Lizards are amniotes with the remarkable ability to regenerate amputated tails. The early regenerated lizard tail forms a blastema, and the regenerated skeleton consists of a cartilage tube (CT) surrounding the regenerated spinal cord. The proximal CT undergoes hypertrophy and ossifies, while the distal CT resists ossification for the lifetime of the lizard. We hypothesize that differences in cell sources and signaling account for divergent cartilage development between proximal and distal CT regions. Exogenous spinal cord implants induced ectopic CT formation in lizard (Anolis carolinensis) blastemas. Regenerated spinal cords expressed Shh, and cyclopamine inhibited CT induction. Blastemas containing vertebrae with intact spinal cords formed CTs with proximal hypertrophic regions and distal non-hypertrophic regions, while removal of spinal cords resulted in formation of proximal CT areas only. In fate mapping studies, FITC-labelled vertebra periosteal cells were detected in proximal, but not distal, CT areas. Conversely, FITC-labelled blastema cells were restricted to distal CT regions. Proximal cartilage formation was inhibited by removal of periosteum and could be recapitulated in vitro by periosteal cells treated with Ihh and BMP-2. These findings suggest that proximal CTs are directly derived from vertebra periosteal cells in response to BMP and Ihh signaling, while distal CTs form from blastema cells in response to Shh signals from regenerated spinal cords. Thus, lizard tail proximal CTs develop independently from tail blastemas, resembling cartilage calluses formed during fracture repair, while distal CTs are derived from the blastemas similar to regenerated salamander tails.
Kristin Winchell’s research on Puerto Rican A. cristatellus evolution in cities is referred to in a nice piece in the New York Times by Menno Schilthuizen.
And an Ecuadorian student has studied the use of their horns in intraspecific interactions. Read all about it on BBC Earth.
For my bachelorette party, my bridesmaids went to an erotic bakery (quite the business niche) in Boston and brought the shop pictures of Anolis lizards. The bakery evidently usually deals in, er, human encounters, so only had skin-toned frosting, and the store clerks weren’t sure if they could do anything lizard themed. But the shop owner evidently got really into the project, did a lot of independent anole research, and produced the cake below. Yes, that is a bridal veil on the yellow one.
Janson Jones is at it again. Actually, he’s been at it for a year, but somehow that slipped below our radar. The former purveyor of Dust Tracks on the Web has a new venue, phosTracks.com: florida wildlife, ecology and more.
Like it’s predecessor, phosTracks is full of keen natural history, engagingly presented and complemented by gorgeous photography. And better yet, anoles are one of Jones’ two favorite animals, neck-and-neck (hard as it may be to believe) with watersnakes.
Check out some of Jones’ recent musings on:
and more! Stay on these pages for some of his giant anole goodness coming up soon!
Just in time for the American Society of Ichthyologists and Herpetologists meeting in New Orleans next week. From the New Orleans Advocate:
It flashed across the walkway like a lightning bolt, so fast that Bob Thomas had to do a double take. In that split second six months ago, he knew they had finally arrived.
“I’d been waiting for them to arrive in my neighborhood in Metairie. What I saw moved too fast for what we’re used to around here,” said Thomas, a herpetologist who taught at Loyola University and served as the founding director of the Louisiana Nature Center.
“It could only be one thing: a brown anole, Anolis sagrei.”
You’ve seen them — the speckled brown lizards that come out of nowhere and streak across the sidewalks. They travel in hordes — tiny, large and everything in between. Careful! You’re liable to step on them if you don’t pay attention.
Thomas’ neighborhood is far from being the first to experience an invasion of brown lizards. But where did they come from? Why are they so plentiful?
“Brown anoles are an invasive species, not native to the United States,” said David Heckard, curator of reptiles and amphibians at the Audubon Institute. “They are natives to Cuba and the Bahamas and first appeared in the U.S. in Florida. From Florida, they’ve been slowly expanding their range across the Gulf Coast. They’re aggressive and competitive and have even been spotted in Taiwan. They hitch rides on plants and are spread inadvertently by plant nurseries.”
The brown anole looks a lot different than the sleek green lizards we grew up with here in New Orleans (Anolis carolinensis). Generally, A. sagrei has a more compact physique and a shorter skull. A prominent hump appears where muscles attach at the back of the skull. When the brown anole extends its orange and red dewlap (the skin flap below its chin), it looks ferocious, indeed.
By contrast, the green anole looks far friendlier, even when its rosy-hued dewlap is extended. Native to the southeastern parts of the United States (although DNA studies suggest they originated in Cuba and came here a couple of million years ago), green anoles range as far north as North Carolina and as far west as Austin, Texas. They have delicately shaped heads and long, lean bodies. They were once plentiful in New Orleans, but sightings are becoming rare.
