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Transcriptomic Analysis of Skin Color in Anole Lizards

Anolis distichus

New literature alert!

Transcriptomic Analysis of Skin Color in Anole Lizards

In Genome Biology and Evolution
de Mello, Hime, & Glor

Abstract

Color and color pattern are critical for animal camouflage, reproduction, and defense. Few studies, however, have attempted to identify candidate genes for color and color pattern in squamate reptiles, a colorful group with over 10,000 species. We used comparative transcriptomic analyses between white, orange and yellow skin in a color-polymorphic species of anole lizard to: (i) identify candidate color and color-pattern genes in squamates, and (ii) assess if squamates share an underlying genetic basis for color and color pattern variation with other vertebrates. Squamates have three types of chromatophores that determine color pattern: guanine-filled iridophores, carotenoid- or pteridine-filled xanthophores/erythrophores, and melanin-filled melanophores. We identified 13 best candidate squamate color and color-pattern genes shared with other vertebrates: six genes linked to pigment synthesis pathways, and seven genes linked to chromatophore development and maintenance. In comparisons of expression profiles between pigment-rich and white skin, pigment-rich skin upregulated the pteridine pathway as well as xanthophore/erythrophore development and maintenance genes; in comparisons between orange and yellow skin, orange skin upregulated the pteridine and carotenoid pathways as well as melanophore maintenance genes. Our results corroborate the predictions that squamates can produce similar colors using distinct color-reflecting molecules, and that both color and color-pattern genes are likely conserved across vertebrates. Furthermore, this study provides a concise list of candidate genes for future functional verification, representing a first step in determining the genetic basis of color and color pattern in anoles.

Read the full paper here!

And see the authors’ own commentary!

#DidYouAnole – Anolis vermiculatus

All anoles are amazing and unique, but some just go above and beyond others.

Anolis vermiculatus (previously seen here), the Cuban aquatic or stream anole, is a semi-aquatic anole endemic to Cuba and one of two anoles that completely lacks a dewlap (the other being Anolis bartschi).

The males can have an SVL of up to 123mm making them a large anole, and the females are smaller at 83mm. They live near streams in dense vegetation and eat (in addition to insects) plant matter, small fish, frogs, crayfish and freshwater shrimp. Like another anole, Anolis pulchellus, the Cuban aquatic anole is able to run across the surface of water to escape predators, aided by the hydrophobic skin that anoles have. Cuban stream anoles are incredibly skittish so in addition to running across the water, they may just jump into it when disturbed or threatened, staying submerged for long periods of time.

Photos: Shea Lambert

Trinidadians Reflect on Their Lizards

Anolis aeneus. Photo by shanelkalicharan.

Vaneisa Baksh is an editor, writer and cricket historian for the Trinidad Saturday Express. She’s written two essays on the local lizards and along the way has chided up herpetologists for not responding to the first one. Let’s get to work!

First she writes several weeks ago, in an article entitled “The LIzards Running Up and Down”:

The first time I heard the sound, I thought a bird had flown into the house, although none of my regular feathered folk chirped like that. I searched and searched, remembering how one time a little dove had come in and had been frantically trying to escape while I tried to guide it to the open window in the kitchen. My efforts were just increasing its anxiety and I had to leave it alone to simmer down until it mercifully found its way to freedom.

This time, there was no bird and eventually, as the sound repeated itself, I spotted the culprit. It was a lizard, a gecko, and although we have co-habited in different houses since I was a child, I’d never heard one of the buggers speak. That was a couple years ago, and curious to know if this was a mutation of the creature we called “24-hours” on account of the myth that if it fell on you, it would stay there for an entire day, I went looking for information.

It turned out that these are really house-loving critters. They prefer to be indoors and are harmless, and might even be regarded as useful. I learned that they feed on insects, cockroaches, termites, wasps, flies, spiders, moths and poor butterflies. I’d decided that I would just have to get used to the unusual sound—the most apt description on Wikipedia was “tchak tchak tchak”, which it said was often sounded six to nine times in sequence. I have a way of seeing words in shapes, and maybe sounds as well. Every time I hear the gecko chirp, I would see the sound like a fairly squared-off pellet. Perhaps it is because the sounds are evenly pitched and last for roughly the same length of time. I don’t know, but I have tried to get used to it suddenly rapping into my consciousness.

At first, it was restricted to my bedroom and my study, but now it seems the lizards are everywhere. Whereas I found it an occasional interruption, now I feel there are colonies of them living in my house and even though I hardly see more than one at a time, I feel that they have taken over.

