SICB 2020: Why Do Anole Heads Fail to Develop Properly When It’s Hot?

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On January 9, 2020

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Sylvia presenting her work at SICB 2020

Another SICB, another great presentation from Sylvia Nunez from Thom Sanger’s lab investigating how the interaction between heat and oxygen availability affects development in the brown anole (Anolis sagrei). Last year, Sylvia presented a poster showing that above 33°C, embryonic survival was greatly reduced and many embryos developed craniofacial malformations. With some potential nesting sites for anoles now exceeding 40°C, understanding mechanisms leading to decreased survival is critical.

Low oxygen at sublethal temperatures can recapitulate negative effects on craniofacial development at high temperatures.

As a follow up to this study, Sylvia set out to understand exactly how it is that heat and oxygen can interact to lead to craniofacial deformities. She posited several hypotheses and was able to eloquently test each one, including the neural degeneration hypothesis and the oxygen limitation hypothesis. Specifically, Sylvia noted that disruption in sonic hedgehog has been linked to facial development and that oxygen demand can often exceed oxygen supply at high temperatures.

First, Sylvia tested the oxygen limitation hypothesis by examining whether low oxygen coupled with sublethal (elevated) temperature conditions recapitulate the effects of craniofacial malformation under thermal stress. Previous work in the lab induced craniofacial malformation at 36°C; Sylvia showed you could mimic this effect using 33°C with low oxygen, with a greater rate of malformation than in 27°C (the standard control temperature) with atmospheric oxygen, 27°C with low oxygen, or 33°C with atmospheric oxygen. She then tested whether an increase in oxygen can rescue embryonic survival at high temperatures. To do so, she split eggs among two treatment conditions: 27°C with high oxygen and a hot nest site temperature with high oxygen. She found further support for the oxygen limitation hypothesis – when oxygen availability was increased above atmospheric conditions there were no differences in embryonic survival. Wow! Further, there were no craniofacial malformations in the high temperature treatment when oxygen conditions were high.

To follow up on this finding, she examined if oxidative stress could be the link between temperature and craniofacial malformations using superoxide dismutase (SOD), an enzyme that helps turn the superoxide radical (O2–) into oxygen (O2) or hydrogen peroxide (H2O2), as a marker for oxidative stress in the telencephalon. Indeed, within mere minutes of a temperature increase, SOD becomes upregulated, suggesting that thermal stress contributes to oxidative stress. But Sylvia didn’t stop there. She then treated some embryos with an SOD inhibitor to show that when SOD is absent craniofacial malformations appear.

Overall, Sylvia has very eloquently shown that increased temperature leads to craniofacial malformations via thermal effects on oxidative stress. I cannot wait to see what she presents next year!

SICB 2020: How Does Triiodothyronine Affect Lizard Metabolism?

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On January 9, 2020

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Undergraduate Yasmeen Khawaja with her poster at SICB 2020 in Austin, TX.

As with every year, Jerry Husak sent another crew of talented undergraduates to present great work at SICB 2020! This year, Yasmeen Khawaja presented a poster on her work on the role of triiodothyronine (T3) on lizard metabolism, with specific interests in its role on mitochondrial function and oxidative phosphorylation.

Yasmeen noted her interest in T3, stating that our understanding of thyroid hormones generally, and T3 specifically, has been a mixed bag of results in nonmammalian systems. To help remedy this, she injected male green anoles (Anolis carolinensis) with either 0.01 mg/g body weight of T3 (n = 20) or saline (n = 19) subcutaneously for 19 consecutive days. Interestingly, there were no apparent effects on change in animal mass nor their standard metabolic or mitochondrial respiration rates between the two treatment groups!

Overall, Yasmeen concluded that T3 may not be the biologically active form of thyroid hormone in ectotherms and plans to conduct tests with T4 in the future. I hope she presents those data at SICB 2021!

SICB 2020: Artificial Light at Night Suppresses CORT Rhythmicity

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On January 9, 2020

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Margaret McGrath at SICB 2020

If you look at a map of the United States at night, the urban areas are aglow with light pollution. Urban light pollution disrupts biological processes from gene expression to ecosystem composition across multiple taxa, including birds, insects, mammals, and fishes. With ever-increasing urbanization, understanding the effects of artificial light at night (ALAN) on organisms is crucial to future conservation efforts.