So, are the brown anoles killing off the green anoles, fighting over territory and winning? Consuming the green anole’s food supply?
“The theory is that the brown anoles are displacing the green anoles but not necessarily replacing them,” Heckard explained. “It’s believed that green anoles are more arboreal than brown anoles, which are more terrestrial. So, green anoles are being pushed to higher elevations — up into trees and the like. It may seem as though there are fewer of them, but they’re present — you just can’t see them hiding in the leaves and up in trees.”
Simon Lailvaux, a professor in UNO’s department of biological sciences, has studied anoles since working on his doctorate and supports the displacement theory.
“In the Caribbean, where there are dozens of species of lizards, they have learned to partition the habitat and have evolved to live in a specific part of it,” Lailvaux explained. “Green anoles there are trunk/crown inhabitants, whereas brown anoles are trunk/ground inhabitants. Over the millions of years that green anoles have been in the United States, they evolved to be able to occupy the ground because they didn’t have any competition for it. So, the relatively recent invasion of brown anoles has simply forced them back up into trees where they originally lived.”
Are we sure about that? Is anybody counting?
“How can you count green lizards way up on tree trunks and in the leaves at the crowns of trees?” answered Lailvaux. “You can’t.”
According to all three scientists, both types of anoles eat the same things: insects and other invertebrates. There are plenty of those to go around here, so it’s improbable that the green anole’s food supply is in jeopardy. Luckily for the green anoles, they may have a significant competitive advantage over the invaders.
“Brown anoles are cold sensitive and can survive only in a limited temperature range. That means the population of brown anoles crashes when we get a hard freeze, and it takes forever for their numbers to recover,” Lailvaux said. “The green anole, on the other hand, has evolved to be able to withstand lower temperatures, so they won’t be bothered by a freeze. We’re seeing, though, that it is taking less and less time after a freeze for the brown anoles to recover, which means they’re already beginning to adapt.”
The mild winters of the past few years may account for the explosion in the visibility of the brown anoles. But if A. carolinensis is being replaced (not merely vertically displaced) by A. sagrei, it would be a case of a native species dying out because an invasive species outcompetes it. Should we be looking into how to reverse that trend?
“The green anole may be a nostalgic favorite, but we don’t know yet what impact the proliferation of the brown anole will have on it or on other species. The sense is, however, that it won’t be wonderful,” Thomas said.
We know too well what an invasive species can do: Witness the nutria. By consuming the marshes, the animals not only reduced storm surge protection for our area but caused the demise of other species that called the marshes home, Thomas pointed out. Without further study, there’s no way to predict if the success of the brown anole could be similarly dire for the green anole and for biodiversity.
I’m not sure I like anoles being referred to as “ditsy,” but here’s a great opportunity to create lovely anole-wear, not to mention anole curtains, anole quilts and all kinds of other anoliana.
Details on Daffodil’s Photo Blog.
Tereza Jezkova helped kick off the anole festivities at Evolution 2016 with her talk entitled: “A peculiar case of hybridization with advantageous mtDNA introgression and lack of nuclear introgression in Caribbean anoles.” Along with a string of co-authors (Todd Castoe; Manuel Leal; Daren Card; Drew Schield; David Elzinga; Javier Rodríguez-Robles), Tereza has discovered that completely normal looking Anolis pulchellus populations in western Puerto Rico (and a bit elsewhere) harbor the DNA of the closely related A. krugi.
What’s going on? Detailed examination revealed two interesting findings. First, this appears to be the result not of a single hybridization event, but minimally of 15 such events, all of them apparently quite recent. The krugi mtDNA has completely displaced the pulchellus mtDNA in these populations, and population genetic analyses rule out genetic drift as the cause. Puzzlingly, genomic analyses find absolutely no krugi nuclear DNA in these populations. The mtDNA is getting in, but not the nuclear genes. Natural selection must be at work, but how? Tereza suggested some sort of genetic mechanism that excludes the nuclear DNA of the introgressing species, somehow kicking it out, likening it to a phenomenon reported in frogs and some insects, but not in any amniotes.
Christian Perez is currently studying anoles at La Selva Biological Station in Costa Rica. Recently, he found a vine snake. Here’s his report:
As I reached towards the snake, I startled an anole (Anolis limifrons) that was hiding nearby. The snake turned rapidly, looked at the anole, and made movements synchronized with the wind to remain inconspicuous among surrounding vegetation. I stayed with them for a while, and after one failed strike, the snake successfully stalked and caught the anole. The snake took under a minute to consume the lizard, and it was very friendly after its meal.