It is one thing to adjust to the sound they make—tchak tchak tchak is far more bearable than the abrasively loud grinding from the welding next door—but these discreet urban dwellers leave their little droppings everywhere. Everywhere. Not only do I have to clean them off the floors, especially at the base of the walls, but the area that really trips me is by my bedside table and on my bed. Yesterday, I washed my sheets and replaced them. As I prepared to turn in last night, I spotted the droppings on the edge of the bed. I suppose that’s why I am bringing them up now.

I would dearly like to know if other householders are experiencing this increased presence that is now forcing a whole different level of housekeeping. I have been getting faint whiffs of urine as well, and it drives me crazy, because I am washing cushion covers, curtains, sheets, everything that could be contaminated, and mopping the floors far too often.

It’s not just being finicky, which I am, but for some time now, my eyes have been unusually sensitive and gritty. While it is true that I am spending a considerable amount of time reading and writing in front of various screens, and that the presence of Saharan dust has been exacerbating things, my ophthalmologist says there is evidence of some kind of persistent irritant, or allergy affecting my eyes.

Naturally, I am mindful that it is possible that the creatures overhead who seem to like my bedroom might be doing numbers over my bed and that might be messing with my eyes. I am not trying to gross anyone out, it just seems that it is likely that there is a growing population of the lizards, which I think we also call woodslaves, and that while we might be adjusting to their presence and their noises, we might not be aware of the side effects.

I’ve never had a problem with lizards. When we were children, the whole brood of about 15 to 20 cousins on any given night would gather in my grandfather’s living room to look at television shows because nobody else had a TV.

We’d start streaming in when the news programme, Panorama, began at seven o’clock. That was when he would turn on the black and white beauty with the wooden cabinetry. Afterwards when some other show began (the real reason we were there), he would sit there with us, and if there was any sign of anything remotely inappropriate for us, like a kissing scene, he would suddenly exclaim, “Look, look, look, the lizard up there!” Naturally, we would all momentarily turn our heads away from the screen at the unexpected shout. Sometimes there was a lizard, but more often not, and he would say, “Ah, he run away!” But his distraction worked well enough, or so he thought.

Harmless enough.

But I feel something has changed. There are more, they are loud and though they love being indoors, they are not house-trained! This might sound creepy though I say it in jest, what if I am now the interloper in the house of the lizards?

—Vaneisa Baksh is an editor, writer and cricket historian.

E-mail: vaneisabaksh@gmail.com

 

And then Vanessa writes yesterday in “Welcome to the Lounge of Lizards”:

I’D hoped that bringing up the ungovernable appearance of house lizards might have elicited a response from a couple of herpetologists. Disappointingly none came; but many people shared their experiences and theories. There was much to learn from these personal stories, and they broadened my sense of community, so I want to share some titbits from a few.

I mean, here we are, locked down in our separate cubicles, not knowing anything about one another, and suddenly, we are sharing lizard tales, revealing snippets of our lives that tell us something about daily trials we have in common. It’s not something we’d chat about, and noticing that our traditionally unobtrusive house mates have become loquacious would hardly qualify as a subject for conversation—unless you have physical visitors and the lizards are contributing their five cents to the discussions. Innocuous things have to force themselves unto your radar—usually by causing some disruption—before they register on your consciousness. Like the jiggly latch on a window that you notice every time you open or close it, but never outside that moment.

Curious if these chirpy critters were mutants or had just been imported, I read of work done by Jonathan Losos, a professor of evolutionary biology and a herpetologist, whose research is mostly concerned with how lizards interact with their environment and how they have diversified. Apparently they have focused on the “evolutionary radiation” of Caribbean Anolis lizards, among others, but they are also looking at how species are adapting to urban environments.

One related study examined the impact of an invasive anole species in Dominica. Up until two decades ago, it was home to a single species until a second species arrived tucked inside a shipment of lumber. Not hard to imagine our lizards coming in by sea. I remember landing in Nevis on one of those small aircraft and as we disembarked, a scorpion scurried down the aisle as soon as the door was opened. Naturally, ­passengers let the hustler disembark first.

A 65-year-old reader sent this: “Our first house was a small ‘board-house’ with a thatched roof and termite-ridden boards. I could knock on a board to find out if it was termite-eaten by the hollow sound that emanated. Prying into the thin cover, I would find the hollow cavities. Here the house-geckos laid their eggs. Unfortunately, sometimes I would remove the eggs. The old Indian people used to call them ‘bistooyas’, the ones about three inches long, sometimes with white stripes from their eyebrows to the body.”

Quite a few people said they had been hearing the noises but couldn’t figure out the source, assuming it was some kind of night bird, and some thought they were alone in this experience.

One person said that around the same time they began hearing those sounds they noticed that “my eyes felt like I had nits in the base of my eyelashes, and the attendant discomfort… At the same time, I had noticed a reduction in small spiders, spider’s webs, and mosquitoes”.

