of forestry practices designed to ensure the presence of suitable trees.

We’ve had a number of previous posts on orange-colored brown anoles, but here’s a nice blog post that discusses them a bit further, with a bonus photo of a yellowish green anole. Christina Chappell, the majordomo of serenityspell.com, reports that the lizard was seen in the northern part of the Everglades. And, no, in case you’re wondering, the photo was not altered in any way.

The Faculty of Arts and Sciences at Harvard University has a quaint but lovely tradition of reading a “memorial minute” to honor deceased members of the faculty. I recently came across the minute concerning Ernest Williams, which was presented in 2009 and published in the Harvard Gazette.

At a Meeting of the Faculty of Arts and Sciences on May 19, 2009, the following Minute was placed upon the records.

Ernest Williams was a man of many contrasts. Biology at Harvard in the third quarter of the last century was full of outsized personalities—titans in the field with strong opinions and no reservations about expressing them. In such company, Williams appeared a wallflower, seemingly wishing to be anywhere but in the midst of their arguments. Yet, one-on-one, Williams had an incisive wit and a dry sarcasm—discussions with him were always stimulating and provocative as he never missed a chance to challenge one’s thinking, sometimes quite pointedly.

To some, Williams’s work came across as old-fashioned. His subject, systematics — the study of the evolutionary relationships of species—is among the oldest in science, and his papers — florid and opinionated and, above all, long—recalled an approach to scholarship no longer in vogue. Yet much of his work was boldly innovative; some papers are still widely cited, and in several cases his work was well ahead of its time, presaging approaches to the study of evolutionary biology that were not to catch on for several decades.

Ernest Edward Williams was born January 7, 1914, in Easton, Pennsylvania, the only child of middle-aged parents. Like many boys, particularly of that time, he grew up loving nature and spent many hours capturing salamanders and other creatures. After attending Lafayette College, Williams joined the Army, serving in Europe during World War II. Upon his return, Williams entered graduate school at Columbia University, where he was the last graduate student of the great anatomist William King Gregory.

Williams’s doctoral thesis focused on the structure of the neck vertebrae of turtles and how variation among species reflects their evolutionary heritage. The work demonstrated the combination of careful attention to detail with the ability to interpret results in the broader context that was to characterize Williams’s career. More than fifty years later the work is still foundational in understanding the evolution of turtle diversity.

In 1950, after completing his degree, Williams moved to Harvard, where he initially served as a laboratory coordinator for the anatomy course of the legendary paleontologist Alfred Sherwood Romer, then subsequently was appointed as an assistant professor and made coordinator of a General Education course on evolution. The Museum of Comparative Zoology’s Curator of Herpetology, Arthur Loveridge, retired in 1957, and Williams was appointed to take his place.  In 1970 Williams rose to the rank of professor and in 1972 became Alexander Agassiz Professor of Zoology.

Williams initially focused on continuing his work on turtle systematics, leading to a series of publications including a still-important treatise published with Loveridge in 1957. Williams soon realized, however, that the museum’s collections were inadequate for the detailed analysis he conceived, which required large samples from many populations. This recognition that the museum’s herpetological collections were wide in scope, but lacking in depth, led Williams in two directions. First, it compelled him to work greatly to expand the Herpetology Department’s holdings, ultimately leading to a quadrupling of the department’s collections (to more than 300,000 specimens) by the time he retired as curator in 1980, making the Museum of Comparative Zoology (MCZ) one of the greatest herpetological repositories in the world. Second, it led Williams’s attention to focus on lizards in the genus Anolis, a very species-rich group from the Caribbean and Central and South America. A previous curator of herpetology and director of the MCZ, Thomas Barbour, had extensively collected anoles in the Caribbean; Williams, whose focus was much more evolutionarily-oriented than most systematists of the day, recognized that this group could be a model for studying large-scale evolutionary and biogeographical phenomena.

And, indeed, they were, and still are.

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Photo by Miguel Landestoy, from the New Yorker’s website

Well, actually it first came to light during a BBC expedition to film solenodons, but more recent legwork by AA  contributor Miguel Landestoy has rediscovered the animals near Pedernales in western Dominican Republic. Miguel’s efforts are chronicled in a delightful article in the New Yorker.

2014 was a good year for AA. 220,000 viewers in 195 countries (and that doesn’t count the 200 subscribers who get each post hand delivered to their email inbox–sign up now!*), 307 new posts, 1570 page views on one day. Guess which post that was? And who do you think the most frequent commenter was, with 76 comments? WordPress has kindly provided a list of information and stats, which you’re welcome to peruse.

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The big question–were they making s’mores?

The first anole paper of 2015 is a doozy. Everyone loves to roast marshmallows around a campfire. Turns out that “everyone” includes crested anoles, A. cristatellus! Read all about it in the paper by Norman Greenhawk in the new journal Life: the Excitement of Biology.

Photo by Julia Klaczko

This is an article wrtten by Stephanie Pappas and posted on livescience. It reports on a paper just published in the Journal of Zoology by Julia Klaczko, Travis Ingram, and me:

A lizard’s penis evolves six times faster than any of its other parts, a new study finds.

The study is the first to directly measure the evolution rate of the penis of any species, though researchers have long suspected that the male genitalia evolve faster than other body parts, said study researcher Julia Klaczko, a biologist at the University of Campinas in Brazil.

“What we see is, sometimes, very close species have very different hemipenes or genitalia,” Klaczko told Live Science. Hemipenes are the pair of organs that make up the version of a penis found in snakes and lizards. But dramatic genital differences are seen among closely related animals with penises, as well. [The 7 Weirdest Animal Penises]

Quick-changing penises

Because penises are often so different even in species that otherwise look almost identical, researchers frequently use genitals to discriminate between different species. Klaczko and her team chose to measure the genitals of 25 species of Anolis, a group of lizards that live in the Caribbean. Anolis lizards are a well-studied group, and researchers have lots of information about the relationships between the species, as well as their habitats and body shapes, Klaczko said.

The lizards’ hemipenes are tubular structures with a groove through which semen can flow. The researchers measured the length and width of the hemipenes in several specimens of each species. For comparison, they also measured the length of the lizards’ limbs, which evolve in response to the vegetation in the animals’ habitats, and the size of their dewlaps, which are the flaps of tissue near the throat that the lizards use for communication.

Next, using mathematical modeling, the researchers estimated the rates of evolution necessary to arrive at the differences in genitals, limbs and dewlaps. The result? Male genitalia change six times faster than either legs or throat flaps, making them more diverse in shape and size from one another than the other body parts.

Picky females or sexual warfare?

Klaczko and her colleagues aren’t sure what drives the rapid alterations in hemipenes. One possibility is that females pick mates with pleasing penises, whether that means their genitals are more stimulating or abetter “fit” in the female genitalia.

Another, less cooperative, possibility is that male and female lizards are locked in an evolutionary arm’s race in which both are trying to control reproduction. If this is the case, then males may be evolving genitals that give them an advantage in fertilization, while females evolve their genitals in an attempt to take that advantage back.

One known example of such a sexual arms race is the duck. Some duck species have corkscrew vaginas that spiral in the opposite direction of the males’ corkscrew penises, so the females can better resist unwanted mating attempts.

So far, the researchers haven’t studied female Anolis genitals, in part because vaginas are just harder to dissect and measure than hemipenes, Klaczko said. The next step, she said, is to try to understand the drivers in the variation in hemipenes’ shape and whether it has to do with differences in habitat, relationships between species, or some other factor.

The researchers reported their findings Jan. 5 in the Journal of Zoology.

Another news article on this research was just published on the Discovery News website.