Also, there is not a single widely supported theory for the snake’s tongue extension when stalking the anole. This is distinct from tongue flickering in other snakes.
Over at Lizards and Friends, Amy Payne from Michele Johnson’s lab reports on her first field experience studying green anoles. Fear not–they kept an eagle eye out for snakes.
We have been remiss here at AA in not reporting on a recent monograph in Novitates Caribaea (the journal of the Museo Nacional de Historia Natural of the Dominican Republic) by Köhler and Hedges dividing the Hispaniolan green anoles into sixteen species, up from the previously recognized four. Specifically, Anolis chlorocyanus is split into four species, A. coelestinus into five species, and A. aliniger is subdivided into six species. Poor A. singularis remains as it is.
The analysis is based on mitochondrial DNA and morphological characters. The monograph is available online and should be consulted for the fine details. Appended below are the abstract and the heart of the methods.
Say what you may about the proliferation of new species (and word on the street is that this will not be the last word on green anole species diversity), some of the new species are spectacular in appearance and certainly there is more variation in this group than many may have realized.
We revise the species of green anoles (i.e., the species related to Anolis aliniger, A. chlorocyanus, and A. coelestinus) occuring on Hispaniola. Based on our analyses of morphological and molecular genetic data we recognize 16 species of green anoles, eight of which we describe as new species (A. apletolepis sp. nov., A. chlorodius sp. nov., A. divius sp. nov., A. eladioi sp. nov., A. gonavensis sp. nov., A. leucodera sp. nov., A. prasinorius sp. nov. and A. viridius sp. nov.) and three of which are raised from subspecific to species level (A. cyanostictus, A. demissus and A. pecuarius) and one is resurrected from synonymy with A. chlorocyanus (A. peynadoi). Because the six syntypes of A. chlorocyanus (MNHN 785, 787, 2007.2066–09) are conspecific with the only available syntype of A. coelestinus (i.e., MCZ 3347), we have petitioned the International Commission of Zoological Nomenclature (ICZN) to use its plenary power to set aside the type status of the syntypes of Anolis chlorocyanus and to allow the designation of a neotype in order to stabilize the current and long established usage of the names A. chlorocyanus and A. coelestinus. For each species we provide a standardized description of external morphology, color descriptions in life, color photographs in life, description and illustration of hemipenis morphology (if available), distribution maps based on the specimens examined, comments on the conservation status, and natural history notes. Finally, we provide a dichotomous key for the identification of the 16 species of green anoles occuring on Hispaniola.
And here’s how they did it:
For this study, we have examined a total of 787 specimens of green anoles from Hispaniola. Head length was measured from the tip of the snout to the anterior margin of the ear opening. Snout length was measured from the tip of the snout to the anterior border of the orbit. Head width was determined with the broad tips of the calipers aligned with the levels of posterior margin of eye and supralabial scales, respectively, with the calipers held in a vertical position relative to the head. Dorsal and ventral scales were counted at midbody along the midline. Tail height and width were measured at the point reached by the heel of the extended hind leg. Subdigital lamellae were counted on Phalanges II to IV of Toe IV of the hind limbs, and separately on distal phalanx. We considered the scale directly anterior to the circumnasal to be a prenasal. Abbreviations used are AGD (axilla–groin distance), dorsAG (number of medial dorsal scales between levels of axilla and groin), dorsHL (number of medial dorsal scales in one head length), HDT (horizontal diameter of tail), HL (head length), HW (head width), IFL (infralabials), IP (interparietal plate), SAM (scales around midbody), ShL (shank length), SL (snout length), SO (subocular scales), SPL (supralabial scales), SS (supraorbital semicircles), SVL (snout–vent length), TL (tail length),VDT (vertical diameter of tail), ventrAG (number of medial ventral scales between levels of axilla and groin), and ventrHL (number of medial ventral scales in one head length). In reporting the frequencies of character states, we used the following terminology (Köhler submitted): if a character state was present in more than 65% of the examined specimens, we coded it as “usually”; <65% but >20% “commonly”; <20% but >5% “occasionally”; and <5% “exceptionally”. The use of size categories also follows Köhler (2014): (1) small: <50 mm SVL; (2) moderate-sized: 50–60 mm SVL; (3) moderately large: 60–80 mm SVL; (4) large: 80–110 mm SVL; (5) giant: >110 mm SVL.