A woman of the West included a delightful description of the upsurge of geckos. “There’s quite a lot of courtship going on between pairs, appropriately, in our bedroom, and each pair seems to play tag, with a pursuer and its quarry. Inevitably, though, they come to an agreement and tiny baby lizards pop up soon after.” She doesn’t mind them, she says, but most of the women harbour strong feelings.

“I detest those creatures. They are annoying. They feed on the insects in the house. If by chance I should see one within easy reach, I implore my husband to get rid of it, and he would hold it using a piece of cloth and throw it outside. He doesn’t harm them,” said one.

A few mentioned that peppermint infused with water makes a reasonable repellent. One had specific directions: peppermint oil may be used by soaking cotton balls and placing them on the top of shelves, inside closets, behind books and similar places. I prefer using a spray bottle, measuring half water and quarter oil and spraying in the same places. It’s been keeping them away so far and the smell becomes less pungent after a few days.” Another said she had tried it, but is worried about the larger implications.

“There is something amiss in the ecosystem. This, what can only be described as an infestation, is a new phenomenon. Is this a new and invasive species or has this lizard been blessed by depleting stock of its natural predators? I do think it is something which the scientists need to investigate. Is there something more sinister at work? And what are the implications? I have always been leery of lizards. Their presence disconcerts me. And now this is like living in some kind of mild horror story—in my own house! Lizards pop up everywhere—in the vegetable basket, in the clean-clothes basket, drop from the roof. One found its way into my glass of water; fortunately, I looked down before I sipped!”

Another said, “I agree with you totally on all that you said, and I believe that these creatures are being used for sinister purposes.”

I don’t know about that, but I enjoyed learning more, like discovering that a group of lizards is called a lounge. I imagine them lounging about our homes and I figure what better place for a lizard to lime than this country!

#DidYouAnole – Anolis transversalis


Photo: dhfischer, iNaturalist

We talked about a lot of Ecuadorean anoles last year and this week we’re revisiting South America.

Transverse anoles, Anolis transversalis, are arboreal lizards that can be found in the Eastern Amazon in Ecuador, Peru, Colombia, Brazil, Bolivia and Southern Venezuela.

These anoles are dramatically sexually dimorphic, so much so that the males were initially described as another species, A. buckleyi (O’Shaughnessy, 1880). The females have a larger banding pattern, sometimes with spots in between and are also different in colouring. The females of this species have dewlaps that are different from the males as well, being smaller and with large vertical banding. Male Transverse anoles have smaller, faint banding overlaid with spots and a larger bright yellow-green dewlap with a pattern of spots (sometimes) and small faint lateral stripes.


Photo: Fernando Ayala-Varela, iNaturalist

Transversalis anole
Photo: Santiago R Ron, BioWeb

Their differences have been noted in previous post on here as well, the differences in their dewlaps.

The average SVL of male Transverse anoles is 88mm, and females is 86mm. They actively defend their territory from other anoles.

Whit Gibbons on Why Anoles Change Colors

From the Tuscaloosa News:

A male green anole flashes its dewlap in a territorial display. Males flaunt the red throat fan to challenge other males. [Photo by Tom Jenssen]

One of the most commonly seen lizards in the Southern states is the green anole, also known as North American green anole or Carolina anole. (Its scientific name is Anolis carolinensis.) Although more than 400 species of anoles are known to science, the green anole is the only one native to the United States. Most people appreciate seeing them in their yards.

Q. A type of lizard we have in Birmingham, Alabama, is sometimes green and sometimes brown. I know it is not two different kinds of lizard because I have watched one change from brown to green. Are these a type of chameleon that can change skin color to match their surroundings?

A. No. Anoles are in a different family of lizards from Old World chameleons. Those are the ones famous for being able to change skin color based on the background, thus creating a true camouflage. In green anoles, color change is a response to external factors, such as temperature and humidity. It may also be influenced by hormonal changes. Whether lizards experience emotions comparable to humans remains a mystery. Researchers continue to investigate why anoles change color, as well as what purpose that change serves for the individual lizard. Most anoles found hidden under bark or leaves on cool days will be brown. If you pick up a brown one and hold it, it will usually turn green.

To learn more, I contacted Tom Jenssen, an expert on the subject of color-changing behavior in green anoles. During his career as a professor at Virginia Tech, Jenssen observed thousands of green anoles while conducting research on the species.

His observations confirmed categorically that the color of a green anole has nothing to do with what the lizard is standing on. One on a green leaf can be brown; one on dark soil can be green. He indicated that factors causing a green anole to exhibit the brown color phase are not completely understood, but he explained the biological mechanism:  “Color-shifting comes from melanophore activity over a sub-dermal layer whose structure reflects green wave lengths.”