Margaret McGrath, an undergraduate in Dr. Christopher Howey’s lab at the University of Scranton, is examining the impact of ALAN on glucocorticoids in green anoles (Anoles carolinensis), which are commonly found in urban environments. Margaret specifically examined the impact of ALAN on the daily rhythmicity of corticosterone (CORT) and CORT responsiveness to an environmental stressor. She exposed green anoles to either a natural light-day cycle of 12 hours of light and 12 hours of dark or 24 hours of light. After six weeks of exposure, Margaret performed competitive immunoassays to measure baseline CORT levels at midnight and noon. Additionally, she measured CORT responsiveness after placing the green anoles in a bag for 30 minutes to simulate an environmental stressor.

Anoles not exposed to ALAN displayed an expected CORT daily rhythmicity with higher levels of CORT during the day than at night. Anoles exposed to ALAN lost this CORT rhythmicity and maintained CORT at a level intermediate to the other group. In contrast, ALAN does not appear to impact the anoles’ CORT responsiveness to environmental stressors. Her results suggest that green anoles exposed to ALAN are still able to respond to environmental stressors. However, there could be downstream effects from the loss of CORT rhythmicity because it has been linked to arrhythmic activity in mammalian studies.

In the future, Margaret plans to investigate if the natural CORT rhythmicity can be regained by anoles exposed to ALAN when placed back into a natural light-dark cycle. This future research can aid in determining the longevity of ALAN’s impacts on organisms. You can reach Margaret at margaret.mcgrath@scranton.edu and find more about her research on chowey.net, Dr. Howey’s website.

SICB 2020: Collecting Ecological Data from iNaturalist Observations: an Example with Anolis Lizards

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On January 9, 2020

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Chris Thawley presenting his work at SICB 2020

Citizen science is a collaboration between scientists and the general public to advance scientific research. A major citizen science project is iNaturalist. In iNaturalist, anyone can submit an observation of an organism, which includes the date and location. It provides a database over a large area and a long time that would be extremely costly for scientists alone to collect. However, the data’s suitability for ecological analysis is uncertain.

To shine some light on the robustness of citizen science data, Chris Thawley, a visiting assistant professor at Davidson College, worked in collaboration with Amy Kostka, an undergraduate at the University of Rhode Island. When the project was developed, Chris was a postdoc in Jason Kolbe’s lab at the University of Rhode Island. As Amy was unable to go into the field, iNaturalist provided the perfect opportunity for her to experience the research process. They decided to compare established hypotheses of native green anoles (Anolis carolinensis) and invasive brown anoles (Anolis sagrei) against the iNaturalist data. They first coded the anoles’ sex, habitat use, behavior, and morphology, and then compared their coded data against existing hypotheses.

Overall, they found that the iNaturalist data corresponded with existing hypotheses of green and brown anoles. Male brown anoles displayed more frequently than male green anoles, in accordance with results in this paper. Males had broken tails more frequently than females regardless of species, likely due to the more risky behaviors conducted by male anoles than females anoles. Green anoles perched more frequently on natural substrates and perched more frequently in a vertical orientation than brown anoles, in accordance with findings by Stuart et al. (2014). Additionally, the brown and green anoles’ reproductive time period (as measured by when hatchlings emerged) matched with the literature.

iNaturalist is a fantastic tool for individuals who are unable to conduct fieldwork, but still want the research experience. However, Chris pointed out that iNaturalist has spatial biases towards urban areas and temporal biases towards the present day. Additionally, it is necessary to sort and clean the data and to train individuals to standardize coding. This study demonstrates that iNaturalist is still a powerful tool and can be used to estimate phenological patterns, differences between sexes, and corroborate existing hypotheses. Chris hopes that, in the future, iNaturalist could be used to generate new hypotheses.

SICB 2020: Artificial Light Keeps Green Anoles Hungry!

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On January 8, 2020

In All Posts, New Research

There are so many great anole talks at SICB 2020, I’d be remiss if I didn’t take this opportunity to shed some light on some of our fantastic undergraduate researchers, who turned out in force to Austin this year! As I’m sure Dr. Kristin Winchell will tell you, anole lizards make awesome model organisms for studying the effects of city life and urbanization on wildlife.

Cities can be dangerous though. A lot of different urban environments will present wildlife that have not lived in cities with numerous pressures they might not have faced before, such as different surfaces and substrates on which to run, different temperatures, and even new predators. One of the relatively new pressures that goes along with city life is light at night, and artificial light to boot. If you’ve ever been too disturbed by light during the moonlight hours to sleep and rest, imagine how small lizards feel!