As lines of evidence for species delimitation, we apply a phenotypic criterion (external morphology: coloration, morphometrics, and pholidosis) and a criterion for reproductive isolation (genetic distinctness of the cytochrome B and ND2 genes). Sequences from 77 ingroup and two outgroup taxa were analyzed (a total of 2217 aligned sites). Alignments (MUSCLE) and best-fit model selection were performed in MEGA 6.06 (Tamura et al., 2013). A maximum likelihood (ML) analysis was performed using MEGA 6.06), unpartitioned, using the evolutionary model GTR + I + Γ. Gaps were treated as missing data. All parameters for the ML analyses were estimated by the program during the run. Branch support in the trees was provided by standard bootstrap analysis (2,000 replicates). A Bayesian phylogenetic analysis using MrBayes 3.2.2 (Ronquist et al., 2012) also was performed, also using the GTR + I + Γ model. The Bayesian analysis was set to two parallel runs for five million generations, sampled every 100 generations, each run employed three heated and one cold chain, with a temperature parameter of 0.10. The first 10% of samples were discarded as burn-in. Convergence was assessed by the standard deviation of split frequencies (< 0.01 in all cases).
Congratulations, Kristin Winchell and co-authors!
And for those of you keeping track, that’s five anoles on the cover of Evolution in the last six years (ending a three-year drought).
photo credit: Robert Eastman/Shutterstock
Small tropical lizards called anoles have adapted to life in the urban jungle by evolving stickier hands and feet as well as longer arms and legs, according to a recent Evolutionstudy. These help them cling to concrete walls, walk across slippery windows, and perch on metal fences with as much ease as their forest-dwelling cousins.
Urbanization is rapidly increasing around the world, with humans living in nearly two-thirds of the planet’s terrestrial areas. As a result, animals are being confronted with new habitats – from decorative, non-native plants to impervious surfaces and artificial lights. And with these come novel selection pressures. While many wildlife species can survive in cities, relatively little research has been done on whether these populations have adapted (in an evolutionary sense) to their newfound environments.
Crested anoles (Anolis cristatellus) are trunk-ground specialists; they use their long limbs and stocky build to navigate across broad surfaces like tree trunks or the forest floor. The species is native to Puerto Rico, which has been utilized intensively for agricultural cash cops like sugar cane, tobacco, and coffee throughout the 19th and 20th centuries. This has led to massive declines in native wildlife and tree cover. Around the same time, the island underwent major industrialization: 94 percent of the 3.7 million citizens now live in urban areas.
To see if the lizards have adapted to urbanization, a team led by Kristin Winchell from the University of Massachusetts Boston compared the ecology, morphology, and DNA of hundreds of male crested anoles living in three high-density Puerto Rican cities – Mayagüez, Ponce, and San Juan – with anoles living in three subtropical forests nearby.
As predicted, the temperature, humidity, and substrate availability varied a lot between urban sites and their neighboring natural areas. Additionally, urban lizards often used artificial substrates, which were generally broader than the substrates in forests. However, city anoles had longer forelimbs and hindlimbs relative to their body size, and they also had more lamellae – tiny scales on the undersides of their toes that help them “stick” to surfaces.
The team also reared the hatchlings of wild-caught adult pairs from one urban and one natural population: 25 males and 25 females from each of the two populations. They found that the differences between urban and natural wild populations were maintained in their captive-reared offspring – which means these differences are likely genetically based.
Cornerstone recently reported abstracts from an undergraduate research symposium at the University of Minnesota Mankato. Included in the event were four projects from the laboratory of Rachel Cohen.
Seasonal Effects on Kisspeptin Concentration in the Green Anole Lizard, Anolis carolinensis
Nicholas Booker, Minnesota State University Mankato
Hyejoo Kang, Minnesota State University Mankato
Gonadal steroid hormones are responsible for reproductive behaviors; disruption in production of these hormones is also linked to fertility issues. The hypothalamic-pituitary- gonadal (HPG) axis controls the production of sex steroid hormones, testosterone and estradiol. A peptide, kisspeptin, stimulates this axis by acting on neurons in the hypothalamus. The green anole lizard, Anolis carolinensis, is a seasonally breeding animal that shows drastic changes in behavior and physiology between the breeding and non- breeding seasons. One such change is a large increase in testosterone levels in the breeding season compared to the non-breeding season. These fluctuations in testosterone concentration in green anoles allows for a great opportunity to study the HPG axis. In the current study, we used brain tissue from breeding and non-breeding season green anoles to perform western blot analysis on kisspeptin concentration. Due to the increase in testosterone in the breeding season, we hypothesized that an increase in kisspeptin concentrations will be observed in breeding season compared to the non-breeding season lizards. These results would suggest that kisspeptin does indeed play a role in stimulating the HPG axis and that kisspeptin could potentially be used as a treatment for infertility.