In other words, the concentration of black or brown pigment cells determines the color exhibited. If the pigment cells are large, they obscure a lower level in the skin that reflects green light. When the cells are concentrated, the lizard looks dark brown, mottled brown or even like a bad bruise of blotchy brown and olive-green. If the pigment cells contract in size, the lower level is exposed, and the lizard appears green.

He further noted that the activity of pigment cells and their concentration are controlled by the endocrine system, the glands that affect hormones and mood changes for many animals.

The remaining biological mystery: What triggers the endocrine system to cause the pigment cells to contract or expand? Body color in anoles is highly complex with no simple answer for why an individual is a particular color at any given time. Social interactions with other lizards may be responsible in some cases. Brown coloration could possibly result in faster warming of the body on a cool sunny day.

Q. Why do these lizards that can change from brown to green sometimes have a bright red throat?

A. Male green anoles use the vivid red throat fan, or dewlap, to challenge other male anoles and sometimes even other animals. The dewlap display is often accompanied by push-ups and head-bobbing. An invasive species from Cuba, the brown anole, now found in Florida, Georgia and Alabama, has an orange dewlap. Next time you see a green anole displaying a red throat, take a moment to watch its performance. Who is its audience? Is it another anole in the vicinity — or is it you?

Native green anoles are completely harmless and offer fun outdoor entertainment. Enjoy watching them stalk bugs and interact with each other. They are indicative of a healthy environment and deserve our appreciation wherever we find them.

Whit Gibbons is professor of zoology and senior biologist at the University of Georgia’s Savannah River Ecology Laboratory. If you have an environmental question or comment, e-mail ecoviews@srel.edu.

Whit Gibbons

#DidYouAnole – Anolis chlorocyanus


Photo: Pedro Genaro Rodriguez, iNaturalist

This week we are going back up the tree to a trunk-crown anole, Anolis chlorocyanus.

The Hispaniolan green anole is endemic to the island of Hispaniola and has been introduced to Florida. The males are bright green, sometimes being mistaken for  the American green anole, but dewlaps that have black. Females and juveniles are the same shade of green, but often have darker green lateral stripes.


Photo: sricher, iNaturalist

Hispaniolan green anoles inhabit orchards and gardens, in addition to forests. They are one of the few species of anoles that have been reported to vocalise (as noted in this past post and another found here). Like many other anoles, they are capable of rapid colour change to brown, depending on temperature, mood or other factors.

This anole is also part of an eponymous series with several closely related anoles, and there has been some talk of renaming them as new research is done about their genetics.


Photo: Yolanda M. Leon, iNaturalist

Ever Seen an Anole Drink?

Charles Leeper shows us a green anole in action from around his home. And here’s an oldie of Anolis smaragdinus doing the same:

 

The Ol’ Dine-and-Dash, Anole-Style

 

Or should we call it dine-dash-and-dewlap? Anole video-chronicler Charles Leeper has provided another view of green anole life around his house. He describes it thusly: I recently captured some anole footage that you might find interesting. In the video, we see the anole repeatedly extending its dewlap after catching the insect. I know dewlap extension is for displaying to a mate and establishing territory, but could it also be a show of triumph or excitement. I ask because there don’t appear to be any other males in sight, and the anole does it immediately after catching the prey.

Brown Anole in Green Bay!

Winter in Wisconsin is about the worst place you can imagine for a tropical lizard, but that didn’t stop this little one! This brown anole (A. sagrei) was spotted last week (April 2021) in a plant nursery in Madison, WI (ok, not exactly Green Bay…) by a friend of mine, Emily Mitchell. Thanks to her for sending the pic! This individual likely got to Wisconsin as an egg in the soil of a potted plant, and hatched in the nursery. It will have a lonely existence in its midwest nursery home, but at least we can appreciate it!

A Female Green Anole Eats a Freshly Laid Egg

 

 

I recently observed one of my female green anoles swallowing a freshly laid egg, which I suspect came from the other female in the harem. I looked online to see if this behavior is common in green anoles and I was unable to find any information about it. It seems that this exceptional behavior has yet to be reported. I am not sure why my lizard did this.

Considering that my anoles have access to ample resources, including fruit baby food and plenty of gut-loaded crickets and mealworms, I do not believe that her behavior was prompted by a nutritional deficiency. Perhaps it is a novel form of intraspecific maternal competition. Maybe it is unique to mating in captivity. Or maybe this behavior is unique to this particular female — she does eat a lot, and rather indiscriminately. It is also worth mentioning that she is the comparatively larger and more dominant female out of the two.

I am curious to know if anyone else has witnessed this sort of behavior in green anoles, or if they have any ideas about why she did it. Luckily, I was able to catch some of it on video with my cellphone (please excuse the quality and my shaky hands!) just before she swallowed the egg in its entirety.

 

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