To address the effects of this pressure on green anoles (Anolis carolinensis), Michelle D’Alessandro, an undergraduate student at the University of Scranton working in the lab of Dr. Chris Howey, measured the effects of artificial light at night (I’m just going to call it ALAN) They exposed anoles to ALAN and described the effects of artificial light on metabolism in green anoles. Initially, they did not find any differences between metabolic rates when lizards were exposed to ALAN, however after a sufficient time period, anoles exposed to ALAN increased their metabolic rates during the evening, but not during the day! During this experiment, they also found that ALAN anoles were far hungrier and ate more often than lizards that weren’t exposed to light at night. The term ‘midnight snack’ definitely comes to mind here! Michelle suggests that much like when humans get exposed to changes in sleeping patterns, anoles undergo some energetic changes, causing them to eat more and having to burn more energy. Maybe next time think twice about keeping that porch light on during the waning hours of the evening- give the wildlife some much needed rest.

SICB 2020: Variation in Anole Sperm and Testis Morphology

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On January 8, 2020

In All Posts, New Research

Another star undergrad alert! If you’ve ever followed the work that comes out of Dr. Michele Johnson’s lab at Trinity University, you’ll know that she produces some incredible science and some even-more incredible undergraduate researchers. Isabela Carson is no exception!

Isabela’s poster was focused on studying intraspecific variation in lizard sperm and testis morphology- she described differences in the size and shape of different testis and sperm features for 6 different species of anole. A lot of this work was founded on Dr. Ariel Kahrl’s dissertation work on describing sperm evolution in anole lizards, and her collaborations with Dr. Johnson’s lab and students always produce some awesome talks and posters wherever they are presented. Isabela wanted to know if longer sperm are produced from lizard species that have larger seminiferous tubules- the part of the testis where sperm are produced, matured, and transported. She found an inconsistent pattern across anole lizards where larger tubules don’t always produce longer sperm.

In talking with Isabela, she noted that there are some big inconsistencies between the external morphology of testes and the sperm they produce, and that there might be some larger ecological or evolutionary patterns at work that go into describing how sperm evolve in different species. I would bet that one day we are going to have data on testis shape and size and sperm length for all anolis species, and there are going to be some awesome patterns and studies that come out of that work. And we definitely have to give heaps of credit to the awesome biologists who are working towards it!

SICB 2020: Artificial Light Doesn’t Influence Immune Responses in Green Anoles

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On January 8, 2020

In All Posts, New Research

The Howey lab showed up to work at SICB 2020! In keeping with the theme of how urbanization and artificial light at night (ALAN) impacts wildlife populations, Elizabeth Kenny, an undergraduate researcher at the University of Scranton performed a study to describe the influence of artificial light on the immune response in green anoles (Anolis carolinensis).

The researchers used a test for immune response called a phytohemagglutinin test (PHA-L), where they injected the hindlimbs of green anoles with PHA-L and measured how much the foot swelled after both a 24 and a 48h hour period. But rest assured! PHA-L tests are temporary, only induce localized swelling, and have no larger impacts on the health of the organism; it’s sort of like if you’ve ever had a tuberculosis test done at your local physician. Interestingly, Elizabeth found no difference in swelling between green anoles exposed to ALAN and to green anoles that had not been exposed to ALAN. However, Elizabeth suggested that green anoles could respond sufficiently to ALAN by changing how they use the energy within their bodies and where they allocated those limited energetic stores, which provides a lot of support for the work of Michelle D’Allesandro and Meg McGrath. Altogether, the three undergraduate researchers of the Howey lab created a convincing and interesting story about how urban environments influence the energetics and physiology of city-dwelling lizards. Great stuff!

SICB 2020: City Anoles Have Bigger Toes!

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On January 8, 2020

In All Posts, New Research

Urbanization was a big theme at SICB 2020 this year, and studies of how city life influences wildlife populations are really important to help us understand the effects of human activity on natural environments and animals. One of the most rapid ways in that city-dwelling animals can adapt to these new environments is by changing the shape and size of various morphological traits.

Anoles in their natural habitat do tend to be tree-dwelling, or arboreal lizards, and they spend a lot of time climbing to find food resources, regulate their body temperature, and do other ecological activities. A lizard that relies so much on climbing performance frequently uses its claws and toe pads in its climbing ventures, so one of the first changes that city anoles might exhibit is changes in toe pad or claw shape to better climb on slick city surfaces (say that 3 times fast!). To get at this question, Bailey Howell from the Mississippi University for Women, along with her co-authors Travis Hagey and Kristin Winchell, compared urban crested anoles (Anolis cristatellus) to forested crested anoles and found that toe pads in urban anoles are longer and wider than toe pads from lizards in natural environments.