The Effect of Steroid Hormones on Neuronal Size and Number in Two Brain Regions Important for Reproduction
Jaeyoung Son, Minnesota State University Mankato
Steroid hormones, such as testosterone (T) and its metabolites (estradiol, E2, and dihydrotestosterone, DHT), are critical for the production of reproductive behavior. These hormones play a role in neural plasticity, such as changes in neuronal size change and brain region volume. Our study is examining the role of steroid hormones in maintaining the morphology of brain areas involved in reproduction, such as the ventromedial hypothalamus (VMH) and preoptic area (POA). We are using the green anole lizard (Anolis carolinensis) as a model because they are seasonally dimorphic, with more reproductive behaviors and higher steroid hormones in the breeding compared to non-breeding season. We treated our animals with different steroid hormones: T, DHT, E2, and blank capsules as a control. We collected the brains, sectioned the tissue and measured neuron size, number and density in the VMH and POA. We are expecting to find smaller and increased numbers of neurons in the animals treated with steroid hormones compared to the controls. This result would support the idea that steroid hormones are critical for the maintenance of brain areas important for reproduction.
Seasonal Variation in the Dorsolateral and Medial Cortex of Green Anole Lizards
Amber Day, Minnesota State University Mankato
Abdi Abdilahi, Minnesota State University Mankato
The hippocampus is a region of the brain involved in spatial learning and memory, and has been shown to add new neurons in adult animals. Steroid hormones, specifically testosterone
(T) and its metabolites (estradiol, E2, and dihydrotestosterone, DHT), have been shown to play a role in the addition of adult-born neurons to the brain. The green anole lizard, Anolis carolinensis, is a seasonally breeding animal that exhibits seasonally dimorphic behaviors, as well as seasonal anatomical differences in the brain. The pronounced differences between the breeding and non-breeding seasons make this lizard an excellent model for the study of how steroid hormone differences impact the brain. We examined the volume of and addition of new adult-born neurons to the dorsolateral and medial cortex in the lizard, which is analogous to the mammalian hippocampus. We sectioned brain tissue from breeding and non-breeding animals, performed a Nissl stain, and are measuring volume of the regions. We expect that the region will be larger in the breeding season due to the increase of territorial and courtship behaviors. We also treated animals with T, DHT, E2 or nothing as a control and performed an immunohistochemistry to examine how steroid hormones impact neurogenesis. We expect to see significantly more neurogenesis in the dorsolateral and medial cortex of T, DHT, E treated animals in comparison to the untreated group. Our experimental results may provide a greater understanding of the mechanisms that regulate the neural control of reproduction and territorial behaviors.
Amygdala Morphology and Neurogenesis in the Green Anole Lizard
Jadden Roddick, Minnesota State University Mankato
Nicholas Booker, Minnesota State University Mankato
Abodalrahman Algamdy, Minnesota State University Mankato
Steroid hormones and their derivatives play a major role in the reproductive system. One region in the brain that is involved in reproduction is the amygdala. We are examining the relationship between steroid hormones and neuron size, number and neurogenesis in the amygdala of the green anole lizard (Anolis carolinensis). Green anoles are exceptionally good models to examine the neural control of reproductive behaviors because they are seasonally breeding animals and exhibit unique behavioral and physiological differences in the breeding season compared to the non-breeding season. These behavioral differences are likely caused by seasonal changes in circulating steroid hormone levels. For our project, breeding green anole males were gonadectomized and a capsule containing testosterone, estradiol, dihydrotestosterone or left empty was inserted under the anole’s skin. The animals were injected with bromodeoxyuridine (BrdU; a new cell marker) for three days after the treatment. After one month, brains were collected, sectioned, and placed on slides. An immunohistochemistry for BrdU and Hu (neuronal marker) was conducted to examine the presence of new neurons in the amygdala. Alternate sections were Nissl stained and used to count cell number and measure soma size. We expect to see a decrease in neuron number, soma size, and neurogenesis in the animals treated with hormones compared to the animals treated with the blank capsule because we see this pattern in breeding season animals. This work will help provide more insight into the neural control of reproduction.
A concerned Anole Annals reader writes in:
My dog just violently chomped a female alone. Along with her entrails protruding from her body we two eggs. One was small, under-developed the other was the size they are laid. I have at the time done my best to put it into a container and emulate the same conditions outside ( I live in Florida) with dirt, leaf litter (small) moisture and heat. I removed the placental outer membrane which would have been separated if she had laid. I feel terrible my young and excitable dog did this. Is there any hope?
Can anyone advise?
Read all about it in Rodríguez-Cabrera et al.’s new paper in IRCF Reptiles & Amphibians.