Bailey goes on to discuss that these toe pads that have an increased area might be better for urban anoles to climb on slicker and smoother substrates found in city environments. Bailey is going to continue adding to her dataset by incorporating more anoles and testing additional hypotheses such as measuring performance differences between urban and forested anoles. Stay tuned for more urban anole work!

SICB 2020: Gene Expression Can Lead to Size Dimorphism in Anole Lizards

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On January 8, 2020

In All Posts, New Research

The Panamanian slender anole (Anolis apletophallus).

In keeping with the previous year, Albert Chung (now a Ph.D. student at UCLA with Shane Campbell-Staton), presented in the prestigious Division of Ecology and Evolution Raymond B. Huey best student paper session of SICB2020. Albert’s work encompasses a very old, enduring, and important question in biology: how males and females of the same species exhibit differences in so many traits, despite the fact that males and females share a common genome.

A male brown anole from the island of Great Exuma, in The Bahamas.

This dynamic is called sexual conflict: when what is best for one sex might not be the best for the other sex, and has challenged biologists for decades to study a multitude of incredible organisms to answer this question, including anoles! Albert and his collaborators addressed this question by studying two species of anole, the brown anole (Anolis sagrei) and the Panamanian slender anole (Anolis apletophallus). Brown anoles are one species where males are super large compared to females, whereas in the slender anole, males and females are relatively the same size.

Albert et al. described differences in the genes expressed in both males and females to understand what factors promote the development of male-biased size dimorphism. They found that differences in gene expression between males and females was highest in gonad tissue compared to liver and brain tissue, and that when female lizards are supplemented with additional testosterone (traditionally viewed as a hormone more highly concentrated in males of a given species), their gene expression profiles look like those of male lizards. They also found that liver tissue exhibits the greatest differences in sex-biased gene expression, because the liver is one organ responsible for supplying the body with the energy and molecules needed for growth. They suggest that differences in gene expression between males and females might be one factor promoting the evolution of size differences between the sexes, and that physiological controls on these genes could play prominent roles in having males and females exhibit huge differences in traits despite sharing a similar genetic makeup.

 

SICB 2020: Brown and Green Anoles Have Similar Activity Levels Across Temperatures

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On January 7, 2020

In New Research

Brown anoles (Anolis sagrei) are found in many urban habitats.

Invasive species are a common ecological issue worldwide. In certain situations, they can prey on, outcompete, or otherwise disrupt the ecology of native species, potentially leading to population declines or extirpation.

The brown anole (Anolis sagrei) is native to Cuba and surrounding Caribbean islands, but has been repeatedly introduced to mainland North America via Florida over the past ≈100 years. Brown anoles have continued to spread and now occupy most of Florida, along with areas of the Gulf Coast. These anoles are particularly adept at exploiting urban habitats, such as Houston and New Orleans, where they may attain higher body size and compete with the native green anole (Anolis carolinensis). Brown anoles can outcompete green anoles in habitats such as the ground or lower levels of vegetation, where they can use their larger, more muscular bodies to chase off the native anoles or even prey on young green anoles. While green anole populations are likely not extirpated by brown anoles, they shift their locations higher into vegetation, to avoid competition with brown anoles.

The ability of these species to maximize their activity at different temperatures may play a role in determining the outcomes of interactions between brown and green anoles. While green anoles are present throughout the southeastern US and can tolerate colder temperatures, brown anoles may be ancestrally adapted to higher, more tropical temperatures. Lucy Ryan, a masters student in the Gunderson Lab at Tulane University decided to investigate this possibility by monitoring the activity levels of each species at a variety of different temperatures. The research team hypothesized that, based on their thermal preferences, brown anoles would have higher activity levels than green anoles at both higher temperatures and over a wider range of temperatures. Lucy conducted focal observations of anoles to quantify activities such as feeding, displaying, and moving. They measured the temperature of each anole’s microhabitat with a copper model containing a thermocouple.

Over an 18° C range of temperatures, Ryan found that there was no difference in the activity levels of the two species. These results, while surprising, suggest that effects of temperature on activity are not driving the competitive advantage of brown anoles over green anoles. In fact, since both species’ activity rates peak at similar intermediate temperatures, this situation may increase competition between brown and green anoles. Ryan plans to continue this work through the winter and spring to determine whether there are any species differences over an entire year of activity which may impact this system. Stay tuned and follow them on Twitter!

Green anole activity rate, including dewlap displaying, shows a peak at intermediate temperatures.

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